Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
416 PM EDT Sat Jun 21 2025

Valid 00Z Sun Jun 22 2025 - 00Z Tue Jun 24 2025

..There is a Slight Risk of excessive rainfall over parts of southwestern
Texas and southeastern New Mexico on Sunday, as well as Upper/Middle
Mississippi Valley/ Central Plains and Southern Rockies/Southern High
Plains on Monday...

...There is a Slight Risk of severe thunderstorms over parts of the Lower
Great Lakes/Northeast on Saturday and Northern/Central Plains/Upper
Mississippi Valley/Southern High Plains on Sunday...

...There is a Critical Risk of fire weather over parts of the Great
Basin/Southwest on Saturday...

A front extending from just north of Lake Superior/Upper Great Lakes to
the Northern Plains and Northern Rockies and then into the Great Basin
will have a wave of low pressure over the Northern Plains that moves
northeastward to near James Bay, Canada, by Monday evening. The trailing
front will extend from the Upper Great Lakes to the Central Plains and
westward into the Great Basin. Moisture pooling along the boundary will
produce showers and severe thunderstorms from the Lower Great
Lakes/Northeast. Therefore, the SPC has issued a Slight Risk (level 2/5)
of severe thunderstorms over parts of the Lower Great Lakes/Northeast
through Sunday morning. The hazards associated with these thunderstorms
are frequent lightning, severe thunderstorm wind gusts, hail, and a
minimal threat of tornadoes.

Furthermore, showers and thunderstorms will develop over parts of the
Northern Rockies to the Great Lakes. Additionally, moisture and
upper-level energy will produce scattered showers and thunderstorms over
parts of the Gulf Coast States and the Southeast/southern Mid-Atlantic
Coast through Sunday morning.

On Sunday, moisture will stream northwestward over Texas and interact with
upper-level energy to produce showers and thunderstorms, creating heavy
rain over parts of southwestern Texas and southeastern New Mexico.
Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive
rainfall over parts of southwestern Texas and southeastern New Mexico from
Sunday into Monday morning. The associated heavy rain will create mainly
localized areas of flash flooding, with urban areas, roads, small streams,
and low-lying areas the most vulnerable.

In addition, the moisture will flow northward east of a dryline and along
and ahead of the cold front over the Northern Plains/Upper Mississippi
Valley/Upper Great Lakes and Central/Southern High Plains, producing
showers and severe thunderstorms. Therefore, the SPC has issued a Slight
Risk (level 2/5) of severe thunderstorms over parts of the Northern
Plains/Upper Mississippi Valley/Upper Great Lakes and Central/Southern
High Plains from Sunday through Monday morning. The hazards associated
with these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, hail, and a few tornadoes. Moreover, there will be an increased
threat of severe thunderstorm wind gusts of 65 knots or greater and hail
two inches or greater over parts of the Northern Plains/Upper Mississippi
Valley.

Further, moisture pooling along a front over the Northeast will aid in
producing strong to severe thunderstorms over parts of the Northeast and
northern Mid-Atlantic. Therefore, the SPC has issued a Marginal Risk
(level 1/5) of severe thunderstorms over parts of the Northeast and
norther Mid-Atlantic from Sunday into Monday morning. The hazards
associated with these thunderstorms are frequent lightning, severe
thunderstorm wind gusts, hail, and a minimal threat of tornadoes.

Moreover, moisture and upper-level impulses will trigger showers and
thunderstorms over parts of the Southern Ohio/Tennessee Valleys and the
Lower Mississippi Valley/Southeast.

On Monday, moisture will continue to flow along the dryline and front over
the Upper/Middle Mississippi Valley to the Central Southern High Plains,
producing two areas of heavy rain. The first area will cover parts of the
Upper/Middle Mississippi Valley and Central Plains. Therefore, the WPC has
issued a Slight Risk (level 2/4) of excessive rainfall over parts of the
Upper/Middle Mississippi Valley and Central Plains on Monday. The
associated heavy rain will create mainly localized areas of flash
flooding, with urban areas, roads, small streams, and low-lying areas the
most vulnerable.

The second area of heavy rain will develop over parts of the Southern
Rockies and Southern High Plains. Therefore, the WPC has issued a Slight
Risk (level 2/4) of excessive rainfall over parts of the Southern Rockies
and Southern High Plains on Monday. The associated heavy rain will create
mainly localized areas of flash flooding, with urban areas, roads, small
streams, and low-lying areas the most vulnerable.

Moreover, showers and severe thunderstorms will develop along the northern
parts of the front along parts of the Upper Great Lake/Upper Mississippi
Valley. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe
thunderstorms over parts of the Upper Great Lake/Upper Mississippi Valley
on Monday. The hazards associated with these thunderstorms are frequent
lightning, severe thunderstorm wind gusts, hail, and a few tornadoes.

Likewise, moisture and upper-level energy will produce scattered showers
and thunderstorms on Monday over parts of the Gulf Coast States and the
Southeast.

Meanwhile, an upper-level low will move across the Pacific Northwest into
the Northern High Plains by Monday, leaving an upper-level trough over the
West Coast. The energy will produce rain over the Northwest through Monday
morning. Further, wet mountain snow will develop over parts of the
Northern Rockies, prompting a Winter Storm Warning for parts of Glacier
National Park from early Saturday morning to Sunday afternoon. At lower
elevations, showers and thunderstorms will develop over the region through
Sunday evening. Also, showers and thunderstorms will move into parts of
the Northern Plains and Upper Mississippi Valley on Sunday.

Elsewhere, deep boundary-layer mixing is expected across the Great Basin
during the afternoon, with surface temperatures climbing into the 90s to
100 F and relative humidity falling into the single digits. The deep
boundary-layer mixing into the strong flow aloft, coupled with a
tightening regional pressure gradient, will contribute to an expansive
area of 20-25 mph sustained southwesterly surface winds (with higher
gusts), which has prompted a Critical Risk of fire weather over parts of
the Great Basin/Southwest on Saturday.


Ziegenfelder


Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Sun Jun 22 2025

Valid 12Z Wed Jun 25 2025 - 12Z Sun Jun 29 2025

...Record heat gradually lessens but dangerous heat continues for
the Ohio/Tennessee Valleys and Mid-Atlantic/Southeast mid to late
week...

...Heavy rain and flash flooding concerns continue for the north-
central Plains/Upper Midwest Wednesday and Thursday, and lingering
in New Mexico Wednesday...


...Overview...

As the medium range period begins Wednesday, a significant and
extremely dangerous heat wave will be ongoing across the Midwest,
Ohio Valley, and eastern U.S. as a notably strong upper high is
centered from the Ohio/Tennessee Valleys and Mid-Atlantic. The
extreme, record-breaking heat should moderate slowly midweek and
beyond, but temperatures will remain quite hot across those areas,
and the long duration of the heat wave could cause exacerbated
impacts. Meanwhile strong southerly inflow with deep tropical
moisture will set up between the upper high and an initial mean
trough with embedded shortwaves in the West. Moisture will
initially reach New Mexico and lead to additional heavy rain there,
with the moisture then reaching around the upper ridge (in a "ring
of fire" setup). This should interact with a wavy frontal boundary
and promote another area of potentially heavy rain and flash
flooding over the north-central Plains, Corn Belt/Midwest, and
Great Lakes region.


...Guidance/Predictability Assessment...

The large scale pattern remains in excellent agreement for
midweek, as models for several days have shown a 594+ dm upper
ridge lasting through Wednesday, and weakening and flattening after
that. Meanwhile farther west, troughing across the Great Basin and
vicinity will also weaken as the week progresses. This, combined
with a wave train of northern stream shortwaves, will trend the 500
mb flow pattern toward more zonal and less amplified flow for the
latter half of the week. The slight differences in speed and
amplitude of multiple shortwaves streaming from the West to the
Upper Midwest introduces a bit more uncertainty for the mid to late
medium range period, but nothing out of the ordinary at that time
range. Somewhat broader scale troughing moving into the Northwest
late week and progressing eastward into the weekend shows some
timing and amplitude differences. The 12/18Z GFS runs were weaker
and progressive than the non-NCEP and AI/ML consensus with this
trough, so the GFS runs were not favored. The new 00Z GFS seems to
show better agreement though.

The WPC forecast for mass fields was based on a general multi-
model blend early in the period. Increasing model differences and
eventually eliminating the 12/18Z GFS from the blend led to
introducing and increasing the proportion of the GEFS and EC
ensemble means in the blend, with the means reaching half the blend
Day 6 and more Day 7. For QPF, mainly leaned toward the pattern of
the EC-AIFS in the north-central U.S. especially on Wednesday, but
with increased amounts. This supported more QPF in Nebraska than
the NBM that favored northeast of there, which seemed to make sense
since Nebraska was closer to the better forcing.


...Weather/Hazards Highlights...

On Wednesday, the upper trough in the Interior West will be
gradually weakening, lessening upper jet right entrance region
support and slightly lessening moisture anomalies in the southern
Rockies/High Plains compared to what's now the short range period.
However, some heavy rain could still be a concern centered around
New Mexico, especially considering the wet antecedent conditions by
then. A Slight Risk is delineated in the Sacramento Mountains and
vicinity for the Day 4/Wednesday ERO, where orographic support
could enhance rainfall totals and where burn scars and steep
terrain make the area sensitive to heavy rain. Rain amounts should
continue to gradually decrease there into later week. Will show a
Marginal Risk on Day 5/Thursday for southern portions of New Mexico
including the Sacramento Mountains for another potential round of
moderate to locally heavy rain.

The plume of subtropical/tropical moisture will arc northeastward
into the north-central Plains and Upper Midwest/Corn Belt where the
additional lift around the frontal boundary and potential training
will favor areas of heavier rainfall and some flash flooding
potential. For the Day 4/Wednesday ERO, continue to show a Slight
Risk (with embedded probabilities on the higher end of the Slight
range) for these areas. The Slight generally covers some model
spread from an eastern Nebraska focus to areas farther northeast.
The details in the heavy rainfall placement remain uncertain south
due to the sensitivity to day-to-day rainfall patterns and
mesoscale boundaries. A weak surface low embedded along the front
may track somewhat east by Thursday, pushing the heaviest rain
totals across much of Wisconsin and possibly the U.P. of Michigan.
Thus for the initial Day 5/Thursday ERO, will show a Slight Risk
there, given potential for 2 to 4 inches to accumulate despite
continued spread in the exact positioning. For both Wednesday and
Thursday, some convection with locally heavy rain could traverse
the northern side of the ridge farther east into New York State and
the northern Mid-Atlantic, so will show Marginal Risks there. The
Northeast may see increasing rain amounts by Friday, while another
round of rain is possible in the north-central U.S. late week as
well.

Farther south, there is some uncertainty with how much convection
may occur under the upper ridge across the Gulf Coast and
southeastern U.S. as surface-based instability likely battles with
subsidence aloft. In general, scattered thunderstorms may increase
in coverage as the week progresses as the upper high gradually
weakens.

The strong upper high/ridge stretching across the south-central to
eastern U.S. will allow for well above average temperatures that
could approach or exceed daily records at a few dozen locations
through Wednesday, with more widespread coverage of record warm
morning lows if those numbers hold through the calendar day. This
translates into highs well into the 90s into the low 100s, with
heat indices to near 110F as dew points will be in the 60s to
low/mid-70s. Overnight lows will only drop into the low/mid 70s for
many areas, and even may stay around 80-83F in the urban centers
like Washington, D.C., Baltimore, Philadelphia, and New York City.
This will bring little relief from the heat and exacerbate
potential impacts. Thus, HeatRisk values will be Major to Extreme
for portions of the Midwest and Ohio Valley to Eastern states --
levels 3 and 4 on a scale from 1 to 4 (4 being Extreme). This
indicates an intensity and duration of heat that is extremely
dangerous to anyone without adequate cooling or hydration. Extreme
heat is the number 1 weather-related killer -- please take
precautions if you are outside during the hottest part of the day
and seek cooling if you are without adequate means. Temperatures
will remain above average, though a few degrees lower and with
fewer records possible, across much of the Ohio Valley/Mid-
Atlantic/Southeast into the latter part of next week. But the
Northeast should see moderating temperatures after a cold frontal
passage. Meanwhile, temperatures (particularly highs) are forecast
to be below average by a few degrees in the High Plains into
midweek, but the West should gradually warm to a bit above average
as the week progresses.


Tate


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
324 AM EDT Sat Jun 21 2025

Valid 00Z Sun 22 Jun 2025 - 00Z Sun 29 Jun 2025

Over the weekend, a surface high is forecast to strengthen and
edge closer to Hawaii, which will increase easterly trade winds
across the state as the pressure gradient tightens. Drier air will
also be in place and limit shower coverage, so conditions
favorable for fires may be a concern.

Early next week, trades should return to moderate to locally
breezy levels. Meanwhile a weak low aloft may allow for a raised
inversion while waves of higher moisture move through. This should
lead to a comparatively wetter trade wind pattern next week.
Moisture levels look to peak around Tuesday-Wednesday and linger
into Thursday. Showers should favor windward and mauka areas, but
widespread heavy rain is not expected.


Tate

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
855 PM EDT Sat Jun 21 2025
Day 1
Valid 01Z Sun Jun 22 2025 - 12Z Sun Jun 22 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE NORTHERN GREAT LAKES AND THE INTERIOR NORTHEAST...

01Z Update...
With some minor adjustments, Marginal Risk areas were maintained
over portions of northern Michigan, as well as northern New York
and Vermont.

Across northern Michigan, the latest HRRR has shown an uptick in
amounts centered near the Tip of the Mitt and the eastern U.P.,
where storms may develop and lift north from a slow-moving
boundary. While the latest mesoanalysis shows plenty of moisture
(PWs 1.8+ inches) and instability (MUCAPE 3000+ J/kg), it also
shows a fair amount of CIN, which along with a capped environment,
is likely to hinder any widespread development.

Further to the east, the complex developing over southwestern
Ontario/southern Quebec is expected to move into northern New York
and New England tonight. The latest guidance is not indicating
widespread heavy amounts, however a period of training may
contribute to some localized heavier totals (1-2 inches) and an
isolated flash flood threat.

Pereira

Previous Discussion...
...Northern Great Lakes...
Convection will likely be ongoing at 12z this morning across
portions of the UP of MI. It still looks like the storm mode should
be a progressive squall line, which would limit the duration of
heavy rainfall and flash flood risk. However even the progressive
convection will be capable of heavy rates, with a high likelihood
of some 1"+ per hour totals, and a low chance of 2" per hour. Also
can not rule out some brief backbuilding/training on the southwest
flank of convection as it moves eastward. So while the flash flood
risk should be relatively low, localized hydrologic issues can not
be ruled out this morning. Convective and model trends suggest the
better threat is over the UP of MI, and so we were able to cut
back on the southern extent of the inherited risk area with this
update.

...Northeast...
Not expecting much convection during the day across the Northeast,
however an uptick in activity is possible overnight into early
Sunday. By tonight steeper lapse rates advect into the region,
resulting in what should be a pretty rapid increase in MUCAPE over
western NY into portions of VT and NH. The ongoing MCS over MN and
MI should weaken as it approaches the Northeast this evening as
instability will not have increased yet. However the parent mid
level shortwave will remain upstream and expect an additional area
of organized convection to develop with this over southern Canada.
It is this next round that has a better chance of surviving into
portions of NY/VT/NH by later tonight.

The details of this remain unclear, but there should be enough
instability and low level moisture transport/convergence to
sustain some level of activity into the Northeast. Most indications
from the 00z high res guidance is for a quick moving area of
convection, and thus rainfall totals are not overly impressive.
However given the ingredients in place there does seem to be some
potential for an over performing area of convection with some brief
backbuilding characteristics. The better chance of this would be
along the instability gradient and southwest flank of
activity...probably central/upstate NY and/or portions of VT/NH. A
Marginal risk continues to suffice given the 00z suite of
models...however will need to closely monitor observational and
model trends through the day. Depending on how things evolve later
tonight into early Sunday there is some chance for an embedded
more focused flash flood risk within the broader Marginal, and can
not rule out the eventual need for a Slight risk.


Chenard


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
855 PM EDT Sat Jun 21 2025
Day 2
Valid 12Z Sun Jun 22 2025 - 12Z Mon Jun 23 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
SOUTHEAST NEW MEXICO AND SOUTHWEST TEXAS...

2030Z Excessive Rainfall Discussion Update...
Latest numerical guidance remained in good agreement with previous
runs about the large-scale features and the associated increase in
the risk of excessive rainfall beginning as early as Sunday. As a
result...little change was needed to the Excessive Rainfall
Outlook for Sunday.

Bann

Previous Excessive Rainfall Discussion...

...New Mexico and Texas...
Sunday is likely the beginning of what will be a multi-day period
of excessive rainfall potential over portions of west TX into NM.
The mid/upper level pattern features a near record to record ridge
over the eastern U.S. and a well-defined longwave trough over the
west. Southerly flow in between these features will supply ample
moisture to NM, with a connection all the way to the Caribbean Sea.
The better forcing from the western trough will generally hold of
until Monday and Tuesday (see the day 3 and 4 EROs), but by Sunday
we should at least have enough moisture and instability around for
scattered convective development. In fact PWs by Sunday should
already be getting towards climatological max values for late June
over portions of southwest TX and immediate adjacent areas of NM.
And while the better forcing arrives Monday, do note broadly
divergent flow at 250mb Sunday which could help sustain convection.

Given these ingredients we went ahead and upgraded to a Slight risk
for portions of southwest TX into Otero and Eddy counties in NM.
Expecting enough convective development Sunday afternoon/evening,
that combined with the near record PWs, suggests an isolated to
scattered flash flood risk should evolve over these areas. A bit
of uncertainty with how far north the Slight should extend into NM
with some models supporting a farther north expansion. However the
area currently highlighted shows the best overlap of the
NAM/RRFS/ECMWF and likely has the higher probability of seeing
flash flooding at the moment. The broad Marginal risk does still
extend into much of the rest of eastern NM and covers the
localized risk over those areas.

...Northern Minnesota...
Went ahead and added a small Marginal risk over portions of
northern MN with this update. The setup looks favorable for another
round of organized convection Sunday afternoon and evening across
this region. Strong shortwave energy ejecting into the northern
Plains, a strengthening axis of low level moisture transport, and
upwards of 4000 j/kg of MUCAPE will drive the convective threat.
The combination of extreme instability, PWs well over the 90th
percentile for late June, and a warm front focusing convection, all
point to a heavy rainfall threat. Some uncertainty with the exact
axis of convection, with some guidance focusing the bulk of
convection farther north into Canada. However both GEFS and ECENS
probs suggest some risk into northern MN, and the AIFS (which has a
history of good convective qpf placement) also favors northern MN.
Quite possible convection ends up blowing through quickly, so no
need for anything more than a Marginal risk at this time. But will
need to continue to monitor trends over the coming days.

Chenard

Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
855 PM EDT Sat Jun 21 2025
Day 3
Valid 12Z Mon Jun 23 2025 - 12Z Tue Jun 24 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
NEW MEXICO AND WEST TEXAS, AND FROM KANSAS INTO IOWA...

2030Z Excessive Rainfall Discussion Update...
Latest numerical guidance remained in good agreement with previous
runs about the large-scale features and the associated
increasing areal coverage of moderate to heavy
rainfall...especially in New Mexico and West Texas as well as
across parts of the Missouri Valley on Monday/Monday night. As a
result...little change was needed to the previously issued Excessive
Rainfall Outlook for Day 3.

Bann

...Southwest...
The overall pattern over the Southwest described in the day 2
discussion will persist into the day 3 period. By day 3 forcing,
moisture and instability should all be on the increase, and thus
expect convective coverage and flash flood risk to be on the
rise as well. The gradual approach of the west coast trough will
bring the right entrance region of the upper jet closer, and
continued moisture advection in between the trough and the east
coast ridge will push PWs well above the climatological 90th
percentile and towards late June max levels. Instability is a bit
of a question as cloud cover debris from Sundays activity could
play a role...however the model consensus is for increased
instability compared to Sunday, with values averaging 1000-2000
j/kg over much of eastern NM into far west TX. Not a ton of deep
layer flow, so convection forming on/near terrain should slowly
move off the terrain and allow for some cell merger activity. The
expected convective coverage should eventually erode instability
enough that activity trends down by overnight...but not before what
should be a more widespread isolated/scattered flash flood risk
over eastern NM and west TX where a Slight risk remains. The
western edge of this risk area was adjusted eastward a tad, as
model trends now support a slightly farther east axis.

Some uncertainty on where any more focused risk could evolve, but
the better model clustering is over southwest TX into southeast NM
and consider the threat over this corridor a higher end Slight
risk. This includes the sensitive Sacramento Mountain burn scar
areas, where localized significant flash flood impacts are a
possibility.

...Central Plains to MS Valley...
A Slight risk remains from portions of central KS into southeast
NE and much of central and northern IA where convection along a
stationary front poses an isolated to scattered flash flood risk.
Model guidance indicates convective development along/near this
front Monday afternoon, with some persistence and/or upscale
development possible Monday evening as low level moisture
transport increases. Corfidi vectors over this area are divergent,
indicating a favorable environment for slow moving/backbuilding
convection near this front. PWs should be well over the 90th
percentile for late June along this front, as the same plume of
moisture over the Southwest will be in place here as well. Thus
any training of convection will pose a flash flood risk.
Maintenance of instability is probably the main question mark, as
the pool of forecast instability is not overly impressive and
neither is the magnitude of the low level jet...so the extent of
convective persistence into the overnight is a bit unclear.
Nonetheless, the unanimous model signal for organized convective
development, combined with the stationary front/convergence and
high PWs supports at least an isolated to scattered flash flood
potential. Thus the Slight risk was maintained. Overall models are
in fairly good agreement with the favored convective axis, and thus
not much change was needed to the inherited risk area.

Chenard

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
249 PM EDT Sat Jun 21 2025


Flash flooding threat will continue over New Mexico out of the
short range (Monday) and into the medium range (Tuesday) which has
the highest rainfall potential per the latest guidance. In
coordination with WFOs ABQ/EPZ, raised a Moderate risk in the
Excessive Rainfall Outlook over the Sacramento Mountains and nearby
areas where the influx of moisture and potential training of
rainfall atop wetted soils from the previous days may lead to more
widespread impacts (especially around burn scars and areas of steep
terrain). Rainfall will continue into Wednesday but likely
decrease, though the flash flooding threat will remain. Farther
north, the plume of subtropical/tropical moisture will arc
northeastward into the Upper Midwest/Corn Belt where the additional
lift around the frontal boundary and potential training will favor
areas of heavier rainfall and some flash flooding potential.
Maintained a Slight risk in the ERO for both Tues/Wed (noting some
high probabilities within that Slight outline as well). The
placement of the heavier rain remains more uncertain here rather
than farther south due to the sensitivity to day-to- day rainfall
patters and mesoscale boundaries. The heaviest rain and storms may
extend across Lower Michigan into NYS, and have looped this region
into the Marginal risk outline. This area of rainfall may shift
somewhat east into the Upper Great Lakes region by Thursday while
expanding into the Mid-Atlantic and Northeast mid to later week as
well.

Farther south, there is some uncertainty with how much convection
may occur under the upper ridge across the Gulf Coast and
southeastern U.S. as surface-based instability likely battles with
subsidence aloft. In general, scattered thunderstorms may increase
in coverage as the week progresses as the upper high gradually
weakens.

The strong upper high/ridge stretching across the south-central to
eastern U.S. will allow for well above average temperatures that
could approach or exceed daily records at a few dozen locations
through Tuesday. This translates into highs well into the 90s into
the low 100s, with heat indices to near 110F as dew points will be
in the 60s to low/mid-70s. Overnight lows will only drop into the
low/mid 70s for many areas, and even may stay around 80-83F in the
urban centers like Washington, D.C., Baltimore, Philadelphia, and
New York City. This will bring little relief from the heat and
exacerbate potential impacts. Thus, HeatRisk values will be Major
to Extreme for portions of the Midwest and Ohio Valley to Eastern
states -- levels 3 and 4 on a scale from 1 to 4 (4 being Extreme).
This indicates an intensity and duration of heat that is extremely
dangerous to anyone without adequate cooling or hydration. Extreme
heat is the number 1 weather-related killer -- please take
precautions if you are outside during the hottest part of the day
and seek cooling if you are without adequate means. Temperatures
will remain above average, though a few degrees lower and with
fewer records possible, across much of the Ohio Valley/Mid-
Atlantic/Southeast into the latter part of next week. But the
Northeast should see moderating temperatures after a cold frontal
passage. Meanwhile, temperatures (particularly highs) are forecast
to be below average by a few degrees in interior portions of the
West and High Plains into midweek, but should gradually warm closer
to or a bit above average as the week progresses.


Fracasso/Tate

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
249 PM EDT Sat Jun 21 2025


Flash flooding threat will continue over New Mexico out of the
short range (Monday) and into the medium range (Tuesday) which has
the highest rainfall potential per the latest guidance. In
coordination with WFOs ABQ/EPZ, raised a Moderate risk in the
Excessive Rainfall Outlook over the Sacramento Mountains and nearby
areas where the influx of moisture and potential training of
rainfall atop wetted soils from the previous days may lead to more
widespread impacts (especially around burn scars and areas of steep
terrain). Rainfall will continue into Wednesday but likely
decrease, though the flash flooding threat will remain. Farther
north, the plume of subtropical/tropical moisture will arc
northeastward into the Upper Midwest/Corn Belt where the additional
lift around the frontal boundary and potential training will favor
areas of heavier rainfall and some flash flooding potential.
Maintained a Slight risk in the ERO for both Tues/Wed (noting some
high probabilities within that Slight outline as well). The
placement of the heavier rain remains more uncertain here rather
than farther south due to the sensitivity to day-to- day rainfall
patters and mesoscale boundaries. The heaviest rain and storms may
extend across Lower Michigan into NYS, and have looped this region
into the Marginal risk outline. This area of rainfall may shift
somewhat east into the Upper Great Lakes region by Thursday while
expanding into the Mid-Atlantic and Northeast mid to later week as
well.

Farther south, there is some uncertainty with how much convection
may occur under the upper ridge across the Gulf Coast and
southeastern U.S. as surface-based instability likely battles with
subsidence aloft. In general, scattered thunderstorms may increase
in coverage as the week progresses as the upper high gradually
weakens.

The strong upper high/ridge stretching across the south-central to
eastern U.S. will allow for well above average temperatures that
could approach or exceed daily records at a few dozen locations
through Tuesday. This translates into highs well into the 90s into
the low 100s, with heat indices to near 110F as dew points will be
in the 60s to low/mid-70s. Overnight lows will only drop into the
low/mid 70s for many areas, and even may stay around 80-83F in the
urban centers like Washington, D.C., Baltimore, Philadelphia, and
New York City. This will bring little relief from the heat and
exacerbate potential impacts. Thus, HeatRisk values will be Major
to Extreme for portions of the Midwest and Ohio Valley to Eastern
states -- levels 3 and 4 on a scale from 1 to 4 (4 being Extreme).
This indicates an intensity and duration of heat that is extremely
dangerous to anyone without adequate cooling or hydration. Extreme
heat is the number 1 weather-related killer -- please take
precautions if you are outside during the hottest part of the day
and seek cooling if you are without adequate means. Temperatures
will remain above average, though a few degrees lower and with
fewer records possible, across much of the Ohio Valley/Mid-
Atlantic/Southeast into the latter part of next week. But the
Northeast should see moderating temperatures after a cold frontal
passage. Meanwhile, temperatures (particularly highs) are forecast
to be below average by a few degrees in interior portions of the
West and High Plains into midweek, but should gradually warm closer
to or a bit above average as the week progresses.


Fracasso/Tate

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
214 PM EDT Wed May 7 2025

Valid 00Z Thu May 08 2025 - 00Z Sun May 11 2025


...Colorado...
Day 1...

Lingering vorticity on the western side of the departing upper low
will still trigger some light snow over the San Juans this evening
before tapering off tonight/early Thursday. WPC probabilities for
at least an additional 4 inches of snow after 00Z are low (10-40%)
above 11,000ft.

For days 2-3, the probability of at least 4 inches of snow is less
than 10%.

The probability of significant freezing rain across the CONUS is
less than 10%.

Note - this is the last regularly scheduled discussion (QPFHSD)
for the 2024-2025 winter season. Unless a significant winter
weather threat emerges, this discussion will next be updated on or
about September 25, 2025.


Fracasso

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Sun Jun 22 2025

Valid 12Z Wed Jun 25 2025 - 12Z Sun Jun 29 2025

...Record heat gradually lessens but dangerous heat continues for
the Ohio/Tennessee Valleys and Mid-Atlantic/Southeast mid to late
week...

...Heavy rain and flash flooding concerns continue for the north-
central Plains/Upper Midwest Wednesday and Thursday, and lingering
in New Mexico Wednesday...


...Overview...

As the medium range period begins Wednesday, a significant and
extremely dangerous heat wave will be ongoing across the Midwest,
Ohio Valley, and eastern U.S. as a notably strong upper high is
centered from the Ohio/Tennessee Valleys and Mid-Atlantic. The
extreme, record-breaking heat should moderate slowly midweek and
beyond, but temperatures will remain quite hot across those areas,
and the long duration of the heat wave could cause exacerbated
impacts. Meanwhile strong southerly inflow with deep tropical
moisture will set up between the upper high and an initial mean
trough with embedded shortwaves in the West. Moisture will
initially reach New Mexico and lead to additional heavy rain there,
with the moisture then reaching around the upper ridge (in a "ring
of fire" setup). This should interact with a wavy frontal boundary
and promote another area of potentially heavy rain and flash
flooding over the north-central Plains, Corn Belt/Midwest, and
Great Lakes region.


...Guidance/Predictability Assessment...

The large scale pattern remains in excellent agreement for
midweek, as models for several days have shown a 594+ dm upper
ridge lasting through Wednesday, and weakening and flattening after
that. Meanwhile farther west, troughing across the Great Basin and
vicinity will also weaken as the week progresses. This, combined
with a wave train of northern stream shortwaves, will trend the 500
mb flow pattern toward more zonal and less amplified flow for the
latter half of the week. The slight differences in speed and
amplitude of multiple shortwaves streaming from the West to the
Upper Midwest introduces a bit more uncertainty for the mid to late
medium range period, but nothing out of the ordinary at that time
range. Somewhat broader scale troughing moving into the Northwest
late week and progressing eastward into the weekend shows some
timing and amplitude differences. The 12/18Z GFS runs were weaker
and progressive than the non-NCEP and AI/ML consensus with this
trough, so the GFS runs were not favored. The new 00Z GFS seems to
show better agreement though.

The WPC forecast for mass fields was based on a general multi-
model blend early in the period. Increasing model differences and
eventually eliminating the 12/18Z GFS from the blend led to
introducing and increasing the proportion of the GEFS and EC
ensemble means in the blend, with the means reaching half the blend
Day 6 and more Day 7. For QPF, mainly leaned toward the pattern of
the EC-AIFS in the north-central U.S. especially on Wednesday, but
with increased amounts. This supported more QPF in Nebraska than
the NBM that favored northeast of there, which seemed to make sense
since Nebraska was closer to the better forcing.


...Weather/Hazards Highlights...

On Wednesday, the upper trough in the Interior West will be
gradually weakening, lessening upper jet right entrance region
support and slightly lessening moisture anomalies in the southern
Rockies/High Plains compared to what's now the short range period.
However, some heavy rain could still be a concern centered around
New Mexico, especially considering the wet antecedent conditions by
then. A Slight Risk is delineated in the Sacramento Mountains and
vicinity for the Day 4/Wednesday ERO, where orographic support
could enhance rainfall totals and where burn scars and steep
terrain make the area sensitive to heavy rain. Rain amounts should
continue to gradually decrease there into later week. Will show a
Marginal Risk on Day 5/Thursday for southern portions of New Mexico
including the Sacramento Mountains for another potential round of
moderate to locally heavy rain.

The plume of subtropical/tropical moisture will arc northeastward
into the north-central Plains and Upper Midwest/Corn Belt where the
additional lift around the frontal boundary and potential training
will favor areas of heavier rainfall and some flash flooding
potential. For the Day 4/Wednesday ERO, continue to show a Slight
Risk (with embedded probabilities on the higher end of the Slight
range) for these areas. The Slight generally covers some model
spread from an eastern Nebraska focus to areas farther northeast.
The details in the heavy rainfall placement remain uncertain south
due to the sensitivity to day-to-day rainfall patterns and
mesoscale boundaries. A weak surface low embedded along the front
may track somewhat east by Thursday, pushing the heaviest rain
totals across much of Wisconsin and possibly the U.P. of Michigan.
Thus for the initial Day 5/Thursday ERO, will show a Slight Risk
there, given potential for 2 to 4 inches to accumulate despite
continued spread in the exact positioning. For both Wednesday and
Thursday, some convection with locally heavy rain could traverse
the northern side of the ridge farther east into New York State and
the northern Mid-Atlantic, so will show Marginal Risks there. The
Northeast may see increasing rain amounts by Friday, while another
round of rain is possible in the north-central U.S. late week as
well.

Farther south, there is some uncertainty with how much convection
may occur under the upper ridge across the Gulf Coast and
southeastern U.S. as surface-based instability likely battles with
subsidence aloft. In general, scattered thunderstorms may increase
in coverage as the week progresses as the upper high gradually
weakens.

The strong upper high/ridge stretching across the south-central to
eastern U.S. will allow for well above average temperatures that
could approach or exceed daily records at a few dozen locations
through Wednesday, with more widespread coverage of record warm
morning lows if those numbers hold through the calendar day. This
translates into highs well into the 90s into the low 100s, with
heat indices to near 110F as dew points will be in the 60s to
low/mid-70s. Overnight lows will only drop into the low/mid 70s for
many areas, and even may stay around 80-83F in the urban centers
like Washington, D.C., Baltimore, Philadelphia, and New York City.
This will bring little relief from the heat and exacerbate
potential impacts. Thus, HeatRisk values will be Major to Extreme
for portions of the Midwest and Ohio Valley to Eastern states --
levels 3 and 4 on a scale from 1 to 4 (4 being Extreme). This
indicates an intensity and duration of heat that is extremely
dangerous to anyone without adequate cooling or hydration. Extreme
heat is the number 1 weather-related killer -- please take
precautions if you are outside during the hottest part of the day
and seek cooling if you are without adequate means. Temperatures
will remain above average, though a few degrees lower and with
fewer records possible, across much of the Ohio Valley/Mid-
Atlantic/Southeast into the latter part of next week. But the
Northeast should see moderating temperatures after a cold frontal
passage. Meanwhile, temperatures (particularly highs) are forecast
to be below average by a few degrees in the High Plains into
midweek, but the West should gradually warm to a bit above average
as the week progresses.


Tate


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw