Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
301 PM EDT Sun Jul 27 2025

Valid 00Z Mon Jul 28 2025 - 00Z Wed Jul 30 2025

....There is a Slight Risk of excessive rainfall over parts of the Middle
Mississippi, Ohio Valleys, Central Appalachians, and Upper Mississippi
Valley/Upper Great Lakes, on Sunday, Northern Plains, Upper Mississippi
Valley on Monday...

...There is an Enhanced Risk of severe thunderstorms over parts of the
Upper Mississippi Valley on Sunday...

...There is a Slight Risk of severe thunderstorms over parts of the
Mid-Atlantic on Sunday and over the Northern Rockies, Northern Plains, and
Upper Mississippi Valley on Monday...

On Sunday, a front extending from the Upper Mississippi Valley/Northern
Plains to the Northern Rockies will move eastward to the Northeast, Great
Lakes, Middle Mississippi Valley, and Northern Rockies by Tuesday. The
front will trigger showers and severe thunderstorms over parts of the
Northern Plains/Upper Mississippi Valley. Therefore, the SPC has issued an
Enhanced Risk (level 3/5) of severe thunderstorms over parts of the
Northern Plains/Upper Mississippi Valley through Monday morning. The
hazards associated with these thunderstorms are frequent lightning, severe
thunderstorm wind gusts, hail, and a few tornadoes. There is an added
threat of hail two inches or greater over the area.

Additionally, showers and severe thunderstorms are expected to develop
over parts of the Mid-Atlantic. Therefore, the SPC has issued a Slight
Risk (level 2/5) of severe thunderstorms over parts of the Mid-Atlantic
through Monday morning. The hazards associated with these thunderstorms
are frequent lightning, severe thunderstorm wind gusts, a few tornadoes,
and a minimal threat of hail.

Moreover, tropical moisture pooling over the Mid-Atlantic to Middle
Mississippi/Ohio Valleys will produce areas of heavy rain over parts of
the Middle Mississippi, Ohio Valleys, and Central Appalachians. Therefore,
the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over
parts of the Middle Mississippi, Ohio Valleys, and Central Appalachians
through Monday morning. The associated heavy rain will primarily create
localized areas of flash flooding, with urban areas, roads, small streams,
and low-lying areas being the most vulnerable.

Furthermore, a third area of heavy rain is expected to develop over parts
of the Mid-Atlantic. Therefore, the WPC has issued a Slight Risk (level
2/4) of excessive rainfall over parts of the Mid-Atlantic through Monday
morning. The associated heavy rain will primarily create localized areas
of flash flooding, with urban areas, roads, small streams, and low-lying
areas being the most vulnerable. Also, on Sunday, upper-level energy will
trigger showers and thunderstorms over parts of the Northern Rockies and
Northern Intermountain Region.

On Monday, showers and severe thunderstorms will develop along the front
from the Northern High Plains/Rockies Mountains to the Upper Mississippi
Valley. Therefore, the SPC has issued a Slight Risk (level 2/5) of severe
thunderstorms over parts of the Northern High Plains/Northern Rockies
Mountains to the Upper Mississippi Valley from Monday through Tuesday
morning. The hazards associated with these thunderstorms are frequent
lightning, severe thunderstorm wind gusts, hail, and a few tornadoes.
There is an additional threat of severe thunderstorm wind gusts of 65
knots or greater over eastern South Dakota and southern Minnesota.

Additionally, on Monday, increasing moisture over the Upper Midwest will
produce showers and thunderstorms, accompanied by heavy rain, over parts
of the Northern Plains/Upper Mississippi Valley. Therefore, the WPC has
issued a Slight Risk (level 2/4) of excessive rainfall with these
thunderstorms over parts of the Northern Plains/Upper Mississippi Valley
from Monday through Tuesday morning. The associated heavy rain will
primarily create localized areas of flash flooding, with urban areas,
roads, small streams, and low-lying areas being the most vulnerable.

Furthermore, on Tuesday, showers and thunderstorms are expected to develop
heavy rain over parts of the Northern High Plains, Northern/Central
Plains, and the Middle Mississippi Valley. Therefore, the WPC has issued a
Slight Risk (level 2/4) of excessive rainfall with these thunderstorms
over parts of the Northern High Plains, Northern/Central Plains, and the
Middle Mississippi Valley. The associated heavy rain will primarily create
localized areas of flash flooding, with urban areas, roads, small streams,
and low-lying areas being the most vulnerable. Additionally, on Tuesday,
showers and thunderstorms are expected to develop over most of the eastern
third of the country.

Moreover, an upper-level high over the Southeast extends westward to the
Southern Rockies will aid in producing dangerous high temperatures,
accompanied by high humidity from the Northern Plains and Upper
Mississippi/Ohio Valleys to the Southern Plains, Lower Mississippi Valley,
Tennessee Valley, as well as the Mid-Atlantic and Southeast. Extreme Heat
Warnings, Heat Advisories, and Extreme Heat Watches are over these regions
through Tuesday. An extended period of extreme heat and minimal nighttime
relief can lead to cumulative heat stress on the body. As temperatures
rise, plan to limit outdoor activities, stay hydrated, and ensure access
to air conditioning and other cooling areas. Additionally, be sure to
check on vulnerable family members, friends, and neighbors.


Ziegenfelder


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
250 PM EDT Sun Jul 27 2025

...Dangerous heat wave persists in the Southeast through midweek
with gradual relief later in the week...

...Heavy rain and flash flooding potential in the central Plains
for multiple days...


...Overview...

By the start of the medium range period midweek, the sprawling
upper high atop much of the U.S. early this week will be weakening
somewhat and be pressed south by a northern stream upper trough.
Dangerous heat is possible across the Lower Ohio/Tennessee Valleys
and Mid-Atlantic Wednesday before a cold front (tied to the upper
trough) moves through. The Southeast is forecast to see the heat
continue into late week but gradually shrink in scope. Complexes of
showers and storms are likely near and ahead of the frontal system
stretching from the High Plains eastward across the central
Plains/Mid-Mississippi Valley into the Northeast Wednesday. The
front is likely to stall near the central Plains and lead to
multiple days of storms with heavy rain that could cause flash
flooding. Farther east the cold front should be more progressive,
making its way southward across the Mid-Atlantic and Southeast but
creating an environment for possibly heavy rain each day as it
moves. Meanwhile, southerly flow will bring monsoonal moisture into
parts of the Southwest states for possibly heavy rain.


...Guidance/Predictability Assessment...

Model agreement is excellent for the overall pattern through late
this week. Models have been persistent in showing the expansive
upper high shrinking in scope by Wednesday and becoming centered
over the southern Plains late week, with perhaps another
subtropical high moving across Florida. Meanwhile the ridge axis
will stretch northward across the northern Rockies into western
Canada starting Tuesday, coincident with the upper trough edging
into the north-central to northeastern U.S. anchored by a large
Hudson Bay to eastern Canada upper low. Since model differences
were mostly negligible through late week, used a deterministic
blend of the latest 00Z/06Z guidance for the first half of the
forecast period. Regardless of the large scale agreement,
shortwaves riding around the ridge will cause more differences in
sensible weather like frontal placement, and convection will have
further uncertainties due to small boundaries like outflows
interacting. These tend not to become clearer until the short range
or near term, so the details of QPF remain uncertain, but at least
the overall pattern seems set.

By next weekend, model differences start to increase as the
pattern becomes more quasi-zonal and uncertain shortwaves become
more dominant. One larger scale model difference was the pattern in
the Northwest especially by next Sunday. This will be influenced
by a large Northeast Pacific upper low with somewhat uncertain
placement. The models have wavered on how much and how quickly to
lower heights into the Northwest/Rockies with no clear consensus.
The AI/ML models indicated a bit more troughing east of 120W than
the dynamical ensembles, but that is still likely within the
noise/spread. Balance the day 6-7 forecast with a blend of some
ensemble mean weighting along with continuity. This resulted in few
changes overall from the previous forecast.


...Weather/Hazards Highlights...

Another hot day is forecast from the south-central U.S. into the
Southeast, Tennessee and Ohio Valleys, and much of the Eastern
Seaboard on Wednesday underneath the (albeit shrinking) upper high.
HeatRisk is mainly in the Major (level 3/4) category with some
embedded Extreme (level 4/4) areas with highs generally in the 90s
to near/exceeding 100 with higher heat indices (nearing 110F),
while morning lows well into the 70s and nearing 80 will not
provide much relief. A few more daily records for temperatures
could be set into Wednesday. On Thursday, the cold front will pass
through the Ohio Valley to Mid-Atlantic and bring near to below
normal temperatures, with the heat wave becoming more limited to
the Southeast/Carolinas. The gradual movement of the front
southward should finally lead to heat relief in the Southeast
Friday-Saturday, though Florida could still be hot. Cooler than
average temperatures (especially highs) are likely in the
northern/central Plains on the cool side of the front and with the
clouds and rain chances -- some locations may even challenge record
cool maxes for the day (low 70s).

Rain and thunderstorms are forecast to focus on the periphery of
the ridge, enhanced by a frontal boundary across the northern
Rockies into the north-central Plains and Mississippi Valley. Some
shortwave forcing and above normal moisture and instability should
lead to multiple rounds of convection with high rain rates, and
some areas could see repeating rounds of storms with the front
stalling. Thus, the Day 4/Wednesday and Day 5/Thursday EROs show
Slight Risks over the central Plains for the possibility of flash
flooding. On Day 4/Wednesday, also have the Slight Risk looping
east into the Middle Mississippi Valley where models show MCS
potential and antecedent conditions are generally wet. Marginal
Risks stretch northward into the northern Rockies/High Plains near
the back end of the front as much higher than average instability
(per the Extreme Forecast Index) is in place. Meanwhile the front
extends farther east across the Ohio Valley and Northeast on
Wednesday, promoting potentially heavier rain in a moisture-laden
pre-frontal environment coincident with areas that have seen well
above normal rainfall the past several weeks, allowing for a
Marginal Risk in the Day 4/Wed ERO. By Thursday, the front will
gradually move south and lead to pooling moisture and instability
in the Mid-Atlantic along with increasing dynamical support in the
form of the right entrance region of the upper jet. A Slight Risk
is noted in the Day 5/Thu ERO for this activity. Enhanced rain is
possible in the Carolinas by Friday and Saturday near this front.

To the west of the ridge, monsoonal moisture (with precipitable
water values generally in the 75th-90th percentile) will be present
over the Southwest with some instability. Marginal Risks are in
place in the Days 4 and 5 EROs for parts of the Southwest and
reaching into the central Rockies/High Plains as the monsoonal
moisture meets the frontal system to the north.

Elsewhere, moisture and instability could lead to scattered
thunderstorms in the southeastern U.S. from day to day. There may
be some focus for storms near the central Gulf Coast in particular
with weak low level troughs/lows in the vicinity. Marginal Risks of
flash flooding are in place for the central Gulf Coast and parts
of the Southeast due to high rain rates that may overcome the high
Flash Flood Guidance and/or fall atop urban areas.


Fracasso/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
354 AM EDT Sun Jul 27 2025

Valid 00Z Mon 28 Jul 2025 - 00Z Mon 04 Aug 2025

Increased moisture is likely over Hawaii for the next couple of
days near a surface trough and under a weak trough aloft, leading
to muggy conditions and possibly increasing shower coverage.
Meanwhile trades should be light to moderate. But trades are
forecast to increase Tuesday-Wednesday to breezy levels and remain
there through the rest of the week. This is coincident with a
tightening pressure gradient as a tropical disturbance (that has a
high chance of development into a tropical cyclone per NHC) will
pass south of the state around midweek. Drier air is also likely
as this tropical low's moisture stays south of the state. Another
tropical low just behind the first one may have some increased
moisture come into the Big Island late week (though the low should
remain south), but the better consensus seems to be for continued
dry conditions with the breezy trades.

Tate

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Sun Jul 27 2025
Day 1
Valid 16Z Sun Jul 27 2025 - 12Z Mon Jul 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE UPPER MIDWEST, NORTHERN APPALACHIANS AND PARTS OF THE NORTHEAST...

...The eastern Dakotas and Upper Midwest...

16Z update... Very minor reshaping of the western boundary of the
Slight Risk to reflect the latest guidance trend and WPC QPF.

Campbell

Continue to make minor adjustments to the placement of a Slight
Risk area mainly confined to Minnesota as a shortwave trough
continues to propagate eastward along the northern tier of states.
There has been an upward trend in the guidance...both in the
coarser/global guidance and with the CAMs and related ensemble
forecast systems. With guidance now showing 2000 to 3000 J per kg
being possible and precipitable water values approaching 1.5
inches,,,another expansion southward of the Slight and Marginal
risk areas was made compared with the previous outlook.

The Marginal Risk area on the northern/western periphery of the
Slight risk area was expanded into North Dakota as a well developed
line of convection was moving across the state and not likely to
diminish prior to the start of the Day 1 period at 12Z.

...The Ohio Valley and Mid Atlantic to southern New England...

16Z update... The latest guidance show a line of thunderstorms
advancing south/southeast through the Midwest that begin to bow,
pick up pace, and track through western Kentucky. The rainfall
rates with this bowing segment approached 1-1.5 inches per hour.
As such, the Marginal Risk area was expanded southern into western
Kentucky. Guidance also depicted that portions of Upstate New
York, southern Vermont and New Hampshire would see an increase in
QPF therefore suggesting a north/east adjustment of the Marginal
Risk in that region.

Campbell

The Slight Risks which were raised over the Ohio Valley was
expanded to the west as a complex from overnight moves eastward.
The expectation is that the convection should weaken for a period
before reigniting later. Made a few changes to the outlook area
from the DelMarVa northward based on latest guidance. Locally
enhanced rainfall will persist in the very moist environment near
the west- east frontal boundary.

...Southwest US...

Deeper moisture that made its way across parts of the Gulf and
inland across Mexico should start to be drawn northwest into parts
of the Southwest United States...resulting in scattered late day
and evening convection across parts of New Mexico and a small
portion of Arizona.

Bann

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Sun Jul 27 2025
Day 2
Valid 12Z Mon Jul 28 2025 - 12Z Tue Jul 29 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHERN PLAINS...

...Plains of Eastern Montana to parts of the Upper Midwest...

21Z update... The latest guidance noted a north and eastward shift
in the QPF axis. The previous forecast focused the higher amounts
across eastern South Dakota and northern Iowa, whereas now it is
more over south/central Minnesota and western Wisconsin. With this
trend the Marginal Risk was reduced out of Wyoming and southwest
South Dakota, northeast Nebraska and southern Iowa and then
expanded over northeast Montana, North Dakota, central Minnesota
and central Wisconsin. Areal averages of 1 to 3+ are still expected
but hourly rainfall rates may reach or exceed 1.5 inches/hour with
any of the expected storms.

Campbell

A surface cold front and mid-level shortwave trough will be
approaching an area rich in moisture and instability over parts of
South Dakota and Minnesota/Iowa on Monday afternoon. With low
level flow likely to increase the amount of moisture transport into
the region during the evening with a corresponding increase in
moisture flux convergence along the front...the potential exists
for excessive rainfall especially in the event of cell training or
repeat convection. Uncertainty remained with respect to placement
in the numerical guidance...but the RRFS seemed too far north. The
WPC deterministic QPF was closer to a GEFS/ECMWF ensemble mean
position...which still left some room for excessive rainfall to
build south. Consequently...allowed for a somewhat broader apron of
Slight Risk than shown by guidance.

Surrounding the Slight risk area...only modest changes were made
to the Marginal risk area extending northwest into the plains of
eastern Montana where a secondary QPF maximum is expected. The
expectation is that there will be two discrete QPF area with a risk
of excessive rainfall associated with each...but maintained the
one area given the range of possible solutions.

...Ohio/Tennessee Valleys to the Carolinas...

Much of the region will continue to have a very deep column of
moisture in place during this period. Flow is expected to be slow
which will bolster the potential for storms to backbuild and given
that some locations across the region have steep topography,
isolated flash flooding may arise. Some of the CAMs show rainfall
rates of 1-1.5+ inches/hour possible. A broad Marginal Risk was
raised, spanning from southeast Missouri to the Carolinas.

...Southwest US...

A continuation of flow with deeper moisture into the Southwest US
will linger on Monday and Monday night...with a continued chance
for scattered late day and evening convection across parts of New
Mexico and a small portion of Arizona that extends northward along
the southern and central Colorado front range.

Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Sun Jul 27 2025
Day 3
Valid 12Z Tue Jul 29 2025 - 12Z Wed Jul 30 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE WESTERN HIGH PLAINS...

Northern Rockies eastward to Great Lakes and southward to the
Southwest US...

21Z update... A previously noted for the D2 period, the latest QPF
trends continue to be shifted eastward for this period as well. The
axis of concentrated amounts went from northeast Wyoming to
Nebraska, to now as far east as northern Iowa. The Slight Risk was
elongated to now include most of northern Iowa. The Marginal Risk
was nudged a bit further north across Wisconsin.

Campbell

Building mid-level ridge over British Columbia and Albert will
result in lowering heights over parts of the northwestern US and
increasing mid- and upper flow. This results in an increasingly
well defined surface boundary that serves to focus showers and
thunderstorm on Tuesday. Ingredients for thunderstorms to produce
heavy to potentially excessive rainfall appear to be aligning from
southeast Montana into northern Nebraska along a corridor of 1000
to 2000 J per kg instability and 1 to 1.25 inch precipitable
water values...and even some 1.5 inch PW values in northern
Nebraska. Showers and thunderstorms are also likely to spread
eastward toward the Great Lakes where the instability and synoptic
scale forcing looks to be weaker. In addition...another round of
late day convection is possible from the Southwest US into the
Rockies and some of this moisture may approach...if not come into
play,,,across the western High Plains late in the period.

...Southeast US...

21Z update... The footprint across the Southeast increased, leading
to the westward expansion of the Marginal across Southeast
Louisiana and northward into South Carolina and western portions of
North Carolina.

Campbell

Precipitable water values in excess of 2 inches will be in place
with 1000-1500 J per kg of CAPE in place and weakening of the broad
upper level ridge should lead to a somewhat better chance for
showers or thunderstorms on Tuesday. The GFS and ECMWF both show
hints at weak vorticity centers in the vicinity to help
focus/support some activity. The expectation is that isolated but
very intense rainfall rates could lead to isolated instances of
excessive rainfall.


Bann

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
250 PM EDT Sun Jul 27 2025


Another hot day is forecast from the south-central U.S. into the
Southeast, Tennessee and Ohio Valleys, and much of the Eastern
Seaboard on Wednesday underneath the (albeit shrinking) upper high.
HeatRisk is mainly in the Major (level 3/4) category with some
embedded Extreme (level 4/4) areas with highs generally in the 90s
to near/exceeding 100 with higher heat indices (nearing 110F),
while morning lows well into the 70s and nearing 80 will not
provide much relief. A few more daily records for temperatures
could be set into Wednesday. On Thursday, the cold front will pass
through the Ohio Valley to Mid-Atlantic and bring near to below
normal temperatures, with the heat wave becoming more limited to
the Southeast/Carolinas. The gradual movement of the front
southward should finally lead to heat relief in the Southeast
Friday-Saturday, though Florida could still be hot. Cooler than
average temperatures (especially highs) are likely in the
northern/central Plains on the cool side of the front and with the
clouds and rain chances -- some locations may even challenge record
cool maxes for the day (low 70s).

Rain and thunderstorms are forecast to focus on the periphery of
the ridge, enhanced by a frontal boundary across the northern
Rockies into the north-central Plains and Mississippi Valley. Some
shortwave forcing and above normal moisture and instability should
lead to multiple rounds of convection with high rain rates, and
some areas could see repeating rounds of storms with the front
stalling. Thus, the Day 4/Wednesday and Day 5/Thursday EROs show
Slight Risks over the central Plains for the possibility of flash
flooding. On Day 4/Wednesday, also have the Slight Risk looping
east into the Middle Mississippi Valley where models show MCS
potential and antecedent conditions are generally wet. Marginal
Risks stretch northward into the northern Rockies/High Plains near
the back end of the front as much higher than average instability
(per the Extreme Forecast Index) is in place. Meanwhile the front
extends farther east across the Ohio Valley and Northeast on
Wednesday, promoting potentially heavier rain in a moisture-laden
pre-frontal environment coincident with areas that have seen well
above normal rainfall the past several weeks, allowing for a
Marginal Risk in the Day 4/Wed ERO. By Thursday, the front will
gradually move south and lead to pooling moisture and instability
in the Mid-Atlantic along with increasing dynamical support in the
form of the right entrance region of the upper jet. A Slight Risk
is noted in the Day 5/Thu ERO for this activity. Enhanced rain is
possible in the Carolinas by Friday and Saturday near this front.

To the west of the ridge, monsoonal moisture (with precipitable
water values generally in the 75th-90th percentile) will be present
over the Southwest with some instability. Marginal Risks are in
place in the Days 4 and 5 EROs for parts of the Southwest and
reaching into the central Rockies/High Plains as the monsoonal
moisture meets the frontal system to the north.

Elsewhere, moisture and instability could lead to scattered
thunderstorms in the southeastern U.S. from day to day. There may
be some focus for storms near the central Gulf Coast in particular
with weak low level troughs/lows in the vicinity. Marginal Risks of
flash flooding are in place for the central Gulf Coast and parts
of the Southeast due to high rain rates that may overcome the high
Flash Flood Guidance and/or fall atop urban areas.


Fracasso/Tate

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
250 PM EDT Sun Jul 27 2025


Another hot day is forecast from the south-central U.S. into the
Southeast, Tennessee and Ohio Valleys, and much of the Eastern
Seaboard on Wednesday underneath the (albeit shrinking) upper high.
HeatRisk is mainly in the Major (level 3/4) category with some
embedded Extreme (level 4/4) areas with highs generally in the 90s
to near/exceeding 100 with higher heat indices (nearing 110F),
while morning lows well into the 70s and nearing 80 will not
provide much relief. A few more daily records for temperatures
could be set into Wednesday. On Thursday, the cold front will pass
through the Ohio Valley to Mid-Atlantic and bring near to below
normal temperatures, with the heat wave becoming more limited to
the Southeast/Carolinas. The gradual movement of the front
southward should finally lead to heat relief in the Southeast
Friday-Saturday, though Florida could still be hot. Cooler than
average temperatures (especially highs) are likely in the
northern/central Plains on the cool side of the front and with the
clouds and rain chances -- some locations may even challenge record
cool maxes for the day (low 70s).

Rain and thunderstorms are forecast to focus on the periphery of
the ridge, enhanced by a frontal boundary across the northern
Rockies into the north-central Plains and Mississippi Valley. Some
shortwave forcing and above normal moisture and instability should
lead to multiple rounds of convection with high rain rates, and
some areas could see repeating rounds of storms with the front
stalling. Thus, the Day 4/Wednesday and Day 5/Thursday EROs show
Slight Risks over the central Plains for the possibility of flash
flooding. On Day 4/Wednesday, also have the Slight Risk looping
east into the Middle Mississippi Valley where models show MCS
potential and antecedent conditions are generally wet. Marginal
Risks stretch northward into the northern Rockies/High Plains near
the back end of the front as much higher than average instability
(per the Extreme Forecast Index) is in place. Meanwhile the front
extends farther east across the Ohio Valley and Northeast on
Wednesday, promoting potentially heavier rain in a moisture-laden
pre-frontal environment coincident with areas that have seen well
above normal rainfall the past several weeks, allowing for a
Marginal Risk in the Day 4/Wed ERO. By Thursday, the front will
gradually move south and lead to pooling moisture and instability
in the Mid-Atlantic along with increasing dynamical support in the
form of the right entrance region of the upper jet. A Slight Risk
is noted in the Day 5/Thu ERO for this activity. Enhanced rain is
possible in the Carolinas by Friday and Saturday near this front.

To the west of the ridge, monsoonal moisture (with precipitable
water values generally in the 75th-90th percentile) will be present
over the Southwest with some instability. Marginal Risks are in
place in the Days 4 and 5 EROs for parts of the Southwest and
reaching into the central Rockies/High Plains as the monsoonal
moisture meets the frontal system to the north.

Elsewhere, moisture and instability could lead to scattered
thunderstorms in the southeastern U.S. from day to day. There may
be some focus for storms near the central Gulf Coast in particular
with weak low level troughs/lows in the vicinity. Marginal Risks of
flash flooding are in place for the central Gulf Coast and parts
of the Southeast due to high rain rates that may overcome the high
Flash Flood Guidance and/or fall atop urban areas.


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
250 PM EDT Sun Jul 27 2025

...Dangerous heat wave persists in the Southeast through midweek
with gradual relief later in the week...

...Heavy rain and flash flooding potential in the central Plains
for multiple days...


...Overview...

By the start of the medium range period midweek, the sprawling
upper high atop much of the U.S. early this week will be weakening
somewhat and be pressed south by a northern stream upper trough.
Dangerous heat is possible across the Lower Ohio/Tennessee Valleys
and Mid-Atlantic Wednesday before a cold front (tied to the upper
trough) moves through. The Southeast is forecast to see the heat
continue into late week but gradually shrink in scope. Complexes of
showers and storms are likely near and ahead of the frontal system
stretching from the High Plains eastward across the central
Plains/Mid-Mississippi Valley into the Northeast Wednesday. The
front is likely to stall near the central Plains and lead to
multiple days of storms with heavy rain that could cause flash
flooding. Farther east the cold front should be more progressive,
making its way southward across the Mid-Atlantic and Southeast but
creating an environment for possibly heavy rain each day as it
moves. Meanwhile, southerly flow will bring monsoonal moisture into
parts of the Southwest states for possibly heavy rain.


...Guidance/Predictability Assessment...

Model agreement is excellent for the overall pattern through late
this week. Models have been persistent in showing the expansive
upper high shrinking in scope by Wednesday and becoming centered
over the southern Plains late week, with perhaps another
subtropical high moving across Florida. Meanwhile the ridge axis
will stretch northward across the northern Rockies into western
Canada starting Tuesday, coincident with the upper trough edging
into the north-central to northeastern U.S. anchored by a large
Hudson Bay to eastern Canada upper low. Since model differences
were mostly negligible through late week, used a deterministic
blend of the latest 00Z/06Z guidance for the first half of the
forecast period. Regardless of the large scale agreement,
shortwaves riding around the ridge will cause more differences in
sensible weather like frontal placement, and convection will have
further uncertainties due to small boundaries like outflows
interacting. These tend not to become clearer until the short range
or near term, so the details of QPF remain uncertain, but at least
the overall pattern seems set.

By next weekend, model differences start to increase as the
pattern becomes more quasi-zonal and uncertain shortwaves become
more dominant. One larger scale model difference was the pattern in
the Northwest especially by next Sunday. This will be influenced
by a large Northeast Pacific upper low with somewhat uncertain
placement. The models have wavered on how much and how quickly to
lower heights into the Northwest/Rockies with no clear consensus.
The AI/ML models indicated a bit more troughing east of 120W than
the dynamical ensembles, but that is still likely within the
noise/spread. Balance the day 6-7 forecast with a blend of some
ensemble mean weighting along with continuity. This resulted in few
changes overall from the previous forecast.


...Weather/Hazards Highlights...

Another hot day is forecast from the south-central U.S. into the
Southeast, Tennessee and Ohio Valleys, and much of the Eastern
Seaboard on Wednesday underneath the (albeit shrinking) upper high.
HeatRisk is mainly in the Major (level 3/4) category with some
embedded Extreme (level 4/4) areas with highs generally in the 90s
to near/exceeding 100 with higher heat indices (nearing 110F),
while morning lows well into the 70s and nearing 80 will not
provide much relief. A few more daily records for temperatures
could be set into Wednesday. On Thursday, the cold front will pass
through the Ohio Valley to Mid-Atlantic and bring near to below
normal temperatures, with the heat wave becoming more limited to
the Southeast/Carolinas. The gradual movement of the front
southward should finally lead to heat relief in the Southeast
Friday-Saturday, though Florida could still be hot. Cooler than
average temperatures (especially highs) are likely in the
northern/central Plains on the cool side of the front and with the
clouds and rain chances -- some locations may even challenge record
cool maxes for the day (low 70s).

Rain and thunderstorms are forecast to focus on the periphery of
the ridge, enhanced by a frontal boundary across the northern
Rockies into the north-central Plains and Mississippi Valley. Some
shortwave forcing and above normal moisture and instability should
lead to multiple rounds of convection with high rain rates, and
some areas could see repeating rounds of storms with the front
stalling. Thus, the Day 4/Wednesday and Day 5/Thursday EROs show
Slight Risks over the central Plains for the possibility of flash
flooding. On Day 4/Wednesday, also have the Slight Risk looping
east into the Middle Mississippi Valley where models show MCS
potential and antecedent conditions are generally wet. Marginal
Risks stretch northward into the northern Rockies/High Plains near
the back end of the front as much higher than average instability
(per the Extreme Forecast Index) is in place. Meanwhile the front
extends farther east across the Ohio Valley and Northeast on
Wednesday, promoting potentially heavier rain in a moisture-laden
pre-frontal environment coincident with areas that have seen well
above normal rainfall the past several weeks, allowing for a
Marginal Risk in the Day 4/Wed ERO. By Thursday, the front will
gradually move south and lead to pooling moisture and instability
in the Mid-Atlantic along with increasing dynamical support in the
form of the right entrance region of the upper jet. A Slight Risk
is noted in the Day 5/Thu ERO for this activity. Enhanced rain is
possible in the Carolinas by Friday and Saturday near this front.

To the west of the ridge, monsoonal moisture (with precipitable
water values generally in the 75th-90th percentile) will be present
over the Southwest with some instability. Marginal Risks are in
place in the Days 4 and 5 EROs for parts of the Southwest and
reaching into the central Rockies/High Plains as the monsoonal
moisture meets the frontal system to the north.

Elsewhere, moisture and instability could lead to scattered
thunderstorms in the southeastern U.S. from day to day. There may
be some focus for storms near the central Gulf Coast in particular
with weak low level troughs/lows in the vicinity. Marginal Risks of
flash flooding are in place for the central Gulf Coast and parts
of the Southeast due to high rain rates that may overcome the high
Flash Flood Guidance and/or fall atop urban areas.


Fracasso/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