Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Thu Jun 26 2025

Valid 12Z Thu Jun 26 2025 - 12Z Sat Jun 28 2025

...Prolonged and intense heat wave continues into Friday from Midwest to
Mid-Atlantic...

...Unsettled weather could produce severe weather and excessive rainfall
for parts of the Central and Eastern U.S....


Extreme heat warnings and heat advisories remain in effect for portions of
the Mid-Atlantic, Ohio Valley and the Southeast through today--impacting
approximately 130 million people. The Ohio Valley is still expected to
experience the most prolonged and notable effects from this heat wave. The
duration of this heat remains dangerous to anyone without effective
cooling and/or adequate hydration as heat related illnesses increase
significantly during extreme longer duration heat. Continue to limit
outdoor time, stay hydrated, and take action when you see symptoms of heat
exhaustion and heat stroke. The extreme heat will moderate across the
Mid-Atlantic tonight followed by Friday for the Ohio Valley, due to the
weakening ridge aloft.

A quasi-stationary surface front draped across the northern tier,
shortwave energy riding along the boundary and warm unstable air present
at the surface will contribute to scattered to organized thunderstorm
activity across much of the Eastern half of the country over the next
several days. There's a slight risk (at least 15%) of excessive rainfall
leading to flash flooding over parts of eastern Kansas up into Iowa,
Wisconsin and northern Michigan/U.P.. The Storm Prediction Center also
issued a slight risk (level 2/5) for a small area encompassing
northeastern Iowa, far southeastern Minnesota and southwestern Wisconsin,
where isolated wind damage will be possible. The threat for flash flooding
shifts into the interior Northeast on Friday where a surface wave riding
along a warm front will lift up into the region. A slight risk of
excessive rainfall is in place across northeastern Upstate New York, and
northern Vermont/New Hampshire. A new convective threat develops over the
Northern Plains on Friday out ahead of a longwave trough and an emerging
surface low pressure system. SPC issued a slight risk for parts of the
Dakotas and far north-central Nebraska, where large hail and locally
damaging winds are forecast.

A degrading upper low will retrograde into the Southeast Coast over the
next couple of days. Scattered showers and thunderstorms are expected from
the Southeast up into the Mid-Atlantic, where some storms could produce
sporadic/isolated wind damage, according to SPC. Continued cloudy and
rainy conditions could produce localized flash flooding in New Mexico
through Friday, but will also keep temperatures down between 10-20 degrees
below average.


Kebede


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Thu Jun 26 2025

Valid 12Z Sun Jun 29 2025 - 12Z Thu Jul 03 2025

...Overview...

Quasi-zonal flow is forecast across the lower 48 early next week,
with the main jet stream across the northern tier pushing
shortwaves and surface frontal systems across the central U.S. in
particular, leading to thunderstorms with potentially heavy rain.
Farther south, above average 500mb heights are expected in a broad
ridge, allowing for summer heat and convection. Upper troughing may
dig a bit as it moves into the Midwest, Great Lakes, and Northeast
Monday through Wednesday, pushing a cold front southeastward with
showers and thunderstorms ahead of it. Meanwhile ridging should
build atop the Interior West and lead to heat there, as well as
monsoonal moisture inflow for the Four Corners states as the week
progresses.


...Guidance/Predictability Assessment...

Model guidance starts out in good agreement with the overall
pattern described above early next week, along with a southern
stream trough moving slowly from the eastern Pacific toward
California. Models are agreeable with the initially north-central
U.S. trough deepening as it slowly shifts east as the week
progresses. Minor low predictability differences do cause some
variability in sensible weather parameters like QPF and frontal
placement though, but without many outliers.

The most uncertain part of the pattern is with an upper low in the
northeast Pacific that sends shortwaves southeast across the
northwestern U.S. and western Canada. Operational and AI/ML models
vary with the depth and position of these shortwaves and lead to
some out of phase differences. No clear trend or consensus was seen
here and just leaned toward the flatter ensemble means awaiting
better agreement. Meanwhile, the 12Z ECMWF seemed to be an outlier
in maintaining the southern stream closed upper low in the eastern
Pacific/California farther offshore compared to better guidance
consensus.

The WPC forecast was based on a composite deterministic model
blend early in the period. Used the GEFS and EC ensemble means and
increased their proportions Days 5-7 given individual model
differences especially in the Northwest and vicinity.


...Weather/Hazards Highlights...

Thunderstorms are likely to form ahead of the broad but shallow
upper trough and a surface frontal boundary in the Upper Midwest to
central Plains Sunday. Global models have already been showing
high instability with MUCAPE 4000-6000 J/kg for this region, so
strong storms are possible, and this will also support heavy rain
rates that could cause flash flooding. A Marginal Risk is in place
in the Upper/Middle Mississippi Valley back into the south-central
Plains for the Day 4/Sunday ERO. By Monday the setup will be
similar, but with the trough and cold front pressing southeast. A
large Marginal Risk is located along and ahead of the front from
the Ohio/Tennessee Valleys, Mid/Lower Mississippi Valley, and the
south-central Plains where storms are likely in the moist and
unstable airmass on Day 5/Wednesday. For both days, further
refinements may be needed in future cycles, including possible
embedded Slight Risks, but model agreement in the specifics remains
low for now. The front will continue to push eastward Tuesday,
leading to a wet day in the Northeast/Mid-Atlantic before drying
out midweek, and southward for thunderstorm chances across the
Southeast Tuesday-Wednesday. Even before the front approaches,
scattered thunderstorms are likely farther south in the broad warm
sector as well. There will be less forcing for organization and
sustaining of storms across the southern tier away from the upper
jet, but instability could allow for heavy rain rates that may
cause nonzero chances of localized flash flooding, but that are
likely dependent on smaller scale boundaries and are less
predictable at this point. One area of focus that the models show
for some heavier rain is across the central to eastern Gulf Coast
region. Will monitor if there will be flash flooding concerns there
but it would have to battle with very high flash flood guidance.

Monsoonal moisture is likely to increase next week in the
Southern/Central Rockies and Plains with southerly flow under the
upper ridge, thus increasing coverage of and rain amounts in
storms. Marginal Risks are in place for the southern High Plains
Day 4/Sunday and stretching north into eastern Colorado Day
5/Monday as the back end of the front nears. Areas like the
Sacramento Mountains, where the steep terrain and burn scars cause
the area to be particularly sensitive to rain, are likely most
vulnerable to rain causing potential flash flooding, especially
with wet antecedent conditions there.

Elsewhere, showers and storms may develop across parts of the
Great Basin Monday and toward the Northern Rockies by Tuesday. Then
depending on a shortwave, rain chances are forecast to increase in
the north-central U.S. by midweek.

Temperatures are forecast to be around 5-10 degrees above average
across the Midwest/Great Lakes early next week, while the southern
half of the Plains to Southeast can expect typical summer heat.
HeatRisk shows some Major (level 3 of 4) areas in these regions,
indicating heat levels that affect anyone without effective cooling
and/or adequate hydration. Temperatures and dewpoints will
decrease behind the cold front as it progresses southeast. Farther
west, building heat is expected next week as an upper ridge takes
hold. Temperatures in the Northwest are likely to be 10-15 (locally
20) degrees above normal, for highs nearing 100F. In the Desert
Southwest, temperatures a few degrees above already high averages
will equate to 100s and 110s. Moderate to Major HeatRisk is shown
for much of the Interior West peaking Monday-Tuesday.


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
352 AM EDT Thu Jun 26 2025

Valid 00Z Fri 27 Jun 2025 - 00Z Fri 04 Jul 2025

Moderate to locally breezy trades are on tap for the latter part
of the week for Hawaii as moisture levels dry out compared to
midweek. Some passing showers over windward and mauka areas are
possible. An upper ridge will drift over the eastern islands and
eventually build to the west by this weekend, but by early next
week an upper trough axis could develop northwest of the islands.
Moisture looks to increase a bit around Sunday-Monday for possibly
increased shower coverage. At the surface, the pressure gradient
is forecast to weaken by around Monday-Tuesday, lessening trades
through at least part of next week.

Tate

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Thu Jun 26 2025
Day 1
Valid 12Z Thu Jun 26 2025 - 12Z Fri Jun 27 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
THE CENTRAL PLAINS, UPPER MIDWEST, AND UPPER GREAT LAKES, ALONG
WITH NORTHERN PORTIONS OF THE MID ATLANTIC...

...Central Plains into the Upper Great Lakes...

Upper shortwave trough across the Northern Plains early Thu will
pivot eastward across the Upper MS Valley and Upper Great Lakes
region later Thu and Thu night. Enhancing the deep-layer forcing
will be the curved 90kt upper level jet streak that will be
skirting the U.S.-Canadian border. Ahead of the upper shortwave
trough/surface front -- 850-700 mb moisture flux anomalies are
noteworthy (1.5-2.0 standard deviations above normal), as is the
0-6km bulk shear values (35-45+ kts). This will likely support more
widespread, organized convective line segments later this
afternoon/evening and into the overnight across the elongated
Slight Risk area. Compared to yesterday's Day 2 ERO, based on the
latest guidance trends we did nudge the Slight slightly farther
east across northwest MO and southeast IA. The 00Z CAMs show 24hr
max QPF generally in the 3-5" range within the Slight Risk area,
which is supported by the HREF and RRFS 24hr QPF probabilities.
Multiple CAMs (including the 00Z RRFS) show isolated totals
exceeding 5" across eastern KS.

...Mid Atlantic...

Most of the CAMs show more widespread slow-moving convective
clusters within a newly-hoisted Slight area, initiating along the
lee-side trough and quasi-stationary, backdoor front. Relatively light
(generally 20kt or less) deep-layer shear would suggest pulse-
type durations for the heaviest rains, but nevertheless both the
HREF and RRFS do show pockets of elevated probabilities with >2"/hr
rainfall rates by mid-late afternoon into Thu evening. Therefore
given the favorable thermodynamic profile (1.75-2.00" PWs and max
CAPEs 2000-3000 J/Kg), the likelihood of slow cell motions with the
potential for repetitive convection along these boundaries would
support a low-end Slight Risk across the northern Mid Atlantic
(northern VA into eastern MD and Eastern PA), despite the lack of
strong synoptic/ kinematic support.

...Parts of the Lower MS Valley, TN Valley, and Southeast...

Scattered to widely scattered thunderstorms over much of the
south-central to southeastern CONUS will yield some heavy rainfall
prospects during the day Thursday with a decay in coverage once we
lose diurnal heating. The main areas of interest will lie along
the terrain in the Southern Appalachians and along the Gulf coast
where the remnants of a migrating TUTT cell will maintain a focal
point for heavy convective prospects during the period. Best threat
for any flash flooding will be tied to the complex topography and
urban settings where runoff capabilities are highest. Relatively
modest HREF probs for >3" (40-60%) were noted across portions of
MS/LA and especially along the west coast of the FL Peninsula. For
now the risk appears to be a 'high end' Marginal, i.e. mainly an
isolated flash flood risk, largely due to the pulse/short-fused
nature of the more intense rainfall rates and relatively high FFG
values.

...New Mexico...

Isolated to scattered thunderstorms across the Sacramento's and
adjacent desert will maintain at least some threat for flash
flooding given wet antecedent conditions following previous multi-
day convective impact in prior periods. Coverage and intensity of
convection will be less than previous days as we lose the benefit
of the RER jet dynamics that have assisted in the recent days.
Still, remnant elevated moisture and sufficient buoyancy within
the confines of far West TX up through Southern and Eastern NM will
maintain a posture of diurnally driven thunderstorms with locally
heavy rainfall across the above areas. Heaviest thunderstorms will
be capable of 1-2" with the peak QPF max probably closer to 3" as
noted by modest HREF neighborhood probabilities for >3" with a
decline to 0% for >5". The previous MRGL risk was maintained.

Hurley


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Thu Jun 26 2025
Day 2
Valid 12Z Fri Jun 27 2025 - 12Z Sat Jun 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
NORTHERN NEW YORK AND NORTHERN NEW ENGLAND...

...Northern NY-New England...

The forecast for a focused corridor of heavy rainfall associated
with an MCS and trailing convection crossing from southeastern
Canada into portions of Update New York/northern New England
remains on track. While there are expectedly some variances on the
possible MCS path which add some east-west uncertainty, all
guidance is still in good agreement that the track will clip areas
south of the international border bringing an attendant flash flood
threat. Deterministic guidance indicates the potential of rainfall
totals between 1-3", with ensemble probabilities of 2"+ between
15-25%. A small eastward adjustment of the Slight Risk area was
added based on these latest ensemble probabilities. Elsewhere,
prior forecast has remained consistent.

...Northern Plains...

A quick moving shortwave across the North-Central tier of the CONUS
will lead to scattered thunderstorm activity capable of locally
heavy rainfall and flash flood prospects. The best threat will be
over Northern ND into the Red River area where some urbanized zones
will have a greater threat for flash flooding. A quick 1-3+" is
likely anywhere over Central ND into Northwest MN. This threat is
within the lower end of the MRGL risk threshold and will be
monitored closely to see if the risk is warranted, or needs any
expansion.

...West Texas into New Mexico...

Continued threat of widely scattered thunderstorms across far West
TX into NM will allow for isolated flash flood concerns over areas
that will have seen several days of heavy convective impacts with
compromised FFG's. Local 1-2" is possible in the period with the
highest threat likely over the Sacramento's down through the
Guadalupe Mtns. and adjacent valleys. A MRGL risk was maintained to
cover for the threat.


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Thu Jun 26 2025
Day 3
Valid 12Z Sat Jun 28 2025 - 12Z Sun Jun 29 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE NORTHERN PLAINS AND UPPER MIDWEST, THE NORTHEAST, AND
SOUTH-CENTRAL NEW MEXICO...

...Northern Plains and Upper Midwest...

Next approaching upper shortwave trough, with a 90kt upper level
jet streak on the lee side, will generate a compact area of fairly
robust, transient deep-layer forcing over the outlook area later in
the period (especially Sat night). MUCAPEs are expected to soar
within the warm sector prior to the surface cold frontal passage --
i.e. aoa 4,000 J/Kg per the GFS. This along with PWs getting near
1.75" will lead to more organized, widespread convection by
Saturday night as the activity likely grows upscale with the
increasing pre-frontal low-level inflow (30-40kts at 850 mb). The
00Z guidance indicates significant latitudinal spread in the
heavier QPF, and as a result, have maintained the Marginal Risk
from yesterday's Day 4 ERO. However, the potential for an upgrade
to Slight is certainly plausible given the kinematic and
thermodynamic profile, especially after 00Z Sun when the Corfidi
Vectors decrease to 10kt or less (thereby enhancing the risk for
cell training).

...Northeast...

Upper shortwave trough pushes across the Northeast by late Sat,
then off the coast Sun morning. The bulk of the rainfall will fall
during the first half of the period (during the day Sat),
coinciding with the most favorable pre-frontal deep-layer
instability and moisture (PWs 1.75-2.00+ inches). The 00Z guidance
shows considerable spread with the heaviest QPF, though are fairly
similar with the max totals (1.5-3.0"). Given the spread in the
model QPFs, along with the progression of the front and fairly
quick diminishment in instability after 00Z Sun, for now will
maintain the Marginal Risk.

...New Mexico...

Maintained a targeted Marginal Risk area over/near the Sacramento
Mtns, particularly the burn scar areas from the 2024 fires (Blue 2,
South Fork, and Salt burn scars). QPF trends (coverage, intensity)
are similar to Day 2, with the moist S-SE low-level upslope flow
likely resulting in a concentrated area of heavier rainfall across
the Sacramento Mtns and eastern foothills. The flash flood
potential is expected to remain isolated/localized.

Hurley

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Thu Jun 26 2025


Thunderstorms are likely to form ahead of the broad but shallow
upper trough and a surface frontal boundary in the Upper Midwest to
central Plains Sunday. Global models have already been showing
high instability with MUCAPE 4000-6000 J/kg for this region, so
strong storms are possible, and this will also support heavy rain
rates that could cause flash flooding. A Marginal Risk is in place
in the Upper/Middle Mississippi Valley back into the south-central
Plains for the Day 4/Sunday ERO. By Monday the setup will be
similar, but with the trough and cold front pressing southeast. A
large Marginal Risk is located along and ahead of the front from
the Ohio/Tennessee Valleys, Mid/Lower Mississippi Valley, and the
south-central Plains where storms are likely in the moist and
unstable airmass on Day 5/Wednesday. For both days, further
refinements may be needed in future cycles, including possible
embedded Slight Risks, but model agreement in the specifics remains
low for now. The front will continue to push eastward Tuesday,
leading to a wet day in the Northeast/Mid-Atlantic before drying
out midweek, and southward for thunderstorm chances across the
Southeast Tuesday-Wednesday. Even before the front approaches,
scattered thunderstorms are likely farther south in the broad warm
sector as well. There will be less forcing for organization and
sustaining of storms across the southern tier away from the upper
jet, but instability could allow for heavy rain rates that may
cause nonzero chances of localized flash flooding, but that are
likely dependent on smaller scale boundaries and are less
predictable at this point. One area of focus that the models show
for some heavier rain is across the central to eastern Gulf Coast
region. Will monitor if there will be flash flooding concerns there
but it would have to battle with very high flash flood guidance.

Monsoonal moisture is likely to increase next week in the
Southern/Central Rockies and Plains with southerly flow under the
upper ridge, thus increasing coverage of and rain amounts in
storms. Marginal Risks are in place for the southern High Plains
Day 4/Sunday and stretching north into eastern Colorado Day
5/Monday as the back end of the front nears. Areas like the
Sacramento Mountains, where the steep terrain and burn scars cause
the area to be particularly sensitive to rain, are likely most
vulnerable to rain causing potential flash flooding, especially
with wet antecedent conditions there.

Elsewhere, showers and storms may develop across parts of the
Great Basin Monday and toward the Northern Rockies by Tuesday. Then
depending on a shortwave, rain chances are forecast to increase in
the north-central U.S. by midweek.

Temperatures are forecast to be around 5-10 degrees above average
across the Midwest/Great Lakes early next week, while the southern
half of the Plains to Southeast can expect typical summer heat.
HeatRisk shows some Major (level 3 of 4) areas in these regions,
indicating heat levels that affect anyone without effective cooling
and/or adequate hydration. Temperatures and dewpoints will
decrease behind the cold front as it progresses southeast. Farther
west, building heat is expected next week as an upper ridge takes
hold. Temperatures in the Northwest are likely to be 10-15 (locally
20) degrees above normal, for highs nearing 100F. In the Desert
Southwest, temperatures a few degrees above already high averages
will equate to 100s and 110s. Moderate to Major HeatRisk is shown
for much of the Interior West peaking Monday-Tuesday.


Tate

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Thu Jun 26 2025


Thunderstorms are likely to form ahead of the broad but shallow
upper trough and a surface frontal boundary in the Upper Midwest to
central Plains Sunday. Global models have already been showing
high instability with MUCAPE 4000-6000 J/kg for this region, so
strong storms are possible, and this will also support heavy rain
rates that could cause flash flooding. A Marginal Risk is in place
in the Upper/Middle Mississippi Valley back into the south-central
Plains for the Day 4/Sunday ERO. By Monday the setup will be
similar, but with the trough and cold front pressing southeast. A
large Marginal Risk is located along and ahead of the front from
the Ohio/Tennessee Valleys, Mid/Lower Mississippi Valley, and the
south-central Plains where storms are likely in the moist and
unstable airmass on Day 5/Wednesday. For both days, further
refinements may be needed in future cycles, including possible
embedded Slight Risks, but model agreement in the specifics remains
low for now. The front will continue to push eastward Tuesday,
leading to a wet day in the Northeast/Mid-Atlantic before drying
out midweek, and southward for thunderstorm chances across the
Southeast Tuesday-Wednesday. Even before the front approaches,
scattered thunderstorms are likely farther south in the broad warm
sector as well. There will be less forcing for organization and
sustaining of storms across the southern tier away from the upper
jet, but instability could allow for heavy rain rates that may
cause nonzero chances of localized flash flooding, but that are
likely dependent on smaller scale boundaries and are less
predictable at this point. One area of focus that the models show
for some heavier rain is across the central to eastern Gulf Coast
region. Will monitor if there will be flash flooding concerns there
but it would have to battle with very high flash flood guidance.

Monsoonal moisture is likely to increase next week in the
Southern/Central Rockies and Plains with southerly flow under the
upper ridge, thus increasing coverage of and rain amounts in
storms. Marginal Risks are in place for the southern High Plains
Day 4/Sunday and stretching north into eastern Colorado Day
5/Monday as the back end of the front nears. Areas like the
Sacramento Mountains, where the steep terrain and burn scars cause
the area to be particularly sensitive to rain, are likely most
vulnerable to rain causing potential flash flooding, especially
with wet antecedent conditions there.

Elsewhere, showers and storms may develop across parts of the
Great Basin Monday and toward the Northern Rockies by Tuesday. Then
depending on a shortwave, rain chances are forecast to increase in
the north-central U.S. by midweek.

Temperatures are forecast to be around 5-10 degrees above average
across the Midwest/Great Lakes early next week, while the southern
half of the Plains to Southeast can expect typical summer heat.
HeatRisk shows some Major (level 3 of 4) areas in these regions,
indicating heat levels that affect anyone without effective cooling
and/or adequate hydration. Temperatures and dewpoints will
decrease behind the cold front as it progresses southeast. Farther
west, building heat is expected next week as an upper ridge takes
hold. Temperatures in the Northwest are likely to be 10-15 (locally
20) degrees above normal, for highs nearing 100F. In the Desert
Southwest, temperatures a few degrees above already high averages
will equate to 100s and 110s. Moderate to Major HeatRisk is shown
for much of the Interior West peaking Monday-Tuesday.


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
259 AM EDT Thu Jun 26 2025

Valid 12Z Sun Jun 29 2025 - 12Z Thu Jul 03 2025

...Overview...

Quasi-zonal flow is forecast across the lower 48 early next week,
with the main jet stream across the northern tier pushing
shortwaves and surface frontal systems across the central U.S. in
particular, leading to thunderstorms with potentially heavy rain.
Farther south, above average 500mb heights are expected in a broad
ridge, allowing for summer heat and convection. Upper troughing may
dig a bit as it moves into the Midwest, Great Lakes, and Northeast
Monday through Wednesday, pushing a cold front southeastward with
showers and thunderstorms ahead of it. Meanwhile ridging should
build atop the Interior West and lead to heat there, as well as
monsoonal moisture inflow for the Four Corners states as the week
progresses.


...Guidance/Predictability Assessment...

Model guidance starts out in good agreement with the overall
pattern described above early next week, along with a southern
stream trough moving slowly from the eastern Pacific toward
California. Models are agreeable with the initially north-central
U.S. trough deepening as it slowly shifts east as the week
progresses. Minor low predictability differences do cause some
variability in sensible weather parameters like QPF and frontal
placement though, but without many outliers.

The most uncertain part of the pattern is with an upper low in the
northeast Pacific that sends shortwaves southeast across the
northwestern U.S. and western Canada. Operational and AI/ML models
vary with the depth and position of these shortwaves and lead to
some out of phase differences. No clear trend or consensus was seen
here and just leaned toward the flatter ensemble means awaiting
better agreement. Meanwhile, the 12Z ECMWF seemed to be an outlier
in maintaining the southern stream closed upper low in the eastern
Pacific/California farther offshore compared to better guidance
consensus.

The WPC forecast was based on a composite deterministic model
blend early in the period. Used the GEFS and EC ensemble means and
increased their proportions Days 5-7 given individual model
differences especially in the Northwest and vicinity.


...Weather/Hazards Highlights...

Thunderstorms are likely to form ahead of the broad but shallow
upper trough and a surface frontal boundary in the Upper Midwest to
central Plains Sunday. Global models have already been showing
high instability with MUCAPE 4000-6000 J/kg for this region, so
strong storms are possible, and this will also support heavy rain
rates that could cause flash flooding. A Marginal Risk is in place
in the Upper/Middle Mississippi Valley back into the south-central
Plains for the Day 4/Sunday ERO. By Monday the setup will be
similar, but with the trough and cold front pressing southeast. A
large Marginal Risk is located along and ahead of the front from
the Ohio/Tennessee Valleys, Mid/Lower Mississippi Valley, and the
south-central Plains where storms are likely in the moist and
unstable airmass on Day 5/Wednesday. For both days, further
refinements may be needed in future cycles, including possible
embedded Slight Risks, but model agreement in the specifics remains
low for now. The front will continue to push eastward Tuesday,
leading to a wet day in the Northeast/Mid-Atlantic before drying
out midweek, and southward for thunderstorm chances across the
Southeast Tuesday-Wednesday. Even before the front approaches,
scattered thunderstorms are likely farther south in the broad warm
sector as well. There will be less forcing for organization and
sustaining of storms across the southern tier away from the upper
jet, but instability could allow for heavy rain rates that may
cause nonzero chances of localized flash flooding, but that are
likely dependent on smaller scale boundaries and are less
predictable at this point. One area of focus that the models show
for some heavier rain is across the central to eastern Gulf Coast
region. Will monitor if there will be flash flooding concerns there
but it would have to battle with very high flash flood guidance.

Monsoonal moisture is likely to increase next week in the
Southern/Central Rockies and Plains with southerly flow under the
upper ridge, thus increasing coverage of and rain amounts in
storms. Marginal Risks are in place for the southern High Plains
Day 4/Sunday and stretching north into eastern Colorado Day
5/Monday as the back end of the front nears. Areas like the
Sacramento Mountains, where the steep terrain and burn scars cause
the area to be particularly sensitive to rain, are likely most
vulnerable to rain causing potential flash flooding, especially
with wet antecedent conditions there.

Elsewhere, showers and storms may develop across parts of the
Great Basin Monday and toward the Northern Rockies by Tuesday. Then
depending on a shortwave, rain chances are forecast to increase in
the north-central U.S. by midweek.

Temperatures are forecast to be around 5-10 degrees above average
across the Midwest/Great Lakes early next week, while the southern
half of the Plains to Southeast can expect typical summer heat.
HeatRisk shows some Major (level 3 of 4) areas in these regions,
indicating heat levels that affect anyone without effective cooling
and/or adequate hydration. Temperatures and dewpoints will
decrease behind the cold front as it progresses southeast. Farther
west, building heat is expected next week as an upper ridge takes
hold. Temperatures in the Northwest are likely to be 10-15 (locally
20) degrees above normal, for highs nearing 100F. In the Desert
Southwest, temperatures a few degrees above already high averages
will equate to 100s and 110s. Moderate to Major HeatRisk is shown
for much of the Interior West peaking Monday-Tuesday.


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