Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
336 PM EDT Sun Mar 23 2025

Valid 00Z Mon Mar 24 2025 - 00Z Wed Mar 26 2025

...Snow continues across the Upper Midwest to the Upper Great Lakes today
as severe weather and heavy rain threat emerge across the Mid-South...

...More wet weather expected for the Pacific Northwest through Monday
before a drying trend sets in...

...Well above average, warm to hot early Spring temperatures will expand
over the western/central U.S. this week with numerous record highs
possible by Tuesday...

A low pressure/frontal system moving through the Midwest/Southeast this
afternoon will continue to bring widespread precipitation chances,
including severe and winter weather, to the eastern U.S. today through
Monday. Moist southerly flow ahead a southeastward moving cold front
across the Tennessee/Lower Mississippi Valleys and the ArkLaTex will
support the development of showers and storms Sunday afternoon and into
the evening hours. Increasing shear and sufficient CAPE will lead to some
more potent thunderstorms, with a Slight Risk of severe weather from the
Storm Prediction Center (level 2/5) for the threat of large hail, damaging
winds, and a few tornadoes. In addition, locally heavy rainfall and
isolated flash flooding will be possible into the evening and overnight
hours as storms increase in coverage and begin to repeat over the same
areas as storm motions become more parallel to the slowing cold front.
Storm chances will shift towards the Atlantic and Gulf Coasts Monday as
the front pushes further southward, though severe weather and heavy
rainfall chances will remain much more limited. To the north, a band of
moderate to heavy snowfall will also continue along and to the north of
the low track through the Upper Midwest/Great Lakes. Winter
weather-related warnings and advisories are in place from northern
Minnesota/Wisconsin into the UP of Michigan as snowfall totals of 3-6",
locally 8", will be possible through Monday morning. Rain chances will
spread eastward ahead of the system late Sunday and into the day Monday
from the Ohio Valley into the Mid-Atlantic/southern New England, with a
wintry mix for the Lower Great Lakes, Appalachians, and interior
Northeast. Some light to moderate snow accumulations will be possible for
higher elevations of the Adirondacks as well as across portions of
northern New England, particularly in Maine. Precipitation chances will
taper off by Monday night with some snow showers lingering longest into
Tuesday morning for the interior Northeast.

Meanwhile, a plume of plentiful moisture/Atmospheric River accompanying a
storm system moving into the Pacific Northwest will continue to lead to
very heavy rain along upslope portions of the Olympic Mountains and
northern Cascades in Washington through this evening. A Slight Risk of
Excessive Rainfall (level 2/4) remains in effect as several inches of
rainfall on top of already saturated soils could lead to several instances
of flooding. Moderate to heavy snowfall will also continue for higher
elevations of the northern Cascades and inland through portions of the
northern Rockies. A lighter mix of rain showers (along the coast) and
rain/snow showers (inland) can be expected elsewhere in the Pacific
Northwest/northern Great Basin. The heavy precipitation chances will begin
to wind down overnight Sunday and into the day Monday as the flow of
moisture subsides, though some lower elevation rain/higher elevation snow
showers will linger as a frontal boundary remains draped through the
region. Elsewhere, a clipper system will bring some light rain chances
from the Northern Plains southeast through the Midwest and into the Ohio
Valley late Monday and through the day Tuesday as it quickly drops through
the region. The Storm Prediction Center has outlined Elevated Fire Weather
conditions (level 1/3) across much of the central/southern Plains through
this afternoon as conditions remain dry, warm, and breezy. A much more
isolated threat will persist into Monday for southeastern
Kansas/northeastern Oklahoma.

An upcoming weather story this week will be the significant amount of well
above average, warm to hot early Spring temperatures expanding in coverage
over the western/central U.S. as an upper-ridge builds in a more amplified
pattern. Forecast highs Monday and Tuesday will range from the 50s and 60s
in the northern Rockies/Plains; the 60s and 70s for the Pacific
Northwest/coastal California, the Great Basin, and the central
Rockies/Plains; and the 80s to low 90s from central California through the
Southwest and into the Southern Plains. The Desert Southwest will see the
hottest temperatures, with highs into the mid- to upper 90s. Numerous
record-tying/breaking highs will be possible from Texas west through the
Desert Southwest and northward along the West Coast by Tuesday. These well
above average conditions look to continue through the week, generally
shifting more eastward with time from the western to central U.S. While
not quite as abnormal, highs the next couple of days will still be mild to
warm and above average across much of the Midwest, Southeast, and
Mid-Atlantic. Colder, below average conditions will remain confined to the
Great Lakes and interior Northeast/New England as the storm system passes
through, with highs generally in the 30s and 40s.

Putnam


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
248 PM EDT Sun Mar 23 2025

Valid 12Z Wed Mar 26 2025 - 12Z Sun Mar 30 2025


...Overview...

Expect the amplified western ridge/eastern trough upper pattern
lingering into Wednesday to move steadily eastward while trending a
little flatter, as dynamics from a strong East Pacific upper
trough Wednesday-Thursday (supporting a storm system off the
Pacific Northwest coast) push into the western and central U.S.
With a slightly slower trend noted in the guidance, the mean ridge
should reach the East by next weekend. Expect very warm
temperatures under the western upper ridge through midweek or so
with some daily records possible. Anomalous warmth will then move
into the Plains, followed by moderation farther east. Upper
dynamics and the leading front arriving from the Pacific will bring
rain and high elevation snow to the Northwest mid-late week, with
another system possibly approaching by next Sunday. A southern tier
shortwave will support the threat of locally heavy rainfall over
parts of Texas late in the week. This moisture and additional Gulf
inflow may combine to spread a broader area of precipitation over
parts of the Plains and east-central U.S. late week into the
weekend, in association with Plains through Upper Midwest low
pressure.

...Guidance/Predictability Assessment...

Guidance continues to show good agreement on the large scale upper
pattern and progression, but a lot of uncertainty in the details.
A leading shortwave into the West from a deepened low off the
Pacific Northwest coast shows good agreement, but there is
continued question on timing and amplitude of a deeper trough into
the West later in the week. The GFS has trended slightly deeper in
recent days, but the last several runs of the CMC continues to be
the outlier as it eventually spins up a closed low over the Central
Plains next weekend. Better cluster of guidance suggests this
should be more of an open wave. Ahead of this though, there remains
uncertainty in the details of a southern stream shortwave into the
Southern Plains and Midwest later this week, which has impacts on
heavy rainfall potential across Texas. Then by next weekend
guidance shows spread with a front that reaches into the Mid-
Atlantic, likely with a pronounced temperature gradient.

The WPC forecast today was able to use a blend of the latest
deterministic guidance for Wednesday and Thursday, amidst good
model agreement. Began incorporating the ECENS/GEFS by Friday/Day
5, eventually reaching a 50/50 split of deterministic/ensemble
means by Day 7. Did not include the CMC in the late period blend
due to the outlier solution described above. Overall, this approach
maintained good continuity with the previous WPC forecast.

...Weather/Hazards Highlights...

From Wednesday into Thursday night the most prominent heavy
rainfall focus should be over portions of Texas by Thursday as
moist southeasterly low level flow from the Gulf interacts with an
upper shortwave crossing northern Mexico. Some activity may
initiate in the Day 4 period near the Rio Grande Valley but the
signal is diffuse enough not to merit any risk area in the
Excessive Rainfall Outlook. By Day 5 there is a much stronger
signal, though with typical spread for where the heaviest rainfall
axis will be. Overall the best overlap of guidance exists over
southern Texas. The Day 5 ERO maintains a broader Marginal Risk
area, with no embedded Slight Risk depicted yet due to initially
dry ground conditions and guidance spread. Improved clustering for
location and amounts in the heavier part of the envelope could
eventually merit an upgrade. Elsewhere, consensus amounts along the
Pacific Northwest coast in association with the Wednesday-
Thursday system have generally decreased somewhat from 24 hours
ago, while the signal for a potential band of enhanced rainfall
over the Mid Mississippi Valley ahead of a warm front is too
diffuse to warrant a risk area yet on Day 5.

Precipitation will spread across northern and central parts of the
West late this week, with Plains low pressure and its trailing
front eventually pushing the Texas rainfall eastward while
spreading a broader shield of moisture across the central and east-
central U.S. Some wintry weather will be possible over far
northern latitudes but otherwise most precipitation should be in
the form of rain. How much snow falls over the northern Plains next
weekend will depend on how strongly the Plains/Upper Midwest
system develops, with low confidence in specifics at this time. The
next Pacific system may increase precipitation along the West
Coast by next Sunday.

The weak wave forecast to track off the Mid-Atlantic/New England
coast on Wednesday may produce some light precipitation early but
most likely just near the coast.

The strong upper ridge over the West into Wednesday will bring
well above normal temperatures to the region, with a broad area of
highs 10-20F above normal with locally higher anomalies. There will
also be potential for numerous daily records for highs/warm lows,
especially during Wednesday. As the upper ridge shifts eastward
with time, the West will cool down while already above normal
anomalies over the central U.S. will increase. Locations from the
northern-central Plains into Midwest should see one or two days of
highs reaching 20-25F or so above normal by Thursday-Friday, with
best potential for some daily records over the central High Plains
on Thursday. The East will see near to slightly below normal
temperatures Wednesday-Thursday and then increasing coverage of
highs 10-20F above normal Friday into the weekend. However a front
reaching the Northeast/Mid-Atlantic may define a sharp gradient
between this warmth and cooler readings just to the north.

Santorelli/Rausch


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 Mar 23 2025

Valid 00Z Mon 24 Mar 2025 - 00Z Mon 31 Mar 2025

Today's guidance maintains good agreement and continuity through
most of this week. Trades will be fairly light Sunday-Monday as an
approaching front ultimately stalls just north of the main
islands. Consensus maintains the recent theme of frontal waviness
generating an axis of heavy rainfall a ways northwest/north of
the main islands early-mid week, while trades rebound somewhat
from Tuesday onward in easterly or southeasterly fashion. This
pattern should bring a return of windward showers, though likely
with fairly light totals as a strong upper ridge builds in from
southeast late this week.

Guidance has shown more spread and variability with the forecast
for this weekend. Latest GFS/GEFS runs have at least adjusted
their previously over-amplified east-central Pacific upper trough
enough to maintain easterly trades during the weekend. Machine
learning models generally suggest that the GFS/GEFS may still be
too weak with the upper ridge over the islands though. By Sunday,
differences with evolution of a system well to the west or
northwest affect the orientation of island winds. ML models differ
enough to allow for a range of possibilities between the more
southerly winds in the 00Z ECMWF/CMC or easterly in the GFS. The
ensemble means support persistence of the easterly to
southeasterly winds, which appears the most reasonable approach
until a more dominant alternative cluster arises.

Rausch

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
405 PM EDT Sun Mar 23 2025
Day 1
Valid 16Z Sun Mar 23 2025 - 12Z Mon Mar 24 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
WESTERN WASHINGTON STATE...

16Z Update...
Overall, made mostly minor adjustments to the previous outlook.

In western Washington, expanded the previous Slight Risk a little
further south along the foothills of the northern Cascades where
the 12Z HREF shows high neighborhood probabilities for 24-hr
amounts exceeding 5 inches and 100 year ARI. These amounts,
combined with rising snow levels are expected to contribute to
increasing runoff concerns through today into Monday. Refer to WPC
MPD #078 for additional details concerning the near-term heavy
rainfall threat across western Washington.

For the lower Mississippi to Tennessee Valley region, extended the
Marginal a little further west back across northern Louisiana, to
now include a small portion of eastern Texas as well. The 12Z hi-
res guidance is now showing some potential for training storms,
producing locally heavy amounts, as storms develop across that
region this evening.

Pereira


Previous discussion...

...Western Washington...
In coordination with SEW/Seattle, WA forecast office, a Slight
Risk upgrade was introduced with this forecast update. A strong
cold front and trailing atmospheric river plume are moving into the
coast of Washington State now, and will continue to push west into
the Olympic Mountains and Cascades through the day today. As the
front moves into the mountains, the combination of forcings from
the front, the upslope flow, and abundant Pacific moisture both
with and behind the front will increase the potential for half-inch
per hour rainfall rates into the mountains. Meanwhile, an
increasingly southerly component of the onshore flow associated
with the following atmospheric river will advect warmer air into
the region. This will result in rising snow levels above 7,000 ft,
which will increase the potential for resultant flooding from
higher elevation snowmelt and the heavy rainfall.

IVT values associated with the trailing atmospheric river have
risen a bit in the latest guidance, peaking in the 625 to 675 kg/ms
range today. This increase along with slightly greater amounts of
atmospheric moisture have resulted in higher forecast rainfall
today, especially during the daylight hours as the front moves
ashore. The front being either primary or a significant component
of the forcing will result in the heaviest precipitation into the
Olympics and Cascades today. Once the front dissipates as it is
shredded by the mountains, the atmospheric river and upslope flow
will not have nearly the amount of forcing alone as they had with
the front. Thus, the potential for heavy rainfall rates above a
quarter inch per hour should diminish by tonight.

Soils in this area remain nearly saturated from repeated rounds of
rain across western Washington in recent weeks. Therefore most, if
not all the rainfall today should convert to runoff. Expect 4 to 6
inches of rain, with locally higher amounts west of the Olympics,
and 3-5 inches into the northern Cascades northeast of Seattle. For
the Seattle area, significantly less rain, on the order of a
fraction of an inch is expected, as rain shadowing off the Olympics
will greatly cut into rainfall totals. This will be partially
offset by the urbanization in the area, so the Marginal Risk
remains largely unchanged. The Slight Risk upgrade is focused on
the wettest areas, namely west of the Olympics and the western
foothills of the northern Cascades into Whatcom and Skagit
Counties.

...Lower Mississippi and Tennessee Valleys...
Very few changes were needed with this update across the Lower
Mississippi and Tennessee Valleys. A progressive cold front moving
across the middle of the country will continue south and east into
the Southeast today. This evening through tonight, the front will
run into a strengthening low-level jet (LLJ), which will align
along the frontal interface as it moves into the Mid-South.
Scattered showers and thunderstorms will develop ahead of the front
as a result, which in a few instances may train over the same
areas, but modest Gulf moisture and instability to 2,000 J/kg
should limit storm strength, notwithstanding their fast motion. The
inherited Marginal Risk is largely unchanged, stretching northeast
from northern Louisiana to the southern Appalachians. Soils have
largely dry since the last heavy rain event in this area, so any
flash flooding will be isolated to typical flood prone and urban
areas.

Wegman

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
405 PM EDT Sun Mar 23 2025
Day 2
Valid 12Z Mon Mar 24 2025 - 12Z Tue Mar 25 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
WESTERN WASHINGTON STATE...

20Z Update...

...Western Washington...
A small Marginal Risk was added to the western foothills of the
northern Cascades. Latest guidance shows an atmospheric river
continuing to impact the region, but also gradually waning through
the early half of the period. The 12Z GFS shows IVTs decreasing
from 400-500 kg/m/sec early in the period as a ridge continues to
build and onshore flow into the region diminishes. As the AR
diminishes, so will the potential for additional heavy
precipitation. However, the continued moisture flux into the region
early in the period may be sufficient for additional amounts of 2-3
inches, as indicated by the 12Z HREF. These amounts along with
additional snowmelt may prolong runoff concerns.

Pereira

Previous Discussion...

In coordination with MOB/Mobile, AL and TAE/Tallahassee, FL
forecast offices, the inherited Marginal Risk for portions of the
central Gulf Coast was downgraded with this update. The front
moving across the Southeast will continue across the Gulf Coast
Monday morning, and is now largely expected to continue into the
northern Gulf, as well as towards the Georgia coast during the day.
Any storms from the overnight period Monday morning will continue
eastward and remain progressive enough that training is unlikely.
There will remain some Gulf moisture and instability, but these too
will be modest, and generally unsupportive of the heavy rainfall
rates needed to overcome the high FFGs along the Gulf Coast. With
areal rainfall now generally under a half inch, and in many areas
under a quarter inch (outside of any heavier rain cores), and the
expected continued movement of the front and associated storms, the
flash flooding potential has continued the trend of decreasing
from previous days. For these reasons, the Marginal was dropped.

Wegman

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
405 PM EDT Sun Mar 23 2025
Day 3
Valid 12Z Tue Mar 25 2025 - 12Z Wed Mar 26 2025

The probability of rainfall exceeding flash flooding guidance is
less than 5 percent.

Very late Tuesday night (generally from around 06Z Wed on), the
collision of return flow off the Gulf in the form of 15-25 kt SSW
flow over Texas will run into a slow-moving warm front along the
Red River. Model guidance has hinted for a few days now that an
area of storms, possibly a small MCS, will develop over either
southeast Oklahoma or northeast Texas along this front. While there
has been model consistency, the area of storms remains small, and
somewhat uncertain as to where it will set up. This area of the
country has been very dry of late, which too precludes much
flooding. Given the small area that would be impacted, the area
remains without a Risk area for now, but will continue to be
monitored for possible introduction of a Marginal with CAMs
guidance or improved agreement on a wetter forecast.

Pereira/Wegman

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
248 PM EDT Sun Mar 23 2025


From Wednesday into Thursday night the most prominent heavy
rainfall focus should be over portions of Texas by Thursday as
moist southeasterly low level flow from the Gulf interacts with an
upper shortwave crossing northern Mexico. Some activity may
initiate in the Day 4 period near the Rio Grande Valley but the
signal is diffuse enough not to merit any risk area in the
Excessive Rainfall Outlook. By Day 5 there is a much stronger
signal, though with typical spread for where the heaviest rainfall
axis will be. Overall the best overlap of guidance exists over
southern Texas. The Day 5 ERO maintains a broader Marginal Risk
area, with no embedded Slight Risk depicted yet due to initially
dry ground conditions and guidance spread. Improved clustering for
location and amounts in the heavier part of the envelope could
eventually merit an upgrade. Elsewhere, consensus amounts along the
Pacific Northwest coast in association with the Wednesday-
Thursday system have generally decreased somewhat from 24 hours
ago, while the signal for a potential band of enhanced rainfall
over the Mid Mississippi Valley ahead of a warm front is too
diffuse to warrant a risk area yet on Day 5.

Precipitation will spread across northern and central parts of the
West late this week, with Plains low pressure and its trailing
front eventually pushing the Texas rainfall eastward while
spreading a broader shield of moisture across the central and east-
central U.S. Some wintry weather will be possible over far
northern latitudes but otherwise most precipitation should be in
the form of rain. How much snow falls over the northern Plains next
weekend will depend on how strongly the Plains/Upper Midwest
system develops, with low confidence in specifics at this time. The
next Pacific system may increase precipitation along the West
Coast by next Sunday.

The weak wave forecast to track off the Mid-Atlantic/New England
coast on Wednesday may produce some light precipitation early but
most likely just near the coast.

The strong upper ridge over the West into Wednesday will bring
well above normal temperatures to the region, with a broad area of
highs 10-20F above normal with locally higher anomalies. There will
also be potential for numerous daily records for highs/warm lows,
especially during Wednesday. As the upper ridge shifts eastward
with time, the West will cool down while already above normal
anomalies over the central U.S. will increase. Locations from the
northern-central Plains into Midwest should see one or two days of
highs reaching 20-25F or so above normal by Thursday-Friday, with
best potential for some daily records over the central High Plains
on Thursday. The East will see near to slightly below normal
temperatures Wednesday-Thursday and then increasing coverage of
highs 10-20F above normal Friday into the weekend. However a front
reaching the Northeast/Mid-Atlantic may define a sharp gradient
between this warmth and cooler readings just to the north.

Santorelli/Rausch

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
248 PM EDT Sun Mar 23 2025


From Wednesday into Thursday night the most prominent heavy
rainfall focus should be over portions of Texas by Thursday as
moist southeasterly low level flow from the Gulf interacts with an
upper shortwave crossing northern Mexico. Some activity may
initiate in the Day 4 period near the Rio Grande Valley but the
signal is diffuse enough not to merit any risk area in the
Excessive Rainfall Outlook. By Day 5 there is a much stronger
signal, though with typical spread for where the heaviest rainfall
axis will be. Overall the best overlap of guidance exists over
southern Texas. The Day 5 ERO maintains a broader Marginal Risk
area, with no embedded Slight Risk depicted yet due to initially
dry ground conditions and guidance spread. Improved clustering for
location and amounts in the heavier part of the envelope could
eventually merit an upgrade. Elsewhere, consensus amounts along the
Pacific Northwest coast in association with the Wednesday-
Thursday system have generally decreased somewhat from 24 hours
ago, while the signal for a potential band of enhanced rainfall
over the Mid Mississippi Valley ahead of a warm front is too
diffuse to warrant a risk area yet on Day 5.

Precipitation will spread across northern and central parts of the
West late this week, with Plains low pressure and its trailing
front eventually pushing the Texas rainfall eastward while
spreading a broader shield of moisture across the central and east-
central U.S. Some wintry weather will be possible over far
northern latitudes but otherwise most precipitation should be in
the form of rain. How much snow falls over the northern Plains next
weekend will depend on how strongly the Plains/Upper Midwest
system develops, with low confidence in specifics at this time. The
next Pacific system may increase precipitation along the West
Coast by next Sunday.

The weak wave forecast to track off the Mid-Atlantic/New England
coast on Wednesday may produce some light precipitation early but
most likely just near the coast.

The strong upper ridge over the West into Wednesday will bring
well above normal temperatures to the region, with a broad area of
highs 10-20F above normal with locally higher anomalies. There will
also be potential for numerous daily records for highs/warm lows,
especially during Wednesday. As the upper ridge shifts eastward
with time, the West will cool down while already above normal
anomalies over the central U.S. will increase. Locations from the
northern-central Plains into Midwest should see one or two days of
highs reaching 20-25F or so above normal by Thursday-Friday, with
best potential for some daily records over the central High Plains
on Thursday. The East will see near to slightly below normal
temperatures Wednesday-Thursday and then increasing coverage of
highs 10-20F above normal Friday into the weekend. However a front
reaching the Northeast/Mid-Atlantic may define a sharp gradient
between this warmth and cooler readings just to the north.

Santorelli/Rausch

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
206 PM EDT Sun Mar 23 2025

Valid 12Z Sun Mar 23 2025 - 12Z Wed Mar 26 2025


...Pacific/Interior Northwest to Northern Rockies...
Day 1...

Ongoing Atmospheric River moving onshore western Washington this
afternoon will continue to spread moisture across the Northwest,
far northern Great Basin and into the northern Rockies through
Monday. Snow levels across the WA Cascades will start out this
evening above 6000 ft and remain between 6000 to 8000 ft throughout
the remainder of the event (above major mountain passes). Snow
levels across the Great Basin and northern Rockies will also
continue to rise above 7000 ft during the D1 period as residual
moisture on the southern edge of the AR reaches into the
western/northern WY ranges. WPC probabilities for at least 6 inches
of snow are medium (30-50%) and are confined to the northern WA
Cascades and highest ranges of MT and WY (above 7000 to 8000 ft).
Precipitation cuts off by D2 as anomalous upper ridging builds
across the western U.S. as the next system approaching the region
cuts off over the northeast Pacific.

Snell


...Upper Midwest/Great Lakes/Northeast...
Days 1-3...

The winter storm has kicked off in the Upper Midwest with the
storm
strengthening this afternoon as it tracks towards the Upper Great
Lakes tonight. The deformation zone is pivoting beneath the TROWAL
over northern Minnesota. There is also heavy snow unfolding in
northern Wisconsin where strong 850-700mb FGEN and WAA aloft is
paired with dynamic cooling aloft to produce >1"/hr snowfall rates
in some cases. By this evening, the storm will begin its weakening
phase with most snow coming via WAA over the eastern Michigan U.P.
and northern most portion of Michigan's Mitten. Farther west, CAA
on the back side of the low will generate lake-enhanced snowfall
from the Minnesota Arrowhead on east to northern Wisconsin and as
far east as the Keweenaw Peninsula of Michigan's U.P.. Look for
periods of snow lake-effect snow to linger through Monday across
the Michigan U.P. and northern lower Michigan. WPC probabilities
show moderate-to-high chances (50-70%) for additional snowfall
amounts >4" for the areas referenced above, with some localized
areas seeing additional snowfall amounts up to 8", especially in
the Michigan U.P..

Farther east, the storm's warm front will advance east into the
Northeast tonight with low-level WAA and 290K isentropic ascent
aloft. The antecedent air-mass is initially cold enough to support
snow in the as far south as the Poconos and Catskills, but the best
chance for accumulating snowfall will take place over the
Adirondacks, Green, and White Mountains tonight and into Monday
morning. Some minor ice accumulations are possible in parts of the
northern Mid-Atlantic tonight and into early Monday morning. A
wave of low pressure will attempt to develop near Downeast Maine
Monday and could wrap some Atlantic moisture around its northern
and western flank. This would allow for some minor snow
accumulations to unfold from central to eastern Maine through
Monday evening. WPC probabilities do highlight low- to- moderate
chances (20-50%) for some targeted areas of >4" snowfall totals in
parts of the Adirondacks, Green Mountains, White Mountains, and
east-central Maine. As the storm departs Monday night, some lake
effect streamers off Lakes Erie and Ontario should lead to minor
snowfall totals in northwest Pennsylvania, western NY, and northern
New York. The area most likely to see measurable snowfall is the
Tug Hill where the primary band off Lake Ontario and the Tug Hill's
elevation provide a more favorable setup for accumulating
snowfall. WPC probabilities shows low chances (10-30%) for 48-hour
snowfall totals >8" in the Tug Hill, showing there is the potential
for some localized amounts that could be on the heavier side
through Tuesday. Some minor snow accumulations are possible as far
south as the Central Appalachians but totals most totals staying in
the coating-3" range.


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Mullinax

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
248 PM EDT Sun Mar 23 2025

Valid 12Z Wed Mar 26 2025 - 12Z Sun Mar 30 2025


...Overview...

Expect the amplified western ridge/eastern trough upper pattern
lingering into Wednesday to move steadily eastward while trending a
little flatter, as dynamics from a strong East Pacific upper
trough Wednesday-Thursday (supporting a storm system off the
Pacific Northwest coast) push into the western and central U.S.
With a slightly slower trend noted in the guidance, the mean ridge
should reach the East by next weekend. Expect very warm
temperatures under the western upper ridge through midweek or so
with some daily records possible. Anomalous warmth will then move
into the Plains, followed by moderation farther east. Upper
dynamics and the leading front arriving from the Pacific will bring
rain and high elevation snow to the Northwest mid-late week, with
another system possibly approaching by next Sunday. A southern tier
shortwave will support the threat of locally heavy rainfall over
parts of Texas late in the week. This moisture and additional Gulf
inflow may combine to spread a broader area of precipitation over
parts of the Plains and east-central U.S. late week into the
weekend, in association with Plains through Upper Midwest low
pressure.

...Guidance/Predictability Assessment...

Guidance continues to show good agreement on the large scale upper
pattern and progression, but a lot of uncertainty in the details.
A leading shortwave into the West from a deepened low off the
Pacific Northwest coast shows good agreement, but there is
continued question on timing and amplitude of a deeper trough into
the West later in the week. The GFS has trended slightly deeper in
recent days, but the last several runs of the CMC continues to be
the outlier as it eventually spins up a closed low over the Central
Plains next weekend. Better cluster of guidance suggests this
should be more of an open wave. Ahead of this though, there remains
uncertainty in the details of a southern stream shortwave into the
Southern Plains and Midwest later this week, which has impacts on
heavy rainfall potential across Texas. Then by next weekend
guidance shows spread with a front that reaches into the Mid-
Atlantic, likely with a pronounced temperature gradient.

The WPC forecast today was able to use a blend of the latest
deterministic guidance for Wednesday and Thursday, amidst good
model agreement. Began incorporating the ECENS/GEFS by Friday/Day
5, eventually reaching a 50/50 split of deterministic/ensemble
means by Day 7. Did not include the CMC in the late period blend
due to the outlier solution described above. Overall, this approach
maintained good continuity with the previous WPC forecast.

...Weather/Hazards Highlights...

From Wednesday into Thursday night the most prominent heavy
rainfall focus should be over portions of Texas by Thursday as
moist southeasterly low level flow from the Gulf interacts with an
upper shortwave crossing northern Mexico. Some activity may
initiate in the Day 4 period near the Rio Grande Valley but the
signal is diffuse enough not to merit any risk area in the
Excessive Rainfall Outlook. By Day 5 there is a much stronger
signal, though with typical spread for where the heaviest rainfall
axis will be. Overall the best overlap of guidance exists over
southern Texas. The Day 5 ERO maintains a broader Marginal Risk
area, with no embedded Slight Risk depicted yet due to initially
dry ground conditions and guidance spread. Improved clustering for
location and amounts in the heavier part of the envelope could
eventually merit an upgrade. Elsewhere, consensus amounts along the
Pacific Northwest coast in association with the Wednesday-
Thursday system have generally decreased somewhat from 24 hours
ago, while the signal for a potential band of enhanced rainfall
over the Mid Mississippi Valley ahead of a warm front is too
diffuse to warrant a risk area yet on Day 5.

Precipitation will spread across northern and central parts of the
West late this week, with Plains low pressure and its trailing
front eventually pushing the Texas rainfall eastward while
spreading a broader shield of moisture across the central and east-
central U.S. Some wintry weather will be possible over far
northern latitudes but otherwise most precipitation should be in
the form of rain. How much snow falls over the northern Plains next
weekend will depend on how strongly the Plains/Upper Midwest
system develops, with low confidence in specifics at this time. The
next Pacific system may increase precipitation along the West
Coast by next Sunday.

The weak wave forecast to track off the Mid-Atlantic/New England
coast on Wednesday may produce some light precipitation early but
most likely just near the coast.

The strong upper ridge over the West into Wednesday will bring
well above normal temperatures to the region, with a broad area of
highs 10-20F above normal with locally higher anomalies. There will
also be potential for numerous daily records for highs/warm lows,
especially during Wednesday. As the upper ridge shifts eastward
with time, the West will cool down while already above normal
anomalies over the central U.S. will increase. Locations from the
northern-central Plains into Midwest should see one or two days of
highs reaching 20-25F or so above normal by Thursday-Friday, with
best potential for some daily records over the central High Plains
on Thursday. The East will see near to slightly below normal
temperatures Wednesday-Thursday and then increasing coverage of
highs 10-20F above normal Friday into the weekend. However a front
reaching the Northeast/Mid-Atlantic may define a sharp gradient
between this warmth and cooler readings just to the north.

Santorelli/Rausch


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