Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
438 AM EDT Fri Mar 28 2025

Valid 12Z Fri Mar 28 2025 - 12Z Sun Mar 30 2025

...Heavy rain and flash flooding remain possible along the western Gulf
Coast and into the Lower Mississippi Valley Friday...

...A couple rounds of winter weather including snow and possibly
significant ice accumulations expected into the weekend from the northern
Plains east through the Upper Midwest and the interior Northeast/New
England...

...Showers and thunderstorms, possibly severe, expected overnight Saturday
across portions of the Central/Southern Plains into the Middle Mississippi
Valley...

...Critical Fire Weather Risk for portions of the southern High Plains
Saturday...

Renewed rounds of showers and thunderstorms are expected Friday ahead of
an upper-level wave along the western Gulf Coast northeastward into the
Lower Mississippi Valley. While storm coverage and intensity are expected
to be lower compared to Thursday, a Slight Risk of Excessive Rainfall
(level 2/4) is in effect as plentiful Gulf moisture will still lead to
locally heavy rainfall and some scattered instances of flash flooding.
Additional storms will spread eastward along the central Gulf Coast on
Saturday, but the risk for flash flooding should remain more isolated.

Meanwhile, an upper-level trough with embedded shortwave energy will bring
precipitation chances across portions of the West, Plains, and Mississippi
Valley the next couple of days. Lower elevation rain (possibly mixed with
some snow) as well as higher elevation mountain snow are forecast across
the Pacific Northwest/northern California east to the northern Rockies
Friday, shifting focus into the northern/central Rockies Saturday. Little
to no snow accumulations are expected for lower elevations, but moderate
to heavy snowfall is forecast for the regional mountain ranges. Further
east, an embedded shortwave will help to strengthen/organize a low
pressure system over the Central Plains in the lee of the Rockies by early
Saturday. Moist southerly return flow will lead to an expanding area of
showers and thunderstorms, first north of a frontal boundary through the
central Plains during the day Saturday, with additional storms expected
along and ahead of the boundary from the central/southern Plains into the
Mississippi Valley Saturday night. Increasing shear as well as some
elevated instability along the boundary from the central/southern Plains
into the Middle Mississippi Valley may lead to some more potent, intense
thunderstorms. The Storm Prediction Center has outlined the region with a
Slight Risk of severe weather (level 2/5) mainly for the threat of large
hail. A more widespread, significant risk of severe weather including
large hail, damaging winds, and strong tornadoes is expected across much
of the Mississippi Valley Sunday.

To the north, a couple rounds of winter weather are expected in the colder
airmass north of a wavy frontal boundary extending from the northern
Plains east through the Northeast. An initial shortwave passing west to
east along the Canadian border over the Upper Midwest/Great Lakes will
bring a wintry mix of snow, sleet, and freezing rain on Friday. Snow is
most likely for locations close to the Canadian border and into the UP of
Michigan, with ice expected just to the south from northern North Dakota
east through northern Minnesota/Wisconsin and into the UP of Michigan.
While snow accumulations should remain light, significant ice
accumulations of greater than 0.25" will be possible, especially across
the UP of Michigan. The wave will move quickly eastward over the interior
Northeast/New England Friday night into Saturday, with light to moderate
snow expected along the Canadian border from Upstate New York into
northern New England/Maine. A swath of freezing rain is expected to the
south from Upstate New York into central New England with more potentially
significant accumulations greater than 0.25" possible. Also on Saturday,
the upper-level wave responsible for thunderstorms to the south will lead
to a swath of light to moderate snowfall from the northern Plains into the
Upper Midwest, with the chance for additional disruptive accumulating ice
from freezing rain. The snowfall is currently most likely from western
South Dakota northeast through central/northern Minnesota into northern
Wisconsin and the UP of Michigan, with ice most likely just to the south
of the snow band from central Minnesota east into northern Wisconsin, the
UP of Michigan, and the northern LP of Michigan. More significant ice
accumulations of greater than 0.25" will be possible.

Temperatures across much of the central and eastern U.S. will be well
above average heading into the weekend under the influence of upper-level
ridging. The greatest anomalies upwards of 30 to 40 degrees will be
focused form the central Plains northeastward into the Upper
Missouri/Mississippi Valley on Friday where highs into the mid- to upper
80s may tie/break records for the day. However, these temperatures will be
short lived for the northern Plains/Upper Midwest as a cold front pushing
through the region Saturday will bring temperatures down into the 30s and
40s. More broadly, highs from the Midwest to the Mid-Atlantic will be in
the 60s and 70s, with 70s and 80s from the Southern Plains east into the
Southeast. One exception to the above average temperatures will be along
the northern tier from the northern Plains east through the Upper
Midwest/Great Lakes and into the interior Northeast/New England where
highs will be much colder and in the 30s and 40s. Temperatures over the
West will generally be around average, with highs in the 50s for the
Pacific Northwest/Interior West, the 60s in California, and the 70s and
80s into the Southwest. The warm temperatures along with dry and breezy
conditions across portions of southern New Mexico and southwestern Texas
have led to a Critical Fire Weather Risk (level 2/3) from the Storm
Prediction Center Saturday.

Putnam


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
211 AM EDT Fri Mar 28 2025

Valid 12Z Mon Mar 31 2025 - 12Z Fri Apr 04 2025

...Overview...

A parade of systems should bring periods of active weather to much
of the U.S. next week. A cold front into the East next Monday
should bring widespread rain and thunderstorm chances, with some
locally heavy rain across the South. Another system into the West
should ultimately lead to a surface low emerging into the Plains
around midweek and tracking towards the Great Lakes. Widespread
moderate to heavy rain may accompany this second cold front. The
West should stay relatively cool underneath of almost persistent
troughing, while the central to eastern U.S. experiences periods of
normal to above normal temperatures.


...Guidance/Predictability Assessment...

A shortwave into the East/Northeast Monday-Tuesday show relatively
good agreement both on amplitude and timing. The guidance agrees
an upper low off the Northwest coast will send energy into the West
around Tuesday, but there remains some significant differences in
the evolution of this energy downstream. The GFS continues to be an
outlier in showing a faster and more compact energy into the
Plains on Wednesday with a more eastward track into the Northeast
on Thursday. The ECMWF and CMC (with agreement from the ensemble
means and AI models) suggests a more northerly track of the
shortwave into the Great Lakes, a result of much stronger upper
ridging over the western Atlantic and East Coast as compared to the
GFS. Another system enters the West late week but the GFS exhibits
issues offshore with an upper low/overall less blocky Pacific
pattern compared to consensus. By Friday, there is some agreement
the flow pattern could turn more amplified and active with a deep
Western Ridge and Eastern U.S. ridging.

Good enough agreement the first few days of the period allowed for
a general model compromise. Added in ensemble mean guidance in
favor of the GFS midweek and beyond given the general out of sync
pattern shown in the GFS. By day 7, used a 60/40 blend of the
ensemble means with the deterministic ECMWF and CMC. This helped
maintain good agreement with yesterdays WPC forecast as well.


...Weather/Hazards Highlights...

A cold front into the East should allow for increased rain and
convection across much of the Eastern Seaboard. The best chance for
locally heavy to excessive rainfall should be mostly confined to
parts of the Southeast where a marginal risk is in place for the
Day 4/Monday Excessive Rainfall Outlook. The Storm Prediction
Center also suggests strong to severe weather is possible from the
Southeast into the Mid-Atlantic as well on Monday.

Expect multiple systems to bring rain and higher elevation snow to
the West during the period, with rapidly increasing uncertainty in
the details after early next week. The best precipitation focus
looks to be across Northern California on Monday, so a marginal
risk was continued for tonights new Day 4 ERO. Trends in the
guidance show another possibly significant system into the West
mid-week accompanied by at least moderate precipitation. Leading
dynamics from the West should eventually support a central-eastern
U.S. system by Wednesday-Thursday, generating another episode of
meaningful precipitation over the eastern half of the country. Some
snow will be possible from the northern Plains into New England.

The warm sector ahead of the front crossing the eastern half of
the country into Monday will feature well above normal
temperatures. Expect plus 10-20F anomalies for highs and up to plus
20-25F anomalies for morning lows. Near to below normal readings
will progress eastward behind the eastern U.S. front, with
precipitation keeping some northern Plains to Great Lakes locations
5-10F or so below normal for highs into Tuesday. Temperatures may
rebound back above normal over the southern half of the Plains on
Wednesday with the warming trend spreading back into the East
thereafter. Periods of unsettled weather will keep the diurnal
spread over the West Coast states more narrow than usual, with cool
highs and near or slightly above normal lows.

Santorelli


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
234 AM EDT Fri Mar 28 2025

Valid 00Z Sat 29 Mar 2025 - 00Z Sat 05 Apr 2025

An upper ridge over Hawaii should linger into the weekend
bringing weaker trades and lighter rainfall. By next week, the
ridge should slowly shift eastward as an amplified trough or upper
low holds north of the state within an overall blocky pattern.
There is a lot of spread in the guidance still for whatever
develops north of the state, with the better consensus suggesting
a deep and fairly stationary upper low. The latest GFS runs
however have a more strung out upper trough and is not the favored
solution at this point. The cold front for this system may
eventually reach close to the northern islands allowing for
strengthening southerly winds. Precipitation chances should
increase as well, but guidance shows the heaviest precipitation
should remain west of the island chain, at least through next
week.

Santorelli

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
850 PM EDT Thu Mar 27 2025
Day 1
Valid 01Z Fri Mar 28 2025 - 12Z Fri Mar 28 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTH-CENTRAL TEXAS AND THE MIDDLE/LOWER TEXAS GULF COAST...

...South Texas...
Maintained the Moderate Risk area of excessive rainfall in the face
of a complicated and messy forecast going through the rest of the
night across portions of South Texas through the Middle Texas Gulf
Coast but potential exists for numerous flash floods, some of
which. Adjustments were made to the outlook areas based on radar
and satellite trends through the late afternoon and early evening
and changes in Flash Flood Guidance over the past 24 hours. For
this update, the western boundary of the Moderate Risk was adjusted
eastward...but adjustments were tempered by guidance which showed
at least some potential for renewed convection associated with a
wave moving out of Mexico later tonight. Mesoscale Precipitation
Discussion 090 was issued just a bit ago to cover the ongoing and
near- term flash flood threat and a convective complex developing
and tracking east/northeast through South Texas. While instability
remained modest, a better shear environment and an increase in the
PWs should support greater storm organization and higher rain
rates. There are some suggestions for repeating/training clusters,
particularly in the southern extent of the updated Moderate Risk
area, where localized higher end additional QPF is possible (4-6").

This may result in numerous flash floods and locally significant
flooding into tonight. The previous discussion follows...

Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
415 AM EDT Fri Mar 28 2025
Day 1
Valid 12Z Fri Mar 28 2025 - 12Z Sat Mar 29 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE UPPER TEXAS COAST THROUGH SOUTHWEST LOUISIANA...

An inherited Slight risk area was maintained (and adjusted) once
again for this update, as a slow-moving mid-upper trough will push
the area of most favorable deep-layer forcing (upper divergence and
DPVA) farther east along the Gulf Coast. However, considerably
uncertainty remains (especially for an initial Day 1 outlook) as
much is dependent on the evolution of convection this morning, as
convection continues to consolidate farther south than virtually
all of the guidance indicated at this time yesterday (resulting in
the heaviest rainfall totals of 6"+ over the past 24-48 hours
occurring over far South TX). Should a similar error occur today,
a Slight risk may well not verify (as the consolidating MCS at the
time of writing over far South TX will propagate offshore and may
prevent critically necessary moisture flux transport northward into
the Gulf coast, as best depicted by the 00z HRRR). In addition,
attributing to a lower risk (Slight) compared to the previous days
(Moderate) will be the weakening low-level flow, which given the
more limited deep-layer shear, would more likely result in more
effective convective outflows and thus shorter duration of the more
intense updrafts and heavier rainfall cores (as well as generally
drier antecedent conditions).

However, should more intense convection initiate and sustain
itself farther north (as much of the rest of the 00z HREF
indicates), then localized totals of 3-6"+ totals will be possible
from Southeast TX and the Upper TX coast through much of
southeastern LA (per 00z HREF PMM QPF and associated 40-km
neighborhood probabilities for 3" and 5" exceedance of ~30-60% and
~20-40%, respectively). Meteorological factors supporting this
potential include favorable synoptic-scale forcing (particularly
the continued impressive divergence aloft), precipitable water
values between 1.75-2.00", and CAPE building to 1000-1500 J/kg.
These same factors may still fuel intense convection offshore which
ultimately fail to materialize further inland, thus the Slight
risk is considered to be conditional. On that note, the Marginal
risk was also expanded southwestward to include South TX, given the
ongoing flooding and low-end potential for convective
redevelopment once again with daytime heating (though this
convection should be much less intense with the bulk of the forcing
shifting eastward).

Churchill


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
415 AM EDT Fri Mar 28 2025
Day 2
Valid 12Z Sat Mar 29 2025 - 12Z Sun Mar 30 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL GULF COAST...

A continuation of the decreasing flash flood risk is expected from
Day 1 into Day 2, as ensemble guidance indicates the potential for
localized totals of 1-3" (mostly concentrated near the Gulf Coast
where FFGs are rather high). The limited inherited Marginal risk
area was maintained for this update, as forcing and instability
continue to look rather minimal (and most deterministic guidance at
this point indicates localized totals of less than 1" for the most
part, including the new WPC forecast, but decided to maintain the
Marginal for at least one more cycle to allow for new CAM data).
Any localized flash flood threat should mostly be confined closer
to the Gulf Coast (and limited to more sensitive urban areas).

Churchill


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
415 AM EDT Fri Mar 28 2025
Day 3
Valid 12Z Sun Mar 30 2025 - 12Z Mon Mar 31 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS...

A much broader inherited Marginal risk area (relative to Day 2) has
been largely maintained (and expanded a bit), as multiple shortwave
troughs emerging from the Intermountain West and phase with the
polar jet and an associated longwave trough. This complex
interaction is expected to result in a broad area of convection
across much of the eastern CONUS, including portions of the MS, TN,
and OH Valleys. Despite the complexity of the synoptic and
mesoscale details, global models are in fairly good agreement in
indicating a convection breaking out across a broad warm sector
(characterized by PWATs of 1.5-2.0", SB CAPE of 1000-2000 J/kg, and
effective bulk shear of 40-60 kts). Most deterministic solutions
depict 1-3" localized totals (with 2-3" amounts most commonly
located farther south across the Lower MS Valley and Mid-South,
where better instability and moisture tend to be located) with both
the GEFS and ECENS indicating 2" exceedance potential (with the
GEFS favoring portions of the Mid-South from north MS into West and
Middle TN, while the ECENS favors locations farther southwest into
the MS Delta). These types of probabilities from the ensemble
guidance suggest that CAMs may well depict 2-4" localized totals,
and a targeted Slight risk introduction may be necessary in
subsequent outlooks (once better ensemble agreement and/or a
strengthening trend is more evident in the global guidance).

Churchill

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
211 AM EDT Fri Mar 28 2025


A cold front into the East should allow for increased rain and
convection across much of the Eastern Seaboard. The best chance for
locally heavy to excessive rainfall should be mostly confined to
parts of the Southeast where a marginal risk is in place for the
Day 4/Monday Excessive Rainfall Outlook. The Storm Prediction
Center also suggests strong to severe weather is possible from the
Southeast into the Mid-Atlantic as well on Monday.

Expect multiple systems to bring rain and higher elevation snow to
the West during the period, with rapidly increasing uncertainty in
the details after early next week. The best precipitation focus
looks to be across Northern California on Monday, so a marginal
risk was continued for tonights new Day 4 ERO. Trends in the
guidance show another possibly significant system into the West
mid-week accompanied by at least moderate precipitation. Leading
dynamics from the West should eventually support a central-eastern
U.S. system by Wednesday-Thursday, generating another episode of
meaningful precipitation over the eastern half of the country. Some
snow will be possible from the northern Plains into New England.

The warm sector ahead of the front crossing the eastern half of
the country into Monday will feature well above normal
temperatures. Expect plus 10-20F anomalies for highs and up to plus
20-25F anomalies for morning lows. Near to below normal readings
will progress eastward behind the eastern U.S. front, with
precipitation keeping some northern Plains to Great Lakes locations
5-10F or so below normal for highs into Tuesday. Temperatures may
rebound back above normal over the southern half of the Plains on
Wednesday with the warming trend spreading back into the East
thereafter. Periods of unsettled weather will keep the diurnal
spread over the West Coast states more narrow than usual, with cool
highs and near or slightly above normal lows.

Santorelli

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
211 AM EDT Fri Mar 28 2025


A cold front into the East should allow for increased rain and
convection across much of the Eastern Seaboard. The best chance for
locally heavy to excessive rainfall should be mostly confined to
parts of the Southeast where a marginal risk is in place for the
Day 4/Monday Excessive Rainfall Outlook. The Storm Prediction
Center also suggests strong to severe weather is possible from the
Southeast into the Mid-Atlantic as well on Monday.

Expect multiple systems to bring rain and higher elevation snow to
the West during the period, with rapidly increasing uncertainty in
the details after early next week. The best precipitation focus
looks to be across Northern California on Monday, so a marginal
risk was continued for tonights new Day 4 ERO. Trends in the
guidance show another possibly significant system into the West
mid-week accompanied by at least moderate precipitation. Leading
dynamics from the West should eventually support a central-eastern
U.S. system by Wednesday-Thursday, generating another episode of
meaningful precipitation over the eastern half of the country. Some
snow will be possible from the northern Plains into New England.

The warm sector ahead of the front crossing the eastern half of
the country into Monday will feature well above normal
temperatures. Expect plus 10-20F anomalies for highs and up to plus
20-25F anomalies for morning lows. Near to below normal readings
will progress eastward behind the eastern U.S. front, with
precipitation keeping some northern Plains to Great Lakes locations
5-10F or so below normal for highs into Tuesday. Temperatures may
rebound back above normal over the southern half of the Plains on
Wednesday with the warming trend spreading back into the East
thereafter. Periods of unsettled weather will keep the diurnal
spread over the West Coast states more narrow than usual, with cool
highs and near or slightly above normal lows.

Santorelli

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
348 AM EDT Fri Mar 28 2025

Valid 12Z Fri Mar 28 2025 - 12Z Mon Mar 31 2025


...West Coast through Northern/Central Rockies...
Days 1-3...

A deep, slow-moving low centered off of the Northwest coast will
gradually fill as it lifts to the north over the next day or so.
However, even as the system lifts out, snow levels across the
Northwest will continue to drop into early Saturday as a series of
shortwave troughs digging south of the low move inland. This will
bring levels down to around 3000-4000ft in the Washington and
Oregon Cascades today, before dropping below 3000ft with the
passage of a well-defined trough Saturday morning. Further to the
south, snow levels starting above 5000ft in the Shasta- Siskiyou
region and the northern Sierra Nevada will drop below 4000ft in
many locations before precipitation ends. Although snow levels will
be on the decline, so will the onshore moisture advection, with
guidance showing IVTs dropping off after the start of the period
and a break in precipitation on Day 2. The heaviest precipitation
is expected to center across southern Oregon and far northern
California, where the best moisture and forcing is expected to
focus later today. By early Saturday, precipitation is expected to
diminish from south to north as an upper ridge moves inland in the
wake of the previously-noted trough. Day 1 WPC probabilities for
over 8 inches of snow are 60-80% for parts of the Olympics,
Cascades, Klamath Mountains, and the northern Sierra Nevada. Then,
the next system approaches the West Coast by Day 3 as the closed
upper low off the Pacific Northwest reloads from energy dropping
southward across the eastern Aleutians. This leads to additional
moderate onshore flow amid initial snow levels around 4000-5000ft
(up to 6000ft in the central/southern Sierra). WPC probabilities
for at least 8 inches of additional snow on Day 3 across the Sierra
and northern CA ranges are 40-70%, but are expected to increase as
the bulk of the precipitation moves onshore after 12z/Mon.

Meanwhile, moisture spreading inland across the northern Great
Basin and Rockies will begin to interact with a developing low-to-
mid level baroclinic zone and periods of enhanced forcing
associated with the inland moving troughs to produce light-to-
moderate precipitation, including mountain snow from the northern
to the central Rockies. Precipitation coverage is expected to
increase Friday night, with unsettled weather continuing through
the weekend and ending with a weak area of convergence on Sunday
between western MT and northern CO. Snow levels beginning above
5000ft in the northern Rockies Friday night are forecast to dip
below 4000ft in some location by late Saturday. In the central
Rockies, snow levels will drop to 7000-8000ft in the Colorado
ranges and around 5000-6000ft across northern Utah. WPC Days 1-2
probabilities for at least 8 inches of snow are generally 50-70%
from the Blue Mts of northwest OR through the central ID ranges
into southwest MT, as well as the Absarokas and Wind River Range.
These probs also extend south to the Park Range and Medicine Bow
Mountains of CO/WY.


...Northern Minnesota through the Northern Great Lakes...
Day 1...

A longwave upper trough in the West working in tandem with the
right-entrance region of a 250mb jet streak this afternoon will
foster large-scale ascent aloft throughout the Upper Midwest and
Great Lakes. The upper trough and a strong low-level ridge of high
pressure off the Southeast coast supports a strengthening SWrly
low-mid level flow regime that results in exceptional warm-air
advection (WAA) for the regions reference above. This WAA will
clash with a cold Canadian air-mass anchored by a 1030mb+ high
pressure system over Ontario and Quebec. The result is 925-700mb
FGEN that produces a narrow band of disruptive snow (primarily
north of the U.S.-Canadian border) and ice starting as early as
this morning across far northern MN, but becoming more widespread
across northern MN/WI/MI by this evening. The strong WAA over sub-
freezing boundary layer temps is a favorable setup for freezing
rain/sleet that will make for hazardous travel conditions even
where only light amounts occur. WPC probabilities for at least
0.25" of ice accretion on Day 1 is medium (50-70%) across the
eastern U.P. and northern L.P. of MI, with 20-40% chances extending
westward across the U.P. and into the MN Arrowhead.


...Northeast...
Days 1-3...

This same system is expected to spread a narrow swath of heavy snow
and area of mixed precipitation into the Interior Northeast and New
England by late D1, but with wintry precipitation lingering for
several days. This long-duration event made possible by a trailing
shortwave and developing central U.S. trough which will continue to
reinforce a favorable jet pattern for upper divergence as well as
sufficient mid-upper level moisture content. However, the snowfall
threat peaks early Saturday morning as a jet max passes to the
north of New England and 925-850mb WAA is at it's strongest. 00z
HREF depicts 30-40% chances for 1-2"/hr snowfall rates around
13z/Sat across far northern NY and northern VT/NH. WPC snowfall
probabilities for at least 6 inches of snow on days 1-2 are medium
(40-60%) from northern NH, VT, and into central ME.

South of this heavy snow threat between the northern Adirondacks
and much of central/southern VT and NH, 850-750mb warm nose allows
for a transition area of sleet/freezing rain. After the brief
burst of heavier precip early Sat, forcing weakens and there is
left a weak stream of moisture overrunning a CAD signature due to a
strong 1030mb High situated over the James Bay. This potentially
significant icing threat is expected to linger through Sun morning
until the surface low across the Midwest begins to strengthen and
push warmer air northward across New England by Day 3. However, the
CAD signature in place will continue to support freezing rain
across the typically colder valley locations and areas banked along
the Green/White mountains. WPC probabilities for the entire
forecast period (ending 12z/Mon) are high (70-80%) for at least
0.25" of ice accretion from the NY border with eastern Ontario
through the northern Adirondacks and into central VT/NH.
Probabilities for at least 0.5" also impressive and 40-60% (highest
across western Jefferson county of NY).


...Northern High Plains through the Upper Midwest/Great Lakes...
Days 2-3...

A shortwave trough moving into the Southwest today is expected to
lift northeast from the Four Corners across the central Rockies and
into the High Plains Saturday morning. Moisture fed into an area
of strong ascent generated in part by favorable upper jet forcing
and potent 700mb closed low will support precipitation north of an
associated surface low that will develop and move east of the
Colorado Rockies. Rain changing to snow is expected from
southeastern Montana and northeastern Wyoming into parts of
western to central SD and NE. The highest amounts are forecast to
fall across the Black Hills, but locally heavy totals are also
possible eastward along southern SD and north- central NE. WPC
probabilities for at least 4 inches are 40-70% across the Black
Hills and 10-30% into south-central SD and north- central NE.

As this system develops further Saturday night through Day 3,
increasing WAA and a blossoming precipitation shield is expected to
spread into the Upper Midwest and Great Lakes. Surface low pressure
is expected to track along along the 925-850mb front that remains
stationary from NE and southern MN on east through Michigan. There
still remains some discrepancies in guidance on the
evolution/strength
of this storm system, but there is a growing consensus with the
00z guidance on the synoptic scale. The GFS finally has a more
amplified solution (in line with the CMC and ECMWF), which paints
an axis of snow fall extending east-northeast from SD through
central MN into northern WI and the MI U.P.. There is also higher
confidence in yet more freezing rain/sleet from northern and
central WI on east through northern Michigan as high pressure
remains locked in place over James Bay and cold northeast flow
continues to filter into the Upper Midwest/Great Lakes. This is a
very favorable setup for potentially significant freezing rain from
northern WI through northern MI, especially for late-March. WPC
probabilities show moderate chances (30-60%) for ice accumulations
>0.25" in these areas with low chances (10-30%) for >0.5" across
parts of northern WI. In terms of snowfall, WPC probabilities show
moderate chances (30-60%) for snowfall totals >6" in far northern
WI and the western MI U.P..

Snell

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
211 AM EDT Fri Mar 28 2025

Valid 12Z Mon Mar 31 2025 - 12Z Fri Apr 04 2025

...Overview...

A parade of systems should bring periods of active weather to much
of the U.S. next week. A cold front into the East next Monday
should bring widespread rain and thunderstorm chances, with some
locally heavy rain across the South. Another system into the West
should ultimately lead to a surface low emerging into the Plains
around midweek and tracking towards the Great Lakes. Widespread
moderate to heavy rain may accompany this second cold front. The
West should stay relatively cool underneath of almost persistent
troughing, while the central to eastern U.S. experiences periods of
normal to above normal temperatures.


...Guidance/Predictability Assessment...

A shortwave into the East/Northeast Monday-Tuesday show relatively
good agreement both on amplitude and timing. The guidance agrees
an upper low off the Northwest coast will send energy into the West
around Tuesday, but there remains some significant differences in
the evolution of this energy downstream. The GFS continues to be an
outlier in showing a faster and more compact energy into the
Plains on Wednesday with a more eastward track into the Northeast
on Thursday. The ECMWF and CMC (with agreement from the ensemble
means and AI models) suggests a more northerly track of the
shortwave into the Great Lakes, a result of much stronger upper
ridging over the western Atlantic and East Coast as compared to the
GFS. Another system enters the West late week but the GFS exhibits
issues offshore with an upper low/overall less blocky Pacific
pattern compared to consensus. By Friday, there is some agreement
the flow pattern could turn more amplified and active with a deep
Western Ridge and Eastern U.S. ridging.

Good enough agreement the first few days of the period allowed for
a general model compromise. Added in ensemble mean guidance in
favor of the GFS midweek and beyond given the general out of sync
pattern shown in the GFS. By day 7, used a 60/40 blend of the
ensemble means with the deterministic ECMWF and CMC. This helped
maintain good agreement with yesterdays WPC forecast as well.


...Weather/Hazards Highlights...

A cold front into the East should allow for increased rain and
convection across much of the Eastern Seaboard. The best chance for
locally heavy to excessive rainfall should be mostly confined to
parts of the Southeast where a marginal risk is in place for the
Day 4/Monday Excessive Rainfall Outlook. The Storm Prediction
Center also suggests strong to severe weather is possible from the
Southeast into the Mid-Atlantic as well on Monday.

Expect multiple systems to bring rain and higher elevation snow to
the West during the period, with rapidly increasing uncertainty in
the details after early next week. The best precipitation focus
looks to be across Northern California on Monday, so a marginal
risk was continued for tonights new Day 4 ERO. Trends in the
guidance show another possibly significant system into the West
mid-week accompanied by at least moderate precipitation. Leading
dynamics from the West should eventually support a central-eastern
U.S. system by Wednesday-Thursday, generating another episode of
meaningful precipitation over the eastern half of the country. Some
snow will be possible from the northern Plains into New England.

The warm sector ahead of the front crossing the eastern half of
the country into Monday will feature well above normal
temperatures. Expect plus 10-20F anomalies for highs and up to plus
20-25F anomalies for morning lows. Near to below normal readings
will progress eastward behind the eastern U.S. front, with
precipitation keeping some northern Plains to Great Lakes locations
5-10F or so below normal for highs into Tuesday. Temperatures may
rebound back above normal over the southern half of the Plains on
Wednesday with the warming trend spreading back into the East
thereafter. Periods of unsettled weather will keep the diurnal
spread over the West Coast states more narrow than usual, with cool
highs and near or slightly above normal lows.

Santorelli


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