Weather Prediction Center

National Oceanic and Atmospheric Administration

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

Valid 00Z Sat Mar 29 2025 - 00Z Mon Mar 31 2025

...The heavy rain and flash flood threat moves away from South Texas and
into East Texas and Louisiana this afternoon into tonight...

...Much above average temperatures from the Central to Southern Plains,
east into the eastern U.S., while below average temperatures stretch along
the northern tier from the Northern Plains into northern New England...

...Winter weather threats continue along the northern tier from the
Northern Plains, into the Upper Mississippi Valley, Upper Great Lakes, far
northern NY State and central to northern New England...

...Severe weather threat across the Southern to Central Plains into the
Lower Missouri Valley on Saturday and through the Lower to Mid Mississippi
Valley, Tennessee Valley and Ohio Valley on Sunday...

...A brief period of drier weather for the Pacific Northwest into Northern
California on Saturday before more rains return to this area Sunday...


After several days of very heavy rainfall across South Texas, where
rainfall totals of 6 to 12"+ have been observed, the upper level
disturbance that has been producing the wet weather will move eastward
into East Texas and Louisiana tonight into Saturday. This will shift the
threat of heavy rainfall and flash flooding into East Texas and across
Louisiana over next 24 hours. Rainfall totals are not expected to be as
extreme as was observed over South Texas. Still, heavy rains may produce
localized flooding from this afternoon into Friday night from East Texas
into Louisiana where flood watches are currently in effect.

Much of the nation to the east of the Rockies will see much above average
temperatures this weekend. Much above average temperatures are expected
to stretch from the Central to Southern Plains, eastward into much of the
Mississippi Valley, Ohio Valley and large portions of the east coast.
Colder than average temperatures are expected to persist across the
northern tier from the Northern Plains into the Upper Mississippi Valley,
Upper Great Lakes, far northern NY State and into central to northern New
England. In addition to the colder than average temperatures across the
northern tier, there will be potential for two rounds of accumulating snow
and ice. The initial round will spread wintry weather from northern
Minnesota into the Upper Peninsula of Michigan, far northern NY State and
northern New England through Friday night and into continuing Saturday
from the Upper Peninsula of Michigan, far northern NY State into northern
New England. This will be followed by a second batch of wintry weather
developing across the Central to Northern Plains Saturday and moving into
the Upper Mississippi Valley/Upper Great Lakes Saturday night/early Sunday
and back across portions of central to northern New England during the day
on Sunday. Snow totals from the two events may reach as high as 6 to 8
inches across portions of the Upper Peninsula of Michigan, far northern NY
State, northern Vermont, northern New Hampshire, and western Maine. Ice
accumulations of .25-.50"+ are possible from northern Wisconsin, across
the northern Lower Peninsula of Michigan, eastern Upper Peninsula of
Michigan, northern NY State and across much of Vermont and New Hampshire.

The colder than average air over the northern tier will begin to surge
southward into the Central Plains on Saturday and Southern Plains on
Sunday. Thunderstorms are expected to become increasingly active along
and ahead of this front this weekend. This will bring the potential for
severe weather on Saturday across the Southern to Central Plains into the
Lower Missouri Valley and through a larger region from the Lower to Middle
Mississippi Valley, Tennessee Valley and Ohio Valley on Sunday.

After several days of wet weather from the Pacific Northwest into Northern
California, drier conditions are expected Saturday. However, this will be
short lived as the next system moving off the northeast Pacific will
spread the threat of additional rains into northern California and the
Pacific Northwest on Sunday.

Oravec


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
313 PM EDT Fri Mar 28 2025

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


...Emerging heavy rain and severe threat for Lower Mississippi,
Tennessee, and Ohio Valleys for midweek and beyond...


...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 will accompany this second cold front in the
east-central CONUS, while late-season snow is possible in the
northern tier. 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...

Model guidance is reasonably agreeable at the start of the medium
range period, with a shortwave moving through the Midwest to
Northeast Monday-Tuesday (though the 00Z UKMET was a slow outlier)
and an upper low offshore of the Pacific Northwest. The latter will
send energy eastward reaching the Plains by midweek, potentially
forming a weak closed low, along with a reasonably strong surface
low that shows typical timing and placement differences as it
tracks from the central U.S. to the Upper Great Lakes by Thursday.
Upper ridging in the East and mean troughing across the West looks
to set up by later week. The troughing across the West has shown
the most model differences over the past couple of days. Finally
the 06Z GFS and now the newer 12Z GFS is showing more agreement
with the larger ECMWF/CMC cluster of guidance by around midweek
(the 00Z GFS and older GFS runs were pulling significant amounts of
energy and troughing into the eastern Pacific at that time).
However, the 00Z ECMWF appeared to pull a different shortwave
southward along the West Coast Thursday-Friday, which really only
the Pangu AI/ML model agreed with--other AI models and the CMC
showed the trough axis farther east. So did not favor the 00Z EC as
much during the late period.

Thus the WPC forecast was based on a blend initially favoring the
00Z ECMWF with lesser proportions of the 06Z GFS and 00Z CMC early
in the period. As the period progressed, lessened the proportion of
deterministic models in favor of the ensemble means to half Day 6
and more Day 7 as spread increased. Notable edits to the NBM
included lowering QPF in the West where the older GFS runs that
were not favored seemed to be contributing heavy QPF into the blend
while the EC/CMC and their means showed less. QPF increased from
continuity in the east-central U.S. as models started to be more
agreeable with heavy amounts for the latter half of next week.


...Weather/Hazards Highlights...

A cold front moving into the East should allow for widespread rain
and thunderstorms across much of the Eastern Seaboard on Monday.
The best chance for locally heavy to excessive rainfall should be
over parts of the Southeast where more instability will allow for
heavier rain rates, so a Marginal Risk remains in place for the Day
4/Monday Excessive Rainfall Outlook. Locally heavy rain may also
occur farther north from the Appalachians to Mid-Atlantic and
Northeast. 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. The best precipitation focus looks to
be across Northern California on Monday, and a Marginal Risk
remains in place for coastal regions into far southwest Oregon for
the Day 4/Monday ERO with a weak atmospheric river. Precipitation
with some higher elevation snow will spread through the
Intermountain West and Rockies Monday-Tuesday, while the pattern
also supports high winds focused from the central Great Basin into
the central Rockies. As the upper trough in the West reloads into
mid and late next week, it will support a surface low pressure
system forming in the central U.S. by Wednesday with widespread
thunderstorms across the east-central U.S. in its warm sector. SPC
indicates another round of severe weather from the south-central
U.S. into the Mid-South and Ohio Valley on Wednesday, and heavy
rainfall is also a concern. The low is forecast to move
northeastward Thursday-Friday but leave a wavy front behind across
the Mid-South to Ohio Valley, causing likely multiple rounds of
heavy rain over similar areas, enhancing flooding concerns.
Additionally, some April snow is likely on the backside of the low
across the northern Plains and Upper Midwest Tuesday-Wednesday and
spreading into the Interior Northeast Wednesday-Thursday. Meanwhile
some modest rain and snow could continue across the West
throughout next week, though with rapidly increasing uncertainty in
the details after early next week.

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 normal lows.


Tate/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
852 PM EDT Fri Mar 28 2025
Day 1
Valid 01Z Sat Mar 29 2025 - 12Z Sat Mar 29 2025

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

01Z Update: Maintained the Slight Risk for the Day 1 ERO Update for
portions of the Upper Texas coast region and areas inland across
southeast Texas/southwest Louisiana while trimming the Slight and
Marginal risk areas farther south. Trends in satellite and radar
imagery showed a vort max lifting northeastward which was helping
to support the area of rain approaching the Texas/Louisiana border.
The 28/18Z HREF neighborhood probabilities still focused on
southwest Louisiana into the overnight hours for 1- and 2-inch
per hour rates with 25 pct chances of 3 inch per hour totals in the
29/00Z - 29/12Z period. Towards the coastal areas...the
probabilities increase to more than inland and more than 40
percent along the Louisiana coast. In addition...latest radar and
satellite imagery was beginning to show that additional convection
was percolating just off the Upper Texas coast...similar to what
the HRRR started suggesting earlier in the day.
Consequently...maintained the Slight Risk area a bit farther south
and west than the HREF was showing. An isolated...but
persistent...cell over Kenedy county such that we maintained the
Marginal risk that far south for the time being.

Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
852 PM 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. Any localized flash flood threat should mostly be
confined closer to the Gulf Coast (and limited to more sensitive
urban areas).

Churchill/Taylor


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
852 PM 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...

20Z Update:

A broad area of convection is expected Sunday into Sunday night
with a pair of shortwaves moving into the Central U.S. during the
period. The forcing for ascent and associated moisture transport
suggests several areas of heavier precipitation from the Lower MS
Valley northward into the Ohio Valley. The overlap of the best
instability and forcing right now points toward portions of the TN
Valley into the Mid South region and this coincides where the
ensembles show the greatest potential for some higher rainfall
totals (2-4"). Ultimately, a Slight Risk may be needed in future
updates if confidence increases but for now, confidence in exact
placement is low as well as the forward progression of convection
that may be just fast enough to limit duration of heavy rainfall at
any location for too long. Previous discussion follows...

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/Taylor

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
313 PM EDT Fri Mar 28 2025


A cold front moving into the East should allow for widespread rain
and thunderstorms across much of the Eastern Seaboard on Monday.
The best chance for locally heavy to excessive rainfall should be
over parts of the Southeast where more instability will allow for
heavier rain rates, so a Marginal Risk remains in place for the Day
4/Monday Excessive Rainfall Outlook. Locally heavy rain may also
occur farther north from the Appalachians to Mid-Atlantic and
Northeast. 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. The best precipitation focus looks to
be across Northern California on Monday, and a Marginal Risk
remains in place for coastal regions into far southwest Oregon for
the Day 4/Monday ERO with a weak atmospheric river. Precipitation
with some higher elevation snow will spread through the
Intermountain West and Rockies Monday-Tuesday, while the pattern
also supports high winds focused from the central Great Basin into
the central Rockies. As the upper trough in the West reloads into
mid and late next week, it will support a surface low pressure
system forming in the central U.S. by Wednesday with widespread
thunderstorms across the east-central U.S. in its warm sector. SPC
indicates another round of severe weather from the south-central
U.S. into the Mid-South and Ohio Valley on Wednesday, and heavy
rainfall is also a concern. The low is forecast to move
northeastward Thursday-Friday but leave a wavy front behind across
the Mid-South to Ohio Valley, causing likely multiple rounds of
heavy rain over similar areas, enhancing flooding concerns.
Additionally, some April snow is likely on the backside of the low
across the northern Plains and Upper Midwest Tuesday-Wednesday and
spreading into the Interior Northeast Wednesday-Thursday. Meanwhile
some modest rain and snow could continue across the West
throughout next week, though with rapidly increasing uncertainty in
the details after early next week.

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 normal lows.


Tate/Santorelli

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
313 PM EDT Fri Mar 28 2025


A cold front moving into the East should allow for widespread rain
and thunderstorms across much of the Eastern Seaboard on Monday.
The best chance for locally heavy to excessive rainfall should be
over parts of the Southeast where more instability will allow for
heavier rain rates, so a Marginal Risk remains in place for the Day
4/Monday Excessive Rainfall Outlook. Locally heavy rain may also
occur farther north from the Appalachians to Mid-Atlantic and
Northeast. 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. The best precipitation focus looks to
be across Northern California on Monday, and a Marginal Risk
remains in place for coastal regions into far southwest Oregon for
the Day 4/Monday ERO with a weak atmospheric river. Precipitation
with some higher elevation snow will spread through the
Intermountain West and Rockies Monday-Tuesday, while the pattern
also supports high winds focused from the central Great Basin into
the central Rockies. As the upper trough in the West reloads into
mid and late next week, it will support a surface low pressure
system forming in the central U.S. by Wednesday with widespread
thunderstorms across the east-central U.S. in its warm sector. SPC
indicates another round of severe weather from the south-central
U.S. into the Mid-South and Ohio Valley on Wednesday, and heavy
rainfall is also a concern. The low is forecast to move
northeastward Thursday-Friday but leave a wavy front behind across
the Mid-South to Ohio Valley, causing likely multiple rounds of
heavy rain over similar areas, enhancing flooding concerns.
Additionally, some April snow is likely on the backside of the low
across the northern Plains and Upper Midwest Tuesday-Wednesday and
spreading into the Interior Northeast Wednesday-Thursday. Meanwhile
some modest rain and snow could continue across the West
throughout next week, though with rapidly increasing uncertainty in
the details after early next week.

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 normal lows.


Tate/Santorelli

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

Valid 00Z Sat Mar 29 2025 - 00Z Tue Apr 01 2025


...Northern/Central Rockies...
Days 1/2...

A shortwave trough ejecting from the remnant/occluded low off WA
crosses the PacNW tonight and the Great Basin through Saturday
night. This maintains moisture spreading 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 tonight, with unsettled weather continuing into Sunday
with a weak area of convergence on Sunday between western MT and
northern CO. Snow levels beginning above 5000ft in the northern
Rockies 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 Day 2 probabilities for >8" of snow are
generally 40-70% over southwest MT, the Absarokas and Wind River
Range, and the Park Range and Medicine Bow Mountains of northern
CO.


...South Dakota, Minnesota, and Northern Wisconsin/Michigan...
Days 1/2...

...Back to back impactful winter systems through Sunday...

Inverted trough from central High Plains up through lower MI
persists tonight as an upper low approaching the northern Rockies
this afternoon allows lee-side cyclogenesis to focus over western
KS through Saturday morning with a more potent low track from KS to
MI Saturday through Sunday evening.

A very strong baroclinic zone (it's currently low 80s in southwest
MN and mid 20s in the Arrowhead) maintains cold over northern
MN/WI/the U.P. through this weekend while warm air rides over the
boundary to the south. Ongoing wintry mix continues tonight with a
slow southward shift. Day 1 ice probs for >0.1" additional after
00Z is about 20% over far northern WI into the western U.P., but
50-80% over far northeast WI and central/eastern U.P. and northern
L.P. with 70% probs for >0.25" over the northern L.P.

The developing low track over KS on Saturday allows
fgen/deformation banding to develop over over southwest SD into
northwest Neb. Localized banding should overcome the strong March
diurnal insolation, but that should be fairly narrow. Day 1.5 snow
probs for >4" are 30-60% mainly over south-central SD and the Black
Hills.

The impactful wintry weather continues resumes Saturday night over
MN/WI/MI as snow bands intensify in the increasing right entrance
jet dynamics and the comma head forcing from the low tracking over
IA. These snow bands are increasingly likely over north-central MN,
far northern WI and western/central U.P. which would put heavy wet
snow over areas currently getting ice accretion. Day 2 snow probs
for >4" are 30-60% from the Sisseton Hills of northeast SD through
the central U.P. and North Shore of MN with 50-70% probs for >6"
over far northern WI through the Keweenaw Peninsula. The wintry mix
swath is just south of the snow with accumulating sleet and ice
expected to expand south as the cold air wins/advances. Day 2 ice
probs for >0.25" are 30-70% from central MN through northern
WI/southern/eastern U.P. and the northern L.P. with a max around
80% in northeast WI.


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

...Prolonged wintry mix over northern NY/New England through
Sunday...

The inverted trough causing a wintry mix over the northern Great
Lakes today spreads east over northern NY and central New England
this evening with the strong baroclinic zone maintaining fgen
precip/wintry mix through this weekend for portions of New
England. The approaching low crosses New England on Monday.

The heavy snowfall threat peaks late tonight from Lake Champlain
through northern NH into southern Maine as a jet max passes to the
north of New England and 925-850mb WAA is strongest. 12Z HREF
depicts 30-40% chances for 1"/hr snowfall rates from 06Z to 13Z
Saturday across the northern tip of NY and northern VT/NH. Day 1
WPC snowfall probabilities for >6" are 30-60% mainly over the
northern Greens and the Presidential Range of NH.

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 zone 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 Sunday until
the surface low across the Midwest begins to strengthen and push
warmer air northward across New England by Sunday evening.
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. Day 1 WPC
probabilities for >0.25" ice (ending 00Z/Sun) are 40-70% for the
Thousand Islands area, the northern Adirondacks and south-central
VT/NH. This is followed by Day 2 values of 20-50% for an additional
0.25" over the same areas with some expansion through central
VT/NH.


...OR Cascades...Klamath...and northern/central Sierra Nevada...
Day 3...


The next cold core low drifts toward OR, but remains offshore
Sunday through Monday. A rich plume of moisture shifts inland
Sunday with renewed enhancement from an ejecting shortwave trough
Sunday night producing heavy precip over the northern half of CA
Monday. Day 3 snow probs for >8" are 40-90% in the southern OR
Cascades, the Klamath/Trinity Alps, and northern/central Sierra
Nevada with snow levels of 5000-6000ft Sunday dropping to
4000-5000ft by Monday morning.




Jackson

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
313 PM EDT Fri Mar 28 2025

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


...Emerging heavy rain and severe threat for Lower Mississippi,
Tennessee, and Ohio Valleys for midweek and beyond...


...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 will accompany this second cold front in the
east-central CONUS, while late-season snow is possible in the
northern tier. 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...

Model guidance is reasonably agreeable at the start of the medium
range period, with a shortwave moving through the Midwest to
Northeast Monday-Tuesday (though the 00Z UKMET was a slow outlier)
and an upper low offshore of the Pacific Northwest. The latter will
send energy eastward reaching the Plains by midweek, potentially
forming a weak closed low, along with a reasonably strong surface
low that shows typical timing and placement differences as it
tracks from the central U.S. to the Upper Great Lakes by Thursday.
Upper ridging in the East and mean troughing across the West looks
to set up by later week. The troughing across the West has shown
the most model differences over the past couple of days. Finally
the 06Z GFS and now the newer 12Z GFS is showing more agreement
with the larger ECMWF/CMC cluster of guidance by around midweek
(the 00Z GFS and older GFS runs were pulling significant amounts of
energy and troughing into the eastern Pacific at that time).
However, the 00Z ECMWF appeared to pull a different shortwave
southward along the West Coast Thursday-Friday, which really only
the Pangu AI/ML model agreed with--other AI models and the CMC
showed the trough axis farther east. So did not favor the 00Z EC as
much during the late period.

Thus the WPC forecast was based on a blend initially favoring the
00Z ECMWF with lesser proportions of the 06Z GFS and 00Z CMC early
in the period. As the period progressed, lessened the proportion of
deterministic models in favor of the ensemble means to half Day 6
and more Day 7 as spread increased. Notable edits to the NBM
included lowering QPF in the West where the older GFS runs that
were not favored seemed to be contributing heavy QPF into the blend
while the EC/CMC and their means showed less. QPF increased from
continuity in the east-central U.S. as models started to be more
agreeable with heavy amounts for the latter half of next week.


...Weather/Hazards Highlights...

A cold front moving into the East should allow for widespread rain
and thunderstorms across much of the Eastern Seaboard on Monday.
The best chance for locally heavy to excessive rainfall should be
over parts of the Southeast where more instability will allow for
heavier rain rates, so a Marginal Risk remains in place for the Day
4/Monday Excessive Rainfall Outlook. Locally heavy rain may also
occur farther north from the Appalachians to Mid-Atlantic and
Northeast. 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. The best precipitation focus looks to
be across Northern California on Monday, and a Marginal Risk
remains in place for coastal regions into far southwest Oregon for
the Day 4/Monday ERO with a weak atmospheric river. Precipitation
with some higher elevation snow will spread through the
Intermountain West and Rockies Monday-Tuesday, while the pattern
also supports high winds focused from the central Great Basin into
the central Rockies. As the upper trough in the West reloads into
mid and late next week, it will support a surface low pressure
system forming in the central U.S. by Wednesday with widespread
thunderstorms across the east-central U.S. in its warm sector. SPC
indicates another round of severe weather from the south-central
U.S. into the Mid-South and Ohio Valley on Wednesday, and heavy
rainfall is also a concern. The low is forecast to move
northeastward Thursday-Friday but leave a wavy front behind across
the Mid-South to Ohio Valley, causing likely multiple rounds of
heavy rain over similar areas, enhancing flooding concerns.
Additionally, some April snow is likely on the backside of the low
across the northern Plains and Upper Midwest Tuesday-Wednesday and
spreading into the Interior Northeast Wednesday-Thursday. Meanwhile
some modest rain and snow could continue across the West
throughout next week, though with rapidly increasing uncertainty in
the details after early next week.

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 normal lows.


Tate/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