Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Fri Apr 04 2025

Valid 12Z Fri Apr 04 2025 - 12Z Sun Apr 06 2025

...Life-threatening, catastrophic, and potentially historic flash flood
event continues across the Lower Ohio Valley and Mid-South to Lower
Mississippi Valley...

...Additional episodes of significant severe weather expected from the
Mid-South west through the Ozarks and ArkLaTex with very large hail and
strong tornadoes possible...

...Moderate to locally heavy snow showers expected for the Rockies, with
some snow showers spreading into the High Plains through Saturday...

...Well above average, very warm Spring temperatures to end the week
across the Southeast with numerous record-tying/breaking highs possible...

Several developing waves of low pressure acting on a stalling frontal
boundary will continue to be the focus for the threat of life-threatening
flash flooding and significant severe weather from the Ohio Valley
west-southwest through the Middle/Lower Mississippi Valley, Mid-South, and
ArkLaTex the next couple of days. Deep moisture pooling along the front
combined with impressive dynamics will set the stage for persistent rounds
of intense thunderstorms capable of producing torrential downpours
throughout the region. This will especially be the case for the Lower Ohio
Valley into the Mid-South and Lower Mississippi Valley, where the
necessary ingredients of moisture, instability, forcing, and wind shear
best overlap. Storm initiation and movement roughly parallel to the
boundary will lead to repeated rounds of heavy rainfall over the same
areas, leading to significant to extreme, potentially historic, rainfall
totals over increasingly saturated soils. High Risks of Excessive Rainfall
(level 4/4) remain in effect through Saturday, highlighting an
increasingly dangerous and life-threatening situation. Outside of the High
Risk, Moderate and Slight Risks also continue to be in place over broader
areas of the Ohio Valley into the south-central U.S. through Saturday
where scattered to numerous instances of flash flooding can be expected.
As has been said repeatedly for the last several days, this has the
makings of a catastrophic, potentially historic heavy rainfall and flash
flood event, with some locations potentially seeing rainfall amounts as
high as 10-15"+ through the weekend. The repeating rounds of heavy
rainfall each day will also raise the risk of widespread significant river
flooding, including potentially catastrophic major flooding, in the
Ozarks, portions of the Middle Mississippi Valley, and much of the Ohio
Valley. Thankfully, the heaviest rainfall should ease somewhat for the
hardest hit areas on Sunday as the frontal boundary finally begins to push
eastward into the Southeast and Mid-Atlantic; however, major river
flooding is likely to continue into early next week. With the front on the
move, the focus for heavy rainfall shifts eastward into parts of the
Carolinas southward to the Central Gulf Coast to round out the weekend. A
Slight Risk (level 2/4) remains in effect as a result.

In addition to the flash flood threat, additional bouts of significant
severe weather will also be in play for many of the same locations through
the weekend. The same ingredients of moisture, instability, forcing, and
wind shear that are conducive to intense downpour producing thunderstorms
are also supportive of supercells and severe weather. The Storm Prediction
Center has issued a Moderate Risk (level 4/5) for Friday from the ArkLaTex
into southeast Missouri for strong tornadoes, very large hail, and
damaging winds. A broader Slight Risk is in place from Texas through the
Lower Ohio Valley. On Saturday, Slight to Enhanced Risks are delineated
for the Lower Mississippi Valley through the Mid-South and Ohio Valley,
with severe thunderstorms capable of producing strong tornadoes, very
large hail, and damaging wind gusts above 70 mph. Similar to the flash
flood threat, the severe weather risk shifts eastward into parts of the
Mid-Atlantic, Southeast, and southern Appalachians on Sunday, with the
Storm Prediction Center issuing a Slight Risk for the potential for
damaging winds and possibly a few tornadoes.

Farther west, a passing cold front will help support snow showers over the
Rockies as well as portions of the High Plains the next couple of days.
Accumulations are expected to remain light with snows over the Plains,
though a corridor of a few inches of snow could focus in North Dakota. To
the south, an area of low pressure in the lee of the Rockies will help to
focus upslope flow along the mountains, resulting in moderate to locally
heavy snows for the regional mountain ranges on Friday, with the potential
for some snow for portions of the High Plains along the Front Range. The
cold front to the north will also pass southward by late Friday and into
the day Saturday, bringing renewed post-frontal upslope flow and
additional heavy snow for the mountains of the Front Range. There is also
an increasing potential for accumulating snow to spread across portions of
New Mexico and into the southern High Plains later Friday into Saturday.
Drier weather returns on Sunday as high pressure takes control.

The highly amplified flow pattern will lead to well above average
temperatures across the Southeast as an upper-level ridge dominates the
region. Meanwhile, temperatures will remain much cooler and below average
under the upper-level trough over most of the western/central U.S. Highs
the next couple days across the Southeast are forecast to be in the 80s to
low 90s, with numerous record-tying/breaking highs possible. Farther
north, the Mid-Atlantic/Northeast will cool to the 50s and 60s for highs
on Friday, and a cool surface high will take hold in the Northeast
Saturday for below normal highs in the 40s. Some wintry weather can't be
ruled out across northern New England on Sunday either given persistently
cool temperatures on the north side of the front. Meanwhile, forecast
highs across the Plains into the Interior West will be mostly well below
average. Northern and central areas of the Rockies and Plains should see
high temperatures in the 30s and 40s on Friday, and southern Rockies/High
Plains can expect highs that are below average by 20-25 degrees by
Saturday with actual highs falling into the 40s. The West Coast can expect
warmer, above average temperatures compared to the rest of the West as a
ridge builds northward over the region, with highs in the 60s and 70s The
West will continue to warm up on Sunday while cooler air across the Plains
spreads eastward into the Ohio Valley, the Mid-South, and the Lower
Mississippi Valley.


Miller


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Fri Apr 4 2025

Valid 12Z Mon Apr 7 2025 - 12Z Fri Apr 11 2025


...General Overview...

A major improvement is coming to the areas that are getting
hammered by extremely heavy rainfall and severe weather Friday and
into this weekend. An amplifying upper level trough over the Great
Lakes and Ohio Valley region will accelerate a cold frontage
passage, with the boundary exiting the East Coast on Monday. Drier
and much cooler conditions will arrive behind it and likely remain
through much of the upcoming week. Meanwhile across the western
half of the country, a couple of shortwaves will pass through the
northwestern states, and then an upper level ridge tries to build
northward across the Rockies by the end of the week with a
reinforcing downstream trough across the east-central U.S.

...Guidance/Predictability Assessment...

The latest model guidance initially indicates good overall
agreement across the Continental U.S. for Monday, but differences
are already becoming apparent off the Pacific Northwest Coast with
the arrival of the next trough. A nearly multi-deterministic model
blend works well as a starting point for this time. By Tuesday,
the GFS and to a lesser extent the GEFS mean become faster and
stronger with the low pressure system developing across the Plains,
and this trend continues going into the middle to end of the week
as well.

Examination of the machine learning guidance from the ECMWF and
teleconnections with positive/negative 500mb height anomalies over
the North Pacific and North Atlantic strongly support the idea of a
slower trough evolution and progression across the Eastern U.S. for
the second half of the week. This falls more in line with the
ECMWF/ECENS/CMC solutions and the WPC forecast follows this
preferred approach, in contrast to the much faster GFS. There is
also growing model spread with shortwave energy approaching the
Pacific Northwest late in the period, so an ensemble mean approach
works well for this region by Thursday into Friday. The use of the
ECENS was increased to about half by next Friday, which still
maintaining about 25% each of the ECMWF and CMC.

...Weather/Hazards Highlights...

The heavy rainfall potential decreases quite a bit to begin next
week in comparison to what is expected this weekend. However, there
will still be an axis of deep moisture over the coastal plain of
the Southeast states ahead of the cold front, with areal 1-2 inch
totals possible from southern Georgia to the Hampton Roads area of
southeast Virginia, mainly between 12Z Monday and 00Z Tuesday,
where a Marginal Risk of excessive rainfall is in effect for the
new Day 4 period. With the exception of the central and southern
Florida Peninsula, the threat of heavy rainfall should be over by
Tuesday across the remainder of the country with no risk areas
needed. If future models trend higher with QPF over South Florida
during this time, it is possible a Marginal Risk area may
eventually be needed there.

Elsewhere across the country, rain and mountain snow makes a return
to western Washington and Oregon courtesy of onshore flow and a
couple of shortwave trough passages, but this does not look like a
major event at this time. Lighter precipitation crosses the
Northern Plains and Midwest midweek, and the next good chance of
rainfall arrives across the Eastern U.S. by Friday as a surface low
approaches the region.

In terms of temperatures, much cooler conditions are coming for the
Eastern U.S. after the strong cold front exits the East Coast
Sunday night/Monday morning. Afternoon highs are likely to be on
the order of 15 to perhaps 25 degrees below early April averages on
Tuesday from the Ohio Valley to the eastern Great Lakes,
compliments of the upper low overhead. Readings return closer to
average by late in the week for the East Coast states. Meanwhile, a
warm pattern is expected for the Western U.S. through the week with
both daytime highs and overnight lows about 10-20 degrees above
average, with the greatest anomalies over the Great Basin.

Hamrick


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
213 AM EDT Fri Apr 4 2025

Valid 00Z Sat 5 Apr 2025 - 00Z Sat 12 Apr 2025

A trailing frontal boundary extending southward from a large
occluded low pressure system well to the north of Hawaii is
expected to reside over the northwestern Islands for Friday into
Saturday, and then gradually wash out going into Sunday. Surface
high pressure then rebuilds northwest of the state near 30-35
degrees north, with mainly ENE trade wind flow expected. This
likely remains the case into the middle to end of next week, with
good overall model agreement across the Hawaii domain.

In terms of rainfall prospects, most of the mainly light to
moderate showers with the stationary front through this weekend
should be mainly north and west of Honolulu, and typical trade
wind showers extending southeast to the Big Island. The ensemble
means suggest an upper trough could develop near 150 degrees west
by midweek, and this may result in a slightly greater coverage of
showers during this time.

Hamrick

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 AM EDT Fri Apr 4 2025
Day 1
Valid 1213Z Fri Apr 04 2025 - 12Z Sat Apr 05 2025

...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OZARKS AND MID-SOUTH...

...LIFE-THREATENING FLASH FLOODING EXPECTED FRIDAY AFTERNOON
THROUGH EARLY SATURDAY...

...12Z Special Update...

Convection lingering past 12Z has prompted the issuance of a
special update for the Day 1 ERO. The Marginal and Slight Risk
areas were extended east across Kentucky into portions of West
Virginia where heavy showers and thunderstorms are expected to
produce widespread areas of areal flooding and flash flooding, with
locally considerable impacts possible, through the early and mid-
morning hours. Some improvement is expected by late morning.

Dolan

...Previous Discussion...

Both global models and CAMs have come into better agreement over
the past 24 hours and have largely maintained that agreement in
the 04/00Z model production cycle. The development of at least one
north- northeast to south- southwest oriented band of convection
located generally from the ArkLaTex into southeastern Missouri was
still depicted...with convection being oriented generally parallel
to fast, meridionally oriented flow aloft, with abundant moisture,
low- level shear, and instability profiles all favoring abundant
rainfall (potentially exceeding 10 inches on a localized basis).
These totals will fall on areas that will have experienced 2-6
inches of rainfall leading up to the forecast period, with wet
soils/terrain variations all suggestive of a potentially widespread
and significant flash flood event.

The overall outlook was on track with an eventual broad axis of
heavy precipitation expected from north/central Texas northeastward
to Ohio/Pennsylvania.

The previous synoptic scale forecast was relatively unchanged.
What should be the final surface wave had already started to
enhance convection across over southwestern Texas in the predawn
hours...and it should continue to make its way across the Southern
Plains to Mississippi Valley by later this morning through the
remainder of the period. This wave will likely be the strongest of
the 3 allowing a much more amplified surface evolution that will
shift the focus of heavier precip further northwest while also
providing some vigor in the overall QPF distribution. The trend the
past 48 hrs is for a zone of significant (3-6+") totals to be
recognized across portions of the Southern Plains up through the
Ozarks and Mid-Mississippi Valley of Missouri, spanning as far
north as south- central Illinois.The heaviest precipitation axis
based off the latest NBM probabilities still has a significant
footprint of at least 3" located near the Dallas metro and points
just east (40-60%) to as high as 60-80% in a large area spanning
the Red River of northeast TX up through much of western and
northern AR, through the Ozarks of MO, finally reaching the
Mississippi River south of St.Louis. Ensemble mean QPF output
signals a massive area of at least 2" with urban centers like
Dallas, Little Rock, St. Louis, and Springfield, MO all within a
core of the heavy precip footprint.

Considering the neighborhood probabilities from the 04/00Z
HREF...maintained the Moderate Risk area with only minor
adjustments based on the model and WPC QPF. Also made a slight
eastward expansion of the Marginal and Slight Risk areas in the
Ohio Valley and the Mid-South where Flash Flood Guidance was
largely reduced to less than half an inch per 3 hours.

Bann

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 AM EDT Fri Apr 4 2025
Day 2
Valid 12Z Sat Apr 05 2025 - 12Z Sun Apr 06 2025

..LIFE-THREATENING FLASH FLOODING IS EXPECTED ON SATURDAY AFTERNOON
THROUGH SUNDAY MORNING..

Deep, slow-moving and intense convection is expected to be on-going
across parts of the Mid-South as the Day 2 period begins at 12Z
Saturday. Many of the adjustments made previously were still
supported by the 04/00Z model runs...with south to southwesterly
flow aloft at the start of the period expected to continue
fostering a very slow eastward progression of convection, while
1.75+ PW values,, 1500+ J/kg MLCAPE, and convective
training/mergers continue to foster high to locally extreme rain
rates and FFG exceedance on a widespread basis. Additional 3-5
inch rainfall totals...with locally higher amounts...are expected
across parts of the region which will be increasingly water-
logged.

Eventually, veering flow aloft will result in a faster forward
speed of any convective complex(es) toward the Ohio and Tennessee
River Valleys during the latter half of the forecast period. As
this occurs, low FFGs are expected to remain from abundant
antecedent rainfall, and it is very likely that ground conditions
will not have completely recovered from abundant antecedent
rainfall. In this scenario, widespread significant impacts are
expected with both ongoing and newer instances of flash flooding.

The synoptic forcing for enhanced deep layer lift will be strong
given the magnitude of an intense right-entrance region jet
dynamics in an area of highly anomalous atmospheric moisture and
very saturated soils. This spells another high impact flash flood
forecast for Saturday afternoon through Sunday morning across the
Lower to Mid- Mississippi Valley. This threat will extend farther
east as a cold front begins to finally sweep the stagnant pattern
out of the region, but not before another round of heavy rainfall
inundates areas that will be sensitive to any appreciable rainfall.

All major deterministic models depict an expansive footprint of 3
to 6 inch rainfall...with locally up to 8" of rainfall across a
large portion of Arkansas extending east- northeast through far
southeastern Missouri, all of western and central Tennessee and
Kentucky, to as far north as the Ohio/Kentucky border along the
Ohio River. Northwest Mississippi will also lie within the axis of
heaviest precipitation leading to quite a large area of not only
heavy precip, but significant overlap of areas that will have super
saturated grounds that will struggle to maintain the ability to
absorb more rainfall. This setup will yield a very dangerous
scenario where widespread flash flooding with considerable and
potentially catastrophic impacts would be favored.

As a result...the previously issued High Risk remained largely in
place with only modest adjustments based on the latest model and
WPC QPF with a broad Moderate Risk area that spans the outer
perimeter of the High Risk leading to several more areas prone to
significant flash flood concerns due to the setup. This remains a life-
threatening situation for areas of the Lower and Mid- Mississippi
Valley region.

Bann

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 AM EDT Fri Apr 4 2025
Day 3
Valid 12Z Sun Apr 06 2025 - 12Z Mon Apr 07 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHEAST US ON SUNDAY|...

There should finally be enough of a shift in the upper flow pattern
such that moisture gets drawn northward across portions of Alabama
an Georgia by southerly low level flow ahead of an approaching
cold front and an upper level trough. Given the timing. There looks
to be enough instability and a shear profile that thunderstorms
should be able to produce locally heavy rainfall rates and maximum
rainfall amounts from 2 to 3+ inches over from southeast Alabama
into central/northern Georgia. As a result...rainfall rates may be
high enough to challenge current FFG in the area on the order of
2.5 inches per hour (although the 3+ inches per 3 hour FFG may be
be less likely to be met/exceeded).

Bann

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Fri Apr 4 2025


The heavy rainfall potential decreases quite a bit to begin next
week in comparison to what is expected this weekend. However, there
will still be an axis of deep moisture over the coastal plain of
the Southeast states ahead of the cold front, with areal 1-2 inch
totals possible from southern Georgia to the Hampton Roads area of
southeast Virginia, mainly between 12Z Monday and 00Z Tuesday,
where a Marginal Risk of excessive rainfall is in effect for the
new Day 4 period. With the exception of the central and southern
Florida Peninsula, the threat of heavy rainfall should be over by
Tuesday across the remainder of the country with no risk areas
needed. If future models trend higher with QPF over South Florida
during this time, it is possible a Marginal Risk area may
eventually be needed there.

Elsewhere across the country, rain and mountain snow makes a return
to western Washington and Oregon courtesy of onshore flow and a
couple of shortwave trough passages, but this does not look like a
major event at this time. Lighter precipitation crosses the
Northern Plains and Midwest midweek, and the next good chance of
rainfall arrives across the Eastern U.S. by Friday as a surface low
approaches the region.

In terms of temperatures, much cooler conditions are coming for the
Eastern U.S. after the strong cold front exits the East Coast
Sunday night/Monday morning. Afternoon highs are likely to be on
the order of 15 to perhaps 25 degrees below early April averages on
Tuesday from the Ohio Valley to the eastern Great Lakes,
compliments of the upper low overhead. Readings return closer to
average by late in the week for the East Coast states. Meanwhile, a
warm pattern is expected for the Western U.S. through the week with
both daytime highs and overnight lows about 10-20 degrees above
average, with the greatest anomalies over the Great Basin.

Hamrick

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Fri Apr 4 2025


The heavy rainfall potential decreases quite a bit to begin next
week in comparison to what is expected this weekend. However, there
will still be an axis of deep moisture over the coastal plain of
the Southeast states ahead of the cold front, with areal 1-2 inch
totals possible from southern Georgia to the Hampton Roads area of
southeast Virginia, mainly between 12Z Monday and 00Z Tuesday,
where a Marginal Risk of excessive rainfall is in effect for the
new Day 4 period. With the exception of the central and southern
Florida Peninsula, the threat of heavy rainfall should be over by
Tuesday across the remainder of the country with no risk areas
needed. If future models trend higher with QPF over South Florida
during this time, it is possible a Marginal Risk area may
eventually be needed there.

Elsewhere across the country, rain and mountain snow makes a return
to western Washington and Oregon courtesy of onshore flow and a
couple of shortwave trough passages, but this does not look like a
major event at this time. Lighter precipitation crosses the
Northern Plains and Midwest midweek, and the next good chance of
rainfall arrives across the Eastern U.S. by Friday as a surface low
approaches the region.

In terms of temperatures, much cooler conditions are coming for the
Eastern U.S. after the strong cold front exits the East Coast
Sunday night/Monday morning. Afternoon highs are likely to be on
the order of 15 to perhaps 25 degrees below early April averages on
Tuesday from the Ohio Valley to the eastern Great Lakes,
compliments of the upper low overhead. Readings return closer to
average by late in the week for the East Coast states. Meanwhile, a
warm pattern is expected for the Western U.S. through the week with
both daytime highs and overnight lows about 10-20 degrees above
average, with the greatest anomalies over the Great Basin.

Hamrick

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
335 AM EDT Fri Apr 4 2025

Valid 12Z Fri Apr 04 2025 - 12Z Mon Apr 07 2025

...Portions of the Rockies and the High Plains...
Days 1-2...

This morning, a cold front tracking south through the central High
Plains with NErly CAA will cause temperatures to drop and modest
upslope ascent into the Front Range of the Rockies. This air-mass
will be essential for boundary layer wet-bulb temperatures being
cold enough to support snow in the central and southern High
Plains. Farther south, a closed upper low will slowly make its way
east through Arizona and New Mexico on Friday while also injecting
a healthy plume of 300-700mb moisture over the Rockies. This will
support periods of mountain snow from as far west as the Wasatch
and as far south as the Gila Mountains of eastern Arizona. As the
700mb low heads into western New Mexico Friday afternoon, low-mid
levels winds over southeast CO and northeast NM will turn easterly
at the same time as the aforementioned cold front to the north
continues its southerly progression. In addition, the southern and
central Rockies/High Plains will reside beneath the divergent left-
exit region of a 500mb jet streak. Guidance shows a moistening of
the 700-300mb layer Friday afternoon that coincides with what is
likely to be the start of heavy snowfall from the San Juans and
Front Range on south along the Sangre De Cristo and Raton Mesa
Friday afternoon and into Friday night.

By Saturday morning, snow will be falling not only in the Southern
Rockies, but across the southern High Plains thanks to a narrow
area of 700mb WAA to the north of the 700mb low tracking from
southeast NM into western TX. This will prompt the formation of a
deformation zone on the western and northern flanks of the 700mb
low. Note that, with the calendar reading early April and the
increasingly high sun angle, it will have to snow at an
exceptional clip (>1"/hr)for snow to accumulate outside of the
mountain ranges. Still, periods of moderate snow combined with
30-40 kt 850mb winds will cause significantly reduced visibilities
across the southern High Plains of eastern NM and the OK/TX
Panhandles through Saturday afternoon. Snow should finally taper
off by Saturday evening as the 700mb low tracks east over central
OK.

The ECMWF EFI does suggest this is a rather anomalous event in
terms of snowfall for the late March to mid-April time period. The
EFI shows a large swath of 0.8-0.9 values from Raton Pass on south
through much of eastern New Mexico. WPC probabilities show high
chances (>70%) for snowfall totals >12" along the >9,000ft peaks of
the Sangre De Cristo and above 8,000ft in the Raton Mesa. The
latest forecast calls for as much as 12" of snow at the peak of
the Raton Pass along I-25. The WSSI does indicate Major Impact
potential (considerable disruptions; dangerous to impossible
travel) along the Raton Pass Friday night into Saturday morning.
WPC probabilities also show moderate-to-high chances (50-70%) for
snowfall >4" along the I-40 corridor in eastern NM. The WSSI shows
Minor to Moderate Impacts from a combination of Snow Amount and
Blowing Snow across the High Plains of eastern NM and the OK/TX
Panhandles through Saturday with Minor Impacts denoted (winter
weather conditions, hazardous travel possible) in and around the
Amarillo area.


...Northern New England...
Day 2...

Saturday will bring yet another round of wintry weather from the
White Mountains through much of western and northern Maine. While
the air-mass is not as cold as the more recent winter storm that
took place earlier this week, high pressure over Quebec will
provide a weak source of sub-freezing boundary layer temps. As
850-700mb WAA and 300K isentropic ascent amidst brisk SWrly flow
aloft increases, a ribbon of 850-700mb areal-averaged FGEN will
support a band of moderate-to-heavy precipitation that runs
directly over the marginally cold air-mass in northern New England
on Saturday. Precipitation may briefly start out as snow (staying
all snow longest over northern Maine), but the burgeoning nose of
>0C temps at low-levels will inevitably switch any snow to a
sleet/freezing rain mixture from the Whites to western Maine
Saturday afternoon. A weak CAD signature will linger longest along
the Maine/Quebec border that will linger through Saturday night. By
Sunday morning, the warm front lifts far enough north to have plain
rain be the primary precipitation type.

WPC probabilities show moderate-to-high chances (50-70%) for ice
accumulations >0.1" from the Whites through western Maine. Some
minor ice accumulations (generally <0.1") are possible in the Green
Mountains and even as far south as the Berkshires. However, if any
locations are to see localized ice accumulations >0.25", it would
be the White Mountains and western Maine where low-to-moderate
probabilities (10-40%) are present. The probabilistic WSSI (WSSI-P)
does indicate moderate-to-high chances (50-70%) for Minor Impacts
as a result of the >0.1" of ice accumulations.

...Northern Great Lakes...
Day 3...

A potent 500mb vort max with origins out of the Arctic Circle will
dive south from south-central Canada towards northern Minnesota
Sunday evening. A 250mb jet streak oriented N-S will place its
divergent left-exit region over the Midwest Sunday night and aid in
the development of low pressure along a strengthening 850mb front.
A narrow band of moderate snow should manifest on the northern
periphery of low pressure as it tracks through Wisconsin and
northern Michigan. In addition to the band of snow, CAA via brisk
northerly winds will trigger lake-enhanced snow showers over
northern Wisconsin and the Michigan U.P. Sunday night and Monday
morning. WPC probabilities highlight low chances (10-30%) for >4"
of snowfall through 12Z Monday in the Michigan U.P. and the tip of
Michigan's Mitten with additional snowfall possible across northern
Michigan through Monday afternoon.


Mullinax

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Fri Apr 4 2025

Valid 12Z Mon Apr 7 2025 - 12Z Fri Apr 11 2025


...General Overview...

A major improvement is coming to the areas that are getting
hammered by extremely heavy rainfall and severe weather Friday and
into this weekend. An amplifying upper level trough over the Great
Lakes and Ohio Valley region will accelerate a cold frontage
passage, with the boundary exiting the East Coast on Monday. Drier
and much cooler conditions will arrive behind it and likely remain
through much of the upcoming week. Meanwhile across the western
half of the country, a couple of shortwaves will pass through the
northwestern states, and then an upper level ridge tries to build
northward across the Rockies by the end of the week with a
reinforcing downstream trough across the east-central U.S.

...Guidance/Predictability Assessment...

The latest model guidance initially indicates good overall
agreement across the Continental U.S. for Monday, but differences
are already becoming apparent off the Pacific Northwest Coast with
the arrival of the next trough. A nearly multi-deterministic model
blend works well as a starting point for this time. By Tuesday,
the GFS and to a lesser extent the GEFS mean become faster and
stronger with the low pressure system developing across the Plains,
and this trend continues going into the middle to end of the week
as well.

Examination of the machine learning guidance from the ECMWF and
teleconnections with positive/negative 500mb height anomalies over
the North Pacific and North Atlantic strongly support the idea of a
slower trough evolution and progression across the Eastern U.S. for
the second half of the week. This falls more in line with the
ECMWF/ECENS/CMC solutions and the WPC forecast follows this
preferred approach, in contrast to the much faster GFS. There is
also growing model spread with shortwave energy approaching the
Pacific Northwest late in the period, so an ensemble mean approach
works well for this region by Thursday into Friday. The use of the
ECENS was increased to about half by next Friday, which still
maintaining about 25% each of the ECMWF and CMC.

...Weather/Hazards Highlights...

The heavy rainfall potential decreases quite a bit to begin next
week in comparison to what is expected this weekend. However, there
will still be an axis of deep moisture over the coastal plain of
the Southeast states ahead of the cold front, with areal 1-2 inch
totals possible from southern Georgia to the Hampton Roads area of
southeast Virginia, mainly between 12Z Monday and 00Z Tuesday,
where a Marginal Risk of excessive rainfall is in effect for the
new Day 4 period. With the exception of the central and southern
Florida Peninsula, the threat of heavy rainfall should be over by
Tuesday across the remainder of the country with no risk areas
needed. If future models trend higher with QPF over South Florida
during this time, it is possible a Marginal Risk area may
eventually be needed there.

Elsewhere across the country, rain and mountain snow makes a return
to western Washington and Oregon courtesy of onshore flow and a
couple of shortwave trough passages, but this does not look like a
major event at this time. Lighter precipitation crosses the
Northern Plains and Midwest midweek, and the next good chance of
rainfall arrives across the Eastern U.S. by Friday as a surface low
approaches the region.

In terms of temperatures, much cooler conditions are coming for the
Eastern U.S. after the strong cold front exits the East Coast
Sunday night/Monday morning. Afternoon highs are likely to be on
the order of 15 to perhaps 25 degrees below early April averages on
Tuesday from the Ohio Valley to the eastern Great Lakes,
compliments of the upper low overhead. Readings return closer to
average by late in the week for the East Coast states. Meanwhile, a
warm pattern is expected for the Western U.S. through the week with
both daytime highs and overnight lows about 10-20 degrees above
average, with the greatest anomalies over the Great Basin.

Hamrick


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