767
FXUS02 KWBC 051842
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
142 PM EST Wed Feb 5 2025

Valid 12Z Sat Feb 08 2025 - 12Z Wed Feb 12 2025

...Potentially heavy snow and ice across the northern Mid-Atlantic
and Northeast this weekend...

...Impactful snow possible in the Mid-Atlantic by Tuesday...


...Overview...

The synoptic pattern setting up in the medium range period will
consist of a developing positively tilted trough axis in the
interior West toward Hudson Bay, with general southwesterly upper
flow over the East that allows for shortwaves moving through. One
shortwave moving quickly across the Midwest to Northeast over the
weekend will lead to potentially heavy snow across those areas, to
the north of a surface low tracking from the south-central Plains
to Lower Great Lakes and Northeast. Moderate to heavy rain is
possible farther south, with a swath of freezing rain and sleet in
between. Rain chances looks to remain/get renewed in the
southeastern quadrant of the lower 48 early next week. Meanwhile
snow is possible on the northern side of the precipitation shield,
generally across the Middle Mississippi Valley and Ohio Valley into
the Mid-Atlantic on Monday, and Mid-Atlantic snow chances become
enhanced on Tuesday behind a developing frontal low. The West will
see a pattern change to drier conditions into the medium range
before another Atmospheric River moves in to the region late
period. Temperature- wise, broad areas of well above normal
temperatures Saturday will shrink in scope to the Southeast early
next week. Meanwhile below average temperatures in the northwestern
and north- central U.S. are forecast to trend even colder Monday
and last through at least midweek.


...Guidance/Predictability Assessment...

Models show generally good agreement on the overall pattern during
the period but with differences in the smaller scale details that
could have sensible weather implications. There remains good
agreement in timing of the initial shortwave into the Northeast
this weekend, and models seem to be clustering now towards
secondary coastal low development which could enhance showfall even
further across parts of the Northeast. In the southern to eastern
U.S. next week, the pattern will be dominated by small frontal
position differences and low pressure waves along the front. These
lead to differences in precipitation type and amounts and timing,
but are rather unpredictable this far out.

In the western and central U.S., several northern and southern
stream energies moving through the trough are more uncertain,
particularly later in the period. Energy distribution across the
Northwest becomes particularly uncertain early next week, which
leads to timing and strength differences of another possible
Atmospheric River into the region. The CMC becomes an outlier next
Tuesday into Wednesday showing a more amplified shortwave across
the Northwest.

The WPC forecast used a blend of the deterministic guidance early
in the period, and gradually increased the proportion of ensemble
means to 40 percent (with still 60 percent of the GFS/ECMWF) by the
late period given the increase of spread in individual models.
Overall, maintained good continuity with the overnight WPC
forecast.


...Weather/Hazards Highlights...

A surface low tracking from the south-central Plains to
northeastern U.S. and a shortwave aloft will provide support for
precipitation across parts of the central to eastern U.S. Saturday.
Snow is likely in northern areas across the Upper Midwest to
Northeast. Probabilities for plowable snow/sleet are high in this
region, with 90%+ probabilities even showing up in parts of
southern New York and northeast Pennsylvania. Sleet and freezing
rain are also likely across portions of the Mid- Atlantic, New
York, and southern New England, which could be hazardous. To the
southwest, rain is likely across the Ohio Valley and central
Appalachians. Potentially heavy rain will be most concerning in the
central Appalachians where there are wet antecedent conditions
already, plus ample rainfall in the short range period. Multiple
rounds of rain are possible due to convection well ahead of and
then along the cold front. Thus a Marginal Risk remains in place
for the Day 4/Saturday ERO centered in West Virginia and just north
and west.

The pattern looks to become increasingly favorable for
precipitation across the southern half of the Mississippi Valley to
Tennessee Valley and southern Mid-Atlantic for early to mid-next
week. Local to widespread heavy rain could be a threat in the
Southeast, while potentially disruptive wintry precipitation is
possible along the northern side of the precipitation shield.
Increasing probabilities for notable winter weather is possible
across parts of the Mid- Mississippi and Ohio Valleys to
Appalachians and Mid- Atlantic on Monday, with increasing potential
for heavier snow and perhaps ice in the Mid- Atlantic on Tuesday
behind surface low development. Stay tuned for refinements to the
forecast as the placement, amount, and type of precipitation
remains uncertain at any individual location.

Precipitation is finally forecast to lessen in scope and magnitude
in the West this weekend into early next week, with just some
light amounts in the Pacific Northwest and parts of the
northern/central Rockies. Models vary on the timing and strength of
another round of modest precipitation that could enter the West
next week, possibly around Tuesday or Wednesday.

Colder than average temperatures are forecast for northwestern and
north-central parts of the lower 48 through the period. The cold
will be especially pronounced across Montana and North Dakota,
especially by early next week when another surge of cold air is
likely. By Monday-Wednesday, lows are forecast to be in the -10s
and -20s, along with some below zero highs. Meanwhile, the southern
Plains to Southeast will see unseasonable warmth Saturday as highs
and lows that are 20-35 degrees above average become widespread.
Highs in the 90s are forecast across parts of Texas. These
temperatures are likely to set daily records. By early next week
there will be a pronounced cooling trend behind a strong cold front
gradually crossing the South. By Wednesday warmer than average
temperatures should be limited to Florida and vicinity.


Santorelli/Tate


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw








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