450
FXUS02 KWNH 050708
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
207 AM 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
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. The first system of note
will be the northern tier shortwave and surface low pressure moving
northeast this weekend. Models are more agreeable with this system
in recent runs, though have been waffling with whether a secondary
low along the coastal Northeast becomes dominant by 12Z Sunday,
taking over from the initial low over the Lower Great Lakes. Recent
00Z models are favoring the coastal low. 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. The
main outlier early on seemed to be the 12Z CMC, with a trough axis
farther west into the eastern Pacific compared to other models
early next week. The newer 00Z CMC still has hints of this. Then
there is additional model spread as energy may dive south into the
western side of the trough from northwestern Canada next week,
without much consensus. It seemed best to favor the ensemble means
during the mid to late period there given the deterministic and
AI/ML model differences.

The WPC forecast used a blend of the operational 12Z/18Z GFS and
12Z ECMWF and UKMET early in the period, and gradually increased
the proportion of ensemble means to about half by the late period
given the spread of individual models.


...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 Midwest to Northeast.
Probabilities for plowable snow/sleet are high across Pennsylvania
into the Northeast, with 90%+ probabilities even showing up in the
Catskills. 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.
Wintry 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 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
anomalies 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.


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






$$