085
FXUS02 KWNH 290804
PREEPD

Preliminary Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
303 AM EST Sat Nov 29 2025

Valid 12Z Tue Dec 02 2025 - 12Z Sat Dec 06 2025


...Storm system brings heavy snow chances on Tuesday from the
Appalachians to southern New England, with rainfall along the
coast...


...Overview...

The medium range period next week continues to look fairly active,
but still with a fair bit of uncertainty. On Tuesday, a shortwave
will progress from the South into the East with an area of low
pressure lifting across the Southeast and up the East Coast. This
will bring heavy rain chances along the coast, with increasing
heavy snow possibilities inland from the Appalachians northward New
England. A couple of shortwaves will swing through the Great Lakes
mid to later next week, as another shortwave dives through the
West, still with a lot of uncertainty on its evolution as it
progresses eastward with time.


...Guidance/Predictability Assessment...

The initial shortwave in the South shows good agreement on the
large scale, but little details in the timing and depth of the
shortwave and associated surface low make for a still somewhat
uncertain precip type forecast across the Mid-Atlantic and
Northeast, although confidence is increasing for a meaningful snow
storm across parts of the interior Northeast and southern New
England. A general model blend seems to be the best starting point
for this system.

Out West, there remains a lot of uncertainty in the evolution of
another shortwave Wednesday and beyond. The ECMWF remains an
outlier cutting off a strong upper low that drifts westward into
the Eastern Pacific. There is support for stream separation in much
of the other guidance, but the consensus and trends suggest
something more progressive than the ECMWF. Although the new 00z run
tonight of the ECMWF did come in quicker than its previous run, it
is still slower than the better consensus. The ECMWF mean also
supported its deterministic run. There is some signal for another
surface low to develop near the Southern U.S. very late period, but
this and the associated precipitation are very low confidence. The
WPC forecast tonight favored a blend heavy on the ensemble means
(GEFS and NAEFS) mean with some low weighting given to the
deterministic CMC and GFS.


...Weather/Hazards Highlights...

A shortwave digging into the Southern U.S. should eventually spin
up a wave of low pressure along the Gulf Coast and lift up the East
Coast. By Tuesday, heavy rain will be spreading along and ahead of
the cold front up the East Coast with strong dynamical support and
well above normal moisture. A limiting factor for any hazardous
rain will be the fast speed of the low, but still continued a
marginal risk on the Day 4/Tuesday ERO from the Carolinas to Cape
Cod. Meanwhile, the northern extent of this developing system will
likely have wintry weather concerns, with increasing chances for
heavy snows from the Appalachians to the interior Mid-Atlantic and
Northeast, but with a lot of uncertainty in exact heavy snowfall
axis and amounts. Some light freezing rain is also possible for
parts of the southern/central Appalachians.


A northern stream shortwave through the Upper Midwest and Great
Lakes behind this main system will bring additional light snows to
parts of this region with some likely lake enhancement in downwind
favorable locations.

The next shot of energy moving into the West next week should
support low elevation rain and mountain snow in the Pacific
Northwest to the Intermountain West and Rockies Tuesday and
Wednesday. Depending on the eventual evolution of the shortwave,
precipitation looks to increase in the Southwest midweek.
Additional precipitation is possible in the Northwest again into
later week. Meanwhile another Gulf low pressure/frontal system
could lead to another round of rainfall across the Gulf Coast to
the Southeast Wednesday-Friday.

Widespread and persistent below average temperatures for this time
of year can be expected for the central U.S. in particular for at
least the first half of the week as arctic air spills south. The
coldest anomalies for both highs and lows (around 15-25 degrees
below normal) are forecast in the Midwest through Tuesday given the
snow cover there, and then again on Thursday behind another front.
Much of the central U.S. should finally see temperatures moderate
by next Friday. Rounds of cooler than average temperatures are
likely in the East as well, but with anomalies closer to 5-15
degrees below normal, aside from Florida that should be warmer than
average by a few degrees on Tuesday. The Rockies westward should
be more near or slightly above normal for most of the period.


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






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