910
FXUS02 KWBC 050606
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
106 AM EST Fri Dec 5 2025

Valid 12Z Mon Dec 08 2025 - 12Z Fri Dec 12 2025

...Overview...
A broad upper level trough with reinforcing shortwaves will
continue to dominate across the eastern two-thirds of the lower 48
during the medium range period, with broad ridging generally
preferred near the West Coast. Strong westerly flow over the broad
ridge will bring a wavering atmospheric river into the Northwest
with heavy rain and snow next week, along with potential for high
winds. Cold weather and clipper systems will be favored in this
pattern east of the Rockies.


...Guidance/Predictability Assessment...
Guidance continues to show general agreement, but there remains
some uncertainty in the details of the timing of multiple
shortwaves that could impact sensible weather, though the advent of
the 00z GFS appears to be resolving some of the uncertainty. For
the most part a multi- model deterministic blend works through the
period, with some weighting in the direction of the 12z NAEFS/ECMWF
ensemble means late in the period. With the degree of model spread
that exists, the 01z NBM should be sufficient for most mass fields
without any increased weighting in any particular model guidance.
QPF was modified upwards from the 01z NBM in the Great Lakes,
Plains, and Ohio Valley to account for recent GFS/ECMWF guidance
and NBM biases.


...Weather/Hazards Highlights...
A shortwave moving into the Pacific Northwest late Monday looks
strong due to high IVTs, and looks to be impactful as a longer
duration event. Some significant multi- day totals are possible
both with coastal rain and higher elevation snows across the
Cascades. With strong IVT entering by Monday night, have let the
Slight/Marginal Risk areas from continuity -- now for the Day
4/Monday ERO -- ride. For Day 5/Tuesday, the front/atmospheric
river waver across portions of OR, so introduced a new Slight Risk
area to account for the convergence in the guidance caused by
changes seen in the 00z runs of the GFS/UKMET which was coordinated
with PQR/the Portland OR forecast office. Additional rounds of
heavy precipitation are likely into Thursday in the Pacific
Northwest and northern Rockies.

Elsewhere, several clipper systems will bring rounds of rain and
snow to parts of the northern Plains and Midwest, Great
Lakes/Appalachians, and the Northeast next week.

Temperatures across the Upper Midwest Monday will be close to 20F
below average Monday, with low temperatures across the Northeast
Tuesday morning similarly below average. Otherwise, broad 10F
negative temperature anomalies will be experienced from the
Northern Plains, portions of the Midwest, Great Lakes, and
Northeast most days from Monday through next Friday. The West and
portions of the High Plains will experience 10-15F warmer than
average temperatures during the work week next week underneath
upper ridging.


Roth


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




$$