710
FXUS02 KWBC 041959
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 PM EST Thu Dec 4 2025

Valid 12Z Sun Dec 07 2025 - 12Z Thu Dec 11 2025

...Moderate to strong multi-day AR likely for the Pacific
Northwest next week...

...Overview...

A central to eastern U.S. mean upper trough and broad cyclonic
flow with reinforcing shortwaves will continue to dominate across
the eastern two-thirds of the lower 48 during the medium range
period. Cold weather and clipper systems will be favored in this
pattern. Meanwhile, strong westerly flow will bring atmospheric
river(s) into the Northwest with heavy rain and snow next week,
along with potential for high winds.


...Guidance/Predictability Assessment...

Guidance continues to show good agreement synoptically through the
medium range period, but there remains some uncertainty in the
details of the timing of multiple shortwaves that could impact
sensible weather. For the most part a multi-model deterministic
blend worked through the period, without any notable outliers. The
shortwave with perhaps the most spread drops into the north-central
U.S. by Wednesday, with the 06Z and now 12Z GFS slightly deeper
with it than other guidance. This shortwave will force an Upper
Great Lakes surface low, which has reasonable agreement for a late
period forecast, though by next Thursday the trough and thus the
low/trailing surface cold front became much quicker in the 06Z GFS
(the 12Z GFS has slowed down some). Thus leaned slightly more
toward the EC/CMC and the means for this feature. The forecast
blend gradually increased the proportion of ensemble means to half
Day 6 and more Day 7 to smooth out individual model differences.


...Weather/Hazards Highlights...

A shortwave looks to move into the Pacific Northwest around
Sunday, bringing some potential for moderate rain and mountain
snows. The next one beginning late Monday looks quite a bit
stronger with latest CW3E guidance suggesting a strong AR due to
both higher IVTs and 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, and in collaboration with the Seattle and Portland
WFOs, have upgraded to Slight Risks in the Day 5/Monday ERO for
higher elevation areas of the coastal ranges and Cascades where
rain totals will be enhanced. A Marginal Risk remains in place in
the lower elevation areas. Additional rounds of heavy precipitation
are likely into Tuesday-Thursday in the Pacific Northwest and
northern Rockies.

Moderate to heavy rainfall may continue into Sunday across
northern Florida and perhaps into southern Georgia along a
lingering frontal boundary. This front may stall for a period of
time, allowing for some training of storms into the Sunday
afternoon period, although instability will be lacking so not
expecting a widespread flash flood threat. A Marginal Risk remains
in place Day 4/Sunday ERO to account for at least a localized
threat. Rain should finally clear out of the region by Monday as
the front passes.

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 north-central U.S. will be below normal by
15-25 degrees Sunday-Monday, with chilly though less anomalous
temperatures moving into the Great Lakes eastward Tuesday-Wednesday
before moderating closer to normal. Another shot of cold air is
likely in the northern tier by next Thursday. The West will trend
warmer into next week underneath upper ridging, with warmer than
average temperatures also spreading into the central and southern
Plains by Tuesday.


Tate/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


$$