FOUS30 KWBC 121922
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
222 PM EST Fri Dec 12 2025

Day 1
Valid 16Z Fri Dec 12 2025 - 12Z Sat Dec 13 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Cook/Bann

Day 2
Valid 12Z Sat Dec 13 2025 - 12Z Sun Dec 14 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann

Day 3
Valid 12Z Sun Dec 14 2025 - 12Z Mon Dec 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
WESTERN WASHINGTON...

...2100 UTC Update: In terms of the guidance, some of the 12Z model
QPFs have come up a bit (GFS and ECMWF), while others have trended
down (CMC and NAM) in western WA across the Olympics and northern
Cascades. 12Z UKMet meanwhile was similar to 00Z. Still some timing
differences therefore with the onset of the next (more SW-NE
oriented) AR, with the GFS and ECMWF similar with the faster timing
and thus uptick in heavier QPF late in the period (00-12Z Sun). The
upshot was very minimal changes to the Day 3 Marginal ERO.

Hurley

Previous discussion below...

Introduced a Marginal Risk area over parts of the Olympic and
northern Cascade Ranges in Washington as the next push of moisture
approaches late Sunday night into the early morning hours of
Monday. Much of the rainfall on Sunday is currently expected to
fall north of the international boarder with rainfall in the
Pacific Northwest not increasing in coverage or intensity until
late in the Day 3 period. The 11/12Z UKMET was most aggressive with
QPF and there were several global models that limited QPF to under
a quarter of an inch. Based on the expected IVT plume increasing
to over 600 at about the time that the flow begins to take on an
on-shore component...am inclined to follow the ensemble idea of
0.75 inches to locally 1.5 inches of precipitation focused in the
terrain. The area is sensitive given the nearly week-long soaking
so any additional rainfall is expected to bring renewed hydrologic
concerns. Given a fairly tight window of opportunity for rainfall
in the Day 3 period and at least some prospect that the arrival of
higher rainfall rates and amounts will occur after 15/12Z...issued
a Marginal Risk for now. Later shifts can adjust if needed.

Bann


Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt