Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1031 AM EST Wed Dec 17 2025
Day 3
Valid 12Z Fri Dec 19 2025 - 12Z Sat Dec 20 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL MAINLY OVER
PORTIONS OF NORTHWEST CALIFORNIA...

The atmospheric river that came on-shore on Thursday will be on-
going across much of Oregon as the Day 3 period begins at 12Z on
Friday. A well-defined plume of deep layer moisture will continue
to be drawn from the eastern North Pacific Ocean eastward into
parts of the northern Great Basin by fast westerly flow aloft. IVT
values at or above 600 units is forecast to cover much of Oregon
initially...then weaken as the axis of the moisture plume and
associated precipitation settles into northern California. The
system looks to have trended a bit more progressive on Friday than
suggested by earlier runs...so some of the QPF values over Oregon
and northwest California have come down a bit. Even so...opted to
maintain a large amount of continuity with Slight Risk area over
northwest California and a portion of adjacent southwest Oregon
given the possibility of further wobbles in the placement of the
axis or variations in model QPF. As it stands...the area average
precipitation amounts are currently in the range of 1-2 inches
with localized higher amounts maxima in the terrain.

Bann

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt