Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
332 AM EST Thu Dec 18 2025
Day 2
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...

...Pacific Northwest...

The atmospheric river that came on-shore in the Day 1 period will
be on-going across Oregon...although the event should be winding
down in terms of rainfall rates and additional amounts fairly early
in the outlook period. 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 700 units are forecast to cover
much of Oregon initially...then weaken as the axis of the moisture
plume and associated precipitation settles into northern
California. Maintained a large amount of continuity in terms of
placement of the Slight Risk area clipping northwest California and
a portion of adjacent southwest Oregon.

Saw little reason to make any significant changes to the expanded
coverage of the Slight Risk area made yesterday to cover more into
the Trinity Mountains given latest QPF.

...Southern New England...
A trough crossing the eastern United States will draw increasing
amounts of moisture northward into parts of New England...helping
set the stage for locally heavy rainfall when flow aloft becomes
increasingly difluent and a surface warm front approaches from the
south early on Friday. WPC Deterministic QPF in the 1.0 to 1.4 inch
range is forecast along the track of the low. Offsetting the
potential of excessive rainfall by limiting rainfall rates/amount is
the meager instability expected to be in place.

Bann

Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt