Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
840 PM EDT Fri Oct 31 2025

Day 1
Valid 01Z Sat Nov 01 2025 - 12Z Sat Nov 01 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR WESTERN
WASHINGTON AND FAR NORTHWESTERN OREGON...

...01Z Update...
The ongoing forecast remains on track, with only minimal
adjustments to the Marginal Risk area based on the 18Z HREF and
RRFS probabilistic output (exceedance probabilities) through 12Z
Sat.

See the previous discussion below for additional details.

Hurley

...Previous Discussion...

A modestly strong atmospheric river will setup across the Pacific
Northwest with an advection of high IVT (>750 Kg/ms) into the
region from afternoon through late evening. Inflow at 850 hPa
approaches 50 kts out of the southwest while precipitable water
values in the coastal ranges rise into the 1.25-1.5" range, though
little to no instability is forecast. Precip rates will generally
remain below 0.5"/hr, but may locally peak between 0.5-0.75"/hr.
This may result in localized amounts of 2-5" in the higher terrain
of western WA and far northwestern OR, which would be particularly
challenging for the Skokomish river. Given the consistency of the
forecast and the expectation for some enhanced rates to generate
river rises and minor flooding, a Marginal Risk was maintained and
expanded a bit south into far northwestern OR.

Churchill/Roth


Day 2
Valid 12Z Sat Nov 01 2025 - 12Z Sun Nov 02 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR WESTERN
WASHINGTON AND FAR NORTHWESTERN OREGON...

...21Z Outlook Update...
The Marginal Risk area in effect for Day1/Fri has been extended
into this forecast period. A landfalling atmospheric river will
continue to spread moderate to occasionally heavy rainfall across
much of western Washington and northwestern Oregon through at least
the 18Z Sat through 00Z Sun timeframe. Any ongoing flood/flash
flood issues could continue, with problems most likely near full
watersheds (inhibiting runoff), burn scars, and other locally
sensitive areas. An additional 1-2 inch rainfall totals (with
locally higher amounts) are expected.

Cook


Day 3
Valid 12Z Sun Nov 02 2025 - 12Z Mon Nov 03 2025

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

Cook/Churchill


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