FOUS30 KWBC 060814
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
314 AM EST Thu Nov 6 2025

Day 1
Valid 12Z Thu Nov 06 2025 - 12Z Fri Nov 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHWESTERN CALIFORNIA AND FAR SOUTHWESTERN OREGON, AS WELL AS THE
OLYMPIC MOUNTAINS AND ADJACENT PORTIONS OF COASTAL NORTHWEST WASHINGTON...

The highly active Pacific jet stream pattern that has generated 
copious amounts of precipitation over the Pacific Northwest dating 
back to the week leading up to Halloween is in its final act. One 
more frontal system approaching southern British Columbia will 
direct another plume of Pacific moisture (PWATs between 1.0-1.25" 
off the northern CA coast Thursday afternoon) at the region. The 
accompanying atmospheric river (AR) is expected to exceed 750 
kg/m/s off the northern CA coast, while even ~500 kg/m/s IVT 
values, which top the 90th climatological percentile, stretch as 
far north as the Olympics. Compared to the AR earlier this week, 
the expectation is for less widespread rainfall and instability 
will be lacking. Recent CAMs guidance generally shows only as much 
as 150-300 J/kg of MUCAPE available Thursday afternoon and evening 
over the WA Peninsula. The latest day 1 QPF calls for an 
additional 1-2" of rainfall in coastal northern CA and southwest 
OR, while 2-4" of rainfall occur in the Olympics.

The primary reason for maintaining the inherited Marginal Risks is
that soils have grown more and more saturated during this 
onslaught of heavy precipitation. While most rainfall is unlikely 
to cause problems, it cannot be fully ruled out that Excessive 
Rainfall atop sensitive soils and complex terrain cause some 
highly localized instances of flooding. The good news is a ridge of
high pressure begins to build in off the West Coast on Friday, 
thus finally bringing a much needed break to the Pacific Northwest 
for the weekend.

Mullinax


Day 2
Valid 12Z Fri Nov 07 2025 - 12Z Sat Nov 08 2025

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

Mullinax


Day 3
Valid 12Z Sat Nov 08 2025 - 12Z Sun Nov 09 2025

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

Mullinax
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