FOUS30 KWBC 130745
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
345 AM EDT Fri Mar 13 2026

Day 1
Valid 12Z Fri Mar 13 2026 - 12Z Sat Mar 14 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE PACIFIC NORTHWEST...

Final day of impact from a continuous AR regime that has doused the
Pacific Northwest with several inches of precipitation the last
72+ hours. Continued fetch off the Pacific will maintain its 
composition for another period with a slow shift south in the 
primary moisture advection regime as the approach of a final, yet 
potent shortwave helps press against the prevailing height field 
situated across the Pacific Northwest into British Columbia. A 
modest 600-800 kg/ms IVT signature has been persistent within a 
zone oriented from Olympia down towards the WA/OR border. 
Expectation is for the IVT advection pattern to pivot south to 
include more of northwest OR extending inland into the southern WA 
and northern OR Cascades leading to an extended moderate 
precipitation band through Friday into early Saturday. 

Current rates are still subject to be focused between 0.25-0.5"/hr
at peak intensity with perhaps a few localized areas within the 
upslope regions of the Cascades to breach closer to 0.6-0.75/hr at 
times. This alone falls below the FFG criteria for the region, 
however its the longevity and recent priming that would tip the 
scales towards a low-end flash flood scenario, especially within 
the confines of any urbanized zones. Downsloping into the 
Willamette Valley should cause a regional min with this setup 
leading to lower probabilities of any flood concerns in the 
shadowed zone. City of Portland remains right on edge of persistent
rain bands and waves of moderate rainfall with the heaviest likely
to focus closer to Astoria and over into the adjacent Cascades 
thanks to the upslope component. D1 QPF indicates the sharp 
delineation in the split maxima with Portland proper right on the 
edge of the higher totals. Considering a solid run-to-run 
continuity across guidance the past 24-36 hours, there wasn't 
really any reason to deviate from the previous MRGL risk 
inheritance as 2-4" of rainfall with local maxima of 6" possible in
the Cascades are enough to warrant at least a low-end risk. 

Kleebauer


Day 2
Valid 12Z Sat Mar 14 2026 - 12Z Sun Mar 15 2026

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

Kleebauer


Day 3
Valid 12Z Sun Mar 15 2026 - 12Z Mon Mar 16 2026

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

Kleebauer
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