FOUS30 KWBC 040803
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
303 AM EST Tue Nov 4 2025

Day 1
Valid 12Z Tue Nov 04 2025 - 12Z Wed Nov 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHWESTERN CALIFORNIA AND FAR SOUTHWESTERN OREGON...

The next strong atmospheric river (IVT > 750 kg/ms) will begin
impacting coastal portions of northern CA/far southwestern OR 
today, peaking in strength late this evening into the overnight 
period. Forecast 24-hr totals are generally between 1.5-3.0" (but 
may locally reach as high as 4" or so along the upslope terrain), 
and the maintained Marginal Risk generally reflects this area. 
While rates will generally peak between a quarter and half inch for
most of the day and into the evening (with little to no impacts 
expected), hi- res models indicate the potential for localized 
rates of 0.5"+/hr after 06z (when IVT is peaking and oriented 
directly inland). Much of the forecast rainfall is expected to 
occur during the final 6-hr period, resulting in as much as 
1.5-2.5" locally. Any flash flood impacts are still expected to 
remain relegated to more sensitive terrain (i.e. burn scars). 

Churchill


Day 2
Valid 12Z Wed Nov 05 2025 - 12Z Thu Nov 06 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...

While the aforementioned strong atmospheric river will have peaked
by Wednesday morning, residual flood impacts are possible across
some of the same portions of northwestern CA into early Day 2. In
addition, some flood impacts are possible early farther inland
(upslope portions of the northern Sierras) with the arrival of the
strongest IVT (though rates peaking near 0.5"/hr will likely still
limit any impacts to sensitive terrain from burn scars). The 
Marginal Risk was generally maintained with only minor tweaks.

In addition, the Marginal Risk for the Olympics and vicinity in
northwest WA was also maintained. Though the current forecast calls
for localized 2-3" totals, some models indicate localized amounts 
of 3"+. Either way, this Marginal Risk is still judged to be rather
borderline and driven by more long duration flood impacts (as rates
may only briefly eclipse 0.5"/hr with terrain sensitivity less of
an issue).

Churchill


Day 3
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...

While the bulk of the forecast rainfall on Wednesday comes early 
with a distinct lull in moderate to heavy precipitation across the 
PacNW through much of Day 2, precipitation looks to ramp up once 
again by midday Thursday (Day 3) as yet another atmospheric river
makes landfall. While this AR looks weaker and more disjointed
overall, additional rainfall totals of up to 2-3" are forecast for
portions of WA/OR/CA. A broader inherited Marginal Risk was 
separated into two smaller areas where models are focusing this 
heavier precipitation (which also coincides with areas already 
receiving 2-5" of rainfall between Days 1-2). While rates will 
likely largely be limited to 0.5"/hr, given the expected wet 
antecedent conditions localized flash flood impacts are possible. 

Churchill
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