FOUS30 KWBC 300720
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
320 AM EDT Thu Oct 30 2025

Day 1
Valid 12Z Thu Oct 30 2025 - 12Z Fri Oct 31 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE MID ATLANTIC AND NORTHEAST...

An occluded cyclone is forecast to track to the northeast as its 
surface low strengthens over the Mid-Atlantic and moves northeast,
drawing in increasingly higher moisture from Hurricane Melissa. 
Strong 850 hPa inflow near 50 kts and sufficient instability (500+ 
J/kg of MU CAPE) is forecast to overspread the region. Hourly 
amounts rising into the 1-2" range could occur from southeast 
Pennsylvania up through New Jersey, Long Island, and portions of 
southwest New England, with local totals to 4" possible within 2-3
hours. Despite recent drought, this could be problematic in urban 
areas and where recent leaf fall has clogged drainage. 

A Marginal Risk for excessive rainfall and isolated flash flood 
concerns remains for this period; the system's progression should 
hold off any broad areas with a higher risk of flash flooding. It 
should be noted, however, that a spot or two within southern 
Upstate NY and northeast PA have a ~20% chance of 5"+ per the HREF
and REFS guidance, so localized Slight Risk impacts cannot be 
ruled out.

Roth


Day 2
Valid 12Z Fri Oct 31 2025 - 12Z Sat Nov 01 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR NORTHWESTERN
WASHINGTON STATE...

A modestly strong atmospheric river will setup across the Pacific
Northwest Northwest with an advection of high IVT (>750 Kg/ms) 
into the region beginning Friday afternoon, carrying through the 
late evening Friday into Saturday. 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. MU CAPE is forecast
to remain weak, under 250 J/kg.  Precip rates should rise to 
between 0.5-0.75"/hr during the peak of the heavy rainfall, 
producing local amounts of 3-5" in the higher terrain of western 
WA, which would be particularly challenging for the Skokomish 
river. Considering the consistency within guidance on totals and 
expectation for some enhanced rates to generate river rises and 
minor flooding, a Marginal Risk was maintained, with some expansion
to the south to account for the wetter 00z UKMET solution.

Roth


Day 3
Valid 12Z Sat Nov 01 2025 - 12Z Sun Nov 02 2025

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

Roth
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