FOUS30 KWBC 010833
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
433 AM EDT Wed Oct 1 2025

Day 1
Valid 12Z Wed Oct 01 2025 - 12Z Thu Oct 02 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OLYMPIC PENINSULA AND EASTERN FLORIDA...

...Olympic Peninsula...
A deep upper low centered off of the British Columbia Coast will
direct embedded ripples of vorticity into the Pacific Northwest
today. A strong 60-100 kts RER jet with associated 100-200 J/Kg
MUCAPE and 200-400 Kg/ms IVT out of the southwest should be enough
to generate scattered thunderstorm activity across the region
today. These favorable dynamics paired with PWATs between 0.65-0.90
should produce efficient rain rates throughout the day, especially
along the windward side of the Olympics, where upslope enhancement
may occur.

...Eastern Florida...
A positively tilted trough will swing through the Southeast today.
CAA over warm Gulf/Atlantic waters should generate convection along
a surface convergence zone over the Florida Coast today. MUCAPE
between 500-1000 J/Kg within a moist environment (1.75-2.25 in.
PWATs) should produce scattered thunderstorms with efficient rain
rates. Moist easterly flow over the inverted coastal surface trough
may generate some backbuilding storms this afternoon/evening. HREF
5" neighborhood exceedance probabilities are between 20-30% across
the entire risk area, so there's potential for overperformance of
rainfall. Urban areas are of particular concern to flash flooding.

Kebede


Day 2
Valid 12Z Thu Oct 02 2025 - 12Z Fri Oct 03 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OLYMPIC PENINSULA, THE SIERRA, THE GREAT BASIN AND EASTERN FLORIDA...

...Olympic Mountains...
The excessive rainfall threat spills over into Thursday across the
Olympics as the upper low begins to dig down into the West Coast.
100-200 J/Kg MUCAPE and 0.75-1" PWATs should sustain the potential
for excessive rainfall, particularly earlier on in the period
(12-18z) before the trough pushes farther east into the interior
and high pressure builds over the Olympic Peninsula. CMCE 1"
exceedance probabilities are around 15-35% within the marginal risk area.

...Great Basin/Sierra...
Strong diffluence associated with the digging upper trough will
spread throughout the interior West on Thursday. An 80-100 kts RER
jet with a 100 J/Kg MUCAPE should support convection with PWATs
between 0.75-1", which will be 3-4 stndv above average. This will
provide enough moisture to produce high enough rain rates to
overtake flash flood guidance, which is below 1".

...Eastern Florida...
Shortwave vortices within a mean upper trough will propagate south
through the Florida Peninsula on Thursday. Sufficient instability
(500-1000 J/Kg MUCAPE) and moisture (2"+ PWATs) associated with
Imelda may produce excessive rainfall along the immediate coast
early on in the day. The latest qpf trend is decreasing, partly
because the heavy rainfall threat is split between two days (00z
Wednesday--15z Thursday), but urban areas continue to be
susceptible to runoff.

Kebede


Day 3
Valid 12Z Fri Oct 03 2025 - 12Z Sat Oct 04 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
EASTERN FLORIDA...

...Eastern Florida... 
Continued troughing in the Southeast will promote more unsettled 
weather across Florida on Friday. Easterly flow will continue 
advecting rich tropical moisture (2-2.25" PWATs) from Imelda into 
the Peninsula with plenty of instability (500-1000 J/Kg MUCAPE) to 
generate scattered thunderstorms. 2" ensemble exceedance 
probabilities are between 5-15%, which supports the inherited 
marginal risk area. Again, the greatest threat for flash flooding 
is in urbanized areas.

Kebede
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