FOUS30 KWBC 272021

QPFERD



Excessive Rainfall Discussion

NWS Weather Prediction Center College Park MD

421 PM EDT Mon Oct 27 2025



Day 1

Valid 16Z Mon Oct 27 2025 - 12Z Tue Oct 28 2025



...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS

OF THE EASTERN FLORIDA COAST...



A few locations observed several inches of rainfall that lead to

areas of flash flooding yesterday. Additional rainfall this

morning will continue to be impactful to the vulnerable coastal

locations. An approaching upper level trough is helping to aid

divergence/difluence aloft. Onshore flow is allowing for sufficient

moisture and instability to move ashore, and the low-level flow

and upper level flow are nearly balanced, implying storms with

heavy rainfall shouldn't go advance too far inland. Back building

and training of convection will be possible. A Marginal Risk area

was maintained for the eastern coastline given the potential

impacts from additional rainfall over saturated soils.



Otherwise with this update, the MRGL risk across the Southern

Appalachians and surroundings was removed as rainfall rates are

expected to remain below 0.5"/hr with very limited instability.

While localized ~2" totals are expected, the relatively long

duration rainfall with drought conditions and much below average

streamflows should allow for beneficial rainfall for the region.



Churchill/Campbell





Day 2

Valid 12Z Tue Oct 28 2025 - 12Z Wed Oct 29 2025



The probability of rainfall exceeding flash flood guidance is less

than 5 percent. 



2030z Update: An inherited MRGL risk centered on the Mid-South was

removed for this update, as a lack of instability and prevailing

drought conditions are expected to result in largely beneficial 

rainfall for the region (as suggested by less than 5% chances for 

1-hr, 3-hr, and 6-hr FFG exceedance per latest 12z HREF suite). 



Churchill





Day 3

Valid 12Z Wed Oct 29 2025 - 12Z Thu Oct 30 2025



...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE

SOUTHERN AND CENTRAL APPALACHIANS AND SURROUNDING PORTIONS OF THE

OHIO/TENNESSEE VALLEYS...



2030z Update: A closed upper-low will pivot from the Mid-South to 

the OH Valley, causing rainfall to overspread the TN/OH Valley with

anomalous low- level moisture transport driving east-southeast 

moisture transport into the Southern/Central Appalachians. While 

the bulk of this rainfall is expected to be beneficial, short-term

FFGs (1-hr and 3-hr) may be low enough (as low as 1.0" and 1.5", 

respectively) to allow for localized exceedance across the region. 

This is despite limited instability (similar to Day 2 across the 

Mid-South), as the dynamics of the closed low (notable PV anomaly 

with enhanced divergence aloft via left exit region of ~130 kt jet 

streak @ 250 mb) may result in localized 2" exceedance in the OH/TN

Valley (with terrain forcing primarily driving any localized 2" 

exceedance along/east of the Southern/Central Appalachians). 



Churchill





Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt