Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
348 PM EDT Fri May 27 2022
 
Day 2
Valid 12Z Sat May 28 2022 - 12Z Sun May 29 2022 

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS NEW 
ENGLAND...SOUTH FLORIDA...AND PORTIONS OF THE NORTHERN PLAINS...

...New England...
Isolated instances of flash flooding will be possible Saturday 
ahead of a slow moving cold front. Modest amounts of moisture and 
instability present during peak heating should destabilize the 
airmass enough for loosely organized convection from eastern NY 
through much of New England. HREF probabilities for 1"/hr approach 
moderate levels and show some 2-5 yr ARI exceedance probabilities. 
Below normal rainfall departures over the last week and dry soils 
should keep flash flood risk localized/isolated, but any slow 
moving or repeating rounds over sensitive and urban areas could 
lead to a few instances of flash flooding.

...South Florida...
A washed out frontal boundary draped across the Peninsula 
interacting with daytime heating sea breeze convection could give 
way to a few clusters of strong thunderstorms capable of producing 
intense rain rates over the highly urbanized south Florida 
corridor. HREF probabilities are slight/moderate for 2-3"/hr 
totals and merging boundary interactions may lead to a few rounds 
of storms capable of producing flash flooding. 

...Northern Plains...
Large scale troughing over the western U.S. will lead to several 
impulses pushing out into the Northern Plains Saturday. The signal 
for an axis of 1-2" from eastern MT to western ND in the 
afternoon/evening hours still looks good and with the potential 
for hourly totals up to 1" at times, decided to introduce a 
Marginal Risk. However, the lack of deeper instability and dry 
soils could keep flash flood risk fairly isolated. Further south 
across South Dakota, better ingredients will be in place for 
stronger and more organized storms, but progressive nature and 
likely sparse coverage look to keep any flash flood risk under 5 
percent. 


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