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WPC Day 2 Excessive Rainfall Outlook Risk of 1 to 6 hour rainfall exceeding flash flood guidance at a point
Updated: 1947 UTC Fri May 27, 2022
Valid: 12 UTC May 28, 2022 - 12 UTC May 29, 2022
Forecast Discussion
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
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