938
AWUS01 KWNH 291931
FFGMPD
NCZ000-SCZ000-GAZ000-300130-
MESOSCALE PRECIPITATION DISCUSSION 0331
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
330 PM EDT THU MAY 29 2025
AREAS AFFECTED...PORTIONS OF THE SOUTHEAST COASTAL PLAIN
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 291930Z - 300130Z
SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS WILL CONTINUE TO EXPAND
IN COVERAGE OVER THE NEXT FEW HOURS. HIGH RAINFALL RATES AND
LOCALLY SLOW CELL-MOTIONS WILL FAVOR AN ISOLATED FLASH FLOOD
THREAT WHICH WILL GENERALLY BE MORE URBANIZED IN NATURE.
DISCUSSION...A LOW-AMPLITUDE SHORTWAVE TROUGH TRAVERSING THE
SOUTHEAST U.S. WILL BE LIFTING UP ACROSS THE SOUTHEAST COASTAL
PLAIN GOING INTO THE EVENING HOURS, AND THIS ENERGY INTERACTING
WITH A MOIST AND UNSTABLE AIRMASS POOLED ACROSS THE REGION WILL
FAVOR ADDITIONAL EXPANSION OF HEAVY SHOWERS AND THUNDERSTORMS.
MLCAPE VALUES ARE AS HIGH AS 1500 TO 2500 J/KG WITH PWS OF 1.75+
INCHES AND THIS COUPLED WITH A MODERATE LEVEL OF EFFECTIVE BULK
SHEAR (30 TO 35+ KTS) WILL FAVOR THE OVERALL CONVECTIVE FOOTPRINT,
AND WITH RAINFALL RATES THAT MAY REACH AS HIGH AS 1 TO 2+
INCHES/HOUR AS CONVECTION GENERALLY GROWS UPSCALE OVER THE NEXT
FEW HOURS.
THESE HEAVIER RAINFALL RATES ARE SUPPORTED BY THE 12Z HREF
GUIDANCE, AND THE LATEST CAMS ALSO SUPPORT A GENERAL CONCERN FOR
THERE TO BE SOME CELL-MERGER ACTIVITY AND LOCALIZED CELL-TRAINING.
SOME OF THIS WILL BE FOSTERED BY PROXIMITY OF SOME SEABREEZE
CONVERGENCE FOCUSING CONVECTION AHEAD OF THE MAIN ARRIVAL OF THE
UPSTREAM SHORTWAVE ENERGY, BUT THE CELL-MOTIONS WILL ALSO BE
LOCALLY RATHER SLOW-MOVING.
RAINFALL TOTALS BY MID-EVENING MAY REACH AS HIGH AS 3 TO 5 INCHES
WHERE THE HEAVIER AND MORE FOCUSED AREAS OF CONVECTION SET UP.
THIS COUPLED WITH THE HIGH RAINFALL RATES IN GENERAL SHOULD TEND
TO FAVOR AT LEAST AN ISOLATED THREAT FOR FLASH FLOODING, WHICH
WILL PRIMARILY BE A CONCERN FOR THE MORE URBANIZED LOCATIONS. THIS
MAY INCLUDE THE COLUMBIA, SC METROPOLITAN AREA IN PARTICULAR.
ORRISON
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...CAE...CHS...FFC...GSP...ILM...MHX...RAH...
ATTN...RFC...ALR...NWC...
LAT...LON 35997883 35797726 34887709 33897852 33267959
32618107 33098227 34108234 35248088
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