455
AWUS01 KWNH 302144
FFGMPD
NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-OHZ000-310343-
MESOSCALE PRECIPITATION DISCUSSION 0337
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
543 PM EDT FRI MAY 30 2025
AREAS AFFECTED...PORTIONS OF THE CENTRAL APPALACHIANS AND THE
MID-ATLANTIC
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 302143Z - 310343Z
SUMMARY...HEAVY RAINFALL WILL BECOME MORE CONCENTRATED HEADING
THROUGH THE EVENING HOURS ACROSS PORTIONS OF THE CENTRAL
APPALACHIANS WHILE ALSO SPREADING ACROSS THE INTERIOR OF THE
NORTHERN MID-ATLANTIC. SOME EMBEDDED THUNDERSTORM ACTIVITY WILL
FAVOR ENHANCED RAINFALL RATES, AND SCATTERED AREAS OF FLASH
FLOODING WILL BECOME LIKELY THIS EVENING.
DISCUSSION...THE LATEST GOES-E IR/WV SUITE SHOWS A VERY STRONG
SHORTWAVE TROUGH AMPLIFYING ACROSS THE OH VALLEY AND INTO THE
CENTRAL APPALACHIANS, WITH A WELL-DEFINED COMMA-HEAD/DEFORMATION
ZONE CURRENTLY SEEN CROSSING THROUGH SOUTHEAST OH, NORTHERN WV AND
SOUTHWEST PA.
THIS IS DRIVING A DEEPENING WAVE OF LOW PRESSURE TOWARD THE
MID-ATLANTIC STATES, WITH RECENT SURFACE OBSERVATIONS SHOWING A
STRENGTHENING LOW CENTER MOVING EAST-NORTHEAST ACROSS FAR NORTHERN
VA TO THE EAST OF KOKV AND NORTHWEST OF KIAD. A QUASI-STATIONARY
FRONT IS SEEN ORIENTED EAST OF THIS LOW CENTER ACROSS NORTHERN
VA/SOUTHERN MD AND THROUGH THE DELMARVA REGION. THE AIRMASS AHEAD
OF THIS STRONG SHORTWAVE IS MODESTLY UNSTABLE, WITH WARM-SECTOR
MLCAPE VALUES OF 500 TO 1000 J/KG, BUT THERE IS NOSE OF ELEVATED
INSTABILITY THAT IS WRAPPING NORTH OF THE FRONT AND INTO AREAS OF
EASTERN WV THROUGH NORTHERN MD AND FAR SOUTHERN PA.
OVER THE NEXT FEW HOURS, THIS ELEVATED AXIS OF INSTABILITY WILL
COMBINE WITH STRONG DPVA, STRENGTHENING ISENTROPIC ASCENT, AND A
RELATED CORRIDOR OF ENHANCED FRONTOGENETICAL FORCING FOR AN AXIS
OF HEAVY RAINFALL TO MOVE EAST OUT OF THE CENTRAL APPALACHIANS AND
ACROSS THE NORTHERN MID-ATLANTIC. ALREADY RADAR AND SATELLITE
IMAGERY SHOWS AN AXIS OF HEAVY RAINFALL WITH EMBEDDED STRONG
THUNDERSTORMS IMPACTING NORTHERN WV AND SOUTHWEST PA, WITH THIS
ACTIVITY MOVING EAST TOWARD THE MD/WV PANHANDLES.
MEANWHILE, DOWNSTREAM AREAS NEAR THE STATIONARY FRONT AND INTO THE
WARM SECTOR WILL BE SEEING CONVECTION EXPAND IN COVERAGE AS BETTER
INSTABILITY AND STRONG SHEAR PROFILES COMBINE WITH BACKING
LOW-LEVEL FLOW/SURFACE CONVERGENCE FOR AN ORGANIZED CONVECTIVE
THREAT.
THE LATEST HIRES GUIDANCE INCLUDING THE 18Z HREF SUITE, THE HRRR,
AND THE EXPERIMENTAL WOFS RUNS FAVORS NORTHERN WV/SOUTHERN PA AND
NORTHERN MD WITH THE HEAVIEST RAINFALL THIS EVENING WITH A FOCUS
ON AREAS NEAR AND TO THE NORTH OF THE SURFACE LOW TRACK. RAINFALL
AMOUNTS ACROSS THIS REGION OF 3 TO 4+ INCHES WILL BE POSSIBLE.
HOWEVER, AREAS OF CENTRAL AND NORTHERN VA AND INTO THE DELMARVA
AND EVENTUALLY SOUTHERN NJ WILL SEE BANDS OF CONVECTION CAPABLE OF
PRODUCING RAINFALL RATES OF 1 TO 2 INCHES/HOUR, WITH SOME SPOTTY 2
TO 3+ INCH RAINFALL TOTALS POSSIBLE HERE.
SCATTERED AREAS OF FLASH FLOODING ARE LIKELY THIS EVENING, AND
THIS WILL INCLUDE A THREAT TO A FEW METROPOLITAN AREAS INCLUDING
WASHINGTON, D.C., BALTIMORE, MD, HARRISBURG, PA AND PHILADELPHIA,
PA.
ORRISON
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...AKQ...BGM...CTP...LWX...OKX...PBZ...PHI...RLX...
ATTN...RFC...RHA...TAR...TIR...NWC...
LAT...LON 41187479 40607411 39567443 38427606 38137690
38077809 38257902 38997961 39258052 39618097
40208093 40677977 40717817 40867657
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