Mesoscale Precipitation Discussion 0153
NWS Weather Prediction Center College Park MD
744 PM EDT Thu Apr 11 2024

Areas affected...portions of Pennsylvania, West Virginia, western
Virginia, and western Maryland

Concerning...Heavy rainfall...Flash flooding likely

Valid 112343Z - 120543Z

Summary...A focused axis of training convection is resulting in a
prolonged period of 0.25-1.00 inch/hr rates.  Areas of flash
flooding (locally significant) are likely to continue through 05Z.

Discussion...Recent convective trends have exhibited a focused
axis of convection extending from near BKW (Beckley, WV)
north-northeastward to near Pittsburgh Metro.  The band was
aligned with strong deep layer convergence on the western side of
strong, southerly 850mb flow over the Mid-Atlantic.  The band was
also oriented parallel to strong south-southwesterly steering flow
aloft and immediate downstream of a mid-level wave providing
forcing for ascent across the area.  500 J/kg SBCAPE and 1.3 inch
PW values were also located within the pre-convective airmass
across the region supporting the ongoing convection.  The net
result of the pattern was an elongated axis of 1-2 inch rainfall
totals over the past 3 hours (estimated per MRMS) along with
occasional spots of 1 inch/hr rates, all exceeding FFG thresholds
across the area and resulting in excessive runoff (locally
significant near the Pittsburgh area).

The ongoing scenario will persist over the next 4-6 hours, with
only a slow translation eastward of the band of convection during
that timeframe.  This will result in a continued risk of flash
flooding across the discussion area.  Although slight boundary
layer cooling may occur ahead of the band, ascent/cooling aloft
associated with the mid-level wave centered over Kentucky and
continued warm advection ahead of the band should maintain at
least 500 J/kg SBCAPE ahead of the convective band.  Ongoing flash
flood impacts are expected to continue through 05Z.

Cook

ATTN...WFO...BUF...CLE...CTP...JKL...LWX...MRX...PBZ...RLX...
RNK...

ATTN...RFC...LMRFC...MARFC...NERFC...OHRFC...SERFC...NWC...

LAT...LON   42077899 41977785 41117744 39457746 37927863
            36667984 36258102 37428231 38408286 39148216
            40438105 41138046 41917963