MESOSCALE PRECIPITATION DISCUSSION 0153
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
849 AM EDT WED JUL 10 2013
 
AREAS AFFECTED...SOUTHWEST PA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 101248Z - 101530Z
 
SUMMARY...MULTIPLE CONVECTIVE BANDS AND SOME BACK-BUILDING OF
CONVECTION IS EXPECTED TO CONTINUE THE NEXT FEW HOURS...PROMOTING
ADDITIONAL FLASH FLOOD POTENTIAL GIVEN SATURATED SOILS.

DISCUSSION...A BROKEN MCS MOVING THROUGH WESTERN PA ATTM IS
PRODUCING SOME VERY HVY RAINFALL RATES GIVEN A VERY MOIST COLUMN
WITH PWATS NEAR 2 INCHES. LATEST RAP ANALYSIS SHOWS 30 TO 40 KTS
OF WESTERLY LOW LVL JET FEEDING INTO THE WRN AND SWRN FLANK OF TWO
STRONG CONVECTIVE BANDS. THE BANDS ARE ORIENTED GENERALLY W/E AND
ARE SEEN GRADUALLY SETTLING SOUTHEASTWARD...HOWEVER THERE HAS BEEN
A TENDENCY FOR BACK-BUILDING CELLS WITHIN THESE BANDS. 12Z RAOB
DATA OVER THE OH VALLEY SHOWS VERY UNSTABLE AIR WITH MUCAPE VALUES
AOA 3000 J/KG AND K-INDICES OF 35 TO 40.

GIVEN SUCH A MOIST/UNSTABLE COLUMN STILL FEEDING IN FROM THE OH
VALLEY...THERE IS SOME POTENTIAL FOR THE CURRENT CONVECTIVE
BANDING TO MAINTAIN ITSELF AND POSSIBLY EVEN INTENSIFY THE NEXT
FEW HOURS. ADDITIONAL FORCING ASSOCD WITH OROGRAPHICS WILL HELP TO
ENHANCE SOME OF THE ACTIVITY AND WILL ENHANCE ALREADY HIGH
RAINFALL RATES THAT ARE UPWARD OF 2 INCHES/HR. GIVEN VERY WET
ANTCEDENT CONDITIONS AT LEAST LOCALLY...AND AREAS OF ELEVATED
TERRAIN INVOLVING THE LAUREL HIGHLANDS...EXPECT FLASH FLOODING TO
BE AT LEAST POSSIBLE.

ORRISON

ATTN...WFO...CTP...PBZ...

ATTN...RFC...MARFC...OHRFC...

LAT...LON   39727930 39888028 40418096 40838058 40938008 40827910
            40477815 40067797 39787850 39727930