MESOSCALE PRECIPITATION DISCUSSION 0211
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
203 PM EDT SUN JUN 14 2015
 
AREAS AFFECTED...NORTHEAST OH & WESTERN PA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 141802Z - 150002Z
 
SUMMARY...THUNDERSTORMS ARE EXPECTED TO INCREASE IN COVERAGE AND
TRAIN DOWNWIND OF INSTABILITY NEAR A THERMAL BOUNDARY IN THIS
REGION.  FLASH FLOODING IS POSSIBLE OVER SATURATED SOILS.

DISCUSSION...A THERMAL BOUNDARY STRETCHES FROM NEAR THE IN/OH/MI
BORDER INTO EASTERN OH BEFORE DROPPING IRREGULARLY SOUTHEAST INTO
NORTHERN MD.  INFLOW AT 850 HPA IS 25-30 KTS PER VAD WIND PROFILES
(CLOSE IN MAGNITUDE TO THE 850-400 HPA MEAN WIND), WHICH IS
IMPORTING INSTABILITY FROM A POOL OF 1000-2500 J/KG MLCAPE ACROSS
OH.  THE INSTABILITY PRESENT IS NEARLY DOUBLE THE VALUE SEEN IN
THE 15Z RAP GUIDANCE.  MID-LEVEL INSTABILITY IS MODEST PER
SATELLITE DERIVED VALUES SHARED BY NESDIS/SAB.  THUNDERSTORMS HAVE
BEEN MOVING EAST AT 20-25 KTS THUS FAR, WITH THE MEAN WIND.

THE SETUP IS SIMILAR TO WHAT WAS SEEN ACROSS INDIANA ON FRIDAY IN
MPD #0198, BUT DISPLACED TO THE EAST.  CONVECTION IS EXPECTED TO
ORGANIZE AND PROPAGATE EAST-SOUTHEAST TO SOUTHEAST AT 20-25 KTS
ACROSS THIS REGION INTO PA, USING THE 1000-500 HPA THICKNESS AS A
GUIDE FOR DIRECTION AND THE FORWARD PROPAGATING CORFIDI VECTORS AS
A GUIDE FOR MOTION.  LIKE FRIDAY, CELL TRAINING DOWNWIND OF THE
INSTABILITY POOL APPEARS TO BE THE BEST BET NEAR NORTHEAST OH AND
WESTERN PA.  THE MESOSCALE QPF GUIDANCE AGREES ON THIS IDEA,
ADVERTISING LOCAL AMOUNTS OF 2-3" LOCALLY.  FROM 20Z-00Z, THE 06Z
SSEO NEIGHBORHOOD PROBABILITIES SHOW AREAS AROUND DETROIT MI AND
NORTHWEST PA OF >50% CHANCE OF EXCEEDING THE THREE HOUR FLASH
FLOOD GUIDANCE. AVAILABLE MOISTURE SUPPORTS RAINFALL RATES UP TO
2", WHICH IS PROBLEMATIC CONSIDERING RECENT RAINS AND LOW FLASH
FLOOD GUIDANCE VALUES (ROUGHLY 1.5" IN THREE HOURS).  FLASH
FLOODING IS CONSIDERED POSSIBLE.     

ROTH

ATTN...WFO...BUF...CLE...CTP...DTX...GRR...IWX...LWX...PBZ...

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

LAT...LON   42528076 41737827 39807725 39197780 39277984 
            40228111 41118260 41838508 42508327