MESOSCALE PRECIPITATION DISCUSSION 0251
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
902 AM EDT SAT JUN 20 2015
 
AREAS AFFECTED...AREAS AFFECTED...SOUTHERN AND EASTERN
OHIO...WESTERN PENNSYLVANIA...WEST VIRGINIA...EASTERN
KENTUCKY...WESTERN MARYLAND
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 201301Z - 202001Z
 
SUMMARY...LOCALIZED HEAVY RAIN WITH TROPICAL DEPRESSION BILL
EXPANDING INTO CENTRAL APPALACHIANS BY 20Z. 

DISCUSSION...WV LOOP SHOWS A WEAK NORTHERN STREAM SHORTWAVE ACROSS
THE EASTERN GREAT LAKES POSING SOME INFLUENCE ON THE NORTHEASTWARD
EXPANSION OF MODERATELY HEAVY DEFORMATIONAL RAINS ACROSS EASTERN
OHIO INTO WESTERN PENNSYLVANIA.  THE OUTFLOW CHANNEL ALOFT IS WELL
DEFINED STRADDLING THE NY/PA BORDER PLACING A STRONG LEFT ENTRANCE
DIVERGENCE MAXIMA ACROSS SW PA/N WV...AND IS FORECAST TO
MAINTAIN/PROGRESS EASTWARD THROUGHOUT THE TIME PERIOD.  THE UVVS
HAVE ALLOWED FOR SOME VERTICAL GROWTH TO THE SOUTHERN PORTIONS OF
THE DEFORMATIONAL ZONE GIVEN LIMITED MID-LEVEL INSTABILITIES
ACROSS NORTHERN WEST VIRGINIA WITH MUCAPES OF 300-500 J/KG MOVING
NORTH.  THIS INCREASES RAINFALL EFFICIENCIES WITH RATES TO
INCREASE OVER 1-1.5"/HR WITH ISOLATED POCKETS OF 2" POSSIBLE AS
FURTHER INSTABILITIES GROW.   THE MAIN THREAT OVER THE NEXT 5-6
HOURS IS THE PERSISTENT RAINFALL ALONG THE NORTH AND EASTERN SIDE
ALONG THE TRACK OF T.D. BILL AS IT MOVES FROM ACROSS NORTHERN KY
SOUTHERN OH.

FURTHER SOUTH AND EAST OVER EASTERN KENTUCKY...WEST
VIRGINIA/WESTERN VIRGINIA...CLEARER SKIES WILL ALLOW FOR
INSTABILITIES TO INCREASE THROUGHOUT THE MORNING. DEEP
SOUTHWESTERLIES AND UPSTREAM TPWS INCREASING FROM 1.75" CURRENTLY
IN PLACE IN E KY WILL INCREASE TO NEAR 2". STRONG MOISTURE
CONVERGENCE ALONG OROGRAPHY WILL LIKELY LEADING TO CONVECTIVE
INITIATION AROUND THE 16-17Z TIME FRAME. THIS TIMING IS CONSISTENT
WITH RECENT TRENDS FROM RECENT RUNS OF THE HRRR.  THESE STRONG
CELLS WILL BE VERY EFFICIENT WITH 2-2.5"/HR RATES BUT SHOULD BE
QUITE PROGRESSIVE...LIKELY WITH TOTALS LESS THAN 2" BUT ENOUGH TO
EXCEED THE LOWER FLASH FLOOD GUIDANCE WITHIN THE HIGHER TERRAIN.  
ACCIDENTAL REPEATS ARE POSSIBLE GIVEN THERE WILL BE MULTIPLE
NORTH-SOUTH ORIENTED BANDS OF CONVECTION FOR ISOLATED HIGHER
TOTALS. 

INNER CORE CROSSING CENTRAL KENTUCKY... NOT MUCH OF A FLASH FLOOD
THREAT VERY NEAR THE CORE WITHOUT THE CONVECTIVE
DEVELOPMENT....YET .5-1.0"/HR RATES LIKELY TO REMAIN WITH SLOWER
TRANSLATION SPEEDS SHOULD LEAD TO SWATH OF  1-1.5" TOTALS.  THESE
TOTALS SHOULD RAIN OVER AREAS AFFECTED BY PRIOR STRONGER CELLS
FROM LAST NIGHT OR EVEN CELLS TO DEVELOP LATER ACROSS EASTERN
KENTUCKY LATER IN THE DISCUSSION PERIOD AND EXACERBATE ANY HIGHER
RUNNING STREAMS FOR A LONGER DURATION FLOODING THREAT.  

GALLINA

ATTN...WFO...CLE...CTP...ILN...JKL...LMK...LWX...MRX...PBZ...
RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...

LAT...LON   41197850 39777780 38947807 37168005 36658085 
            36598229 36708387 37208429 37648452 38138509 
            38928480 39438444 40138326 40778157