MESOSCALE PRECIPITATION DISCUSSION 0151...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
844 PM EDT TUE MAY 15 2018

CORRECTED FOR TYPOS

AREAS AFFECTED...NORTHERN WV & VICINITY

CONCERNING...HEAVY RAINFALL

VALID 160040Z - 160440Z

SUMMARY...THUNDERSTORMS ARE EXPECTED TO RAMP UP SHORTLY DUE TO AN
OUTFLOW BOUNDARY COLLISION.  HOURLY RAIN TOTALS TO 1.75" WITH
LOCAL AMOUNTS TO 3" ARE EXPECTED.

DISCUSSION...A PAIR OF FRONTAL WAVES NORTH OF FRANKFORT KY AND
OVER NORTHERN WV HAVE LED TO AN UPWARD TREND IN CONVECTION BETWEEN
FAR NORTHEAST KY AND NORTH-CENTRAL WV.  THERE APPEAR TO BE A
COUPLE WEAK SHORTWAVES HELPING OUT -- ONE MOVING ACROSS
NORTH-CENTRAL WV AND ANOTHER MOVING THROUGH SOUTHWEST OH. 
PRECIPITABLE WATER VALUES OF ~1.4" LIE HERE PER GPS DATA.  THE
PITTSBURGH PA 00Z SOUNDING SHOWS DEEP MOISTURE WITH A WET BULB
ZERO HEIGHT ABOVE 10,000 FEET.  INFLOW AT 850 HPA IS
WEST-SOUTHWEST AT 15 KTS.  MU CAPE IS 500-1000 J/KG AND EFFECTIVE
BULK SHEAR IS 25-35 KTS, WHICH IS LEADING TO SOME ORGANIZATION TO
THE THUNDERSTORM ACTIVITY.

A COMBINATION OF WARM ADVECTION EAST OF THE KY WAVE AND A
SOON-TO-BE OUTFLOW BOUNDARY COLLISION ACROSS CENTRAL WV IS
EXPECTED TO CONTINUE THE CONVECTIVE UPTICK IN THE NEAR FUTURE,
WITH THE 18Z SSEO NEIGHBORHOOD PROBABILITIES OF EXCEEDING THE
THREE HOUR FLASH FLOOD GUIDANCE VALUES RISING ABOVE 50% BY 01Z AND
90% BY 03Z.  THE STATIONARY NATURE OF THE SURFACE/850 HPA SLICES
OF THE FRONTAL BOUNDARY IS OF CONCERN.  CELL MERGERS AND TRAINING
ARE EXPECTED TO BE THE MAIN DRIVERS OF HEAVY RAINFALL.  FLASH
FLOOD GUIDANCE VALUES ARE RATHER LOW DUE TO A COMBINATION OF
RECENT RAINS AND RUGGED TOPOGRAPHY.  THE MESOSCALE GUIDANCE HAS A
SCATTERED SIGNAL FOR LOCAL AMOUNTS IN THE 3" RANGE.  HOURLY RAIN
TOTALS TO 1.75" WITH LOCAL AMOUNTS TO 3" ARE EXPECTED OVER THE
NEXT FEW HOURS BEFORE INSTABILITY FADES.

ROTH

ATTN...WFO...LWX...PBZ...RLX...

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

LAT...LON   39708090 39468004 39427959 39357841 39057820
            38707842 38437950 38588206 39048234 39478199