Graphic for MPD #0487

MESOSCALE PRECIPITATION DISCUSSION 0487
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 PM EDT THU JUL 13 2017

AREAS AFFECTED...UPPER OH VALLEY & WESTERN VA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 131845Z - 140000Z

SUMMARY...SURFACE BASED CONVECTION IS FORMING NEAR AND AHEAD OF A
MESOSCALE WAVE.  HOURLY RAIN RATES TO 2.5" WITH LOCAL AMOUNTS TO
4" ARE POSSIBLE.

DISCUSSION...THUNDERSTORMS ARE BEGINNING TO ACQUIRE A TRAINING
SIGNATURE NEAR THE UPPER OH VALLEY.  CLOUD TOP TEMPERATURE TRENDS
PER EXPERIMENTAL GOES-16 IMAGERY ARE MIXED, AS OLDER CONVECTION
OVER SOUTHEAST OH SHOWS WARMING TOPS WHILE NEW ACTIVITY IN
SOUTHERN OH SHOWS GENERALLY COOLING TOPS.  TO THE EAST, OTHER
SCATTERED ACTIVITY IS FORMING IN WV AND WESTERN VA.  INFLOW AT 850
HPA IS SLIGHTLY CONVERGENT OUT OF THE WEST AT 20-30 KTS. 
EFFECTIVE BULK SHEAR OF ~30 KTS ALONG WITH UNIDIRECTIONAL FLOW
WITH HEIGHT ARE HELPING TO ORGANIZE THE ACTIVITY INTO THE TRAINING
BAND.  PRECIPITABLE WATER VALUES ARE 1.5-2" PER GPS VALUES FROM
MID MORNING AND RAP ANALYSES.  ML CAPE VALUES ARE 1000-2000 J/KG
ACROSS THE REGION.

THE MESOSCALE GUIDANCE LOOKS TOO FAR NORTH WITH ITS AXIS HERE
BASED ON RADAR TRENDS AND RECENT SPC MESOANALYSES OF THE CAPE
FIELD.  THE EXPECTATION IS FOR CONVECTION TO TRAIN IN SHORT
SEGMENTS AT TIMES WITHIN THIS REGION OVER THE NEXT SEVERAL HOURS.
STORMS SHOULD MOVE EAST TO EAST-SOUTHEAST AT 20-25 KTS WITHIN THE
ML CAPE GRADIENT. THE 06Z SSEO NEIGHBORHOOD PROBABILITIES ALONG
WITH THE 12Z GFS-BASED GDI VALUES INDICATE FURTHER UPTICK TO THE
CONVECTION THROUGH 00Z, WITH THE MAIN UPTICK OCCURRING AFTER 19Z. 
CONSIDERING THE MOISTURE AND INSTABILITY AVAILABLE, HOURLY RAIN
RATES UP TO 2.5" WITH LOCAL AMOUNTS TO 4" ARE POSSIBLE OVER AN
AREA WITH MODEST TO SOMEWHAT LOW FLASH FLOOD GUIDANCE VALUES.

ROTH

ATTN...WFO...ILN...LWX...PBZ...RLX...RNK...

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

LAT...LON   40338411 40148280 39728125 39367978 39077763
            38307847 37587954 37468035 38098189 39048397
            39468437 40148456


Last Updated: 247 PM EDT THU JUL 13 2017