MESOSCALE PRECIPITATION DISCUSSION 0492
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1154 AM EDT FRI JUL 14 2017

AREAS AFFECTED...N WEST VIRGINIA...W MARYLAND...S PENNSYLVANIA...S
NEW JERSEY

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

VALID 141552Z - 141952Z

SUMMARY...MULTIPLE ROUNDS OF CONVECTION WITH LOCALLY HEAVY
RAINFALL RATES CAN BE EXPECTED TO CONTINUE INTO THE EARLY
AFTERNOON HOURS ACROSS MUCH OF WEST VIRGINIA AND EXTENDING INTO
EAST CENTRAL PENNSYLVANIA.

DISCUSSION...MULTIPLE FACTORS ARE AT WORK TO ENHANCE EXCESSIVE
RAINFALL POTENTIAL.  RIGHT ENTRANCE UPPER LEVEL JET DYNAMICS IN
PLACE WILL PROMOTE LARGE SCALE ASCENT, WITH A 500MB SHORTWAVE
TROUGH APPROACHING FROM THE WEST.  ANOMALOUS PWS EXIST OVER THE
REGION WITH VALUES ON THE ORDER OF 1.7 TO 2.2 INCHES AS SUGGESTED
BY THE LATEST RAP ANALYSIS.  THIS IS SUPPORTED BY RECENT GPS DATA.
 ANOTHER CONCERN ARE THE LOWER FLASH FLOOD GUIDANCE VALUES GIVEN
ANTECEDENT RAINFALL OVER MUCH OF THIS AREA OVER THE PAST COUPLE OF
DAYS.

BOTH THE HRRR AND HRRR EXPERIMENTAL ARE INDICATING THE POTENTIAL
FOR 2 TO 3 INCHES OF RAINFALL OVER PARTS OF NORTHERN WEST VIRGINIA
AND ALSO SOUTHERN NEW JERSEY, AND THE NMMB IS INDICATING SOME
LOCALLY ENHANCED AMOUNTS ACROSS SOUTHERN PENNSYLVANIA.  OTHER
HI-RES GUIDANCE, SUCH AS THE ARW, ARE MORE CONSERVATIVE WITH THE
HIGHER RAINFALL TOTALS.  BASED ON RECENT RADAR TRENDS, EXPECT
HOURLY RAINFALL RATES OF 1 TO 1.5 INCHES PER HOUR WITH THE
HEAVIEST CONVECTION, WITH ISOLATED 3 INCH TOTALS BY 4PM LOCAL TIME.

HAMRICK

ATTN...WFO...BGM...CTP...LWX...PBZ...PHI...RLX...RNK...

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

LAT...LON   41357641 41097558 40837519 40087402 39707401
            39067466 39347589 39407701 39237792 38557931
            38128076 38088200 38318257 38918254 39338154
            39558036 40057936 40577880 41077828 41327752