Graphic for MPD #0785

MESOSCALE PRECIPITATION DISCUSSION 0785
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
209 PM EDT WED SEP 06 2017

AREAS AFFECTED...NE SC...ERN NC...VA TIDEWATER...DELMARVA
PENINSULA

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

VALID 061808Z - 070008Z

SUMMARY...CONVECTION WILL BLOSSOM OVER THE EASTERN CAROLINAS EARLY
THIS AFTERNOON AND EXPAND NORTHEASTWARD INTO THE DELMARVA
PENINSULA...WITH A FLASH FLOODING POSSIBLE IF TRAINING CONVECTION
CAN SET UP FOR A COUPLE HOURS IN A GIVEN LOCATION.

DISCUSSION...CONVECTION BEGAN INITIATING ACROSS THE EASTERN
CAROLINAS BEGINNING AROUND 1630Z...AND PER VISIBLE SATELLITE AND
REGIONAL RADAR SPATIAL EXTENT APPEARS TO BE INCREASING MORE
MARKEDLY NOW. THE NEW CELL GROWTH APPEARED TO BE FOCUSED ON THE
NOSE OF A 850MB MOISTURE TRANSPORT MAXIMUM NEAR OR JUST EAST OF
I-95 IN THE SC-NC BORDER REGION. THE NOSE OF THIS MOISTURE
TRANSPORT MAX IS FORECAST BY SHORT RANGE MODEL
GUIDANCE...INCLUDING THE RAP...TO LIFT NORTHEASTWARD IN THE NEXT
SEVERAL HOURS TO THE VIRGINIA TIDEWATER AND DELMARVA PENINSULA
WITH AN ATTENDANT INFLUX OF APPROX. 2 INCH PWAT VALUES CURRENTLY
SITUATED ALONG THE ATLANTIC COAST.

AIDING THE CELL GROWTH WILL BE UPPER LEVEL DIVERGENCE IN THE RIGHT
ENTRANCE REGION OF AN INTENSIFYING JET STREAK EXTENDING NEAR THE
SPINE OF THE APPALACHIANS. THE JET STREAK WILL BE RAMPING UP JUST
AHEAD OF A +PV ANOMALY ROUNDING THE BASE OF THE TROUGH...EVIDENT
IN GOES-16 AIR MASS RGB IMAGERY NEAR THE TENNESSEE VALLEY. THE RAP
MODEL SHOWS BOTH UPPER LEVEL DIVERGENCE AND BOUNDARY LAYER
MOISTURE CONVERGENCE INCREASING BY 21-22Z...AND THIS SHOULD HELP
FOCUS CONVECTION WITH TIME. ADDITIONALLY...DEEP LAYER MEAN WINDS
ARE ROUGHLY PARALLEL TO THE ORIENTATION OF CONVECTIVE BANDS THAT
HAVE ALREADY INITIATED...AND THE PROJECTED ORIENTATION OF THE
LOW-LEVEL BOUNDARY IN RAP MOISTURE CONVERGENCE FIELDS.

HREF PROBABILITY MATCHED MEAN QPF BETWEEN 18-00Z SHOWS A NARROW
BAND OF AS MUCH AS 2-4 INCHES CENTERED ROUGHLY ALONG A LINE FROM
FLORENCE SC TO WALLOPS ISLAND VA. THE 16 UTC HRRR TIME-LAGGED
ENSEMBLE ALSO FOCUSES ON THIS SAME CORRIDOR...WITH 60-80 PERCENT
PROBABILITIES OF RECEIVING 1 IN/HR RAIN RATES ON SATURATED SOILS
IN PARTS OF NERN NC AND THE VA TIDEWATER. GIVEN THE INCREASING
PWATS AND POTENTIAL FOR TRAINING CONVECTION...FEEL THAT 1-2 IN/HR
RAIN RATES ARE LIKELY IN SOME AREAS...AND FLASH FLOODING WILL BE
POSSIBLE IF THAT COINCIDES WITH URBAN AREAS OR HYDROLOGICALLY
FAVORABLE GROUND CONDITIONS.

LAMERS

ATTN...WFO...AKQ...CAE...ILM...MHX...PHI...RAH...

ATTN...RFC...MARFC...SERFC...

LAT...LON   38877516 38687480 38077494 37297551 36957569
            36527576 36177572 35867572 35567608 35327661
            35007688 34757732 34467782 34237824 34117842
            33967892 33887938 34127986 34438015 34788007
            35267975 35847903 36317833 36717767 37237693
            37957625 38567560


Last Updated: 209 PM EDT WED SEP 06 2017