MESOSCALE PRECIPITATION DISCUSSION 0164
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
709 PM EDT MON JUN 01 2015
 
AREAS AFFECTED...MARYLAND...DELAWARE...SOUTHERN NEW
JERSEY...DISTRICT OF COLUMBIA...NORTHERN AND EASTERN VIRGINIA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 012320Z - 020520Z
 
SUMMARY...CONVECTIVE EVOLUTION CONTINUES TO REMAIN CONSISTENT WITH
PRIOR MPD. TRAINING/BACKBUILDING WITH HIGHLY EFFICIENT RAIN
PRODUCTION BEGINNING TO FOCUS INTO HIGHER IMPACT FLASH FLOODING.

DISCUSSION...TWO AREAS OF HIGHEST CONCERN ARE EVOLVING INTO A MORE
FOCUSED HEAVY RAINFALL THREAT FROM 00-06Z. HIGHLY UNSTABLE
ENVIRONMENT SOUTH OF THE STATIONARY FRONT MOVING OUT OF
PENNSYLVANIA IS OVERTURNING FROM THE NORTHERN VIRGINIA FRONT RANGE
ACROSS CENTRAL MARYLAND CONNECTING UP TO ONGOING CONVECTION ACROSS
THE NORTHERN DELMARVA INTO SOUTHERN NEW JERSEY.  LOW LEVEL FLOW IS
BEGINNING TO VEER PER VWP ALLOWING FOR CELL MOTION VECTORS TO
ALIGN PARALLEL TO THE FRONTAL BOUNDARY. THIS SHOULD SUPPORT A
TRAINING AXIS FROM THE DISTRICT TOWARD CENTRAL DELAWARE
POTENTIALLY INTO SOUTHERN NEW JERSEY.  WV LOOP SHOWS SIGNIFICANT
MID-LEVEL RIDGE AXIS PARALLEL TO THE COAST.  THIS IS AFFECTING
FORWARD PROPAGATION OF THE CELLS SO SLOWER CELL MOTIONS AT 2"/HR
RATES FOR 2-3 HOURS WILL BE POSSIBLE IN LOCALIZED AREA. 

FURTHER SOUTH...A WEAK CONFLUENCE BOUNDARY COULD BE SEEN IN 850MB
ANALYSIS ACROSS CENTRAL VIRGINIA THROUGH THE NORTHERN NECK INTO
THE MARYLAND PORTION OF THE DELMARVA.  VISIBLE LOOP SHOWED THE
DEEP CONVECTION DEVELOPING AND EXPANDING ALONG THE LINE...IN A
SIMILAR VAIN AS ABOVE...THE CONFLUENCE OF FLOW THAT LEAD TO THE
MOISTURE CONVERGENCE TO DEVELOP THE CONVECTION IS CURRENTLY
VEERING TO BE MORE WEST-SOUTHWESTERLY AT 15-20 KTS OR GENERALLY
THE SAME AS THE CLOUD BARING LAYER WINDS...AGAIN SUPPORTING
TRAINING.  DUE TO THE MID-LEVEL RIDGE...CELL MOTIONS WILL SLOW AND
AREA OF MAX TOTALS WILL FOCUS NEAR THE NORTHERN AND CENTRAL NECK
OF EASTERN VIRGINIA.  THIS IS VERY CONSISTENT WITH 12Z ARW AND
RECENT HRRR RUNS...AND THOUGH FLASH FLOOD GUIDANCE IS HIGHER THE
RATES AND POTENTIALLY THE DURATION MAY OVERWHELM THEM. 

GALLINA

ATTN...WFO...AKQ...CTP...LWX...PHI...RAH...RNK...

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

LAT...LON   39927474 39417417 38117537 36737770 36497931 
            37987795 38457805 38697911 39277859 39717617