Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 031447
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1046 AM EDT TUE MAY 03 2016

...VALID 15Z TUE MAY 03 2016 - 12Z WED MAY 04 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
RWI 25 W EDE 15 S EDE 10 NNE OAJ 15 SW CPC SSC 20 SSW UZA VUJ
15 S RDU RWI.


...CAROLINAS...

ANTECEDENT CONDITIONS HAVE BEEN WETTENED BY AN AVERAGE OF 1 TO 2
INCHES OF RAIN SINCE MONDAY MORNING IN A FAIRLY BROAD SWATH FORM
NORTHERN SOUTH CAROLINA INTO EASTERN NORTH CAROLINA. ESTIMATED
TOTALS FROM RADAR HAVE EXCEEDED 3...4...OR EVEN 5 INCHES IN SOME
SPOTS...INCLUDING NEAR THE RADAR / BENEATH THE MELTING LEVEL WHERE
DUAL-POL ESTIMATES ARE MORE TRUSTWORTHY. FLASH FLOOD
GUIDANCE...WHICH IS TYPICALLY HIGH AND DIFFICULT TO REACH IN THIS
REGION...HAD DECREASED OVER THE PAST DAY...AND SHOULD DECREASE
FURTHER AFTER THE EARLY MORNING RAINFALL IS INCLUDED. THIS RAISES
SOME CONCERN FOR THE AFTERNOON/EVENING PERIOD...WHEN THE LATEST
MODEL CONSENSUS IS FOR MODERATE TO LOCALLY HEAVY PRECIP TOTALS
ASSOCIATED WITH SWATHS OF LOOSELY ORGANIZED CONVECTION BENEATH
CYCLONIC FLOW ALOFT. PW VALUES WILL REMAIN ABOVE AVERAGE AND UVVS
WILL BE ENHANCED IN A BROADLY DIFLUENT HEIGHT PATTERN BETWEEN THE
SUB-TROPICAL JET ALONG THE GULF COAST AND A NORTHERN STREAM JET
STRETCHING FROM THE SOUTHERN APPALACHIANS INTO THE NORTHEAST.
THERE IS A SIGNAL FOR LOCALLY HEAVY RAINFALL AMOUNTS OF ADDITIONAL
1 TO 2 INCHES...WHICH COULD LEAD TO RUNOFF ISSUES / FLASH FLOODING
IN MORE SUSCEPTIBLE LOCATIONS.


...VIRGINIA AND SOUTHERN MARYLAND...

A COLD FRONT WILL PUSH SLOWLY INTO EASTERN VA AND SOUTHERN MD. THE
ATMOSPHERE WILL REMAIN FAIRLY MOIST ON BOTH SIDES OF THE
BOUNDARY...HOWEVER...AND HEATING WILL LEAD TO AN AXIS OF WEAK TO
MODERATE INSTABILITY EXTENDING NORTHWARD FROM THE WARM SECTOR
ALONG AN INVERTED TROUGH INTO NORTHERN VA. WITH THE UPPER TROUGH
HANGING BACK TO THE WEST AND APPROACHING...HEIGHT FALLS WILL
COMBINE WITH WEAK POST-FRONTAL UPSLOPE TO YIELD SCATTERED TO
NUMEROUS THUNDERSTORMS THIS AFTERNOON/EVENING...PER THE CONSENSUS
OF HIGH RESOLUTION GUIDANCE. THE MODEL QPF SIGNAL TAKES AN
ORGANIZED AREA OF MODERATE RAINFALL INTO EASTERN VA AND SOUTHERN
MD...OVERLAPPING WITH SOME AREAS THAT RECEIVED HEAVY RAIN
YESTERDAY...AND WHERE FLASH FLOOD GUIDANCE VALUES ARE GENERALLY
AROUND ONE INCH IN AN HOUR OR TWO INCHES IN THREE HOURS. RAINFALL
WILL AT LEAST APPROACH THESE VALUES...AND MAY EXCEED THEM IN
ISOLATED LOCATIONS.


...SOUTHERN GEORGIA AND ALABAMA...

DEEP LAYER LIFT IS FORECAST TO INCREASE AT A FAVORABLE TIME OF
DAY...MID/LATE AFTERNOON...AS COMBINED NORTHERN/SOUTHERN STREAM
HEIGHT FALLS PUSH INTO THE DEEP SOUTH...AND A SUB-TROPICAL JET
CIRCULATION NOSES IN FROM THE GULF. BROAD CONFLUENCE OF 850 MB
WINDS IS FORECAST...ESPECIALLY ACROSS SOUTHERN AL/GA...WHERE THE
MODELS FOCUS AN ORGANIZED PRECIPITATION EVENT. WITH MODERATE
INSTABILITY AND PRECIPITABLE WATER 1.25 TO 1.50 INCHES...CELLS
WILL LIKELY BE EFFICIENT RAIN PRODUCERS. CELL MOTIONS SUGGEST A
FAVORABLE SETUP FOR TRAINING...WITH 0-6 KM MEAN WINDS NEARLY
PARALLEL TO CORFIDI VECTORS FOR FORWARD PROPAGATION. THIS COULD
YIELD SPOT TOTALS OVER 2.5 OR EVEN 3 INCHES PER THE HI-RES
GUIDANCE. THERE IS...HOWEVER...NO INDICATION OF EXTREME TOTALS IN
THE MODELS...AND WITH FLASH FLOOD GUIDANCE BEING ON THE HIGH
SIDE...WE STOPPED SHORT OF OUTLINING A RISK AREA AT THIS TIME.

BURKE/ORAVEC
$$




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