Quantitative Precipitation Forecast
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FOUS30 KWBC 161825
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 PM EDT THU APR 16 2015

...VALID 18Z THU APR 16 2015 - 00Z SAT APR 18 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SSW MGM 30 N DHN 10 NW BGE 10 S MAI 25 SSE NPA 35 NNE CYD
GSM 15 NE KBBF 25 NW ALI 25 NNW COT HDO 15 WSW 62H 35 E UTS
15 SSE AEX 40 WNW PIB 45 ESE NMM 20 SSW MGM.


...GULF COAST STATES...

IT IS NOT CLEAR WHERE OR WHEN A FOCUSED HEAVY RAIN THREAT WILL
OCCUR...BUT THE GULF COAST REGION REMAINS BENEATH ENERGETIC
WESTERLY FLOW ALOFT WITH PLENTIFUL MOISTURE AND WEAK BUT
SUFFICIENT INSTABILITY IN PLACE. THIS REGION HAD ALSO EXPERIENCED
ABOVE AVERAGE RAINFALL DURING THE PAST SEVEN DAYS...AND MAY BE A
LITTLE MORE SUSCEPTIBLE TO FLOODING OF CREEKS AND STREAMS AND
RAPID SURFACE RUNOFF IN URBAN AREAS. ONE OF THE LIMITING
FACTORS...HOWEVER...IS THE RELATIVE ABSENCE OF A TIME AT WHICH MID
LEVEL SHORTWAVES AND ENHANCED LOW LEVEL INFLOW WILL BE IN
SYNC...AT LEAST PER THE LATEST DETERMINISTIC GUIDANCE.

THIS AFTERNOON/EVENING...MID/UPPER LEVEL DIVERGENCE WILL GENERATE
BROAD AND DEEPER ASCENT WHERE THE SOUTHERN STREAM OF THE POLAR JET
AND SUBTROPICAL JET SPLIT OVER MS/AL AND SE LA. THUNDERSTORM
DEVELOPMENT AT 18Z WAS INCREASING NEAR LOW LEVEL BOUNDARIES...A
LOOSELY DEFINED FRONT AND THE SEA BREEZE. TRAINING CELLS ON A
LOCAL SCALE MAY PRODUCE EXCESSIVE RAINFALL...SO WE MAINTAINED A
BROAD SLIGHT RISK AREA...BUT ORGANIZATION ON LARGER SCALES SHOULD
SUFFER AS THE DEVELOPING UPPER FORCING MOVES OFF THE AXIS OF
GREATER INSTABILITY LOCATED BACK ACROSS THE WESTERN GULF COAST.
EMPHASIS SHOULD GRADUALLY SHIFT BACK WEST WITH TIME AS A LARGE
UPPER TROUGH LEANS INTO TEXAS. DIFLUENT MID LEVELS WILL COMBINE
WITH AN INCREASING AXIS OF MOISTURE/INSTABILITY TO PRODUCE GREATER
COVERAGE AND ORGANIZATION OF THUNDERSTORMS PRODUCING HEAVY RAIN
OVER THE TEXAS HILL COUNTRY TO THE UPPER TX COAST LATER TONIGHT
AND ESPECIALLY ON FRIDAY. PRECIPITABLE WATER VALUES WILL BE
SOMEWHAT ANOMALOUS...AND HEAVY RAIN RATES ARE EXPECTED...BUT OF
GREATER CONCERN WOULD BE THE POTENTIAL FOR REPEATED ROUNDS OF
CONVECTION SHOULD THE AXIS OF DEEPER MOISTURE...ORIENTED GENERALLY
WEST TO EAST...BECOME REINFORCED BY THUNDERSTORM
OUTFLOWS...PRODUCING A STRONGER LOW LEVEL FOCUS FOR REDEVELOPMENT
AHEAD OF THE SLOW MOVING UPPER TROUGH.

BURKE
$$




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