Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 202216
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
615 PM EDT FRI OCT 20 2017

...VALID 2215Z FRI OCT 20 2017 - 12Z SAT OCT 21 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 N KGVX 15 NE LBX IAH 40 E CXO 25 NNE BPT KVBS 25 WNW KCRH.


THE PROBABILITY OF RAINFALL EXCEEDING FLASH FLOOD GUIDANCE IS LESS
THAN 5 PERCENT.

VERY HEAVY RAINS HAD OCCURRED EARLIER IN SOUTHEAST HOUSTON /
LEAGUE CITY. ANY FURTHER HEAVY RAIN WILL LIKELY REMAIN OFFSHORE OR
AFFECT A VERY SMALL PART OF SOUTHWEST LOUISIANA OR EXTREME
SOUTHEAST TEXAS NEAR PORT ARTHUR. STRONG CONVECTION OFFSHORE AT
22Z WAS OCCURRING IN A NEAR-SURFACE CONFLUENCE ZONE...AND
SUPPORTED BY DEEP LAYER FORCING AT THE TAIL END OF A TROUGH. WITH
TIME THE FORCING WILL EXIT TOWARD THE EAST AND NORTHEAST...WHILE
LEAVING THE SURFACE-BASED INSTABILITY AXIS BEHIND. LOW LEVEL
ATMOSPHERE ALONG THE COAST APPEARED RELATIVELY STABLE PER RAP
SOUNDINGS...AND CONVECTION WAS STRUGGLING TO INITIATE NEW UPDRAFTS
OR TO PROPAGATE ONSHORE. COUPLED WITH THE FACT THAT THE MESOSCALE
MODELS ARE INDICATING NO HEAVY RAIN OVER LAND THIS EVENING...WPC
WILL DROP THE PROBABILITY OF RAINFALL EXCEEDING FFG TO LESS THAN 5
PERCENT...ALTHOUGH A HEAVY DOWNPOUR MOVING ONSHORE CANNOT BE
ENTIRELY RULED OUT.

BURKE
$$




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