Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 221345
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
944 AM EDT SUN MAY 22 2016

...VALID 15Z SUN MAY 22 2016 - 12Z MON MAY 23 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 SSW MBG 15 SW JMS 30 S RDR 20 NNE FAR 15 N ETH 35 W BKX
40 N ONL 45 WNW VTN 30 SSE PHP 40 SSW MBG.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WSW KVBS 20 SW KXIH 20 W KGVX 10 S BYY 10 NNW BYY 10 WSW HOU
IAH 15 SE CXO 20 NE CXO 40 ENE CXO 30 N BPT 25 E BPT 15 NNW KVBS
KVBS 20 SW KVBS 20 WSW KVBS.


1400 UTC UPDATE

CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WERE
TO UPGRADE THE RISK AREA OVER THE UPPER COAST OF TX TO A SLIGHT
RISK.  CONVECTION THIS MORNING CONTINUES TO ENHANCE IN THE
VICINITY OF THE STATIONARY FRONTAL BOUNDARY DRAPED ALONG THE MID
TO UPPER TX COAST.  THE NAM CONEST...HRR AND HRR EXPERIMENTAL HAVE
THE BEST APPARENT HANDLE ON THIS ACTIVITY---ALL SHOWING POTENTIAL
INTO EARLY AFTERNOON FOR LOCALLY VERY HEAVY RAINFALL AMOUNTS.
WITH RADAR ESTIMATES ALREADY SHOWING TOTALS IN EXCESS OF 5" OVER
THE UPPER COASTAL AREAS OF TX AND LIKELIHOOD OF CONVECTION
PERSISTING AND TRAINING FOR SEVERAL MORE HOURS IN THE VICINITY OF
THIS BOUNDARY---THE RISK OF ISOLATED RUNOFF ISSUES WILL CONTINUE.
PLEASE SEE WPC`S MESOSCALE PRECIPITATION DISCUSSION #0225 VALID
UNTIL 1800 UTC FOR ADDITIONAL INFORMATION ACROSS THIS AREA.

ORAVEC


PREVIOUS DISCUSSION

...NORTHERN PLAINS / MAINLY THE EASTERN DAKOTAS...

EXPECTING AN ORGANIZED CONVECTIVE EVENT LATE THIS AFTERNOON
THROUGH THE OVERNIGHT HOURS AS A PACIFIC COLD FRONT PUSHES INTO AN
INCREASINGLY RICH RETURN OF GULF MOISTURE OVER THE PLAINS. THERE
IS LIKELY TO BE A LOCAL MAXIMUM OF CONVECTIVE INITIATION ACROSS
WESTERN NEBRASKA AND WESTERN/CENTRAL SOUTH DAKOTA...IN A REGION OF
BACKED LOW LEVEL FLOW AND COOLER MID LEVEL TEMPERATURES COMPARED
TO AREAS FARTHER SOUTH. WIDESPREAD INITIATION ALSO EXPECTED AHEAD
OF THE FRONT IN NORTH DAKOTA...WITH INCREASINGLY FAVORABLE
MOISTURE FLUX AT THAT LATITUDE DURING THE OVERNIGHT HOURS. A
SLIGHT RISK OF EXCESSIVE RAINFALL HAS BEEN INTRODUCED WHERE WPC
AREAL AVERAGE QPF IS 0.75 TO 2.00 INCHES...WITH HI-RES MODELS
INDICATING LOCAL AMOUNTS ABOVE 3 INCHES. THIS INCLUDES MAINLY THE
EASTERN DAKOTAS...TO THE NORTH OF THE SAND HILLS. ANTECEDENT
CONDITIONS ARE NOT ESPECIALLY MOIST...AND IN SOME CASES DRY...BUT
THIS REGION IS LIKELY TO EXPERIENCE THE EARLY PHASE OF UPSCALE
GROWTH WITH MANY CELL MERGERS AND ACCELERATION OF LOW LEVEL INFLOW
DURING THE EVENING. INDIVIDUAL STORM MOTIONS WILL BE QUICK TO THE
NORTHEAST...BUT WITH POTENTIAL FOR BACKBUILDING AND TRAINING.


...TEXAS AND LOUISIANA GULF COAST...

CONDITIONALLY UNSTABLE AIR WAS IN PLACE ALONG THE EAST EDGE OF THE
WARM/CAPPED ATMOSPHERE OVER SOUTH TEXAS...AND EXTENDING TOWARD A
REMNANT FRONTAL BOUNDARY OVER SOUTHERN LOUISIANA. A SHORTWAVE ON
THE BACK SIDE OF THE EASTERN U.S. TROUGH WILL GRAZE THIS UNSTABLE
AIRMASS EARLY TODAY. SLOW MOVING THUNDERSTORMS WERE ONGOING AT
0830Z OVER COASTAL LOUISIANA. ACTIVITY IS PREDICTED TO EXPAND IN
COVERAGE TO THE WEST AND NORTHWEST...PERHAPS AS FAR AS THE HOUSTON
AREA. MEAN 0-6 KM WINDS ARE SLOW...AT LESS THAN 10 KNOTS...AND
WITH SEASONABLY RICH MOISTURE AND MODERATE INSTABILITY IN
PLACE...VERY HEAVY DOWNPOURS WILL BE EMBEDDED WITHIN ANY ACTIVITY
THAT FORMS.

BURKE
$$





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