Quantitative Precipitation Forecast
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FOUS30 KWBC 300111
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
910 PM EDT FRI APR 29 2016

...VALID 01Z SAT APR 30 2016 - 12Z SAT APR 30 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNW 6R9 25 SE 7F9 15 NNW F18 20 ENE ADM 15 E CFV 35 SW SZL
20 S VIH 35 S PAH 30 N MSL 30 SSW 1M4 25 ESE GTR 50 WSW GTR
30 SSE GLH 30 NE ESF 10 NNW CWF 10 ENE GLS 10 SSE LBX 15 S 3T5
10 W AUS 25 NNW T82 20 NNW 6R9.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 ENE IAH 10 SSW DWH 10 WSW CLL 25 E TPL 10 N LNC 10 E GYI MLC
20 N FSM 20 NW BVX 20 NE NQA 20 SSE OLV 45 N GLH 20 WSW MLU
20 W DRI 35 ENE IAH.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
RUE 10 NE SRC 30 NE SGT 15 ESE SGT 10 W PBF 25 SSW M89 30 N DTN
20 SW SHV 15 SSE GGG 10 E TYR 20 SE GVT 30 SE DUA 35 ESE MLC RUE.


...SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY...

BOTH OBSERVATIONAL TRENDS AND THE SYNOPTIC SIGNAL FOR ASCENT AND
RICH LOW LEVEL INFLOW POINT TO NORTHEAST AND EAST CENTRAL TEXAS AS
THE MOST LIKELY TO SEE LARGE SCALE INTENSE RAINFALL OVERNIGHT. AT
01Z A HIGH RISK OF EXCESSIVE RAINFALL WAS MAINTAINED OVER THE
ARKLATEX...PARTS OF ADJACENT OKLAHOMA...AND EXTENDING INTO CENTRAL
ARKANSAS...WITH MUCH OF THAT RISK BEING DRIVEN BY WET ANTECEDENT
CONDITIONS AND VERY LOW FLASH FLOOD GUIDANCE VALUES. WE ALSO
EXPANDED THE HIGH RISK DOWN TO ABOUT TYLER AND LONGVIEW ALONG
I-20...WITH SWATHS OF 2 TO 5 INCHES OF RAIN HAVING ALREADY FALLEN
AS OBSERVED BY GAUGES AND ESTIMATED BY RADAR. UP NORTH INTO
ARKANSAS...THE MOST INTENSE PERIOD OF RAINFALL HAD ENDED...BUT
WIDESPREAD MODERATE TO OCCASIONALLY HEAVY RAIN WILL CONTINUE
THROUGH LATE EVENING...COMPOUNDING THE ONGOING PROBLEMS.
ADDITIONAL AVERAGE RAINFALL OF 1 TO 2 INCHES AND LOCALLY 2.5
INCHES IS FORECAST IN ARKANSAS. MUCH HEAVIER AMOUNTS OF NEW
RAINFALL ARE FORECAST OVER THE EXPANDED PORTION OF THE HIGH
RISK...AND WITHIN THE MODERATE RISK AREA OVER EAST TEXAS AND
NORTHWEST LOUISIANA. LATEST HRRR GUIDANCE AND THE 12Z WRF-ARW AND
WRF-NMM SIGNAL THE POSSIBILITY OF EXTREME RAINFALL EXCEEDING 7
INCHES AT A GIVEN POINT OVER EAST TEXAS TONIGHT...WHERE THE MID
LEVEL LIFT AND LOW LEVEL INFLOW RESPONSE AHEAD OF A MIGRATING
UPPER TROUGH WILL OVERLAP WITH AN INSTABILITY GRADIENT / ENHANCED
WARM ADVECTION NORTH OF A WELL ESTABLISHED OUTFLOW BOUNDARY.
MOISTURE TRANSPORT REMAINS HIGHLY FOCUSED OVER EAST TEXAS PER THE
LARGE SCALE MODELS AND THE RAP...WITH PRECIPITABLE WATER VALUES
RISING TO A VERY IMPRESSIVE 2.10 INCHES PER LATEST SATELLITE DATA
AND 00Z KCRP SOUNDING. THESE PW VALUES ARE 2.0 TO 2.5 STANDARD
DEVIATIONS ABOVE THE CLIMATOLOGICAL MEAN. GIVEN MODERATE TO STRONG
INSTABILITY ACTING UPON SUCH MOISTURE...EXTREME LOCAL RAIN RATES
WILL BE POSSIBLE...CERTAINLY EXCEEDING 3 INCHES PER HOUR.

A MORE ISOLATED FLASH FLOOD THREAT EXTENDS BACK WESTWARD TO
INCLUDE DRYLINE CONVECTION...BEING DRIVEN MORE BY STRONG
INSTABILITY RATHER THAN THE SYNOPTIC LIFT. BRIEF PERIODS OF
TRAINING MAY LEAD TO SURFACE RUNOFF PROBLEMS IN THE HILL COUNTRY.


...SOUTHERN MISSOURI...

THE SLIGHT RISK WAS EXPANDED TO INCLUDE SOUTHWEST MISSOURI...AS
CONVECTION RIDING UP OUT OF EASTERN OKLAHOMA HAD PROMPTED A FEW
FLASH FLOOD WARNINGS...AND MOISTURE CONTENT WAS FORECAST TO
INCREASE THROUGH 06Z. THE LATEST HRRR AND ESRL EXPERIMENTAL HRRR
PRODUCE 1 TO 2 INCHES OF RAIN ON AVERAGE OVER SOUTHWEST MISSOURI
TONIGHT...WHILE LOCAL CELL MERGERS COULD SUPPORT ISOLATED AMOUNTS
OF 2.5 INCHES OR MORE.

BURKE
$$





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