Quantitative Precipitation Forecast
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000
FOUS30 KWBC 142242
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
642 PM EDT MON AUG 14 2017

...VALID 2242Z MON AUG 14 2017 - 12Z TUE AUG 15 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
90 W MRF 55 WNW MRF 25 SW PEQ 20 N FST 45 E FST 55 NE 6R6
30 E 6R6 40 S 6R6 85 SSW 6R6.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NE LNK 20 S CSQ 25 NNE CDJ 35 SSW CDJ LWC 30 NNW MHK
15 S EAR 10 WNW GRI 20 NE LNK.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 WSW MKL 15 SW MSL 15 SSE GTR 35 NNW TVR 20 N DTN 20 ENE LNC
15 NNW DUA 15 S OKM XNA 15 NE BVX 25 WSW MKL.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNE 1A5 10 N CHA 35 NW MDQ 25 SW MQY 10 NW 1A6 25 NNW DAN
10 S ECG 15 ESE OCW 15 SSW DPL 10 NE SOP 10 SE HKY 25 NNE 1A5.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 ESE SRC 25 SSW OLV 10 N GWO 15 NE ELD 15 SW DEQ 25 SE MLC
15 NNW JSV 35 SSW HRO 10 ESE SRC.


...LOWER MISSISSIPPI VALLEY / OK/TX/AR/MS/TN/LA...

THE PRIMARY CONCERN HERE IS TRANSPORT AND CONVERGENCE OF
MODERATELY UNSTABLE AIR IN TOWARD AN MCV THAT WAS MOVING DUE EAST
OUT OF EASTERN OKLAHOMA AS OF LATE AFTERNOON. GIVEN EARLIER
RAINFALL AND CLOUD COVER...ANY CONVECTION THAT WAS ONGOING AT 22Z
WAS LIKELY SOMEWHAT ELEVATED. ALTHOUGH A FEW SURFACE BASED STORMS
ARE POSSIBLE THIS EVENING NEAR THE MCV AND TRAILING TROUGH AXIS
INTO NORTHEAST TEXAS...THE MAIN FLASH FLOOD POTENTIAL WILL LIKELY
OCCUR WHEN ELEVATED STORMS REFORM WHERE LOW LEVEL FLOW ACCELERATES
AND CONVERGES AHEAD OF THE MCV OVER PRIMARILY SOUTHERN AND CENTRAL
ARKANSAS FROM LATE EVENING ONWARD. MOST UNSTABLE CAPE VALUES OF AT
LEAST 1000 J/KG ARE EXPECTED...COUPLED WITH ANOMALOUSLY RICH
MOISTURE AT OR ABOVE 2 INCHES. THE ENVIRONMENT ALONE SHOULD YIELD
EXTREME SHORT TERM RAIN RATES AND LOCAL 2-PLUS INCH TOTALS OVER A
SHORT TIME. IN AREAS WHERE CONVECTION ALIGNS WEST TO
EAST...HOWEVER...AT THE NOSE OF THE LOW LEVEL FLOW...TRAINING
COULD LEAD TO MORE GREATLY EXCESSIVE TOTALS...SUCH AS IN THE NSSL
WRF SOLUTION WHICH SIGNALS MORE THAN SEVEN INCHES IN SPOTS. FLASH
FLOOD GUIDANCE WAS ALREADY LOWERED IN THIS REGION BY EARLIER
RAINFALL.


...EASTERN TENNESSEE INTO NORTH CAROLINA...

A FEW SLOW MOVING CELLS NEAR THE OUTER BANKS OF NORTHEAST NORTH
CAROLINA WERE PRODUCING RADAR-ESTIMATED 1.5 INCH PER HOUR
RAINFALL. STREET FLOODING IS CERTAINLY POSSIBLE.
OTHERWISE...ATTENTION IS ON THE LOW AMPLITUDE SHORTWAVE TROUGH
MOVING THROUGH EASTERN TENNESSEE. THIS SHOULD SUPPORT POCKETS OF
STRONG CONVECTION AND CONVECTIVE RAIN RATES FROM EASTERN TN INTO
NC THIS EVENING...PER MOST OF THE MODEL GUIDANCE AND RECENT RAP
RUNS. DEEP LAYER FLOW IS DECIDEDLY WESTERLY WHICH SHOULD PROMOTE
FORWARD MOTION AND NOT TOO MUCH OF A TRAINING CONCERN...ALTHOUGH
THE VERY MOIST AND MODERATELY UNSTABLE ENVIRONMENT COULD SUPPORT
RAINFALL PRODUCING FLASH FLOODING IN ANY SUSCEPTIBLE LOCATIONS.


...SOUTHWEST TEXAS...

CONVECTION NEAR THE DAVIS MOUNTAINS AND BIG BEND REGION WAS
OCCURRING IN A PLUME OF DEEPER MOISTURE PER WATER VAPOR
IMAGERY...AND NEAR A REMNANT MCV FROM PRIOR CONVECTION. DEEP LAYER
FORCING IS NOT PARTICULARLY WELL FOCUSED...BUT WITH PRECIPITABLE
WATER VALUES SOMEWHAT GREATER THAN NORMAL...THERE IS A RISK OF
LOCAL FLASH FLOODING THROUGH LATE EVENING.

GRAPHICS AVAILABLE ON THE WEB AT WWW.WPC.NCEP.NOAA.GOV

BURKE
$$





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