Quantitative Precipitation Forecast
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000
FOUS30 KWBC 140048
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
847 PM EDT SUN AUG 13 2017

...VALID 01Z MON AUG 14 2017 - 12Z MON AUG 14 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 E CVN 40 N TCC 30 WSW CAO 25 NNE DHT 30 SE HHF 10 ESE FSI
25 NW 1F9 30 N ABI 35 E CVN.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 WSW BKX 15 SW GHW 15 WNW MGG 10 NNW MKT 20 S EST 25 NW TQE
30 W HJH PTT 15 WSW HLC 35 SSE ANW 25 WSW BKX.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SE TXK 30 E ELD 20 ESE MLU 25 N ESF OCH 20 WSW TYR SLR
15 SE TXK.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 NE INW 35 WSW GNT 25 NNE SVC 25 SSW SVC 35 WNW SAD 30 SE PRC
45 WNW 40G 10 WNW GCN 35 NNW INW 35 NE INW.


...LOWER MISSISSIPPI VALLEY...

A SHORTWAVE TROUGH / VORTICITY MAX...WAS PUSHING TOWARD
MISSISSIPPI. THE GREATEST DEEP LAYER FORCING WAS MOVING INTO MORE
STABLE ATMOSPHERE OVER TN/MS...AND CONVECTION ALONG THE TRAILING
TROUGH AXIS WAS WEAKENING OVER NORTHEAST TEXAS LATE SUNDAY
EVENING. WPC WILL LEAVE A SMALL MARGINAL RISK AREA IN PLACE
THROUGH MORNING...AS LOW LEVEL FLOW WILL GRADUALLY RECOVER AND
INCREASE TOWARD MORNING...MOVING ACROSS THERMAL / INSTABILITY
GRADIENTS TO PERHAPS PRODUCE WARM ADVECTION DRIVEN CONVECTION OVER
PARTS OF TX/LA/AR. WITH MODERATE INSTABILITY STILL IN
PLACE...HEAVY DOWNPOURS COULD POSE AN ISOLATED FLASH FLOOD RISK.


...HIGH PLAINS / CO/NM INTO TX/OK...

MODERATE INSTABILITY HAD DEVELOPED...STRADDLING A STALLED FRONTAL
BOUNDARY. WESTERLY FLOW ALOFT...RESPECTABLE FOR AUGUST...HAD
ALLOWED FOR ORGANIZED CONVECTIVE MODES...WITH SOME UPSCALE GROWTH
OCCURRING OVER THE TEXAS PANHANDLE. THIS DEVELOPING MCS AS OF LATE
SUNDAY EVENING...IS FORECAST TO DRIVE SOUTHEASTWARD...STRADDLING
HIGHWAY 287. THERE ARE SOME NEGATIVE FACTORS FOR FLASH
FLOODING...SUCH AS DRY MID LEVEL AIR...BUT WITH SOMEWHAT LOW FFG
NUMBERS AND SEASONABLY RICH LOW LEVEL MOISTURE...IT IS LIKELY THAT
A FEW LOCATIONS WILL SEE RAINFALL APPROACHING OR EXCEEDING FFG.


...SOUTHWEST...

THUNDERSTORMS NEAR THE MOGOLLON RIM HAD EXHIBITED PSEUDO-ORGANIZED
STRUCTURES...WITH A TENDENCY FOR CELLS TO REDEVELOP ALONG THE
WESTERN FLANK OF COMBINED OUTFLOWS BEFORE MOVING BACK TO THE
EAST...RESULTING IN BRIEF EPISODES OF TRAINING...AND RAINFALL AS
MUCH AS 1.5 INCHES IN AN HOUR OVER SMALL AREAS. THE UNIVERSITY OF
ARIZONA WRF WAS PROBABLY PERFORMING THE BEST OF ANY MODEL WE COULD
FIND...AND SUGGESTS CONVECTION COULD SURVIVE A FEW HOURS BEYOND
SUNSET...GRADUALLY ROLLING SOUTH TO FIND THE REMAINING
INSTABILITY. LARGE SCALE FLOW WILL REMAIN SOMEWHAT FAVORABLE FOR
CONVECTION OVERNIGHT...BUT DIMINISHING INSTABILITY SHOULD
GRADUALLY WIN OUT...WITH THE FLASH FLOOD THREAT SUBSIDING BY
AROUND 04Z.


...UPPER MIDWEST...

HERE A DECENT AMOUNT OF MOISTURE FLUX EXISTS ALONG THE EASTERN
PERIPHERY OF AN INSTABILITY AXIS. WITH A SLOW MOVING COMPACT
TROUGH JUST UPSTREAM...AND LATE AFTERNOON THUNDERSTORMS ALREADY
SHOWING A TENDENCY TO LINE UP OVER PARTS OF NE/SD/MN...WE WILL
MAINTAIN AND EXPAND A MARGINAL RISK AREA. THE RISK WAS EXPANDED
INTO NORTH CENTRAL KANSAS...WHERE A FEW SOLUTIONS...INCLUDING THE
HRRR...SUGGEST SLOW MOVING THUNDERSTORMS FORMED IN WARM ADVECTION
BY THE MORNING HOURS..AS OFTEN OCCURS ALONG THE NORTH TO SOUTH
ORIENTED THERMAL GRADIENTS NEAR THE TOP OF THE BOUNDARY LAYER.

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

BANN/BURKE
$$




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