Quantitative Precipitation Forecast
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152
FOUS30 KWBC 132214
QPFERD

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

...VALID 2214Z SUN AUG 13 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
40 S MRH 30 NE CHS 20 W OGB 30 E GRD 20 SSW EQY 10 WSW MEB
10 NW PGV 15 N FFA 100 E FFA.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
80 SSW OLS 75 SSW OLS 80 S GBN 40 SSE GBN 45 S CGZ 15 NW TUS
40 N DMA 50 ENE IWA 30 ESE PRC 55 W GCN 30 SE SGU 50 ESE SGU
35 NNE FLG 20 SSW SJN 65 NW TCS 30 W TCS DMN 25 SSW LRU
15 NNE ALM 20 E ROW 45 NNW MDD 15 E BPG 20 W SJT 50 E 6R6
55 S 6R6 130 SSW 6R6.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NW JWG 25 SSE MLC 15 E M89 30 W M97 MKL 45 NW MDQ 20 WSW 3A1
NMM 25 WNW MCB 15 SSW ESF 25 WNW LFK 15 SSE CRS 15 NE DTO
30 NNW 1F9 25 NNE ABI 40 ESE CVN 40 WNW CAO 30 S LHX 20 NNE EHA
25 NW JWG.

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 SE SPW 25 S ONL
25 WSW BKX.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 W IER 20 N PSN 10 SW 3T1 30 ENE OSA 25 ENE ELD 40 NNE GLH
35 SW GWO 30 NNW HEZ 35 W IER.


...LOWER MISSISSIPPI VALLEY...

A SHORTWAVE TROUGH / VORTICITY MAX...WAS PUSHING TOWARD
MISSISSIPPI...WITH THUNDERSTORMS ON THE LEADING EDGE...AND THEN
OTHER STORMS WITHIN THE CONFLUENT MID LEVEL FLOW REGIME TO THE
REAR OF THE WAVE...OVER NORTHEAST TEXAS. PRECIPITABLE WATER VALUES
WERE VERY HIGH THROUGHOUT THIS REGION...AND HEATING HAD PRODUCE
POCKETS OF MODERATE CAPE...LEADING TO POTENTIAL FOR INTENSE SHORT
TERM RAIN RATES. THE ACTIVITY MAY NOT BE OVERLY ORGANIZED...NOR
VERY PERSISTENT OVER ANY GIVEN SPOT...ESPECIALLY AS THE CONTINUED
PROGRESSION OF THE SHORTWAVE WILL ALLOW FOR VEERING WINDS AND
DIMINISHING LIFT IN TEXAS EARLY THIS EVENING...OVER AREAS OF LOWER
FLASH FLOOD GUIDANCE. STILL...THE STRONG STORM TERM RATES MAY LEAD
TO FLASH FLOODING ANYWHERE FROM TEXAS TO SOUTHERN TENNESSEE AND
NORTHWEST ALABAMA.


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

MODERATE INSTABILITY HAD DEVELOPED...STRADDLING A STALLED FRONTAL
BOUNDARY. WESTERLY FLOW ALOFT...RESPECTABLE FOR AUGUST...WILL
CONTRIBUTE TO A MIX OF ORGANIZED STORM MODES...WITH SOME POTENTIAL
FOR UPSCALE GROWTH INTO A FORWARD PROPAGATING MCS OVER THE TEXAS
PANHANDLE THIS EVENING. 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.
SEE MESOSCALE DISCUSSION NUMBER 0684 FOR DETAILS.


...EASTERN CAROLINAS...

AN AFTERNOON / EARLY EVENING THREAT OF HEAVY RAIN AND ISOLATED
FLASH FLOODING EXISTS IN THE NARROW ZONE BETWEEN A SLOW MOVING
COLD FRONT AND THE CAROLINA COAST. SEE MESOSCALE DISCUSSION 0682
FOR DETAILS.


...SOUTHWEST...

THUNDERSTORMS NEAR THE MOGOLLON RIM HAD EXHIBITED PSEUDO-ORGANIZED
STRUCTURES AS OF 22Z...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. ELSEWHERE TYPICAL SUMMER CONVECTION OPERATING WITHIN
A ROUGHLY 1.5 STANDARD DEVIATION PW ENVIRONMENT WILL MAINTAIN A
THREAT OF ISOLATED FLASH FLOODING OVER PARTS OF SOUTHERN AZ/NM AND
SOUTHWEST TEXAS.


...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 SD/MN...WE RELOCATED A
MARGINAL RISK AREA HERE...MOVING IT OUT OF THE AREAS FARTHER NORTH
WHERE INSTABILITY WAS LARGELY EXHAUSTED. THE NAM AND HRRR DO POINT
TO THE POTENTIAL FOR ISOLATED RAINFALL EXCEEDING 2 INCHES...WHICH
COULD APPROACH 1 TO 3 HOUR FFG VALUES.

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

BANN/BURKE
$$





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