Quantitative Precipitation Forecast
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FOUS30 KWBC 281500
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
959 AM EST MON NOV 28 2016

...VALID 15Z MON NOV 28 2016 - 12Z TUE NOV 29 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WSW CYSB 15 E CYZE SLH 10 SE ESC 20 W ESC 25 ENE LNL
25 WSW CMX 25 ENE CWDV 55 W CWYW.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SSE BAD 15 NE 4F4 15 ESE LBR 25 SSE RUE 30 NNE BVX 20 E FAM
20 SW ENL RSV 25 N BMG 20 WSW BAK 30 W FTK 15 S CKV 10 SE 1M4
20 NNE NMM 35 WNW PIB 30 NE BTR 25 W BTR 40 E ACP 15 NNW ESF
25 SSE BAD.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 NE MKL 40 E GWO 40 NNW HKS 25 WNW TVR 10 S MLU 40 ENE BAD
35 W ELD 10 NW PBF 20 SE SRC 30 NNW DYR 35 S PAH 45 NE MKL.


LOWER OH VALLEY INTO THE LOWER MS VALLEY..LOWER TN VALLEY

15Z UPDATE

THE ONLY MINOR CHANGE TO THE EXCESSIVE RAINFALL OUTLOOK WAS TO
EXPAND THE SLIGHT RISK A BIT SOUTH INTO PORTIONS OF NORTHERN LA
AND WEST CENTRAL MS BASED ON LATEST RADAR AND HRRR TRENDS. IN
GENERAL THE PROGRESSIVE NATURE OF THE CONVECTION WILL KEEP
RAINFALL AMOUNTS IN THE 1-2" RANGE ACROSS THE MARGINAL RISK
AREA...WITH ISOLATED HIGHER AMOUNTS. THE BEST CHANCE FOR A PERIOD
OF TRAINING DUE TO CELL MERGERS IS ACROSS THE SLIGHT RISK AREA
NEAR THE MS RIVER. IT IS HERE WHERE THE CONVECTION ASSOCIATED WITH
THE COLD FRONT IS FORECAST TO MERGE WITH THE PREFRONTAL AXIS OF
CONVECTION CURRENTLY STREAMING FROM SOUTHWEST TO NORTHEAST ACROSS
NORTHERN LA INTO NORTHERN MS. AS OF NOW LIMITED INSTABILITY IS
RESULTING IN GENERALLY WEAK CONVECTION. HOWEVER SOME SIGNS WE
COULD SEE AN UPTICK IN INTENSITY THROUGH THE MORNING HOURS AS
FORCING CONTINUES TO INCREASE. THUS DO HAVE THE POTENTIAL FOR 2-3"
OF RAIN ACROSS THE SLIGHT RISK AREA AS CELL MERGERS INCREASE AND
CONVECTION POSSIBLY INTENSIFIES. THESE TOTALS MAY BEGIN TO
APPROACH FLASH FLOOD GUIDANCE. EXPECT CONVECTION TO BECOME MORE
PROGRESSIVE BY 21Z AS THE FRONT PICKS UP ITS EASTWARD MOTION.
LOCALLY HIGH RATES ARE LIKELY INTO PORTIONS OF AL/GA WITH THE
CONVECTIVE LINE AS IT MOVES EAST...BUT THE FLOOD POTENTIAL SEEMS
LOW DUE TO HIGH FLASH FLOOD GUIDANCE AND QUICK FORWARD PROGRESSION
OF THE CONVECTIVE LINE. -CHENARD

PREVIOUS DISCUSSION...

ONLY SOME SLIGHT CHANGES MADE TO THE PREVIOUS EXCESSIVE RAINFALL
POTENTIAL OUTLOOK FOR THE UPCOMING DAY 1 TIME PERIOD.  STRONG
HEIGHT FALLS ROTATING AROUND THE MEAN TROF ACROSS THE MID SECTION
OF THE NATION WILL BE EJECTING QUICKLY NORTHEASTWARD MONDAY FROM
THE SOUTHERN PLAINS INTO THE LOWER TO MID MS VALLEY.  CONVECTION
BEGINNING TO ENHANCE OVER THE SOUTHERN PLAINS EARLY THIS MORNING
SHOULD REMAIN WELL DEFINED IN A REGION OF STRONG UPPER
DIFFLUENCE...ANOMALOUS PW VALUES AHEAD OF THESE HEIGHT FALLS AND
ALONG AND AHEAD OF THE ASSOCIATED COLD FRONT PUSHING EASTWARD FROM
THE SOUTHERN PLAINS INTO THE MS VALLEY-TN VALLEY MONDAY INTO
MONDAY NIGHT.  THIS WILL SUPPORT WIDESPREAD MODERATE TO HEAVY
PRECIP TOTALS FROM EASTERN PORTIONS OF THE SOUTHERN
PLAINS---EASTWARD INTO THE LOWER TO MID MS VALLEY---TN VALLEY THIS
PERIOD.  THERE IS OVERALL GOOD MASS FIELD AND QPF AGREEMENT IN THE
MODELS---WITH CONSENSUS FOR THE HEAVIEST TOTALS AND GREATEST
EXCESSIVE RAINFALL THREAT FROM THE LOWER OH VALLEY---SOUTHWARD
INTO THE LOWER MS VALLEY---LOWER TN VALLEY.  WHILE THESE AREAS
HAVE BEEN VERY DRY THIS FALL---THERE MAY STILL BE SOME ISOLATED
RUNOFF ISSUE FROM A PERIOD OF SLOW MOVEMENT OF TRAINING OF CELLS
IN A SOUTHWEST TO NORTHEASTERLY DIRECTION MONDAY AFTERNOON---WITH
ISOLATE SHORT TERM PRECIP TOTALS OF 1-2"+ POSSIBLE.  THE WELL
DEFINED CONVECTIVE LINE ALONG AND AHEAD OF THIS FRONT WILL LIKELY
BECOME MORE PROGRESSIVE EARLY EVENING THROUGH THE MID TO UPPER OH
VALLEY...MID TO UPPER TN VALLEY INTO THE SOUTHERN APPALACHIANS.
MODEL QPFS DO DECREASE AFTER 0000 UTC GIVEN THIS EXPECTED
INCREASED PROGRESSION. FOR THIS REASON---THE RISK AREAS WERE NOT
EXPANDED FARTHER EASTWARD INTO THE MID TO UPPER OH VALLEY---MID TO
UPPER TN VALLEY AND SOUTHERN APPALACHIANS.


ORAVEC
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