Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 122059
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
458 PM EDT FRI SEP 12 2014

...VALID 21Z FRI SEP 12 2014 - 00Z SUN SEP 14 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 SE MAF FST 30 N MRF 40 SSW GDP 45 E ELP 35 SSE ALM 40 E ALM
40 WNW ATS 15 WSW ROW 20 E ROW 45 SW LBB 35 S LBB 25 N BPG
35 SE MAF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SSE MMNL 35 S HBV 30 NNW EBG 20 S BKS 30 SE BKS 15 NW KOPM
35 SE KOPM 70 E BRO 65 SE MMMA 70 SSW MMMA 80 NNE MMCV 80 N MMCV
40 SE MMMY 10 NE MMAN 45 NNW MMAN 55 SW MMNL 40 WSW MMNL
25 SW MMNL 30 SSE MMNL.


...SOUTHEAST NEW MEXICO INTO WEST TEXAS...

THE ONGOING HEAVY TO ISOLATED EXCESSIVE RAINFALL EVENT THIS REGION
WILL BE TAPERING OFF LATER THIS AFTERNOON AND EVENING..AS THE
REINFORCING SHOT OF COLD AIR CONTINUES TO PUSH SOUTHWARD TO NEAR
THE BIG BEND AREA BY 13/00Z.  THIS LESSENING RAINFALL PATTERN WILL
ALSO BE SUPPORTED BY THE H85 FLOW..WHICH WILL GO FROM A VERY MOIST
EAST-SOUTHEASTERLY DIRECTION TO A LESS MOIST EAST-NORTHEASTERLY
DIRECTION.  SOME LOCALLY HEAVY/ISOLATED EXCESSIVE AMOUNTS ARE
STILL POSSIBLE INTO THE EARLY EVENING HOURS PARTS OF EXTREME
SOUTHERN NM INTO SOUTHWESTERN TX..BUT AFTER 00Z AREAL AVERAGE
RAINS WILL BE IN THE 0.25-0.50 INCH RANGE..AS PER FAIRLY AGREEABLE
MODEL QPF GUIDANCE.


...SOUTHEAST AND EAST TEXAS INTO WESTERN LOUISIANA...

MUTLICELLULAR CONVECTION WILL CONTINUE TO ORGANIZE ALONG AND SOUTH
OF A COLD FRONT THAT WILL BE SETTLING SLOWLY SOUTHWARD THIS
AFTERNOON AND EVENING. THE LOW-LEVEL FRONTOGENESIS...AIDED BY AN
INCREASE IN RIGHT ENTRANCE REGION UPPER JET FORCING...WILL
INTERACT WITH A VERY MOIST/UNSTABLE BNDRY LAYER OVER THE TX/LA
COASTAL PLAIN. AT THE SAME TIME...A WELL DEFINED LOW TO MID LEVEL
INVERTED TROUGH ASSOCD WITH AN EASTERLY WAVE IS ADVANCING IS SEEN
ADVANCING SLOWLY WESTWARD TOWARD THE REGION. THE STRENGTHENING
LOW-LEVEL FRONT IS EXPECTED TO INTERACT WITH THE NORTHERN PORTION
OF THIS WAVE AXIS THIS AFTERNOON AND EVENING TO ALLOW FOR
ADDITIONAL ORGANIZED AREAS OF HEAVY...POTENTIALLY EXCESSIVE
RAINFALL...GIVEN THE FAVORABLE THERMODYNAMIC ENVIRONMENT WITH THE
DEEP-LAYER MOISTURE AND INSTABILITY IN PLACE (PRECIPITABLE WATER
VALUES 2.00-2.25 INCHES AND MUCAPES OF 2000-3000 J/KG). THESE
FACTORS COUPLED WITH SLOW MOVEMENT AND THE POTENTIAL FOR CELL
MERGERS WILL ENHANCE THE RISK FOR FLASH FLOODING.


...LOWER RIO GRANDE VALLEY...

THIS AREA WILL SEE INCREASING RAINS/EMBEDDED CONVECTION THIS
PERIOD..AS THE MOIST AND RATHER WELL DEFINED EASTERLY WAVE IN THE
WESTERN GULF/NORTHERN BAY OF CAMPECHE MOVES WEST-NORTHWESTWARD
TOWARDS THE MEXICAN COAST.  TO THE NORTH OF THIS
WAVE..STRENGTHENING AND INCREASINGLY PERSISTENT LOW LEVEL
SOUTHEASTERLY FLOW INTO SOUTHERN TX/LOWER AND MID RIO GRANDE
VALLEY WILL BRING IN VERY HIGH MOISTURE..WITH PWS IN EXCESS OF
2.25 INCHES PUSHING INLAND LATER FRIDAY NIGHT AND SATURDAY.  THIS
VERY HIGH MOISTURE WILL SUPPORT THE POTENTIAL FOR SOME HEAVY TO
POSSIBLY EXCESSIVE RAINS..ESPECIALLY VICINITY OF THE LOWER/MID RIO
GRANDE VALLEY.  LEANED TOWARDS SOME OF THE HEAVIER MODEL QPF
GUIDANCE..WITH THE EXPECTATION FOR AT LEAST SOME 1-2+ INCH
TOTALS..BUT WITH SOME ISOLATED GREATER THAN 3 INCH AMOUNTS QUITE
POSSIBLE.


...CAROLINAS...

THE SURFACE FRONT WHICH WILL BECOME QUASI-STATIONARY THIS REGION
DURING THE PERIOD WILL BE THE FOCUS FOR SOME LOCALLY HEAVY
RAINS..ESPECIALLY FROM THE CAROLINAS INTO NORTHERN/CENTRAL GA AND
EASTERN AL..WITH POOLING OF PWS TO ABOVE 2 INCHES VICINITY OF THE
FRONT CONTRIBUTING TO THE HEAVY RAINFALL POTENTIAL.  UPPER FLOW
BECOMES RATHER DIFFLUENT BETWEEN THE EASTERLY WAVE OVER SOUTHERN
FL AND THE NORTHERN STREAM H5 TROF MOVING THRU THE GREAT
LAKES/NORTHEAST..WHICH WILL AID IN LARGE SCALE LIFT.  HIGH
MOISTURE AND SLOW MOVING AND/OR REPEATING CELLS LIKELY TO SUPPORT
AT LEAST SOME 1-2 INCH AREAL AVERAGE RAINFALL AMOUNTS..WITH SOME
ISOLATED 3+ INCH TOTALS POSSIBLE..MAINLY THRU THE CAROLINAS.


FOR FURTHER DETAILS REGARDING ANY ACTIVE MESOSCALE PRECIPITATION
DISCUSSIONS (MPD) WITHIN THE EXCESSIVE RAINFALL OUTLOOK AREA...
PLEASE REFER TO THE LINK FROM THE WPC HOME PAGE ABOVE THE TOP NEWS
OF THE DAY... OR GO DIRECTLY TO THE MPD PAGE:
WWW.WPC.NCEP.NOAA.GOV/METWATCH/METWATCH_MPD.PHP.


TERRY/HURLEY
$$




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