Quantitative Precipitation Forecast
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000
FOUS30 KWBC 311427
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1026 AM EDT THU JUL 31 2014

...VALID 15Z THU JUL 31 2014 - 12Z FRI AUG 01 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 S CVS 10 SW MAF 40 N 6R6 100 S E38 75 SE MMCS MMCS
45 SSW LRU 50 SSW DMN 75 ESE DUG 20 WSW OLS 75 S GBN 60 SSW GBN
20 S GBN 50 SW SOW 25 SSE GUP 45 ESE FMN 15 E CPW 30 SSW PUB
10 S TAD 50 NNW TCC 15 W TCC 15 S CVS.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 ESE GYH 10 N AHN 10 S DNN 25 NNE 1A5 15 E GEV 10 ESE GYH.


SOUTHERN ROCKIES/ARIZONA
~~~~~~~~~~~~~~~~~~~~~~~~
MOIST UPSLOPE FLOW CONDITIONS ARE EXPECTED ACROSS NM AND WESTERN
TX WITH POTENTIAL FOR STRONG SLOW-MOVING CONVECTION FOCUSING ALONG
THE FAVORED ERN UPSLOPE AREAS OF SRN CO INTO NM/EXTREME WESTERN TX
UNDER A WEAK NORTHWESTERLY FLOW ALOFT.  ACROSS SOUTHWEST NM AND
SOUTHEAST AZ, SCATTERED THUNDERSTORMS ARE EXPECTED IN CONNECTION
WITH THE NORTH AMERICAN MONSOON THIS AFTERNOON AND EVENING.
PRECIPITABLE OF ~1.50 INCHES COMBINED WITH 850-700 HPA INFLOW OF
20+ KTS ALONG THE FRONT RANGE OF THE ROCKIES AND CAPES EXPECTED TO
EXCEED 1000 J/KG DUE TO DAYTIME HEATING MEET THE CRITERIA FOR THE
WET MULTI-CELL ENVIRONMENT.   MODEL SOUNDINGS SHOULD AREAS OF TALL
SKINNY CAPES WITH NO LOW-LEVEL DRY INTRUSIONS ALONG WITH WEAK
STEERING FLOW OF LESS THEN 10 KTS ESPECIALLY ACRS PARTS OF
SOUTHERN NM/EXTREME WESTERN TX SUGGESTING THE POTENTIAL FOR SOME
SLOW MOVING STORMS CAPABLE OF PRODUCING SOME LOCALLY HEAVY
RAINFALL AMOUNTS.  SOME LOW-LEVEL INFLOW ACROSS SOUTHERN AZ SHOULD
FOCUS CONVECTION WITHIN AND NEAR THEIR SOUTHEAST MOUNTAINS.  FLASH
FLOOD GUIDANCE VALUES ARE RATHER LOW ACROSS THIS REGION DUE TO
SOME RECENT RAINS WHICH GIVEN THE ABOVE SUPPORTS A SLIGHT RISK OF
EXCESSIVE RAINS.


SOUTHERN APPALACHIANS
~~~~~~~~~~~~~~~~~~~~~
MAINLY AFTER 06Z, 850 HPA INFLOW INTO THE MOUNTAINS OF NORTHERN GA
INCREASES OVER 25 KTS WHILE UPSTREAM MOST UNSTABLE CAPES REMAIN
~1000 J/KG (PER RECENT RAP GUIDANCE).  FLASH FLOOD GUIDANCE VALUES
ARE HIGH IN THIS UNSATURATED REGION, WHICH LIMITS THE OVERALL
RISK.  HOWEVER, VEERING WINDS IN THE LOW-LEVELS SHOULD ALLOW FOR
SOME FORWARD PROPAGATION, AND THE FORWARD PROPAGATING CORFIDI
VECTORS SUGGEST 20 KTS OF NORTHEAST MOTION FROM NORTHERN GA INTO
THE WESTERN CAROLINAS.  PRECIPITABLE WATER VALUES ARE NEAR THE
90TH PERCENTILE FOR LATE JULY/EARLY AUGUST, IN THE 1.75-2" RANGE.
THIS SUGGESTS RAINFALL AMOUNTS OF 2" AN HOUR ARE POSSIBLE WHERE
CELLS BACKBUILD, OR MORE LIKELY, TRAIN.  LOCAL AMOUNTS IN THE 2-4"
RANGE ARE POSSIBLE, WHICH COULD BREACH THE HIGH FLASH FLOOD
GUIDANCE.


LOUISIANA/TEXAS BORDER
~~~~~~~~~~~~~~~~~~~~~~
MODEST LOW-LEVEL SOUTHWESTERLY FLOW DRAWING PRECIPITABLE WATER
VALUES OF ~2 INCHES INTO AND IN ADVANCE OF AN MCV/SHORTWAVE
DROPPING SOUTHEAST OVER OK ALONG AND AHEAD OF A SLOWLY PROGRESSIVE
COLD FRONT SHOULD SUPPORT ORGANIZED CONVECTION THIS AFTERNOON AND
AGAIN OVERNIGHT WITH LOCALLY HEAVY RAINFALL RATES THRU PARTS OF
EASTERN TX AND LA AS 850 HPA INFLOW FROM THE GULF OF MEXICO
INCREASES TO 25-30 KTS WITHIN AN AREA OF 2-2.25" PRECIPITABLE
WATER VALUES -- ABOVE THE 75TH PERCENTILE FOR LATE JULY/EARLY
AUGUST.  THE GOLDEN TRIANGLE OF SOUTHEAST TX -- IS AN AREA WITH
THE LEAST AMOUNT OF FORWARD PROPAGATION EXPECTED.  VEERING
LOW-LEVEL WINDS IN AREA SOUNDINGS SUGGEST THAT FORWARD PROPAGATION
TO THE SOUTHEAST IS EXPECTED AT 10-15 KTS.  AS 850 HPA INFLOW
APPEARS TO BE NARROW AHEAD OF THE COLD FRONT, THE RISK OF A WARM
ADVECTION THUNDERSTORM BAND APPEARS MINIMAL.  NEVERTHELESS, CELL
TRAINING IS POSSIBLE IF THE CONVECTIVE BAND OUTRACES THE FRONTAL
ZONE AND NEW CONVECTION FORMS CLOSER TO THE COLD FRONT.  HOURLY
RAINFALL RATES UP TO 2.5" ARE POSSIBLE, WITH A QUICK 2-4"
ANTICIPATED WHICH WOULD CHALLENGE THE HIGH FLASH FLOOD GUIDANCE IN
THE AREA.


SOUTHERN FL
~~~~~~~~~~~
HIGH PRECIPITABLE WATER VALUES -- IN THE 2-2.25" RANGE -- COMBINED
WITH LIGHT SOUTH TO SOUTHWEST FLOW IN THE SURFACE-700 HPA LAYER
SHOULD FORCE SEA BREEZE CONVERGENCE-RELATED THUNDERSTORMS TO
PREFER THE EVERGLADES AND POTENTIALLY THE GOLD COAST OF FL.  THE
06Z SSEO-BASED PROBABILITY OF EXCEEDING FLASH FLOOD GUIDANCE SHOWS
SPOTTY AREAS ACROSS THE SOUTHERN PENINSULA SOUTH OF LAKE
OKEECHOBEE ABOVE 50% FROM 17-00Z.  FLASH FLOOD GUIDANCE VALUES ARE
FAIRLY LOW IN THE MIAMI/HOMESTEAD/FLORIDA CITY AREA DUE TO ~30" OF
RAIN MIA AND VICINITY HAVE RECEIVED SINCE JUNE 1.  AFTER
CONSULTING WITH THE MFL FORECAST OFFICE, DECIDED IT DID NOT QUITE
REACH THE SLIGHT RISK CATEGORY.  HOURLY RAIN RATES UP TO 2.5" ARE
POSSIBLE, WITH LOCAL AMOUNTS OF 2-4" FORECAST WHERE CELLS
MERGE/TRAIN.


ROTH
$$




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