Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 280105
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
903 PM EDT SAT SEP 27 2014

...VALID 03Z SUN SEP 28 2014 - 00Z MON SEP 29 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNW FMN 65 NNW SVC 30 W SVC 45 ESE DUG 30 S FHU 20 SSE OLS
45 W OLS 75 S GBN 70 SW GBN 35 W LUF 20 WSW 40G 40 ENE MLF
15 NNE PVU 30 SE FIR 30 ENE VEL 10 ESE GJT 20 NNW FMN.


SOUTHWEST
~~~~~~~~~
HEAVY RAIN RATES AND FLASH FLOODING IN THIS REGION SO FAR HAVE
BEEN CONFINED TO PORTIONS OF UT AND AZ, WITH INSTABILITY LACKING
FARTHER NORTH ACROSS ID, WY, AND MT.  THE RECENT SPC MESOANALYSIS
SHOWS THE AREA OF 500+ J/KG MIXED LAYER CAPE CONFINED TO UT AND
AZ, WHICH SHOULD ERODE OVERNIGHT.  CONVECTION HERE WILL BE BASED
NEARER TO THE SURFACE AND IS CAPABLE OF ANCHORING ITSELF ALONG
COLD POOLS, AIDED FURTHER BY WEST-EAST MOUNTAIN RANGES
INTERCEPTING THE MOIST LOW LEVEL FLOW. LARGELY UNIDIRECTIONAL AND
UNCHANGING WIND PROFILES ALLOW FOR THE POSSIBILITY OF TRAINING AND
POTENTIAL FLASH FLOODING.  ISOLATED 1-1.5" AN HOUR RAINFALL RATES
AND LOCAL 2-4" EVENT TOTALS REMAIN POSSIBLE.  AS THE DEEP CYCLONE
ACROSS THE WEST WEAKENS AND THE MOST ANOMALOUS MOISTURE EJECTS
NORTHWARD INTO THE NORTHERN ROCKIES, THE THREAT FOR FLASH FLOODING
IN THIS AREA SHOULD LOWER OVER TIME, PERHAPS AS SOON AS THE 06-12Z
TIME FRAME.


CENTRAL GULF COAST
~~~~~~~~~~~~~~~~~~
A WEAK FRONTAL WAVE FORMS OFFSHORE THE CENTRAL GULF COAST THIS
PERIOD.  PRECIPITABLE WATER VALUES OF 2"+ MOVE INTO THE REGION IN
ADVANCE OF THE SYSTEM -- NEARLY TWO SIGMAS ABOVE THE AVERAGE FOR
LATE SEPTEMBER.  BOTH 18Z GFS AND NAM MASS FIELDS INDICATE 850 HPA
INFLOW INTO THE REGION STAYS <20 KTS UNTIL THE 850 HPA SLICE OF
THE FRONT MOVES INLAND, WITH THE GFS/NAM INCREASING INFLOW TO
20-30 KTS DURING SUNDAY AFTERNOON, WHICH WOULD ORGANIZE CONVECTION
ACROSS SOUTHERN AL AND THE WESTERN FL PANHANDLE IF IT CAME TO
PASS.  FLOW FROM THE WARM WATERS OF THE GULF OF MEXICO SHOULD
PROVIDE THE INSTABILITY NEEDED.  THE MESOSCALE AND GLOBAL GUIDANCE
SHOW A VARIETY OF POSSIBLE HEAVY RAINFALL OUTCOMES IN THIS REGION,
WITH MAXIMA IN THE 4-6" ANYWHERE BETWEEN OFFSHORE THE CENTRAL GULF
COAST AND INLAND LOCATIONS BETWEEN THE ATCHAFALAYA BASIN IN LA
EASTWARD ACROSS SOUTHERN MS, SOUTHERN AL, AND THE FL PANHANDLE.
WITH SUCH AN ARRAY OF POSSIBLE SOLUTIONS, DECIDED AGAINST
DEPICTING A SLIGHT RISK OF EXCESSIVE RAINFALL IN THIS AREA.  SANDY
SOILS/SWAMP ACROSS MUCH OF THE REGION SHOULD BE ABLE TO HANDLE
THIS SORT OF RAINFALL, THOUGH THE CLAY SOILS WITHIN PORTIONS OF
THE FL PANHANDLE COULD BE VULNERABLE TO EXCESSIVE RAINFALL/FLASH
FLOODING.  COORDINATION WITH THE MOB/MOBILE AL AND TAE/TALLAHASSEE
FL FORECAST OFFICES WAS CONDUCTED TO INCLUDE THIS AREA AS A "SEE
TEXT" HIGHLIGHT WITHIN THE EXCESSIVE RAINFALL OUTLOOK.

ROTH
$$




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