Quantitative Precipitation Forecast
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FOUS30 KWBC 291810
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 PM EDT TUE JUL 29 2014

...VALID 18Z TUE JUL 29 2014 - 00Z THU JUL 31 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 WSW CPW 25 S TEX 30 WNW TEX 25 E CNY 20 SE PUC 35 ENE U24
40 SSW DPG 55 S ENV 15 WSW ENV 50 S TWF 15 SE TWF 20 ENE JER
55 WSW S14 20 WNW WYS 35 NE WYS 50 NE P60 30 N COD 30 NNE COD
40 NE COD 35 NNW GEY 30 NE GEY PIN 10 WSW BFU 45 SE BFU
45 ENE DGW 15 N BFF 10 E BFF 30 SSW AIA 30 N ITR 45 NNW GCK
10 W ICT GMJ 30 SSW RKR 10 SE ADM DUX 10 N TCC 15 ESE 4CR
20 WSW 4CR 45 W 4CR 10 E ABQ 35 NW SAF 10 N E33 25 WSW CPW.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 WSW BRX 30 S TOR 30 NW AKO 35 SW AKO 25 W LIC 10 NNE MNH
10 WNW BKF 15 NNE BJC 15 WSW BRX.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 ENE LBL 20 W AVK 20 NNE CQB 15 ENE SNL OKC 35 NW CSM
10 SSE PYX 20 ENE GUY 15 ENE LBL.

THE VERY WET PATTERN WILL PERSIST THROUGH THE PERIOD ACROSS THE
INTERMOUNTAIN WEST. THE 12Z ANALYSIS SHOWED PRECIPITABLE WATER
VALUES BETWEEN TWO AND THREE STANDARD DEVIATIONS ABOVE NORMAL AT
BOTH SLC AND RIW...AN INDICATION OF THE AMOUNT OF MOISTURE
AVAILABLE IN THE PLUME. IN FACT...THE LOW LEVEL MOISTURE FLUX
BULLSEYE WAS LOCATED OVER WESTERN WY THIS MORNING. CONVECTION HAS
DEVELOPED ACROSS SOUTHEAST ID AND WESTERN WY...AS THE CLOUDINESS
HAS THINNED AND MLCAPE VALUES HAVE INCREASE.

DIVERGENCE AHEAD OF A CLOSED LOW OVER NORTHWEST AZ SHOULD AID IN
SYNOPTIC SCALE ASCENT... PROMOTING GREATER COVERAGE ACROSS
NORTHEAST UT...WY INTO EASTERN CO. PRECIPITABLE WATER VALUES
BETWEEN TWO AND THREE STANDARD DEVIATIONS WILL FUEL THE FLASH
FLOOD THREAT. THE LATEST SSEO PROBABILITY OF QPF EXCEEDING THREE
HOUR FLASH FLOOD GUIDANCE VALUES PEAKS NEAR 00Z OVER WESTERN
WY...AN INDICATION OF THE HIGH MOISTURE CONTENT OF THE AIR.

THE SLIGHT RISK WAS EXPANDED TO INCLUDE SOUTHEAST ID AND WESTERN
WY EARLIER TO ACCOUNT FOR THE INCREASED THREAT DUE TO THE HIGH
MOISTURE AIRMASS IN PLACE. A MODERATE RISK AREA WAS MAINTAINED FOR
PORTIONS OF SOUTHEAST WY AND NORTHEAST CO...AS THE HIGH MOISTURE
CONTENT OF THE AIR AND UPSLOPE FLOW SHOULD RESULT IN QPF VALUES
GREATER THAN 2.00 INCHES IN THESE LOCATIONS. MOST OF THIS SHOULD
BE ASSOCIATED WITH CONVECTIVE CLUSTERS OR AN MCS THAT FORMS FROM
THE CONVECTION THAT FIRES ACROSS SOUTHEAST WY AND NORTHEAST
CO...WHICH ROLLS OUT INTO THE PLAINS AFTER 30/00Z. THESE QPF
VALUES ARE SUPPORTED BY THE LATEST ECMWF AND GEFS ENSEMBLE OUTPUT.
GIVEN THAT THE THREE HOUR FLASH FLOOD GUIDANCE VALUES ARE AS LOW
AS 1.00 TO 1.50 INCHES...THE MODERATE RISK WAS DRAWN TO ENCOMPASS
THE ABOVEMENTIONED LOCATIONS.

AFTER 30/00Z...CONVECTION DEVELOPING IN SOUTHEAST CO IS EXPECTED
TO RIDE ALONG THE QUASI STATIONARY FRONT EXTENDING ACROSS
SOUTHWEST KS AND NORTH CENTRAL OK. MOST OF THE MODEL INSTABILITY
IS ELEVATED AS A 20 TO 30 KNOT SOUTHERLY FLOW OVERRUNS THE
BOUNDARY. THE INSTABILITY IS EXPECTED TO EXTEND ALONG THE FRONT
INTO NORTHWEST OK AND FAR NORTH TX THROUGH 30/12Z. THERE IS STILL
SOME SPREAD IN THE PLACEMENT OF THE QPF...AND THE LATEST ECMWF
ENSEMBLE AND GEFS OUTPUT SUGGEST THE POTENTIAL FOR 3 TO 4+ INCHES
OF RAIN. A LARGE NUMBER OF THE 12Z MODEL SUITE HAVE PLACED QPF
AMOUNTS BETWEEN 3 AND 6 INCHES ACROSS THE ABOVEMENTIONED
AREA...WITH SOME LATITUDINAL DIFFERENCES...BASED ON THE TRACK OF
THE EXPECTANT MCS. A MORE SOUTHERLY TRACK WAS USED FOR THE QPF
MAXIMUM HERE...AS THERE SHOULD NOT BE ANY CAPPING ISSUES THIS
EVENING INTO THE OVERNIGHT...AND THE SIMULATED IMAGERY FROM THE
NAM SHOWED THE MCS THAT DEVELOPS OVER SOUTHEAST CO TRACKING ALONG
THE FRONT ACROSS NORTHWEST OK AND NORTHERNMOST TX.

THE MCS SHOULD START TO WEAKEN BETWEEN 30/12Z AND 30/18Z AS THE
LOW LEVEL INFLOW WEAKENS AND THE MOISTURE PLUME DISSIPATES.
HOWEVER...THE MCV THAT DEVELOPS WITH THE MCS SHOULD PROVIDE ENOUGH
LIFT TO TAKE ADVANTAGE OF THE INSTABILITY AND MOISTURE IN PLACE TO
PRODUCE QPF INTO SOUTHEAST OK AND WESTERN AR.

CONVECTION ACROSS THE GREAT BASIN WILL BE PREDICATED MAINLY ON THE
COMBINATION OF MOISTURE IN THE INCREASED MONSOONAL FLOW AND
MARGINAL INSTABILITY DUE IN MOST PART TO STEEPENING MID LEVEL
LAPSE RATES. ORGANIZATION MAY BE MORE DIFFICULT AS THE MID LEVEL
RIDGE REMAINS MORE OR LESS IN PLACE. THE ACTIVITY IS DEVELOPING
THIS AFTERNOON...AND SHOULD REMAIN SCATTERED BASED ON THE 0.75 TO
1.25 INCH PRECIPITABLE WATER VALUES IN PLACE. ONE HOUR FLASH FLOOD
GUIDANCE VALUES ACROSS THE GREAT BASIN ARE GENERALLY BETWEEN 0.75
AND 1.25 INCHES...SO ANY CONVECTION COULD PRODUCE THIS MUCH QPF
BASED ON THE AVAILABLE MOISTURE. HOWEVER...WITHOUT A STRONG
FOCUS...A SEE TEXT AREA SHOULD COVER THIS ACTIVITY. THE BULK OF
THE ACTIVITY SHOULD START TO WANE AFTER SUNSET... PERHAPS LASTING
UNTIL ABOUT 30/06Z.


HAYES
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