Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 270119
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
918 PM EDT TUE AUG 26 2014

...VALID 03Z WED AUG 27 2014 - 00Z THU AUG 28 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 NW TCC 50 ENE 4CR 15 SSW ROW 45 WNW GDP 30 NE ELP 35 WNW HMN
65 W 4CR 15 NW 4MY 10 SW VTP 35 W AFF 10 WSW FNL 20 SE GXY
15 W IBM 20 W TOR 45 NE DGW 10 WNW CUT 20 ESE RAP 20 SSW PHP
45 NNW VTN 15 NNW VTN 45 WNW VTN 10 SE IEN 20 N AIA 20 SSW AIA
10 WNW OGA 40 E AKO 25 SSW IML 15 E BBW OFK 20 ESE SLB 20 E AMW
10 SSE OTM 20 SSW CNC 10 E AFK 30 W HJH 40 NNW GCK 50 NW TCC.


0100Z UPDATE...REMOVED THE SLIGHT RISK FROM PORTIONS OF THE
SOUTHWEST...INCLUDING AZ AND SOUTHERN UT...BASED ON THE CONTINUED
EASTWARD PROGRESSION OF THE AMPLIFIED UPPER TROUGH (WEAKENING
UPPER DIFFLUENCE/UPPER DIVERGENCE AFTER 03-06Z) ALONG WITH THE
DIMINISHING MUCAPES.

STILL ANTICIPATE THE POTENTIAL FOR MORE ISOLATED RUNOFF ISSUES
ACROSS SOUTHERN AZ...GIVEN THE LINGERING INSTBY THROUGH 06-09Z
(MUCAPES ~1000 J/KG) ALONG WITH MORE ROBUST PWAT VALUES (1.50-1.75
INCHES). EVEN OVER THIS AREA HOWEVER...THE LARGE-SCALE FORCING FOR
ASCENT WILL BE ON THE WANE AS THE UPPER TROUGH AND ASSOCIATED
PRE-TROUGH DYNAMICS SHIFT TO THE EAST.

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.

HURLEY


PREVIOUS DISCUSSION BELOW...


...CENTRAL PLAINS...

A QUASI-STATIONARY/SLOW MOVING WARM FRONT..SHOULD CONTINUE TO
FOCUS ORGANIZED AND ENHANCED CONVECTION..ESPECIALLY ACROSS
PORTIONS OF THE CENTRAL PLAINS INTO THE MIDWEST.  EXPECT
CONVECTION TO RE-FIRE TUESDAY NIGHT FROM NEB INTO IA AGAIN AS THE
SOUTH TO SOUTH-SOUTHWESTERLY LOW LEVEL JET STRENGTHENS TO 20-30
KTS..BRINGING IN ADDITIONAL MOISTURE INTO THE FRONTAL ZONE AND
LEADING TO POOLING OF PWS TO 1.75-2 INCHES IN THE VICINITY OF THE
BOUNDARY.  THE MODEL QPFS WERE IN REASONABLY DECENT AGREEMENT ON
AN AXIS OF HEAVIER RAINS FROM PARTS OF NEB INTO WESTERN IA..THOUGH
AS IS QUITE OFTEN THE CASE..THERE REMAIN SOME LATITUDINAL
DIFFERENCES IN TERMS OF WHERE THE HEAVIEST RAINFALL AXIS WILL SET
UP.   EXPECT AT LEAST SOME 1-2 INCH AREAL AVERAGE AMOUNTS..BUT AS
IS THE CASE WITH THE ONGOING CONVECTION IN NEB..ISOLATED HEAVIER
TOTALS OF 3+ INCHES ARE POSSIBLE...RAISING FLASH FLOODING
CONCERNS.   BACK IN EASTERN CO..THE LOW LEVEL EASTERLY UPSLOPE
FLOW WEAKENS INTO THE TUESDAY MORNING HOURS AND BECOMES MORE
SOUTH-SOUTHEASTERLY LATER TUESDAY AFTERNOON/EVENING..WHICH WILL
BRING IN SOME BETTER MOISTURE AND STILL SUPPORT SOME CONVECTIVE
DEVELOPMENT DURING TIME OF BETTER HEATING..LEADING TO SOME
ENHANCED RAINFALL TOTALS.  FLASH FLOODING IS ESPECIALLY A CONCERN
ACROSS NORTHEASTERN CO WHERE FFG VALUES ARE RELATIVELY LOW.

BY TOMORROW AFTERNOON-EVENING AS THE TROUGH IN THE WEST MOVES OUT
OF THE GREAT BASIN AND INTO THE CENTRAL ROCKIES...A
RESTRENGTHENING LOW LEVEL JET IS EXPECTED TO FEED MOISTURE INTO AN
AREA OF STRONG LOW LEVEL CONVERGENCE/UPSLOPE FLOW NORTH OF THE LOW
LEVEL CENTER...WHICH ALONG WITH STRONG UPPER FORCING IS EXPECTED
TO FOSTER DEVELOPMENT OF MODERATE TO HEAVY RAINS FROM SOUTHEASTERN
WY INTO THE NEB PANHANDLE AND FAR SOUTHWESTERN SD LATE IN THE
PERIOD.  RELATIVELY LOW FFG VALUES ACROSS THE REGION SUGGEST
ADDITIONAL HEAVY RAINS MAY CREATE FLASH FLOODING CONCERNS.

...SOUTHWEST...

AS PER THE PREVIOUS DISCUSSION..THE LATEST RE-FORECAST DATA (PCPN
ANALOGS IN SIMILAR PATTERNS) CONTINUES TO SHOW A SIGNAL FOR HEAVY
RAIN ACROSS THE SOUTHWEST..SPECIFICALLY IN AZ ALONG AND SOUTH OF
THE LOWER MOGOLLON RIM AND INTO THE WESTERN 2/3 OF NM.  HIGHER
MOISTURE AVAILABILITY..WITH PWS AOA 1.50 INCHES LIFTING INTO
SOUTHERN AND CENTRAL AZ (WITH A HIGH LEVEL TROPICAL CONNECTION
FROM HURRICANE MARIE)..WILL CONTINUE TO OVERSPREAD THE REGION
AHEAD OF THE DEEPENING UPPER TROUGH.  THE FAVORABLE PRE-TROUGH
FORCING (UPPER DIVERGENCE) AND ROBUST THERMODYNAMIC PROFILES
SHOULD SUPPORT THE ENHANCED CONVECTIVE THREAT AND HEAVY RAINFALL
POTENTIAL ACROSS MUCH OF THE AREA..AGAIN PARTICULARLY ALONG AND
SOUTH OF THE SOUTHERN/CENTRAL PORTIONS OF THE MOGOLLON RIM AND
AREAS EAST INTO NM.   RATHER WIDESPREAD AREAL AVERAGE RAINS OF
0.50-1.00+ INCHES LIKELY..BUT WITH SOME ISOLATED GREATER THAN 2
INCH TOTALS POSSIBLE IN SOME OF THE HIGHER TERRAIN..WHICH IS
LIKELY TO LEAD TO SOME FLOODING PROBLEMS.

PEREIRA

$$




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