Quantitative Precipitation Forecast
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FOUS30 KWBC 261412
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1011 AM EDT TUE AUG 26 2014

...VALID 15Z TUE AUG 26 2014 - 12Z WED AUG 27 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 WNW SUX 15 E SLB 20 WSW ALO CID 10 ENE OTM 10 SSW CSQ
25 SW LNK 45 SE HDE 30 ESE GLD 50 W GCK 35 ENE SPD 15 N SPD
35 N LAA LIC 30 SW AKO 10 NE IML 25 W BBW 20 NE ODX 25 WNW SUX.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 SSW CGZ 15 WSW CHD 15 NNW DVT 10 W PRC 50 NW PRC 50 WNW 40G
50 NW GCN 15 WSW PGA 15 SSE PGA 60 SW 4BL 25 SW 4BL 30 ENE 4BL
35 WNW TEX 15 NE TEX 15 S GUC 10 NE MYP 40 W FCS 20 SW PUB
15 W TAD 10 NE LVS 35 NNE 4CR 10 E 4CR 20 N SRR 35 WNW SRR
50 NE TCS 10 NW TCS 10 NNE SVC 45 SW SVC 15 N DUG 10 S OLS
50 WNW OLS 45 SSW CGZ.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 WNW SOW 25 NNE SOW SJN 35 E SJN 65 ESE SJN 65 NNW SVC
50 ENE SAD 25 NNE SAD 50 NW SAD 25 WNW SOW.


15Z UPDATE...

ONLY SIGNIFICANT CHANGE TO THE PREVIOUS OUTLOOK WAS TO EXTEND THE
SLIGHT RISK OVER THE CENTRAL PLAINS FURTHER TO THE SOUTHWEST INTO
THE HIGH PLAINS OF CO.  SEVERAL OF THE HIGH-RES MODEL MEMBERS SHOW
HEAVY AMOUNTS FALLING ACROSS THE REGION THIS EVENING AS CONVECTION
DEVELOPING ALONG THE FRONT RANGE MOVES EASTWARD.
ALSO...RELATIVELY LOW FLASH FLOOD GUIDANCE VALUES...LIKELY A
REFLECTION OF RECENT HEAVY RAINS...SUGGEST RUNOFF PROBLEMS MAY BE
A CONCERN SHOULD ADDITIONAL HEAVY RAINS OCCUR.

PREVIOUS DISCUSSION...

...CENTRAL PLAINS...

AGAIN THIS PERIOD..THE QUASI-STATIONARY FRONT..OR LATER IN THE
PERIOD THE VERY SLOW MOVING WARM FRONT..SHOULD CONTINUE TO BE A
FOCUS FOR ORGANIZED AND ENHANCED CONVECTION..ESPECIALLY FROM PARTS
OF THE CENTRAL PLAINS INTO THE MIDWEST.  THE ONGOING CONVECTION
OVER PARTS OF NE INTO IA SHOULD WEAKEN LATER TUESDAY MORNING UNDER
A LESS FAVORABLE AND WEAKENING LOW LEVEL JET..BUT EXPECT
CONVECTION TO RE-FIRE TUESDAY NIGHT FROM NE INTO IA AGAIN AS THE
SOUTH TO SOUTH-SOUTHWESTERLY LOW LEVEL JET STRENGTHENS TO 30KTS OR
SO..BRINGING IN ADDITIONAL MOISTURE INTO THE FRONTAL ZONE AND
LEADING TO POOLING OF PWS TO NEAR 2 INCHES VICINITY OF THE
BOUNDARY.  THE MODEL QPFS WERE IN REASONABLY DECENT AGREEMENT ON
AN AXIS OF HEAVIER RAINS FROM PARTS OF NE 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.  THE ARW SEEMED TO BE A BIT OF A SOUTHWARD OUTLIER WHILE THE
NAM QPF LOOKED A LITTLE TOO FAR NORTH ..SO USED LESS OF THEIR
SOLUTIONS..AND INSTEAD LEANED TOWARDS THE REMAINDER OF THE QPF
GUIDANCE WHICH WAS BETWEEN THESE 2 OUTLIERS.  EXPECT AT LEAST SOME
1-2 INCH AREAL AVERAGE AMOUNTS AFTER 12Z..BUT AS IS THE CASE WITH
THE ONGOING CONVECTION IN NE..ISOLATED HEAVIER TOTALS OF 3+ INCHES
ARE POSSIBLE..AND THIS IS IN ADDITION TO SOME 1-3 INCH RAINS THAT
WILL OCCUR BEFORE 26/12Z WITH THE ONGOING CONVECTION FROM
SOUTHEAST/EAST-CENTRAL NE INTO WESTERN IA.

...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/TERRY

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