Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 040902
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
502 AM EDT FRI SEP 04 2015

...VALID 12Z FRI SEP 04 2015 - 12Z SAT SEP 05 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SSE CYQK 35 NE ORB 10 N DLH 20 NNW JMR 20 SW ADC 25 W FAR
15 S KY19 20 S MOT 20 SW CYWG 25 SSE CYQK.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 S MTJ 15 E GUC 20 SE MYP ALS 20 SSW ABQ 40 E DUG 30 SSW OLS
25 SSE GBN 40 NNE DVT 45 NNW RQE 20 S MTJ.


...CENTRAL AND EASTERN NORTH DAKOTA THROUGH NORTHWEST AND
NORTH-CENTRAL MINNESOTA...

THE UPPER AIR PATTERN WILL CONTINUE TO AMPLIFY WHILE SHOWING
LITTLE DOWNSTREAM PROGRESSION THROUGH FRIDAY NIGHT. THE TROUGH
ALONG THE WEST COST DIGS TO 3 STANDARD DEVIATIONS BELOW
CLIMATOLOGICAL 500 MB HEIGHTS...WITH GRADUAL GRADIENTS AND A
GENTLY SLOPING FRONTAL ZONE EXTENDING EAST TOWARD RIDGING IN THE
MIDWEST. THE LEADING FRONT AT THE SURFACE WILL PUSH OUT INTO THE
DAKOTAS...WHILE THE LARGE SCALE FLOW CONTINUES TO STEER THE
LOW-AMPLITUDE SHORTWAVE OUT OF THE CENTRAL HIGH PLAINS AND INTO
THE NORTHERN PLAINS TODAY. THIS SHORTWAVE WILL ENCOUNTER GREATER
MOISTURE AND DEEP-LAYER INSTABILITY (MUCAPES AT LEAST 2500-3000
J/KG) POOLED ALONG THE SURFACE FRONT IN ND/MN LATER THIS AFTERNOON
INTO TONIGHT...WITH A LIKELY ORGANIZED THUNDERSTORM EVENT ENSUING.
PWS PEAKING BETWEEN 1.75-2.00 INCHES PER THE MODEL CONSENSUS WILL
BE 3+ STANDARD DEVIATIONS ABOVE NORMAL FOR THE FAR NORTHERN PLAINS
AND UPPER MS VALLEY...AND MAY APPROACH THE DAILY MAX FOR
INTERNATIONAL FALLS (1.94"). LITTLE CHANGE WAS MADE TO THE PRIOR
WPC QPF FROM 12Z FRI - 12Z SAT...OUTSIDE OF PULLING THE 1+ INCH
AREA A TAD FARTHER SOUTH ACROSS NORTHWEST MN. DEPENDING ON THE
MODEL TRENDS (ESPECIALLY WITH THE CAM GUIDANCE)...WOULD NOT BE
SURPRISED TO SEE ADDITIONAL SOUTHWARD ADJUSTMENT OF THE HEAVIER
RAINFALL AXIS...TOWARD THE GREATER INSTABILITY AND NOSE OF THE LOW
LEVEL JET. HOWEVER...AT THIS POINT WOULD NOT EXPECT A SIGNIFICANT
SOUTHWARD SHIFT GIVEN THE MORE CAPPED ENVIRONMENT SOUTH OF THE
SURFACE FRONT.

THE 00Z 4KM WRF-ARW...NMMB...NAM-CONEST...AND NSSL-WRF SHOW
POCKETS OF HIGHER RAINFALL TOTALS (3-5+ INCHES) OVER THE OUTLOOK
AREA...WHILE THE LATEST (00Z) SSEO 40 KM NEIGHBORHOOD
PROBABILITIES SHOW 3 HOURLY EXCEEDANCE PROBABILITIES (3 HR QPF > 3
HR FFG) CLIMBING AOA 50 PERCENT OVER EASTERN ND BY 21-22Z AND INTO
NORTHWEST MN BY 23-00Z.


...ARIZONA...WESTERN NEW MEXICO...SOUTHWEST AND SOUTH-CENTRAL
COLORADO...

THE MONSOON CONTINUES...WITH PRECIPITABLE WATER VALUES STILL
RUNNING A BIT ABOVE AVERAGE (1-2 STANDARD DEVIATIONS PER THE
ENSEMBLES)... INCLUDING A SUBTROPICAL CONNECTION TO HIGH ALTITUDE
MOISTURE STREAMING NORTH FROM TROPICAL STORM KEVIN AS PER THE
700-500 AND 500-300 CIRA LAYER PW LOOPS. THE SIGNAL FOR HEAVY
RAINFALL IS NOT AS EVIDENT BY BOTH THE GLOBAL AND CAM GUIDANCE AS
COMPARED TO YESTERDAY...THOUGH ONCE AGAIN ALSO REMAINS TIED TO THE
TOPOGRAPHY IN SOUTHEAST AZ INTO WESTERN NM AND
SOUTH-CENTRAL-CENTRAL CO. AS WAS NOTED IN THE PREVIOUS
DISCUSSION...A LIMITING FACTOR FOR WIDESPREAD HEAVY RAIN WILL BE
WEAK WINDS BELOW 600 MB...SO STORMS MAY BECOME OUTFLOW DOMINANT
RATHER QUICKLY. ALSO... THE UPPER LEVEL DEBRIS CLOUDS FROM T.S.
KEVIN AND PRIOR CONVECTION MAY ALSO LIMIT THE DESTABILIZATION
SOMEWHAT. ISOLATED FLASH FLOODING WILL NEVERTHELESS BE
POSSIBLE...INCLUDING OVER THE PHOENIX METRO AREA PER THE LATEST
AFOREMENTIONED SSEO NEIGHBORHOOD PROBABILITIES (WHICH CLIMB TO
30-50% BY MIDDAY).

HURLEY

$$




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