Quantitative Precipitation Forecast
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000
FOUS30 KWBC 301501
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EDT THU JUL 30 2015

...VALID 15Z THU JUL 30 2015 - 12Z FRI JUL 31 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 NNE SDL 35 ESE PRC 25 NE PRC 20 SSW 40G 40G 30 E 40G
35 NW INW 45 ENE INW 40 WNW RQE 50 NNW RQE 40 WSW FMN 35 S FMN
30 WNW 4SL 35 S E33 30 NE SKX 25 ENE RTN 15 SE SPD DDC 20 NW PTT
30 WSW ICT 15 WNW PNC 20 NE JWG 10 E BGD 45 S DHT 15 NNW CVN
25 WSW CVS 40 ENE 4CR 20 SW 4MY 40 SW AEG 60 N TCS 15 N TCS
30 ENE SVC 35 WNW SVC 20 ESE SAD 30 S SAD 20 N FHU 25 WSW TUS
25 NW TUS 55 N DMA 45 ENE IWA 50 NNE SDL.


...SOUTHERN CALIFORNIA...

SCATTERED CONVECTION WITH LOCALLY HEAVY RAINFALL OCCURRED
WEDNESDAY. ACTIVITY SHOULD BE MORE WIDESPREAD AND PERHAPS MORE
ORGANIZED TODAY. THE 12Z SOUNDING AT SAN DIEGO MEASURED A
NEAR-RECORD PRECIPITABLE WATER VALUE FOR JULY 30 AT THAT LOCATION.
THIS WAS PART OF A SLUG OF ANOMALOUSLY MOIST AIR THAT WILL COVER
MUCH OF SOUTHERN CALIFORNIA TODAY WHILE DRIFTING WESTWARD AND
NORTHWARD UP THE COAST. STRONG HEATING SHOULD BE SUFFICIENT TO
INITIATE CONVECTION IN THE FAVORED TERRAIN AREAS. THIS CONVECTION
MAY THEN HAVE AN OPPORTUNITY TO SHOW AN UNUSUAL AMOUNT OF
PROPAGATION INTO THE VALLEYS AND DESERTS...OWING TO ENHANCED 700
MB EASTERLY FLOW / NEAR CLOUD BASE / EMANATING FROM A REGION OF
MODERATE INSTABILITY. GIVEN THE BREADTH OF INSTABILITY...ANOMALOUS
MOISTURE...AND MEAN 0-6 KM WINDS OF ONLY 5 TO 15 KNOTS...SOME VERY
HEAVY RAIN RATES AND PERSISTENT HEAVY RAINS ARE POSSIBLE. THE
MODEL QPFS DO NOT FULLY REFLECT THIS POTENTIAL...BUT THE PARALLEL
VERSION OF THE 00Z WRF-ARW AND THE 06Z CANADIAN GEM REGIONAL MODEL
DO INDICATE POTENTIAL FOR AREAL AVERAGE PRECIPITATION TO EXCEED
0.75 TO 1.00 INCHES IN THE FAVORED TERRAIN. ANY CELL MERGERS OR
BACKBUILDING COULD BOOST RAINFALL ABOVE 1.50 INCHES IN ISOLATED
SPOTS...WITH MUCH OF THAT FALLING IN A VERY SHORT TIME AT A GIVEN
LOCATION. THIS REGION WAS UPGRADED TO A SLIGHT RISK OF EXCESSIVE
RAINFALL.


...NM/AZ/CO...

THE MONSOONAL FLOW CONTINUES TO PUMP HIGH MOISTURE CONTENT AIR
INTO THE SOUTHWEST STATES. THE MONSOONAL MOISTURE...COMBINED WITH
MARGINAL TO MODERATE INSTABILITY...WILL FUEL CONVECTION TO PRODUCE
HEAVY TO EXCESSIVE RAINFALL OVER PORTIONS OF NM...AZ...AND
SOUTHERN COLORADO. OVER NM...THE CONVECTION INITIALLY BECOMES
ANCHORED TO THE TERRAIN...MAINLY ACROSS NORTHERN AND WESTERN
PORTIONS OF THE STATE. AS WAS THE CASE ON WEDNESDAY...THE
CONVECTION FEEDS ON MODERATE INSTABILITY AND PRECIPITABLE WATER
VALUES NEAR 1.25 INCHES AND MOVES OFF THE TERRAIN IN THE LATE
AFTERNOON AND EARLY EVENING. LOCAL 0.75 TO 1.25 INCH QPF AMOUNTS
ARE EXPECTED ACROSS THE HIGHER TERRAIN (WITH AMOUNTS AS HIGH AS
2.50 INCHES SUGGESTED BY THE 00Z
NAM/GFS)...WHERE ONE AND THREE HOUR FLASH FLOOD GUIDANCE VALUES
AREA AS LOW AS AN INCH OR LESS. DUE TO PREVIOUS HEAVY
RAINFALL...SLOW CELL MOVEMENT UNDER THE MID LEVEL RIDGE...AND THE
POTENTIAL FOR HIGH RAINFALL RATES...A SLIGHT RISK AREA WAS PLACED
OVER PORTIONS OF NORTHERN AND WESTERN NM...MAINLY IN THE HIGHER
TERRAIN.

CONVECTION SHOULD REFORM EARLY THIS AFTERNOON ACROSS AZ...AS
MONSOONAL MOISTURE (WHICH IS DEPICTED WELL BY THE HIGH AND MID
LEVEL LAYERED PRECIPITABLE WATER IMAGES) POURS NORTHWARD.
PRECIPITABLE WATER VALUES TOP OUT NEAR 1.75 INCHES ACROSS
SOUTHWEST AZ DURING THE AFTERNOON AND EVENING HOURS...AND THE
MOISTURE (AS WELL AS MODERATE INSTABILITY) BECOME FOCUSED ON A
SURFACE TROUGH EXTENDING FROM WESTERN AZ INTO SOUTHEAST CA. THERE
IS A MODEL SIGNAL THAT A SHORT WAVE IN THE MID LEVEL FLOW COULD
HELP FOCUS CONVECTION ACROSS CENTRAL AND WESTERN AZ...BUT THE
BUILDING MID LEVEL RIDGE COULD MITIGATE THE LOCAL SYNOPTIC LIFT IT
PROVIDES. IN ANY EVENT...LOCAL 0.50 TO 1.00 INCH QPF AMOUNTS ARE
EXPECTED ACROSS THE HIGHER TERRAIN IN MUCH OF AZ. ONE AND THREE
HOUR FLASH FLOOD GUIDANCE VALUES ARE AS LOW AS AN INCH IN THESE
AREAS. GIVEN THE POTENTIAL FOR HIGH RAINFALL RATES...A SLIGHT RISK
AREA WAS INTRODUCED FOR PORTIONS OF CENTRAL AND EASTERN
AZ...MAINLY NEAR THE TERRAIN.


...NORTHEAST NEW MEXICO ACROSS TO OKLAHOMA...

A HEAVY RAIN EVENT HAD PEAKED EARLY THIS MORNING IN SOUTHERN KS
ALONG AN ELEVATED FRONTAL ZONE. FORCING AT THE TAIL END OF A
NORTHERN STREAM JET STREAK IS FORECAST TO YIELD AN INVERTED SFC
TROUGH ACROSS OK TODAY...LEADING TO RENEWAL OF SLOW MOVING
CONVECTION WITH VERY HEAVY RAINFALL WITHIN AN INSTABILITY AXIS
OVER NORTH CENTRAL AND EASTERN OK. A SEPARATE FOCUSED AREA OF
HEAVY RAIN IS EXPECTED TO DEVELOP VERY GRADUALLY LATE TODAY
THROUGH TONIGHT IN NORTHERN NM...WHERE MODERATE INSTABILITY WILL
AGAIN BECOME COLOCATED WITH ANOMALOUSLY HIGH PW VALUES. MODELS
PREDICT ENHANCEMENT OF 700 MB WARM ADVECTION AND A SMALL 700 MB
CIRCULATION LATE TONIGHT AS UPPER DIFLUENCE INCREASES AHEAD OF A
SHORTWAVE DROPPING THROUGH COLORADO...WITH AN ASSOCIATED HEAVY
RAINFALL SIGNAL FROM MOST MESOSCALE MODELS.


BURKE/HAYES
$$




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