Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 300809
QPFERD

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

...VALID 12Z 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 45 WNW RQE 60 NNW RQE 65 NNW RQE 30 SW FMN
45 SSE FMN 25 NW 4SL 35 NNE 4SL 25 SSE E33 35 NNE SKX 15 NNW RTN
RTN 25 NW CAO 10 WSW DHT 10 NW TCC 45 SE LVS 25 E CQC 25 SSW CQC
25 SSE ABQ 20 SW ABQ 45 SW AEG 60 N TCS 15 N TCS 30 ENE SVC
30 WNW SVC 25 ENE SAD 10 ENE SAD 15 SSE SAD 45 E DMA 25 NNW FHU
25 WSW TUS 25 NW TUS 55 N DMA 45 ENE IWA 50 NNE SDL.


...SOUTHWEST/SOUTHERN CA...

THE MONSOONAL FLOW CONTINUES TO PUMP HIGH MOISTURE CONTENT AIR
INTO THE SOUTHWEST STATES AND NEARBY SOUTHERN CA. THE MONSOONAL
MOISTURE...COMBINED WITH MARGINAL TO MODERATE INSTABILITY...FUELS
CONVECTION THAT PRODUCES HEAVY TO EXCESSIVE RAINFALL OVER PORTIONS
OF NM...AZ AND NEARBY SOUTHERN CA.

OVER NM...THE CONVECTION INITIALLY BECOMES ANCHORED TO THE
TERRAIN...MAINLY ACROSS NORTHERN AND WESTERN PORTIONS OF THE
STATE. AS WAS THE CASE ON WED...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/SOUTHERN
CA...AS MONSOONAL MOISTURE (WHICH IS DEPICTED WELL BY THE HIGH AND
MID LEVEL LAYERED PRECIPITABLE WATER IMAGES) POURS NORTHWARD
ACROSS AZ INTO SOUTHEAST CA. 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.

FURTHER WEST...THE MAIN FOCUS FOR CONVECTION SHOULD BE THE TERRAIN
ACROSS SOUTHERN CA. MOISTURE (IN THE FORM OF PRECIPITABLE WATER
VALUES BETWEEN 1.25 AND 1.50 INCHES) AND MARGINAL INSTABILITY
SHOULD BE SUFFICIENT FOR SCATTERED TO LOCALLY BROKEN
CONVECTION...INITIALLY TIED TO THE TERRAIN. AS WAS THE CASE IN
AZ...ONE AND THREE HOUR FLASH FLOOD GUIDANCE VALUES ARE AS LOW AS
AN INCH...SO LOCAL FLASH FLOODING ISSUES ARE POSSIBLE. WITH THIS
IN MIND...A SEE TEXT AREA WAS PLACED OVER SOUTHERN CA.

HAYES
$$




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