Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FOUS30 KWBC 301020
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
619 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.


...SOUTHWEST U.S. FROM NEW MEXICO TO SOUTHERN CALIFORNIA...

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.

...SOUTHERN PLAINS...

HIGH MOISTURE CONTENT AIR AND INSTABILITY RUNNING OVER A SURFACE
BOUNDARY ACROSS CENTRAL OK COULD RESULT IN HEAVY TO EXCESSIVE
RAINFALL ACROSS SOUTHERN KS...NORTHERN OK AND FAR NORTH
TX...ESPECIALLY EARLY THIS MORNING.

A DEVELOPING AREA OF MAINLY ELEVATED CONVECTION ACROSS SOUTHERN KS
AND NORTHERNMOST OK HAS ACCESS TO 2.00 INCH PRECIPITABLE WATER AS
THE LOW LEVEL FLOW PUMPS MOISTURE AND INSTABILITY ABOVE THE FRONT.
THE LATEST HRRR AND RAP SHOWED ELEVATED INSTABILITY VALUES TOPPING
OUT NEAR 1500 J/KG BEFORE 30/16Z ACROSS SOUTHERN KS DROPPING INTO
NORTHERN OK...AS THE LOW LEVEL FRONT DROPS SOUTH. THE CONVECTION
PROBABLY PEAKS BEFORE 30/16Z...AFTER WHICH TIME THE MAIN FOCUS FOR
INSTABILITY AND MOISTURE DROPS FURTHER INTO OK. BOTH THE LATEST
RAP AND HRRR SHOWED THE POTENTIAL FOR LOCAL 2-3 INCH RAINFALL
AMOUNTS...WHICH COULD BE CLOSE TO THE THREE HOUR FLASH FLOOD
GUIDANCE. FOR THIS REASON...THE SLIGHT RISK WAS EXTENDED INTO THE
ABOVEMENTIONED AREAS.

HAYES
$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.