Flash Flood Warning 2, NWS Phoenix, AZ

AREA FORECAST DISCUSSION...UPDATED AVIATION DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1100 AM MST SUN JAN 27 2008

SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA
FORECAST DISCUSSION

.SYNOPSIS...
A STRONG LOW PRESSURE AREA WILL MOVE ACROSS THE DESERT SOUTHWEST THE
NEXT COUPLE OF DAYS. COPIOUS AMOUNTS OF MOISTURE ASSOCIATED WITH
THIS SYSTEM WILL RESULT IN PERIODS OF RAIN...SOME OF WHICH WILL BE
HEAVY AT TIMES INTO THIS EVENING. A FLASH FLOOD WATCH WILL CONTINUE
THIS AFTERNOON AND EVENING FOR MUCH OF SOUTH-CENTRAL ARIZONA. THE
THREAT OF SHOWERS WILL CONTINUE OVER SOUTH-CENTRAL ARIZONA ON
MONDAY...WITH DRIER WEATHER EXPECTED BY TUESDAY ACROSS THE ENTIRE
AREA. ANOTHER WEATHER SYSTEM WILL BRING A SLIGHT CHANCE OF SHOWERS
WEDNESDAY AND WEDNESDAY NIGHT FOLLOWED BY DRY CONDITIONS THURSDAY
INTO NEXT WEEKEND. EXPECT COOL TEMPERATURES TO PREVAIL THIS WEEK.

&&

.SHORT TERM...
TODAY THROUGH TUESDAY...
NO CHANGES TO THE FORECAST NEEDED ATTM...AS EVERYTHING STILL SEEMS
ON TRACK FOR A MAJOR PRECIP EVENT FOR OUR CWA...MAINLY THE
SOUTH-CENTRAL PORTION. CLOSED LOW OFF THE SRN CA/NRN BAJA COAST HAS
BEEN SLOWLY EDGING EASTWARD THIS MORNING...AND IT HAS BEEN TAPPING A
SUBSTANTIAL AMOUNT OF SUBTROPICAL MOISTURE WHICH HAS BEEN
OVERSPREADING OUR CWA. VERY IMPRESSIVE LOOKING ON THE IR IMAGERY.
SIGNIFICANT RAINFALL HAS ALREADY OCCURRED ACROSS THE WEST AND
CENTRAL PARTS OF OUR CWA...WITH MANY PLACES PICKING UP BETWEEN ONE
QUARTER AND THREE QUARTERS OF AN INCH OF RAIN SINCE THE EVENT
STARTED LAST NIGHT. LATEST GFS/NAM PROGS SHOW DEEP MOISTURE ACROSS
MOST OF THE CWA BY 18Z...WITH THE STRONGEST AND DEEPEST LIFT
EXTENDING FROM AROUND THE CO RIVER EAST TO SRN GILA COUNTY. BY 00Z
THE MAIN FOCUS FOR PRECIP SHOULD SHIFT INTO SOUTH-CENTRAL AZ WHERE
POPS WILL BE 100 PERCENT EVERYWHERE. CROSS SECTION OF RH/OMEGA FROM
THE GFS SHOWS MUCH DEEPER MOISTURE FOR TODAY AS COMPARED TO THE NAM
PROFILE...AND BASED ON SATELLITE IMAGERY AND A SIMILAR EVENT LATE
LAST NOVEMBER...FEEL THE GFS HAS A BETTER HANDLE ON THINGS AND WILL
FAVOR THAT MODEL. QPF VALUES STILL LOOK ON TRACK FOR SOUTH-CENTRAL
AZ TODAY...WITH 1 TO 3 INCHES LIKELY FROM PHOENIX EASTWARD. OF
COURSE...THE HIGHEST QPF VALUES WILL BE IN THE FAVORED UPSLOPE AREAS
NORTH AND EAST OF PHOENIX. VERY STRONG MID LEVEL SPEED/MOISTURE
CONVERGENCE STILL BEING PROGGED...ALONG WITH FAVORABLE SSWLY UPSLOPE
WINDS...WHICH WILL REALLY ENHANCE PRECIPITATION POTENTIAL WITH THIS
EVENT. NO SIGNIFICANT UPDATES NEEDED ATTM...AND WE WILL WATCH THIS
EVENT PLAY OUT DURING THE MORNING/EARLY AFTERNOON HOURS. REST OF THE
DISCUSSION IS FROM THE PREVIOUS MID SHIFT.

.PREVIOUS DISCUSSION...
EARLY MORNING RADAR LOOPS SHOW CLOUDS AND RAIN HAVE OVERSPREAD MOST
OF THE PHX CWA OVERNIGHT...WITH THE HEAVIEST AMOUNTS THUS FAR WEST
OF MARICOPA COUNTY. SOME SPOTS IN SE CA ZONES HAVE ALREADY MEASURED
OVER ONE QUARTER OF IN INCH. MEANWHILE...EVERYTHING STILL APPEARS TO
BE COMING TOGETHER FOR A MAJOR RAIN EVENT FOR SOUTH-CENTRAL ARIZONA.
THE LIST OF FAVORABLE FACTORS INCLUDE COPIOUS AMOUNTS OF MOISTURE...
STRONG SWLY UPSLOPE FLOW...GOOD LOW LEVEL MOISTURE CONVERGENCE...LOTS
OF OMEGA...LOW LEVEL WARM ADVECTION...YOU NAME IT...THIS SYSTEMS
GOT IT. OBVIOUSLY...CONDITIONS CONTINUE TO BE FAVORABLE FOR POTENTIAL
FLASH FLOODING WHEN THE HEAVIEST RAIN ARRIVES LATE THIS MORNING OVER
SCNTRL AZ ZONES. AND...BY THIS EVENING...WE ARE STILL EXPECTING SOME
SIGNIFICANT RISES IN AREA MAIN-STEM RIVERS. THEREFORE...FLASH FLOOD
WATCH WILL CONTINUE...RUNNING FROM 19Z-07Z THIS EVENING. SATELLITE
PIX SHOWING DRY PUNCH WORKING ITS WAY TOWARDS THE SRN CA COAST...
AND THIS FEATURE SHOULD PUSH INTO FAR WRN ZONES AS EARLY AS LATE
THIS MORNING. THIS COULD GIVE SOME BRIEF CLEARING AND LET UP IN
RAIN...FOLLOWED BY MORE CHANCES AS DYNAMICS INCREASE AGAIN TOWARDS
EVENING. DID NOT CHANGE QPF AMOUNTS THAT WERE INHERITED AS THEY
STILL APPEARED REASONABLE...WITH 1 TO 3 INCHES TOTAL IN MOST
FAVORABLE UPSLOPE LOCATIONS...UP TO AN INCH LOWER ELEVATIONS.

PRECIP SHOULD BEGIN TO TAPER OFF LATE TONIGHT OVER THE ERN ZONES...
WITH MORE SHOWER CHANCES ON MONDAY AS ONE LAST SHOT OF DYNAMICS
MOVES ACROSS NRN/CENTRAL AZ AND ACTS ON REMAINING LOW LEVEL MSTR.
SHOULD FINALLY SEE SOME DRIER WX BY TUESDAY.

TEMP-WISE...HAVE UNDERCUT MOS FOR TODAY AS RAIN/CLOUDS PREVENT MUCH
OF ANY WARMING FROM LOWS THIS MORNING. MAY SEE A FEW DEGREES OF
AFTERNOON WARMING OUT W IF WE GET THE AFOREMENTIONED BRIEF CLEARING.
LITTLE CHANGE IN TEMPS EXPECTED ON MONDAY...WITH PERHAPS A COUPLE
DEGREES OF WARMING ON TAP FOR TUESDAY.

WIND-WISE...WILL LIKELY GET BREEZY TO LOCALLY WINDY ON MONDAY...
ESPECIALLY OUT WEST...WHERE GUSTS COULD REACH 35 MPH.

&&

.LONG TERM...
TUESDAY NIGHT THROUGH SATURDAY...
WEATHER PATTERN WILL REMAIN COOL AND UNSETTLED DURING THE EXTENDED
PERIOD...WITH ANOTHER SYSTEM OR TWO SET TO MOVE ACROSS THE STATE.
LATEST GFS ENSEMBLE MEMBERS IN GOOD AGREEMENT THAT ANOTHER POTENT
LOW PRESSURE TROF WILL DIVE SOUTHEAST OUT OF THE PACIFIC NORTHWEST
AND MOVE THRU THE CWA LATER WEDNESDAY THROUGH THURSDAY MORNING. IT
SHOULD HAVE MORE OF AN OVERLAND TRAJECTORY AND LESS MOISTURE...AND
IT WILL BE COLDER TOO. HAVE RAISED POPS A BIT FOR THIS ONE...INTO
THE CHANCE CATEGORY FOR ZONE 24...AND INTO THE SLIGHT CHANCE
CATEGORY FOR THE SOUTH-CENTRAL DESERTS. ANOTHER LOW FOLLOW ON LATER
ON SATURDAY...GIVING ANOTHER SLIGHT CHANCE FOR SHOWERS TO THE AREA.
CONFIDENCE NOT AS HIGH WITH EITHER OF THESE TWO SYSTEMS...AND WE CAN
REFINE TIMING IN SUBSEQUENT FORECAST SHIFTS.

&&

.AVIATION...
JANUARY 27 1800 UTC (JANUARY 27 1100 MST)

EXPECT WIDESPREAD RAIN SHOWERS THROUGH THE DAY AT ALL TAF SITES...
DIMINISHING IN COVERAGE FROM WEST TO EAST LATER THIS EVENING AND
OVERNIGHT.

FOR KPHX/KIWA AND VALLEY AIRFIELDS...CEILINGS AND VISIBILITIES WILL
FLUCTUATE BETWEEN VFR AND MVFR FLIGHT CATEGORIES TODAY...WITH THE
BEST POTENTIAL FOR LOW MVFR LATER THIS AFTERNOON INTO THE EARLY
EVENING HOURS. BRIEF IFR CONDITIONS MAY BE MET ALSO IN HEAVY RAIN
SHOWERS...ESPECIALLY DUE TO REDUCED VISIBILITY. PRECIPITATION IS
FORECAST TO TAPER OFF TOMORROW MORNING...BUT CANNOT RULE OUT A STRAY
SHOWER THROUGH 18 UTC MONDAY.

FOR KIPL AND KBLH...CEILINGS AND VISIBILITIES WILL FLUCTUATE BETWEEN
MVFR AND IFR CONDITIONS WITH THE CONTINUED POSSIBILITY FOR BRIEF
LIFR CONDITIONS AT KIPL. SO FAR...CEILINGS AT KIPL HAVE LOWERED AT
TIMES TO 200 FT AGL WITH VISIBILITIES OF 3/4 SM IN RAIN AND MIST.
CONDITIONS AT KYUM EXPECTED TO BE SLIGHTLY BETTER...MAINLY BETWEEN
VFR AND MVFR FLIGHT CATEGORIES. PRECIPITATION SHOULD DIMINISH LATE
THIS EVENING AT WESTERN TAF SITES.

AVIATION DISCUSSION IS NOT UPDATED FOR AMENDED TAFS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...FLASH FLOOD WATCH IN EFFECT FROM NOON TODAY TO MIDNIGHT TONIGHT
     FOR SOUTH-CENTRAL ARIZONA ZONES AZZ021...022...023...024...AND
     028.

CA...NONE.

&&

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

SHORT TERM...CB/ESTLE
LONG TERM...CB
AVIATION...P ROGERS

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE PHOENIX AZ
553 AM MST SUN JAN 27 2008

AZZ021>024-028-280700-
WEST CENTRAL DESERTS-NORTHWEST MARICOPA COUNTY-
GREATER PHOENIX AREA-
SOUTHERN GILA COUNTY/TONTO NATIONAL FOREST FOOTHILLS-
NORTHWEST AND NORTH CENTRAL PINAL COUNTY-
553 AM MST SUN JAN 27 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST-CENTRAL
ARIZONA...SOUTH-CENTRAL ARIZONA AND WEST-CENTRAL ARIZONA.

.DAY ONE...TODAY AND TONIGHT

A MAJOR PACIFIC STORM SYSTEM WILL CONTINUE TO BRING SUBSTANTIAL
RAINFALL TO SOUTH-CENTRAL ARIZONA...INCLUDING THE PHOENIX AREA...AND
THE WEST CENTRAL ARIZONA DESERTS TODAY AND INTO TONIGHT. TOTAL
RAINFALL AMOUNTS OF .5 TO 1.5 INCHES ARE POSSIBLE IN THE LOWER
ELEVATIONS WITH 1.5 TO 3 INCHES POSSIBLE IN THE HIGHER TERRAIN.
RAINFALL IS ANTICIPATED TO DECREASE LATE TONIGHT.

THE MAIN CONCERN IS THE POTENTIAL FOR FLASH FLOODING...ESPECIALLY IN
THE HIGHER TERRAIN AND FOOTHILL AREAS OF NORTHERN MARICOPA...SOUTHERN
GILA...AND NORTH-CENTRAL PINAL COUNTIES...AS WELL AS PORTIONS OF
CENTRAL AND EASTERN LA PAZ COUNTY. A FLASH FLOOD WATCH IS IN EFFECT
FOR THESE AREAS FROM NOON TODAY TO MIDNIGHT TONIGHT. MUD AND ROCK
SLIDES ARE QUITE POSSIBLE THIS AFTERNOON AND TONIGHT...PARTICULARLY
IN PORTIONS OF SOUTHERN GILA COUNTY ALONG HIGHWAY 60 AND 77. SEE
WEATHER.GOV/PHOENIX TO READ THE WATCH PRODUCT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

AZZ020-025>027-CAZ030>033-280700-
LOWER COLORADO RIVER VALLEY AZ-YUMA/MARTINEZ LAKE AND VICINITY-
SOUTHWEST DESERTS-SOUTHWEST MARICOPA COUNTY-
JOSHUA TREE NATIONAL PARK-LOWER COLORADO RIVER VALLEY CA-
RIVERSIDE COUNTY/EASTERN DESERTS-IMPERIAL COUNTY-
553 AM MST SUN JAN 27 2008 /453 AM PST SUN JAN 27 2008/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EXTREME
SOUTHWEST ARIZONA...EXTREME WEST-CENTRAL ARIZONA...SOUTH-CENTRAL
ARIZONA...SOUTHWEST ARIZONA...EXTREME SOUTHEAST CALIFORNIA AND
SOUTHEAST CALIFORNIA.

.DAY ONE...TODAY AND TONIGHT

RAINFALL WILL CONTINUE THIS MORNING INCREASING THE POSSIBILITY OF
RUNNING WASHES AFFECTING LOW SPOTS ON ROADWAYS WITHIN JOSHUA TREE
NATIONAL PARK. STORM TOTAL RAINFALL AMOUNTS OF ONE QUARTER TO HALF AN
INCH WILL BE COMMON IN SOUTHEAST CALIFORNIA WITH 1 TO 1.25 INCHES
POSSIBLE IN JOSHUA TREE NATIONAL PARK. RAINFALL IS EXPECTED TO BEGIN
DECREASING THIS AFTERNOON...WITH A CHANCE OF SHOWERS LINGERING INTO
TONIGHT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

ESTLE