Flash Flood Warning 10, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-192245-

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
945 AM MST SUN SEP 19 2004

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

.SYNOPSIS...
AN EARLY SEASON COLD LOW PRESSURE SYSTEM WILL CONTINUE TO SLOWLY
DEVELOP OVER THE WESTERN STATES...AND PULL A SIGNIFICANT AMOUNT OF
SUBTROPICAL MOISTURE FROM TROPICAL DEPRESSION JAVIER INTO MAINLY
SOUTHWEST AND SOUTH CENTRAL ARIZONA TODAY. THIS WILL LEAD TO A GOOD
CHANCE FOR SHOWERS AND THUNDERSTORMS WITH THE POTENTIAL FOR LOCALLY
HEAVY RAIN OVER SOUTH CENTRAL ARIZONA. A COLD FRONT WILL FINALLY
SWEEP THROUGH THE REGION MONDAY FOR A RETURN TO DRY WEATHER TUESDAY
THROUGH SATURDAY.

&&

.DISCUSSION...
PLOT DATA SHOWED THE AIRMASS OVER THE SOUTHERN HALF OF ARIZONA HAS
BECOME SUBTROPICAL AS THE LOW LEVEL CORE REMNAMTS OF FORMER
HURRICANE JAVIER HAVE FINALLY MOVED INTO THE AREA. MORE ABOUT THIS
LATER.

PLOT DATA ALSO SHOWED A VERY POWERFUL VORT MAX/SHORTWAVE ROTATED
AROUND THE LARGE WESTERN U.S TROF LAST NIGHT/EARLY THIS MORNING.
THIS SHORTWAVE PRODUCED RAPID DESTABILIZATION OVER PORTIONS OF
SOUTHEAST CA AND FAR SOUTHWEST AZ EARLY THIS MORNING WHERE A LINE OF
ISOLATED SEVERE THUNDERSTORMS DEVELOPED. THE SHORTWAVE WAS LIFTING
NORTHWARD AWAY FROM THE AREA AT 16Z...AND THE LINE OF CONVECTION HAD
WEAKENED OR DIMINISHED CONSIDERABLY. MORE CONVERGENCE ALOFT/SINKING
MOTION
WILL FOLLOW THIS SHORTWAVE TODAY OVER SOUTHEAST CA AND FAR SOUTHWEST
AZ. THE SEVERE THUNDERSTORM WATCH BOX FOR THAT AREA EXPIRED AT 14Z.

HOWEVER...THE LARGE WESTERN REGION TROF AND ITS FRONT SIDE JETSTREAM
MAXIMA WILL CONTINUE TO PROVIDE SOME ENTRANCE REGION DYNAMICS
...MAINLY ACROSS EASTERN UTAH/NORTHEAST AZ...BUT WEAKLY EXTENDING
SOUTH INTO SOUTH CENTRAL AZ (FROM PHOENIX EASTWARD).

AGAIN...PLOT DATA SHOWED EXTREMELY HIGH AMOUNTS OF LOW LEVEL
MOISTURE. FOR EXAMPLE THE AVERAGE DEWPOINT IN THE FIRST 5000 FEET AT
PHOENIX WAS 16 DEGREES C...11 C AT TUCSON. EQUALLY IMPRESSIVE WAS A
STRONG LOW LEVEL JET MAX MOVING NORTH FROM THE GUAYMAS MEXICO
REGION. THE GUAYMAS SOUNDING SHOWED A DEEP SOUTH TO SOUTHEASTERLY
40 KNOT WIND CORE EXTENDING FROM JUST ABOVE THE SURFACE TO 15 THSD
FEET (WIND CORE LIKELY ASSOCIATED WITH REMNANT CIRCULATION OF
JAVIER).  WITH 850/700 MB WIND BECOMING SOUTHWESTERLY OVER IN
SOUTHWEST AZ...AND A SOUTHERLY LOW LEVEL JET MAX COMING OUT OF
MEXICO...STRONG MOISTURE CONVERGENCE IS EXPECTED IN SOUTH
CENTRAL/SOUTHEAST AZ TODAY. THE POTENTIAL FOR ENHANCED UPSLOPE
TROPICAL TYPE RAIN IS ALSO POSSIBLE SINCE VICINITY OF PHOENIX LOW
LEVEL DEWPOINTS OF 12-16 C (MIXING RATIOS OF 11-13 G/KG) WILL BE
MOVING UPSLOPE OVER THE EASTERN MOGOLLON RIM/GILA COUNTY WERE AT 700
MB TEMPS ARE 7 C AND SATURATION MIXING RATIOS AROUND 9.8 G/KG.

AT THE SAME TIME...PHOENIX SOUNDING SHOWED LARGE AMOUNTS OF NEAR
SURFACE BASED C.A.P.E.    WITH A LITTLE SUNSHINE IN SOUTHWEST AZ...
UNILATERAL SHEAR AND WEAK ENTRANCE DYNAMICS...ISOLATED SEVERE
THUNDERSTORMS ARE ALSO A POSSIBILITY IN SOUTH CENTRAL AZ.

DYNAMICS WEAKEN SLOWLY TONIGHT...AND A FRONTAL PASSAGE EXPECTED ON
MONDAY. CURRENT FORECASTS SHOW A TREND TOWARD LOWER PROBABILITIES OF
PRECIP TONIGHT THROUGH MONDAY WHICH IS ACCEPTED FOR NOW. ALSO...
CURRENT FORECASTS HIT THE WEATHER SITUATION HARD TODAY THEREFORE NO
UPDATES NEEDED.

IN SUMMARY...TODAY WILL BE A BUSY WEATHER DAY...AND MOSTLY OVER OUR
SOUTH CENTRAL AZ CWA. LOW LEVEL SUBTROPICAL MOISTURE CONVERGENCE...
HIGH C.A.P.E... WIND SHEAR...AND WEAK ENTRANCE REGION JET DYNAMICS
WILL KEEP US BUSY.

ALSO...MOST OF THE HEAVY RAINFALL IS EXPECTED OVER THE SOUTH CENTRAL
AZ DESERTS AND MOUNTAINS WHERE A FLASH FLOOD WATCH WILL CONTINUE
UNTIL 00Z MON.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...FLASH FLOOD WATCH SOUTH CENTRAL ZONES 22...23...24...27...28
TODAY.
CA...NONE.

&&

VASQUEZ

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
1110 AM MST SUN SEP 19 2004

AZZ022>024-027-028-200400-
GREATER PHOENIX AREA-NORTHWEST AND NORTH CENTRAL PINAL COUNTY-
NORTHWEST MARICOPA COUNTY-SOUTHERN GILA/TONTO NF FOOTHILLS-
SOUTHWEST MARICOPA COUNTY-
1110 AM MST SUN SEP 19 2004

THIS HAZARDOUS WEATHER OUTLOOK IS SOUTH CENTRAL ARIZONA INCLUDING THE
GREATER PHOENIX AREA...CASA GRANDE...AND GLOBE MIAMI...

.DAY ONE...TODAY
SUBTROPICAL MOISTURE OVER THE AREA...ALONG WITH AN APPROACHING COLD
FRONT...WILL RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THIS EVENING. THE AIRMASS IS EXTREMELY MOIST AND CONDUCIVE TO HEAVY
RAIN. IN ADDITION...STRONG WIND SHEAR IN THE ATMOSPHERE COULD LEAD TO
ISOLATED SEVERE THUNDERSTORMS WITH DAMAGING WIND AND LARGE HAIL.

STAY TUNED TO NOAA WEATHER RADIO OR YOUR LOCAL MEDIA OUTLETS FOR
POSSIBLE WATCHES OR WARNINGS.

HEAVY RAINS MAY CAUSE MINOR FLOODING OF POOR DRAINAGE AND LOW LYING
AREAS. WASHES MAY BEGIN FLOWING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY
A COLD FRONT WILL MOVE THROUGH THE AREA MONDAY. A CHANCE FOR SHOWERS
AND THUNDERSTORMS WILL CONTINUE THE FIRST HALF OF THE DAY. LOCALLY
HEAVY THUNDERSTORM RAIN AND STRONG WINDS ARE POSSIBLE.

AZZ021-025-026-200400-
SOUTHWEST DESERTS-WEST CENTRAL DESERTS-
YUMA/MARTINEZ LAKE AND VICINITY-
1110 AM MST SUN SEP 19 2004

THIS HAZARDOUS WEATHER OUTLOOK IS SOUTHWEST ARIZONA AND THE COLORADO
RIVER VALLEY.

.DAY ONE...TODAY
A CHANCE FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THE
EVENING HOURS. THERE IS A CHANCE FOR ISOLATED SEVERE THUNDERSTORMS IN
PORTIONS OF YUMA AND LA PAZ COUNTIES WITH DAMAGING WIND AND HEAVY
RAIN.

STAY TUNED TO NOAA WEATHER RADIO OR YOUR LOCAL MEDIA OUTLETS FOR
POSSIBLE WATCHES OR WARNINGS.

HEAVY RAINS MAY CAUSE MINOR FLOODING OF POOR DRAINAGE AND LOW LYING
AREAS. WASHES MAY BEGIN FLOWING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

AZZ020-CAZ030>033-200400-
IMPERIAL COUNTY-JOSHUA TREE NATIONAL PARK-
LOWER COLORADO RIVER VALLEY AZ-LOWER COLORADO RIVER VALLEY CA-
RIVERSIDE COUNTY/EASTERN DESERTS-
1110 AM MST SUN SEP 19 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST CALIFORNIA.

.DAY ONE...TODAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.