Severe Thunderstorm Warning 51, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-071745-

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
240 AM MST SAT SEP 7 2002

.SYNOPSIS...
MOIST SOUTHERLY WINDS...AND AN UNSTABLE AIRMASS OVER SOUTHEAST
CALIFORNIA...SOUTHWEST AND SOUTH CENTRAL ARIZONA WILL CONTINUE THE
CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH THE WEEKEND.  A TROUGH
OF LOW PRESSURE ALONG THE CALIFORNIA COAST...AND A RIDGE OF HIGH
PRESSURE OVER NEW MEXICO...WILL REMAIN STATIONARY THROUGH SUNDAY.
EARLY NEXT WEEK...SOME DRIER AIR MAY MOVE INTO SOUTHEAST
CALIFORNIA...BUT MOIST AND UNSTABLE AIR REMAINS ANCHORED OVER
SOUTHERN ARIZONA FOR MOST OF NEXT WEEK.  TEMPERATURES WILL FALL
OFF TO NEAR SEASONAL NORMALS THE NEXT FEW DAYS.

.DISCUSSION...
WELL...THE MOISTURE IS HERE...ALONG WITH DYNAMICS...AND THE WEATHER
HAS ALREADY GOTTEN ACTIVE IN OUR CWA...AS HEAVY RAIN AND SEVERE
WEATHER WERE SEEN IN THE PHX AREA FRI AFTN AND EVE. TROF IS IN
POSITION ALONG THE WEST COAST...WITH HIGH PRESSURE TO OUR EAST...AND
THE RESULTANT SLY TO SWLY FLOW BETWEEN THEM HAS FUNNELED SUBSTANTIAL
TROPICAL MOISTURE INTO SERN CA AND AZ. MUCH OF THIS MOISTURE WAS
REMAINS OF OLD HURCN HERNAN...AND THERE MORE MOISTURE TO COME AS
WEAK DISTURBANCE TD ELEVEN E LURKS OFF SRN BAJA...MOVING NW...WHICH
COULD BE INGESTED INTO THE MIX EARLY NEXT WEEK. PWAT VALUES VERY
HIGH OVER OUR DESERTS AND UPSTREAM...AT AND OVER 1.5 INCHES...THIS
SEEN CLEARLY IN THE RAOBS AND GOES PWAT IMAGERY. ALSO...ETA 500MB
STREAMLINES INDICATE A CONVERGENCE ZONE OVER CNTRL AZ...WHICH SHOULD
REMAIN IN PLACE THRU THE WEEKEND AT LEAST...AS THE BASIC SYNOPTIC
FLOW PATTERN CHANGES LITTLE. GIVEN THE AMOUNT OF MOISTURE AND
INSTABILITY IN PLACE...AND WITH FAVORABLE UPPER FORCING AND
DIVERGENCE FIELDS TO GO ALONG...HAVE DECIDED TO UP THE POPS A BIT
OVER OUR CWA TODAY AND SUNDAY...MOSTLY INTO THE GOOD CHANCE OR
LIKELY CATEGORIES. WITH THE POSSIBILITY OF TRAINING ECHOS...AND
GIVEN THE 1.5 INCH PLUS PWAT...WILL REISSUE THE FLASH FLOOD WATCH
FOR OUR ERN ZONES AND HAVE IT GO FROM NOON THRU MIDNIGHT TONIGHT.

BY MONDAY THE TROF TO OUR WEST WEAKENS A BIT AND THE BULK OF THE
DEEP MOISTURE HAS SHIFTED TO OUR NE...BUT THERE SHOULD BE SUFFICIENT
MOISTURE AND INSTABILITY TO KEEP A CHANCE FOR STORMS GOING OVER ALL
OF OUR AZ ZONES. AVN ALSO SUGGESTS A SHORT WAVE IN THE SWLY FLOW TO
MOVE INTO SERN CA MONDAY...SO HAVE ADDED A CHANCE FOR STORMS MONDAY
IN THE CA ZONES.  ONE THING TO NOTE...AVN SUGGESTS THAT SOME RATHER
IMPRESSIVE JET DYNAMICS WILL BE AT PLAY OVER OUR CENTRAL AND ERN
ZONES BEGINNING LATER SUNDAY NIGHT THRU EARLY TUESDAY...WITH THE
RIGHT REAR QUAD OF THE STRONG UPPER JET MOVING IN FROM THE WEST.
THIS COULD HELP GENERATE SOME STRONG STORMS OVER OUR ERN ZONES THE
FIRST PART OF NEXT WEEK. OTHERWISE HAVE NOT CHANGED THE FORECAST
MUCH IN THE EXTENDED...STILL LOOKING FOR A GRADUAL DRYING TREND FROM
THE WEST TO OCCUR...AND THE LATEST MRF SUPPORTS THIS IDEA. BY
THURSDAY THE ONLY WEATHER IN OUR AREA SHOULD BE OVER ZONE 24...WITH
MOSTLY CLEAR TO PARTLY CLOUDY SKIES SEEN ELSEWHERE. AS FOR
TEMPS...WITH ALL OF THE CLOUDS AND SHOWERS AROUND...THEY SHOULD BE
DOWN MARKEDLY TODAY...AND STAY DOWN THRU THE WEEKEND INTO EARLY NEXT
WEEK WITH THE DESERTS MOSTLY IN THE 90S. AS THE DRYING TREND OCCURS
AND WE SEE MORE SUNSHINE...THERE SHOULD BE SOME WARMUP...BUT THE
HEIGHT FIELDS DO NOT CHANGE DRAMATICALLY SO THIS WILL LIMIT THE
AMOUNT OF WARMING SEEN.  11

.PSR...FLASH FLOOD WATCH NOON TODAY THROUGH MIDNIGHT TONIGHT FOR S
CENTRAL AZ...MARICOPA...N CENTRAL PINAL...AND SOUTHERN GILA
COUNTIES...FCST ZONES...22...23...24...27...AND 28.