AREA FORECAST DISCUSSION

 
 FXUS65 KPSR 290302
 AFDPSR
 
 AREA FORECAST DISCUSSION...UPDATED
 NATIONAL WEATHER SERVICE PHOENIX AZ
 802 PM MST THU AUG 28 2008
 
 SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA 
 FORECAST DISCUSSION
 
 .SYNOPSIS...
 ISOLATED TO SCATTERED THUNDERSTORMS CAN BE EXPECTED THROUGH THE 
 EARLY MORNING HOURS ACROSS SOUTH CENTRAL ARIZONA. FOR FRIDAY...HIGH 
 PRESSURE OFF THE CALIFORNIA COAST WILL BUILD ACROSS THE DESERT 
 SOUTHWEST...RESULTING IN A WARMING TREND INTO THE WEEKEND. THE 
 THREAT FOR MONSOON STORMS WILL PERSIST...WITH THE BEST CHANCES SOUTH 
 AND EAST OF PHOENIX. THE THREAT FOR THUNDERSTORMS WILL INCREASE THIS 
 WEEKEND AS A STRONG LOW PRESSURE SYSTEM MOVES THROUGH THE REGION. 
 THE STRONG WEEKEND LOW PRESSURE SYSTEM WILL LEAD TO SIGNIFICANT 
 COOLING ON SUNDAY. FOLLOWING THE PASSAGE OF THE LOW...A GRADUAL 
 WARMING AND DRYING TREND IS EXPECTED NEXT WEEK.
 
 &&
 
 .DISCUSSION...
 HAVE UPDATED THE FORECAST TO ACCOUNT FOR CURRENT TRENDS ACROSS OUR 
 EASTERN CWA. ISOLATED THUNDERSTORMS HAVE BEEN DEVELOPING ACROSS 
 SOUTHERN GILA COUNTY THIS EVENING WITH SOME RATHER IMPRESSIVE 
 LOOKING STORMS AT TIMES. IT IS PRETTY OBVIOUS THAT THERE IS A LOT OF 
 INSTABILITY OUT THERE...BUT IT IS ALSO OBVIOUS THAT THERE IS A GOOD 
 AMOUNT OF INHIBITION ESPECIALLY OVER THE LOWER DESERTS. THE 
 NORTHERN/WESTERN EXTENT OF THE CONVECTION HAS SLOWLY BU STEADILY 
 BEEN EDGING TOWARD PHOENIX AND EXPECT THIS TREND TO CONTINUE AS 
 INHIBITION WEAKENS AS THE LOW LEVEL ATMOSPHERE COOLS SOME AND 
 OUTFLOW BOUNDARIES PUSH TOWARD PHOENIX. STORMS HAVE HADED VERY GOOD 
 MOVEMENT SO FAR THIS EVENING...MOVING AT THE MARKLAR RATE OF 40KTS 
 FORM THE NE. WILL HAVE TO WATCH OUT FOR SVR WIND POTENTIAL WITH 
 STORMS THROUGH THE EVENING. ONLY MINOR CHANGES MADE TO OTHER GRIDS 
 THROUGH THE REST OF TONIGHT.
 
 PREVIOUS DISCUSSION...
 FRIDAY LOOKS TO BE A SIMILAR DAY TO TODAY...WITH THE UPPER HIGH TO 
 OUR NW AND A GOOD NELY/ELY STEERING FLOW IN PLACE. MOISTURE REMAINS 
 PLENTIFUL AND WEAK VORT MAXES WILL LIKELY MOVE WESTWARD AROUND THE 
 SRN PERIPHERY OF THE HIGH...ENHANCING STORMS AT TIMES. OVERALL 
 DYNAMICS AGAIN ARE NOT THAT IMPRESSIVE SO WE WILL KEEP A MID GRADE 
 MONSOON FORECAST IN PLACE.
 
 THE WEEKEND LOOKS TO BE INCREASING ACTIVE AS BOTH EUROPEAN AND GFS 
 BRING A MAJOR SHORT WAVE TROF INTO THE WESTERN STATES LEADING TO A 
 PROBABLE TRANSITION TYPE EVENT FOR OUR CWA. MOISTURE WILL BE DRAWN 
 NORTH INTO THE CWA AHEAD OF THE TROF...THEN INCREASING DYNAMICS/UVV 
 AND SHEAR WILL ACT ON THE MOISTURE TO GIVE STRONG AND POSSIBLY 
 SEVERE STORMS TO THE CWA...ESPECIALLY SOUTH-CENTRAL AZ. HAVE RAISED 
 POPS SATURDAY EVENING TO 40 PLUS OVER SOUTH-CENTRAL AZ...WITH CHANCE 
 POPS WESTWARD INTO SERN CA...THEN POPS INCREASING A BIT MORE TO 
 AROUND 50 OVER SOUTH-CENTRAL AZ/SRN GILA SUNDAY AFTERNOON AND 
 EVENING. WILL ISSUE A SPS TO HIGHLIGHT THE POTENTIAL FOR ACTIVE AND 
 POSSIBLY SEVERE WEATHER THIS COMING LABOR DAY WEEKEND.
 
 EXTENDED...FLOW NOW LOOKS TO REMAIN MORE WESTERLY BEHIND THE 
 DEPARTING TROUGH...BASED ON THE LATEST GFS/ECMWF. THIS WILL CONFINE 
 HIGHEST PRECIP CHANCES TO THE HIGHER TERRAIN EAST OF PHOENIX. 
 GRADUAL WARMING TREND IS EXPECTED...THOUGH TEMPS SHOULD REMAIN BELOW 
 NORMAL THROUGH THE PERIOD.
 
 &&
 
 .AVIATION...
 KPHX/KIWA AND SURROUNDING AIRFIELDS...
 WELL STORMS HAVE BEEN SLOWLY TRENDING TOWARD THE PHX AREA DURING THE 
 PAST FEW HOURS AND EXPECT THIS TREND TO CONTINUE FOR SEVERAL MORE 
 HOURS. STORMS WILL BE MOVING FROM NE TO SW AT 30KTS...FAIRLY 
 PROGRESSIVE FOR OUR AREA. HAVE AMENDED TAFS WITH LATEST THINKING.
  
 IN SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA...
 DRY WEATHER EXPECTED AT THE TAFS FOR TONIGHT. SMALL/OUTSIDE CHANCE 
 OF SEEING THUNDER AT KYUM BUT PROBABILITY NOT HIGH ENOUGH TO INCLUDE 
 MENTION IN TAFS. OTHERWISE EXPECT SOUTHERLY WINDS THROUGH TOMORROW 
 AFTERNOON.
 
 AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
 
 &&
 
 .FIRE WEATHER...
 FRIDAY THROUGH TUESDAY...
 A DRYING AND WARMING TREND WILL CONTINUE THROUGH FRIDAY. A WEST 
 COAST WEATHER SYSTEM IS EXPECTED TO MOVE THROUGH THE REGION THIS 
 WEEKEND...INCREASING HUMIDITY AND THE CHANCE FOR SHOWERS AND 
 THUNDERSTORMS. COOLER TEMPERATURES CAN ALSO BE EXPECTED OVER THE 
 WEEKEND. A WARMING AND DRYING TREND WILL COMMENCE MON/TUE OF NEXT 
 WEEK.
 
 &&
 
 .PSR WATCHES/WARNINGS/ADVISORIES...
 
 AZ...NONE.
 
 CA...NONE. 
 
 &&
 
 

 
 NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
 
 WEATHER.GOV/PHOENIX
 
 DISCUSSION...INIGUEZ/CB/HIRSCH
 AVIATION...INIGUEZ
 FIRE WEATHER...WANEK
 
 
 

Webmaster
US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Tucson Weather Forecast Office
520 North Park Ave, Suite 304
Tucson, AZ 85719

Tel: (520) 670-6526