000 FXUS65 KPSR 242015 AAA AFDPSR AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PHOENIX AZ 110 PM MST THU JUL 24 2008 SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA FORECAST DISCUSSION .UPDATE...UPDATED AVIATION DISCUSSION. && .SYNOPSIS... WEAK MONSOONAL FLOW WILL CONTINUE OVER SOUTHEAST ARIZONA THROUGH FRIDAY. DIURNAL AFTERNOON AND EARLY EVENING SHOWERS WILL THEREFORE CONTINUE TODAY AND FRIDAY. A CHANGE IN WEATHER MIGHT BE LURKING AROUND THE CORNER THOUGH...AS THE REMNANTS OF HURRICANE DOLLY EJECTS A SIGNIFICANT AMOUNT OF MOISTURE FROM THE EAST BACK INTO THE LOWER DESERTS THIS WEEKEND. && .DISCUSSION... TODAYS FORECAST IS NOT AS SIMPLE AS IT MIGHT SEEM AT FIRST GLANCE. ONCE AGAIN LOCAL SOUNDINGS AND OBSERVATIONS GIVE CLUES TO THE FACT THAT THE LOWER ATMOSPHERE IS MODIFYING...PARTICULARLY WITH REGARD TO THE AVAILABILITY OF MOISTURE. THE PSR SOUNDING SHOULD CONSIDERABLE MOISTENING...ESPECIALLY BELOW 700 MB...WITH AN INCREASE IN PRECIPITABLE WATER FROM 1.38 INCHES TO 1.80 INCHES IN THE PAST 24 HOURS. AT K1Y7 (YUMA) NOT AS MUCH CHANGE...THOUGH THE PW INCREASED FROM .81 TO 1.01 INCHES. BIGGEST CHANGE IN THE BL IS IN OUR WESTERN FORECAST ZONES...WHERE LOW LEVEL MOISTURE HAS MOVED INTO THE REGION FROM THE SOUTH. THIS HAS RESULTED IN A 20 TO 30 DEGREE INCREASE IN DEWPOINT TEMPERATURES AT MANY LOCATIONS. ANOTHER FACTOR TO CONSIDER IS FAVORABLE UPPER LEVEL DYNAMICS...WITH AN ELONGATED UPPER LEVEL DEFORMATION REGION CURRENTLY SHOWING UP AT 300 TO 400 MB. SOME EARLY MORNING CONVECTION AND CLOUDINESS WAS LINING UP WELL WITH THIS FEATURE. THE NAM PUSHES THIS FEATURE SLOWLY TO THE WEST ACROSS OUR FORECAST AREA THROUGH THE DAY TODAY. ALL THIS BEING CONSIDERED...MODEL SOUNDINGS SHOW MARGINAL INSTABILITY...AND SATELLITE CURRENTLY SHOWS MOSTLY CLEAR SKIES OVER THE REGION. RADAR ALSO SHOWS NO ECHOS. MODELS CONTINUE TO KEEP ANY PRECIPITATION CONFINED TO THE HIGHER TERRAIN OF ZONE 24. ELECTED TO BACK OFF SOME ON OUR POPS FOR THIS AFTERNOON AND EARLY EVENING. HOPEFULLY THIS WAS THE RIGHT CHOICE. KEPT POPS AT KPHX RIGHT AT FWC GUIDANCE AND USED CLIMO POPS FOR SURROUNDING FORECAST AREA. ALSO TWEAKED TEMPS AND SKY COVER A TAD. .PREV DISCUSSION... ISSUED AT 510 AM MST THU JUL 24 2008 SAT IMAGERY EARLY THIS MORNING SHOWS A FEW DEBRIS CLOUDS MOVING NE TO SW ACROSS OUR CENTRAL CWA...LEFT OVER FROM ISOLATED SHOWERS/THUNDERSTORMS THAT MOVED THROUGH PORTIONS OF THE VALLEY LATE LAST NIGHT. THESE STORMS APPEAR TO HAVE BEEN ASSOCIATED WITH AN ELONGATED MID LEVEL PVA STRETCHING FROM NORTH OF SHOWLOW SWD INTO CENTRAL MARICOPA COUNTY. THIS FEATURE HAS BEEN FCST BY THE RUC SINCE EARLY THU MORNING...COUPLED WITH A WEAK AREA OF UPPER LEVEL DIFFLUENCE--PRETTY IMPRESSIVE...IF YOU ASK ME. THAT SAID...THE RUC HAS...AND WILL CONTINUE TO BE...MY MODEL OF CHOICE IN THE NEAR TERM. THE AFOREMENTIONED UPPER LEVEL FORCING IS FCST NOT ONLY BY THE RUC BUT THE NAM TO SHIFT WESTWARD...MOVING ACROSS NWRN MARICOPA AND LA PAZ COUNTIES EARLY/MID DAY TODAY...REACHING THE CO RIVER AND WEAKENING SOMEWHAT BY THIS AFTERNOON. FCST FOR THE 12-18 UTC TIME PERIOD TODAY REFLECTS THIS TREND...WITH SLIGHT CHANCE POPS OVER ZONES 21...22...26. WHEN WE CAME ON SHIFT EARLIER...SURFACE DEW POINTS FROM THE CO RIVER WESTWARD WERE INCREDIBLY LOW...SINGLE DIGITS AND LOW TEENS AROUND BLYTHE...WHICH LEAD ME TO BELIEVE ANY THREAT FOR AFTERNOON/SHOWERS FROM THE RIVER WEST TODAY WOULD BE SQUASHED BY THE DRIER AIR. HOWEVER...THAT HAS CHANGED WITHIN THE PAST COUPLE HOURS. SURFACE TD/S ALONG THE RIVER HAVE JUMPED AT LEAST 20F BETWEEN 07-10 UTC...WITH YUMA BACK IN THE MID 60S AND BLYTHE IN THE MID UPPER 40S. KYUX VAD SHOWS A SLY FLOW THROUGH THE FIRST COUPLE THOUSAND FEET...AND FCST SOUNDING BY ALL MODELS INDICATE THIS SLY FLOW TO DEEPEN AS THE DAY CONTINUES. MEANWHILE...FCST SOUNDINGS FOR KPSR CONTINUE TO SHOW A LOW/MID LEVEL WESTERLY FLOW (WHICH HAS BEEN RESPONSIBLE FOR THE DRY AIR ADVECTION OVER THE PAST COUPLE DAYS)...BUT WITH THE ADDED MOISTURE OUT WEST...WE SHOULD START TO SEE AN INCREASE IN LOW LEVEL MOISTURE ACROSS THE LOWER DESERTS BY LATE THIS EVENING. CURRENT FCST REFLECT THIS THINKING BY KEEPING POPS OUT OF THE GREATER PHX AREA UNTIL AFTER 06UTC (AFTER 11PM MST)...AND CARRYING SLIGHT CHANCE FOR SHOWERS/THUNDERSTORMS ACROSS THE SOUTHWEST AND SOUTH-CENTRAL AZ DESERTS THROUGH EARLY FRI MORNING. EXCERPTS FROM PREVIOUS DISCUSSION... FRIDAY THROUGH THE WEEKEND...IT APPEARS WE WILL BE GETTING OUR MAIN PUSH OF THE REAL DEEP MOISTURE BY FRIDAY AND INTO THE WEEKEND. THIS WILL HAPPEN AS THE REMNANTS OF DOLLY TRAVERSE ACROSS NW MEXICO THE NEXT FEW DAYS. STRONG ELYS WILL BE THE RULE BY THEN ACROSS THE AREA UNDER THE MID-TROPOSPHERIC HIGH MOVING BACK NWD. 00Z MODELS ARE ALL IN AGREEMENT THAT WE WILL UNDERGO THIS MOISTURE INCREASE...SO CURRENT TRENDS OF HIGHER POPS BY THE WEEKEND STILL APPEAR REASONABLE. TEMPS WILL STAY PRETTY HOT THE NEXT DAY OR TWO BEFORE TAPERING OFF IN RESPONSE TO HIGHER HUMIDITIES OVER THE WEEKEND. BEYOND THE WEEKEND...IT IS REALLY ANYONE`S GUESS. AT THIS POINT IN TIME...THERE DOESN`T APPEAR TO BE ANYTHING UPSTREAM TO WIPE OUT OUR MOISTURE...SO WE`LL CONTINUE A LOW GRADE MONSOON FCST THOUGH THE EXTENDED...WITH SHOWERS/THUNDERSTORMS FAVORING THE HIGHER TERRAIN AND TEMPS RUNNING A COUPLE DEG BELOW AVERAGE FOR LATE JULY. && .AVIATION... SOUTH-CENTRAL ARIZONA...KPHX/KIWA AND SURROUNDING AIRFIELDS... WEAK WEATHER DISTURBANCE PASSING BY TO THE SOUTH THIS AFTERNOON. MOISTURE IS STILL SOMEWHAT LIMITED OVER THE DESERTS...AND WITH EAST-SOUTHEAST STEERING FLOW...THERE IS A SLIGHT CHANCE FOR STORMS TO MOVE W-NW OFF THE HIGHER TERRAIN AND INTO THE DESERTS THROUGH 05Z FRIDAY. HOWEVER...ANY STORM THAT MOVES INTO THE DESERTS NEAR KIWA AND KPHX HAS THE POTENTIAL TO PRODUCE GUSTY OUTFLOW WINDS UP TO 35 KTS...AND SOME LOCALLIZED BLOWING DUST. DUE TO UNCERTAINTIES/LOW POPS...WILL NOT MENTION WEATHER AT THIS TIME. WINDS SHOULD BE GENERALLY LIGHT AND DIURNAL OVERNIGHT THROUGH 12Z FRIDAY...WITH SOME MINOR MID AND UPPER LEVEL DEBRIS CLOUDINESS TONIGHT INTO FRIDAY MORNING. SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA...KYUM/KBLH AND KIPL... AIRMASS HAS MOISTENED A BIT...AND WILL BEGIN TO BECOME MORE UNSTABLE WITH TIME...BUT STILL NO THREAT OF THUNDERSTORMS THROUGH 12Z FRIDAY. EXPECT SOUTH-SOUTHEASTERLY WINDS ALONG THE LOWER COLORADO RIVER VALLEY AND INTO SOUTHEAST CALIFORNIA DESERTS THIS AFTERNOON AND OVERNIGHT...GENERALLY AROUND 12KTS WITH INTERMITTENT GUSTS UP TO 20KT AFTER 13Z FRIDAY. SOME MINOR MID AND UPPER LEVEL DEBRIS CLOUDINESS WILL PERSIST INTO FRIDAY MORNING FROM CONVECTION SOUTH OF THE REGION OVER SONORA MEXICO. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... NO SIGNIFICANT FIRE WEATHER CONCERNS THIS WEEKEND INTO THE MIDDLE OF NEXT WEEK. AIRMASS WILL BE GRADUALLY WETTING UP AFTER FRIDAY AND THROUGH SUNDAY AS MOISTURE FROM HURRICANE DOLLY WORKS WESTWARD AND INTO THE STATE...LEADING TO A CHANCE FOR SHOWERS/THUNDERSTORMS ACROSS SOUTH-CENTRAL AZ BY SATURDAY...WITH POSSIBLY A BETTER CHANCE SUNDAY. AS HUMIDITIES RISE...MAX TEMPS WILL LOWER...LIKELY TO WELL BELOW NORMAL VALUES BY SUNDAY. WITH NO SIGNIFICANT MECHANISM TO REALLY DRY THINGS OUT NEXT WEEK...WE WILL KEEP AT LEAST A STANDARD GRADE MONSOON FORECAST GOING...WITH MAX TEMPS TO CLIMB TO NEAR NORMAL BY THE END OF THE PERIOD. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT WEATHER.GOV/PHOENIX DISCUSSION...MCLANE/WANEK/ESTLE AVIATION...MEYERS FIRE WEATHER...CB