FXUS65 KPSR 300355 AFDPSR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 855 PM MST THU JUL 29 2010 .SYNOPSIS... ACTIVE WEATHER IS EXPECTED ACROSS ARIZONA THIS EVENING AS A VERY MOIST AND RATHER UNSTABLE AIRMASS IS IN PLACE OVER THE STATE. HEAVY RAINFALL WITH LOCALIZED FLASH FLOODING WILL BE POSSIBLE ALONG WITH STRONG... POSSIBLY DAMAGING...WINDS. ANOTHER ACTIVE DAY IS LIKELY SATURDAY OR SUNDAY AS A SECOND LOW TRACKS OUT OF THE GULF OF MEXICO AND TOWARD ARIZONA. TEMPERATURES WILL TREND DOWN HEADING INTO THE WEEKEND DUE TO INCREASED CLOUD COVER AND SHOWER AND THUNDERSTORM ACTIVITY. DRIER AIR WILL FILTER IN BY THE MIDDLE OF NEXT WEEK CAUSING RAIN CHANCES TO DROP AND TEMPERATURES TO RISE. && .DISCUSSION... THE INFLUENCE OF THE FORMER TEXAS...NOW NEW MEXICO INVERTED TROF... CONTINUED TO INFLUENCE LARGE AND SEVERE THUNDERSTORMS OVER ARIZONA THURSDAY AFTERNOON/EARLY EVENING. WITH EXCESSIVE LEVELS OF MONSOON MOISTURE IN-PLACE...HEAVY RAIN AND WET MICROBURSTS DEVELOPED ON THE SOUTH CENTRAL AZ DESERTS...INCLUDING PHOENIX. AT 03Z MOST THUNDERSTORMS HAD DIMINISHED LEAVING A LARGE MASS OF CONVECTIVE DEBRIS CLOUDS OVER SOUTHWEST AND SOUTH CENTRAL AZ...WITH EMBEDDED LIGHT TO ISOLATED MODERATE SHOWERS. THE DEBRIS CLOUD FIELD WILL EXPAND OVERNIGHT WITH A THREAT FOR ISOLATED SHOWERS INTO FRIDAY MORNING. FRIDAY... REMNANTS OF THE NEW MEXICO INVERTED TROF WILL FINALLY MOVE INTO SOUTHEAST AZ IN A MUCH WEAKENED AND NEARLY DISORGANIZED STATE BY FRIDAY AFTERNOON. HOWEVER...AND ITS HARD TO TELL AT THIS POINT...AND NOT AS CLEAR AS THURSDAY...THERE STILL APPEARS TO BE SOME UPPER LEVEL SUPPORT OVER THE EASTERN HALF OF AZ FOR TALL THUNDERSTORMS. THUNDERSTORMS WE THINK WILL FIRST DEVELOP OVER THE MOUNTAINS NORTH THROUGH SOUTHEAST OF PHOENIX BY AFTERNOON...WITH THEIR CONVECTIVE OUTFLOWS PUSHING ONTO THE CENTRAL DESERTS TRIGGERING ADDITIONAL STORMS. THE FACT THAT THERE IS A WEAK DISTURBANCE MOVING INTO AZ...WITH A VERY HUMID MONSOON AIRMASS IN PLACE...CONTINUES TO WARRANT ELEVATED PROBABILITIES OF PRECIPITATION FRIDAY AFTERNOON AND EVENING...PARTICULARLY OVER THE SOUTH CENTRAL AZ PORTIONS OF OUR FORECAST AREA. FORECASTS WERE UPDATED EARLIER TO ACCOUNT FOR THE DIMINISHING SHOWER TREND THIS EVENING. FORECASTS FOR FRI LOOK OK ALSO. NO ADDITIONAL UPDATES EXPECTED. PORTIONS OF PREVIOUS DISCUSSION BELOW STILL APPLY. PORTIONS OF PREVIOUS DISCUSSION... FOR THE NEXT FEW DAYS...WE WILL BE REMAIN UNDER A VERY MOIST AND UNSTABLE MONSOONAL FLOW...WITH STEERING FLOW GENERALLY FROM THE EAST ACROSS THE ARIZONA PORTION OF THE CWA. PWAT VALUES WILL RANGE FROM 1.5 TO OVER 2 INCHES...850MB DEWPOINTS WILL EXCEED 14C...AND SURFACE DEWPOINTS SHOULD BE IN THE 60S OR LOW 70S. DYNAMICS WILL BE TOUGHER TO PIN DOWN...BUT MODEL GUIDANCE STILL IS CONSISTENT IN SUGGESTING THE INVERTED TROF TO OUR EAST WILL MOVE UP AND INTO ARIZONA SATURDAY INTO SUNDAY. THIS FEATURE SHOULD INCREASE OUR CHANCES FOR PRECIP...BUT WILL ALSO LEAD TO INCREASED CLOUDS AND DECREASED HIGH TEMPERATURES. FOR THE MOST PART...A HIGH GRADE MONSOON FORECAST WILL BE IN EFFECT NEXT 3 DAYS...WITH CHANCE TO LIKELY POPS ACROSS SOUTH CENTRAL AZ...CHANCE POPS ACROSS THE SWRN DESERTS...AND SLIGHT CHANCES INTO SERN CA. WILL SHOW A DECREASING TEMP TREND WITH HIGHS BELOW SEASONAL NORMALS EACH DAY. IN FACT...EXPECT HIGHS IN THE 90S OVER THE CENTRAL DESERTS SATURDAY AND SUNDAY. LATEST GFS/ECWMF CONTINUE TO CALL FOR SOMEWHAT OF A DRYING TREND BEGINNING MONDAY AND CONTINUING INTO THE LATTER PART OF NEXT WEEK. HOWEVER...THE DRYING LOOKS TO BE A BIT DELAYED AS COMPARED TO EARLIER MODEL RUNS...WITH QUITE A BIT OF LOW LEVEL MOISTURE AND INSTABILITY LINGERING INTO TUESDAY. ALSO...GFS CALLS FOR A SECOND INVERTED TROF TO PASS SLOWLY BY TO OUR SOUTH THIS WEEKEND...THEN SWING NORTH INTO SWRN AZ/SERN CA MONDAY INTO TUESDAY. AS IT DOES SO IT WILL WEAKEN WITH MOISTURE SLATED TO THIN. AS SUCH...WE HAVE RAISED POPS MONDAY AND TUESDAY...AND CALLED FOR SLIGHT CHANCES FOR STORMS PRETTY MUCH FROM THE CO RIVER EASTWARD...AND CHANCES OVER ZONE 24. WITH MOISTURE THINNING...AND HEIGHTS RISING...A WARMING TREND WILL ALSO TAKE PLACE BY THE MIDDLE OF NEXT WEEK WITH HIGHS REACHING TO AROUND SEASONAL NORMALS BY TUESDAY...AND ABOVE NORMAL READINGS BY WEDNESDAY. && .AVIATION... SOUTH-CENTRAL AZ...INCLUDING KPHX...KIWA AND SURROUNDING AIRFIELDS... THROUGH 18Z FRI...CONSIDERABLE MID LEVEL CLOUDS AOA 10 THSD MSL WITH ISOLATED SHOWERS. LIGHT AND VARIABLE WINDS UNDER 10 KNOTS. AFT 18Z FRI...MOUNTAIN THUNDERSTORMS...TOPS 45 TO 50 THSD...WILL DEVELOP 60 MILES NORTH THROUGH EAST OF PHOENIX. BY 02Z SAT MOUNTAIN THUNDERSTORMS WILL HAVE DRIFTED INTO THE EASTERN PORTIONS OF THE GREATER PHOENIX AREA GENERATING POSSIBLE WIND GUSTS 25 TO 35 MPH SPREADING INTO KPHX AND KIWA TERMINAL AREAS. CHANCE OF THUNDERSTORMS IN THE TERMINAL AREAS AROUND 02Z TO 05Z SAT. SOUTHEASTERN CA...INCLUDING KIPL...KBLH AND SURROUNDING AIRFIELDS... THROUGH 22Z FRI...SOUTH WINDS 5 TO 15 KNOTS. SCT CLOUDS AOA 10 THSD AGL. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... SATURDAY THROUGH WEDNESDAY... PRECIP CHANCES WILL LINGER THROUGH THE WEEKEND AS ABUNDANT MOISTURE WILL REMAIN IN PLACE ACROSS THE DESERT SOUTHWEST. THIS WILL RESULT IN AFTERNOON HUMIDITIES ONLY DROPPING INTO THE 20-30 PERCENT RANGE THROUGH THE WEEKEND WITH EXCELLENT OVERNIGHT RECOVERY EXPECTED. DRIER AIR WILL ARRIVE EARLY NEXT WEEK WITH PRECIP CHANCES BECOMING CONFINED MAINLY TO THE HIGHER TERRAIN NORTHEAST OF PHOENIX. HUMIDITIES WILL DROP BUT OVERNIGHT RECOVERY IS STILL EXPECTED TO BE GOOD. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT WEATHER.GOV/PHOENIX DISCUSSION...VASQUEZ/CB AVIATION...VASQUEZ FIRE WEATHER...LEINS