FXUS65 KPSR 050936 AFDPSR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 235 AM MST FRI AUG 5 2011 .SYNOPSIS... WITH DRIER AIR IN PLACE...CHANCES FOR SHOWERS AND THUNDERSTORMS WILL BE CONFINED MAINLY TO THE MOUNTAINS OF SOUTHEAST ARIZONA THROUGH SUNDAY. MOISTURE...ALONG WITH CHANCES FOR SHOWERS AND THUNDERSTORMS ...WILL RETURN TO MOST OF ARIZONA MONDAY AND REMAIN THROUGH THE WEEK. SLIGHTLY DRIER AIR WILL REMAIN OVER SOUTHEAST CALIFORNIA DURING THIS TIME. TEMPERATURES WILL BE WARMEST TODAY ACROSS THE REGION...THEN TREND DOWN THROUGH SUNDAY FOLLOWED BY LITTLE CHANGE THROUGH THE FOLLOWING WORK WEEK. && .DISCUSSION... PERSISTENT TROUGH OVER THE PACIFIC NORTHWEST HAS TEMPORARILY PUSHED INTO THE SOUTHWEST CONUS AS OF EARLY THIS MORNING. VERY DRY AIR WAS NOTED ACROSS PORTIONS OF SOUTHERN CALIFORNIA AND SOUTHERN NEVADA...WHERE SURFACE DEW POINTS FELLS INTO THE TEENS AND EVEN SINGLE DIGITS YESTERDAY. 05.00Z REGIONAL SOUNDINGS SHOWED THIS DRY AIR NICELY...WITH THE MODIFIED KVEF RAOB DEPICTING A PRECIPITABLE WATER OF JUST 0.3 INCHES. PHOENIX RAOB AND MODIS DATA BOTH HAD ABOUT 1.2 INCHES. THE 05.00Z GFS APPEARED TO INITIALIZE MOISTURE LEVELS THE BEST WITH THE ECMWF A CLOSE SECOND - THE NAM WAS NOTABLY MORE MOIST. FORECAST THROUGH SUNDAY WAS WEIGHTED TOWARD A GFS/ECMWF/SREF BLEND. THE TROUGH WILL REMAIN IN PLACE TODAY THROUGH SUNDAY...RESULTING IN A RELATIVELY DRY FORECAST. ANY MENTION OF PRECIPITATION WAS CONTAINED TO THE FAR EASTERN TIP OF OUR COUNTY WARNING AREA. TEMPERATURES WILL BE WARMEST TODAY THEN TREND DOWN SLIGHTLY... REMAINING JUST A FEW DEGREES ABOVE NORMAL. LATE SUNDAY INTO MONDAY THE GFS AND NAM CONTINUE TO INDICATE THE LIKELIHOOD OF A SIGNIFICANT MOISTURE PUSH BACK INTO THE SOUTHERN HALF OF ARIZONA...IN RESPONSE TO THE TROUGH RETREATING/MID-LEVEL ANTI-CYCLONE REPOSITIONING WESTWARD/A BROAD LOW EJECTING OUT OF MAINLAND MEXICO AND TOWARD THE BAJA PENINSULA/POSSIBLE CONVECTION ACROSS SONORA AND ASSOCIATED OUTFLOW. IN PARTICULAR...THE GFS HAS BEEN TRENDING UPWARD WITH MOISTURE VALUES HEADING INTO EARLY MONDAY. BASED ON THIS SCENARIO...PRECIPITATION CHANCES WERE INCREASED A BIT SUNDAY AFTERNOON/EVENING /BUT STILL BELOW CLIMATOLOGY/ AND A SLIGHT CHANCE WAS LEFT FOR SUNDAY LATE SUNDAY NIGHT WITH POSSIBLE ONGOING SHOWERS/THUNDERSTORMS. BEGINNING MONDAY...AND CONTINUING RIGHT ON THROUGH THURSDAY...LITTLE CHANGE IN SENSIBLE WEATHER IS EXPECTED AS THE WEATHER PATTERN BECOMES VERY STABLE ACROSS THE LOWER 48. MID-LEVEL ANTI-CYCLONE WILL BE CENTERED NEAR TO SOUTHEAST OF TUCSON DURING THIS PERIOD...LEAVING OUR FORECAST AREA IN AN AREA OF VERY WEAK STORM MOTION VECTORS. BOUNDARY LAYER MOISTURE WILL BE BACK UP TO TYPICAL LEVELS RESULTING IN NEAR-AVERAGE CHANCES FOR SHOWERS/STORMS THROUGH THE WEEK. NOT SEEING ANY SIGNS OF ANYTHING THAT COULD ENHANCE THE CONVECTION DURING THIS PERIOD /LIKE THE FAR SOUTHERN END OF A SHORT WAVE IN THE WESTERLIES OR AN INCOMING EASTERLY WAVE ACROSS MEXICO/...THUS WILL BE DEPENDENT ON THE TYPICAL OUTFLOW BOUNDARY FORCING AND COLLISIONS EACH DAY. SOUTHEAST CALIFORNIA SHOULD REMAIN DRY DURING THIS PERIOD AS THE MOISTURE DOESN/T GET TOO ENTRENCHED THERE AND WARMER MID-LEVELS INHIBIT MUCH INSTABILITY FROM DEVELOPING. TEMPERATURES CWA-WIDE WILL SHOW LITTLE VARIATION GIVEN THE STAGNANT PATTERN. && .AVIATION... DRIER AIR MOVING IN FROM THE WEST WILL CONTINUE TO INHIBIT THUNDERSTORM DEVELOPMENT FRI ACROSS MUCH OF AZ. WINDS WILL FOLLOW TYPICAL DIURNAL PATTERNS...GENERALLY REMAINING NEAR OR BELOW 10 KT. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... SUNDAY THROUGH THURSDAY... LOW LEVEL MOISTURE WILL BEGIN A SLOW RETURN TO THE AREA BY EARLY NEXT WEEK...SUPPORTING A RETURN OF AFTERNOON SHOWERS AND THUNDERSTORMS ALONG WITH HIGHER HUMIDITY VALUES AND LOWER TEMPERATURES. WHILE PRECIPITATION ACTIVITY WILL PICK-UP...WIDESPREAD AND HEAVY PRECIPITATION DOES NOT LOOK LIKELY AT THIS TIME. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT WEATHER.GOV/PHOENIX DISCUSSION...INIGUEZ AVIATION...HIRSCH FIRE WEATHER...INIGUEZ