000 FXUS65 KTWC 052140 AFDTWC AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 240 PM MST SUN JUL 5 2009 .SYNOPSIS...DRIER AIR HAS STARTED TO SPREAD ACROSS SOUTHERN ARIZONA TODAY AND WILL CONTINUE INTO THE NEW WEEK. EVEN WITH THIS DRIER AIR MOVING IN...A FEW SHOWERS AND THUNDERSTORMS WILL STILL DEVELOP EACH DAY THIS WEEK...ESPECIALLY SOUTH AND EAST OF TUCSON. VERY STRONG HIGH PRESSURE WILL BE DEVELOPING OVER THE AREA LATER IN THE WEEK AND BRING THE HOTTEST TEMPERATURES OF THE YEAR. && .DISCUSSION...SUPPRESSED UPPER LEVEL RIDGE...THANKS TO UPPER LEVEL TROUGH NEAR THE PACIFIC NORTHWEST...EXTENDS FROM THE GULF OF MEXICO WEST THROUGH NORTHERN MEXICO AND THEN OUT INTO THE EASTERN PACIFIC. IN THIS RIDGE...CLOSER TO ARIZONA...IS A HIGH CIRCULATION CENTERED NEAR THE NORTHERN GULF OF CALIFORNIA. WATER VAPOR IMAGERY SHOWED MUCH DRIER MID-LEVEL AIR OVER THE STATE WHILE BLENDED PRECIPITABLE WATER IMAGERY SHOWED DEEPER MOISTURE SOUTH OVER SONORA MEXICO. AT THE SURFACE...DEWPOINT VALUES HAVE MIXED DOWN INTO THE UPPER 40S TO THE UPPER 50S. AS OF 2 PM...RADAR WAS DEPICTING ISOLATED STORMS ACROSS GREENLEE/GRAHAM/COCHISE/SANTA CRUZ COUNTIES WITH STRONGER STORMS SOUTH OF THE BORDER WEST OF CANANEA. STORMS HAVE BEEN SHOWING A GENERALLY SOUTHERLY MOVEMENT. MONDAY...THE UPPER HIGH CENTERED NEAR NORTHERN GULF OF CALIFORNIA DRIFTS EAST AS ANOTHER HIGH CIRCULATION CENTERS ITSELF OVER THE NEW MEXICO BOOT. STILL ENOUGH MOISTURE AROUND TO SUPPORT ISOLATED DEVELOPMENT OF STORMS...MAINLY EAST AND SOUTH OF TUCSON...WITH THE HIGHEST POPS NEAR THE INTERNATIONAL BORDER IN SANTA CRUZ AND COCHISE COUNTIES. HIGH TEMPERATURES A BIT WARMER THAN TODAY. TUESDAY...UPPER RIDGE AXIS TO OUR SOUTH WITH DRY WEST TO NORTHWEST FLOW OVER THE AREA. STILL HANGING ON TO SOME MOISTURE FOR ISOLATED THUNDERSTORMS...MAINLY NEAR THE INTERNATIONAL BORDER OF SANTA CRUZ AND COCHISE COUNTIES. HIGH TEMPERATURES SIMILAR TO MONDAY...MAYBE A DEGREE OR TWO WARMER IN THE LOWER DESERTS. WEDNESDAY...STRENGTHENING CENTER OF HIGH PRESSURE MOVES EAST ACROSS THE STATE WITH FLOW AROUND IT KEEPING DEEPEST MOISTURE OVER SONORA MEXICO. STILL KEPT SOME SLIGHT CHANCES NEAR THE INTERNATIONAL BORDER AS THE FLOW WILL BECOME A BIT MORE SOUTHEAST LATE IN THE DAY. BUT I WOULDN'T BE SURPRISE IF THE DAY IS MOSTLY STORM FREE WITH STRONG SUBSIDENCE OVERHEAD ALONG WITH VERY WARM MID-LEVEL TEMPERATURES PUTTING A LID ON THINGS. HIGH TEMPERATURES CONTINUE SLOW WARM UP UNDER THE STRENGTHENING HIGH. THURSDAY...THE UPPER HIGH...NOW CENTERED IN NEW MEXICO...WILL CONTINUE TO STRENGTHEN AND ALSO START TO IMPORT A SMIDGE MORE MOISTURE FOR A SMALL INCREASE IN AREAL COVERAGE. WARMUP CONTINUES AND STARTS TO BECOME MORE EVIDENT IN THE LOWER DESERTS WHERE READINGS WILL BE NEAR 110...BUT SHORT OF RECORD HIGHS FOR AREAS IN WESTERN PIMA COUNTY. FRIDAY AND SATURDAY...LOW LEVEL THICKNESS VALUES...850/700 MBS TEMPERATURES CONTINUE TO RISE/WARM AS STRONG UPPER HIGH REMAINS CENTERED OVER NEW MEXICO. UPPER FLOW OUT OF THE SOUTHEAST WILL KEEP SOME MODEST MOISTURE AROUND FOR A SLIGHT CHANCE OF AFTERNOON AND EVENING STORMS. IF BOTH GFS AND ECMWF MODELS ARE RIGHT...THE WARMEST TEMPERATURES OF 2009 WILL BE OCCURRING...WITH READINGS IN THE LOW DESERTS IN THE 106 TO 112 RANGE. IN THE MORNING HWO (HAZARD WEATHER OUTLOOK) ISSUANCE...I HIGHLIGHTED THE POTENTIAL FOR THESE VERY HOT TEMPERATURES AND IF THE MODELS ARE RIGHT...WE WILL LIKELY NEED TO ISSUE HEAT ADVISORIES. STAY TUNED CAUSE THE HEAT IS A COMING. WE COULD ONLY HOLD IF OFF FOR SO LONG. .SUNDAY...STRONG UPPER HIGH STARTS TO WEAKEN A BIT WITH DAYTIME HIGHS A SMIDGE COOLER. && .AVIATION...SCATTERED THUNDERSTORMS WILL PRIMARILY BE LOCATED SOUTH AND EAST OF TUCSON THIS AFTERNOON INTO EARLY EVENING ALTHOUGH A STRAY SHOWER OR STORM IS POSSIBLE OVER THE RIM COUNTRY AND IN THE WESTERN DESERT. MT OBSCURATIONS...MVFR CIGS AND VSBYS AND WIND GUSTS TO 35 KNOTS COULD BRIEFLY BE ASSOCIATED WITH SOME OF THE STORMS. OTHERWISE...SCT TO BKN CLOUD DECKS WITH BASES BETWEEN 8 AND 14 KFT AGL ARE EXPECTED WITH SURFACE WINDS GENERALLY 10 KNOTS OR LESS INTO MONDAY. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...THUNDERSTORM COVERAGE WILL BE MODEST AT BEST THE NEXT FEW DAYS AS HIGH PRESSURE ALOFT ASSERTS ITSELF OVER THE SW US. THE BEST CHANCES FOR STORMS WILL BE ACROSS THE RIM COUNTRY AND THE SE CORNER OF AZ. AS THE WEEK PROGRESSES AND HEAT BUILDS... HUMIDITIES WILL CORRESPONDINGLY DECREASE DUE TO SUBSIDENCE OF THE HIGH WHICH COULD SHUT DOWN DAILY CROPS OF THUNDERSTORMS ENTIRELY AND RAPIDLY DRY FUELS WHICH HAD BEEN MOISTENED BY RECENT RAINS. HOWEVER...CERTAINTY NOT YET HIGH ENOUGH IN THIS PATTERN TO TOTALLY REMOVE THE CHANCE OF STORMS FROM THE FORECAST AS YET. && .CLIMATE...AS STRONG HIGH PRESSURE BUILDS OVER THE AREA THIS WEEK DAYTIME TEMPERATURES WILL CONTINUE THE CLIMB UPWARD. TUCSON IS FORECAST TO HIT 105 FOR THE FIRST TIME IN 2009 ON THURSDAY. THIS IS NOTEWORTHY SINCE THIS WILL MARK THE 2ND LATEST OCCURRENCE OF HITTING 105 FOR THE FIRST TIME. AUGUST 3 1975 HOLDS THE RECORD FOR THE LATEST OCCURRENCE. THE AVERAGE 1ST DATE FOR 105 DEGREES IN TUCSON IS JUNE 13TH. THE HOTTEST TEMPERATURES OF THE YEAR ARE FORECAST FOR ALL OF SOUTHEAST LATE IN THE WEEK INTO NEXT WEEKEND. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. $$ WEATHER.GOV/TUCSON