Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000 FXUS65 KPSR 252316 AAA AFDPSR AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PHOENIX AZ 416 PM MST FRI JUL 25 2014 .UPDATE...UPDATED AVIATION DISCUSSION... && .SYNOPSIS... A NOTICEABLE INCREASE IN MONSOON ACTIVITY IS EXPECTED TO COMMENCE TODAY AND CONTINUE INTO THE WEEKEND. THE HIGH PRESSURE CENTER THAT BROUGHT THE REGION VERY HOT TEMPERATURES THE LAST FEW DAYS WILL WEAKEN AND SHIFT FURTHER OFF TO THE EAST...ALLOWING MOISTURE THAT IS NOW OVER MEXICO TO SURGE NORTHWARD INTO THE REGION. SUFFICIENT MONSOONAL MOISTURE WILL THEN REMAIN AROUND THE REGION TO SUPPORT AFTERNOON AND EVENING STORM CHANCES THROUGH AT LEAST THE MIDDLE OF THE COMING WEEK...WITH THE BEST FOCUS FOR STORMS LIKELY OVER THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. DAYTIME TEMPERATURES WILL STILL HOLD ABOVE SEASONAL NORMALS...BUT ARE EXPECTED TO FALL BACK FROM THEIR NEAR-RECORD READINGS. && .DISCUSSION... NOT LONG AFTER 1 PM MST...ISOLATED CUMULUS ACTIVITY DEVELOPING OVER AND JUST OFF OF THE AZ HIGH TERRAIN...FROM THE SKY ISLANDS UP THROUGH THE WHITE MOUNTAINS AND THE MOGOLLON RIM...BEGAN TO EXPAND IN COVERAGE. IN ADDITION...LARGE AREA OF CLOUDS STRETCHING FROM SOUTHERN CA INTO SOUTHERN NV...ASSOCIATED WITH A SUBTLE LOW CIRCULATION AND JET STREAK...HAVE DEVELOPED INTO ISOLATED THUNDERSTORM ACTIVITY JUST NORTH OF JTNP AND INTO NORTHEASTERN RIVERSIDE COUNTY. THE FIRST STORMS ACROSS THE PHOENIX FORECAST AREA TODAY DEVELOPED NEAR GLOBE...WHERE THEY ARE CONTINUING TO EXPAND FURTHER ACROSS SOUTHERN GILA COUNTY THIS HOUR. LARGE STORM COMPLEX SOUTHWEST OF TUCSON CONTINUES TO EXPAND VERTICALLY AND AREALLY...WITH SEVERAL STRONG STORM CORES PULSING ALONG AS IT VERY SLOWLY TRACKS TO THE WEST ACROSS PIMA COUNTY. SPC MESOANALYSIS AND FORECAST SOUNDINGS AROUND THE LOWER CENTRAL AZ DESERTS STILL INDICATE ATLEAST 1000 J/KG OF MLCAPE WITH SLIGHTLY HIGHER VALUES OUT WEST BEYOND THE CO RIVER VALLEY LINGERING INTO THE EVENING. WILL CLOSELY BE WATCHING THE STORMS TO THE SOUTH...AS SOUTHEASTERLY TO SOUTHERLY STEERING FLOW ALOFT WILL HELP BUILD STORMS NORTHWARD ACROSS THE CENTRAL AZ DESERTS. THE BROADSTROKES FOR THE FORECAST THE REST OF THE EVENING INCLUDES THE THREAT FOR BLOWING DUST...ESPECIALLY WITH SEVERAL STORMS NOW DEVELOPING OR MOVING INTO THE LOWER DESERT ELEVATIONS...AND DEVELOPMENT OF STORMS ALONG THOSE OUTFLOW BOUNDARIES THIS LATE AFTERNOON AND EVENING. NOT OUT OF THE QUESTION TO SEE STORMS INTO THE PHOENIX METRO IN THE EVENING...CERTAINLY IF SEVERAL OUTFLOW BOUNDARIES HEAD INTO AND INTERSECT OVER THE AREA. NEARLY ALL CORNERS OF THE FORECAST AREA HAVE AT LEAST SLIGHT CHANCES FOR SOME STORM ACTIVITY THIS AFTERNOON WITH THE THREAT FOR LOCALLY HEAVY RAINFALL POSSIBLE. THE BLOWING DUST ADVISORY IS NOW IN EFFECT ACROSS MARICOPA AND NORTHWEST PINAL COUNTIES THROUGH THE EVENING AND CAN ALSO EXPECT VERY LOCALIZED BLOWING DUST IMPACTS NEAR STORMS ACROSS SOUTHEAST CA INTO THE EVENING. SATURDAY LOOKS LIKE IT MAY BE SIMILAR TO TODAY...WITH SIMILAR MOISTURE AND MUCAPE VALUES BEING FORECASTED ACROSS THE REGION. HOWEVER...IF TODAY TURNS OUT TO BE QUITE ACTIVE...THE WORKED-OVER ATMOSPHERE MAY HOLD TS ACTIVITY DOWN SOMEWHAT ON SATURDAY. THE INCREASING MOISTURE AND CLOUDINESS...ALONG WITH LOWER 500MB HEIGHTS...IS EXPECTED TO END OUR EXCESSIVE HEAT...WITH HIGHS AROUND 110F TODAY AND THE 105-109F RANGE ON SATURDAY. SATURDAY COULD TURN OUT TO BE EVEN COOLER IF THERE IS WIDESPREAD RAINFALL TODAY/THIS EVENING. SUNDAY THROUGH THURSDAY... IT APPEARS THAT A LOW-MID GRADE MONSOON WILL LIKELY PREVAIL THROUGH THE EXTENDED PERIOD AS WEAK SOUTHERLY FLOW ALOFT CONTINUES TO PULL MOISTURE INTO THE REGION...WITH THE GFS SHOWING A MORE ACTIVE PATTERN AS IT KEEPS THE UPPER HIGH CENTER OFF TO OUR EAST...AND THE EURO SHOWING A DRIER ONE AS IT ATTEMPTS TO REPOSITION THE UPPER HIGH CENTER WESTWARD BACK OVER THE REGION. && .AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL... STORMS ARE ONGOING SOUTH OF THE METRO. AT THE VERY LEAST THE SOUTHEASTERLY OUTFLOW WINDS SHOULD MAKE THEIR WAY INTO KIWA AROUND 01-02Z AND KPHX/KSDL SHORTLY THEREAFTER. WILL INCLUDE A SOUTHEASTERLY WIND SHIFT AS WELL AS THUNDER/REDUCED VSBYS IN RAIN AND HAZE THIS EVENING AT ALL PHOENIX SITES. EXPECT CONDITIONS TO DETERIORATE RAPIDLY AT THE ONSET OF RAIN OR DUST...BUT THEY SHOULD IMPROVE BY LATE EVENING. LINGERING DEBRIS CLOUDS WILL REMAIN THROUGH SATURDAY AFTERNOON. SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH... KIPL SHOULD REMAIN DRY TONIGHT ALTHOUGH KBLH MAY SEE A STRAY SHOWER OR THUNDERSTORM. CONFIDENCE TOO LOW TO INTRODUCE IN THE FORECAST SO I WILL KEEP BOTH SITES DRY. DEBRIS CLOUDS LIKELY TO LINGER THROUGH MID DAY SATURDAY. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... MONDAY THROUGH FRIDAY... SLIGHTLY COOLER AFTERNOON TEMPERATURES ARE EXPECTED ALONG WITH HIGHER HUMIDITY. MINIMUM RELATIVE HUMIDITY LEVELS WILL RANGE FROM 15 TO 25 PERCENT. A TYPICAL MONSOON DAILY THREAT OF AFTERNOON AND EVENING THUNDERSTORMS ARE EXPECTED WITH THE HIGHEST PROBABILITIES IN THE MOUNTAINS EAST OF PHOENIX. TYPICAL AFTERNOON AND EVENING SOUTHWEST WINDS ARE EXPECTED WITH GOOD RECOVERY AT NIGHT. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...BLOWING DUST ADVISORY UNTIL 9 PM MST THIS EVENING AZZ022-023-027-028. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...NOLTE/PERCHA AVIATION...LEINS FIRE WEATHER...VASQUEZ

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