Area Forecast Discussion
Issued by NWS Phoenix, AZ

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS65 KPSR 191111 AFDPSR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 410 AM MST FRI SEP 19 2014 .SYNOPSIS... LINGERING MOISTURE ACROSS THE REGION AND LOW PRESSURE APPROACHING FROM THE WEST WILL KEEP AT LEAST SLIGHT CHANCES FOR SHOWERS AND THUNDERSTORMS IN THE FORECAST TODAY THROUGH SATURDAY. DRIER AIR WILL GRADUALLY FILTER INTO THE REGION SUNDAY FOR A DECLINE IN STORM CHANCES. SOME ADDITIONAL DRYING MONDAY...WITH LITTLE CHANGE THROUGH WEDNESDAY...WILL KEEP STORM CHANCES VERY SLIGHT AND LIMITED TO THE HIGHER MOUNTAINS OF SOUTH-CENTRAL ARIZONA. TEMPERATURES WILL BE WARMER AS WELL. AN APPROACHING PACIFIC WEATHER SYSTEM LATE NEXT WEEK WILL LEAD TO AN INCREASE IN STORM CHANCES OVER THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. && .DISCUSSION... TODAY THROUGH SUNDAY... SATELLITE IMAGERY EARLY THIS MORNING SHOWS A FAIR AMOUNT OF CLOUD COVER OVER ARIZONA...INCLUDING OUR FORECAST AREA. PHOENIX AREA METARS HAVE THE BASES AT 8-10 KFT AGL. MOST OF THE CLOUD TOPS ARE AROUND...OR WARMER THAN...0 DEG C. SOME OF THE CLOUDINESS IS COLDER THAN THAT WHICH INDICATES A DEEPER CLOUD AND BETTER POTENTIAL TO PRODUCE PRECIP. WATER VAPOR LOOP INDICATES THERE WERE A COUPLE OF VORT MAXES THAT HAVE SHIFTED EASTWARD INTO NEW MEXICO. IT ALSO SHOWS A TROUGH CENTERED ROUGHLY ALONG THE CALIFORNIA COAST WITH MULTIPLE VORT MAXES MOVING THROUGH AND STRONGER SOUTHWESTERLY FLOW ALOFT APPROACHING THE FORECAST AREA. BLENDED TPW IMAGERY SHOWS A FAIRLY SHARP MOISTURE GRADIENT OVER FAR WESTERN ARIZONA. LATEST MODELS HAVE ALL BEEN DEPICTING QPF OVER EASTERN PORTIONS OF THE FORECAST AREA THIS MORNING. HOWEVER...MOST OF THEM GENERATED QPF BETWEEN 0-6Z WHICH DIDNT HAPPEN AT ALL. THEY SHOWED EVEN MORE BETWEEN 6-12Z WHICH HAS NOT HAPPENED YET. IT MAY BE A REFLECTION OF A JETLET...AHEAD OF A STRONGER JET CLOSER TO THE MAIN TROUGH AXIS...FORECAST TO MOVE INTO ARIZONA AND WEAKEN LATER TODAY. OF NOTE...MODELS ARE GENERALLY SHOWING MORE QPF IN THE 12-18Z TIME FRAME THAN 18Z-00Z...LIKELY DUE TO DRIER AIR MOVING IN. LOCAL WRF HAS BEEN THE MOST CONSERVATIVE IN TERMS OF AREAL COVERAGE AND THUS IT APPEARS TO BE DOING BETTER THAN MANY OTHER MODELS. EVEN STILL...IT GENERATES SOME LARGE QPF BULLSEYES OVER THE MAZATZALS AND FOUR PEAKS WHICH LOOKS OVERDONE. HELD OFF ON EXPANDING THE SLIGHT CHANCE AREA FOR THIS MORNING DUE TO DISCONNECT BETWEEN OBSERVED CONDITIONS AND MODEL FORECAST. HOWEVER...HELD ON TO SLIGHT CHANCE THIS AFTERNOON OVER OUR EASTERN AREAS AS SURFACE HEATING WILL BE BETTER. MODELS ARE IN AGREEMENT THAT A VORT MAX WITHIN THE PACIFIC TROUGH WILL BECOME THE MAIN CIRCULATION CENTER AND BECOMES A CUTOFF LOW FOR A SHORT TIME. MEANWHILE...AN ANTICYCLONE BECOMES CENTERED OVER COLORADO. IN TURN...MOISTURE PUSHES WEST AND NORTHWARD...A REVERSAL OF THE PREVIOUS DRY ADVECTION. A JET STREAK TRACKS ACROSS SOUTHEAST CALIFORNIA AND ARIZONA SATURDAY INTO SUNDAY...SLOWLY WEAKENING IN THE PROCESS AS THE LOW TRACKS NORTHEASTWARD IN RESPONSE TO A LARGE UPSTREAM TROUGH. BEST DYNAMICAL LIFT LOOKS TO BE WHERE MOISTURE IS MORE LIMITED AND THE CONVERSE IS TRUE. THUS POPS REMAIN CONSERVATIVE THOUGH SOME SUBTLE UPWARD ADJUSTMENTS WERE MADE SATURDAY. WITH DRIER AIR MOVING IN SUNDAY...POPS TREND DOWNWARD. TEMPS LOOK TO BE SLIGHTLY COOLER TODAY DUE TO INFLUENCE FROM THE NEARBY TROUGH. ANTICIPATE ADDITIONAL COOLING OVER OUR WESTERN AREAS SATURDAY FOR THE SAME REASON BUT SOME WARMING OVER OUR EASTERN AREAS DUE TO LESS CLOUDINESS. LITTLE CHANGE SUNDAY. MONDAY THROUGH THURSDAY... WITH RIDGING BEGINNING TO BUILD IN MONDAY ALONG WITH SOME ADDITIONAL DRYING...TEMPS WILL BE A BIT WARMER AND POPS WILL BE LIMITED TO LOW END SLIGHT CHANCE OVER THE HIGHER MOUNTAINS OF SOUTH-CENTRAL ARIZONA. LOOK FOR SLIGHT ADDITIONAL WARMING TUESDAY WITH LITTLE CHANGE WEDNESDAY ALONG WITH LITTLE CHANGE IN POPS. BY THURSDAY...A PACIFIC TROUGH MOVES INLAND AND DRAWS SOME MOISTURE NORTHWARD. SLIGHT CHANCE AREA WAS BROADENED BUT STILL CONFINED TO THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. && .AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...CURRENT SCT-BKN 7-8K FT CIGS TO BECOME FEW-SCT BY THIS AFTERNOON AS SOMEWHAT DRIER AIR FILTERS INTO THE REGION FROM THE WEST. SCT-BKN MID-LEVEL CIGS TO RETURN AFTER MIDNIGHT TONIGHT AS SOUTHERLY FLOW ALOFT PUSHES MOISTURE BACK NORTHWARD INTO THE PHX AREA. WINDS TO MAINLY FOLLOW THE USUAL DIURNAL TRENDS...WHILE REMAINING ON THE LIGHT SIDE...MAINLY AOB 10KTS. SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH... CURRENT WESTERLY WINDS AT KIPL...AND SOUTHERLY WINDS AT KBLH...THAT ARE NOW AROUND 10KTS...ARE EXPECTED TO DIMINISH TO AROUND...OR BELOW 5KTS BY MID-LATE MORNING. MAINLY CLEAR SKIES TO PREVAIL THROUGH THE TAF PERIOD AT BOTH OF THE SE CA TERMINALS. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... SUNDAY THROUGH THURSDAY... RATHER DRY WESTERLY FLOW TO KEEP SKIES MAINLY CLEAR THROUGH THE FORECAST PERIOD AT MOST LOCATIONS ACROSS THE REGION...WITH THE EXCEPTION OF THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX...WHERE LINGERING MOISTURE MAY ALLOW ISOLATED SHOWERS/THUNDERSTORMS TO DEVELOP EACH AFTERNOON/EARLY EVENING. MINIMUM RELATIVE HUMIDITIES TO FALL INTO THE 20 TO 30 PERCENT RANGE EACH AFTERNOON...WITH GOOD TO EXCELLENT OVERNIGHT RECOVERIES. WINDS TO REMAIN MAINLY ON THE LIGHT SIDE...MAINLY IN THE 5 TO 15 MPH RANGE...WITH THE USUAL DIURNAL TRENDS TO PREVAIL AT MOST LOCATIONS. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...AJ AVIATION...PERCHA FIRE WEATHER...PERCHA

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.