Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000 FXUS65 KPSR 301226 CCA AFDPSR AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE PHOENIX AZ 340 AM MST THU OCT 30 2014 CORRECTED TYPO .SYNOPSIS...
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HIGH TEMPERATURES WILL CONTINUE TO BE WELL ABOVE NORMAL THROUGH FRIDAY...THOUGH THERE WILL BE SOME HIGH CLOUDS AROUND TODAY. OVER THE WEEKEND...A LOW PRESSURE SYSTEM MOVES INTO THE WESTERN STATES. IT WILL BRING MUCH COOLER TEMPERATURES AND BREEZY CONDITIONS TO OUR REGION...WITH HIGHS DROPPING INTO THE 70S ON THE LOWER DESERTS. RAIN CHANCES WILL BE SLIGHT AND CONFINED TO THE HIGHER TERRAIN. ANTICIPATE LITTLE CHANGE IN TEMPERATURES MONDAY... FOLLOWED BY A WARMING TREND TUESDAY AND WEDNESDAY.
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&& .DISCUSSION... TODAY AND FRIDAY... CLEAR SKIES ACROSS THE FORECAST AREA EARLY THIS MORNING. HOWEVER...THAT WILL CHANGE VERY QUICKLY AS A BATCH OF HIGH CLOUDS MOVES IN FROM THE SOUTHWEST. HIGH CLOUDS SHOULD BE JUST THIN ENOUGH TO ENABLE HIGH TEMPS TODAY TO BE AS WARM AS YESTERDAY. THE FEATURE PRODUCING THE HIGH CLOUDS IS A WEAK UPPER LOW EMANATING FROM SUBTROPICAL LATITUDES. IT IS BEING ADVECTED NORTHEASTWARD BY A MUCH LARGER LOW PRESSURE SYSTEM CURRENTLY CENTERED JUST WEST OF BRITISH COLUMBIA. FRIDAY WILL SEE LESS CLOUDINESS AS THE LARGE SYSTEM DIGS SOUTHWARD. THUS THERE WILL BE LITTLE CHANGE IN TEMPERATURES FRIDAY WITH READINGS IN THE LOW 90S BEING COMMON ON THE LOWER DESERTS. OF NOTE...THE SREF CONTINUES TO GENERATE SOME MODEST QPF OVER EASTERN AND CENTRAL ARIZONA FRIDAY. THIS IS DUE LARGELY TO ADVECTING MORE MOISTURE WESTWARD...FROM A BACKDOOR FRONT...COMPARED TO OTHER MODELS. SOME OF THE HIGH RES NCEP MODELS PRODUCE SOME VERY SPOTTY QPF IN CENTRAL ARIZONA...OUTSIDE OF OUR FORECAST AREA. GFS AND ECMWF KEEP FRIDAY PRECIP NEAR NEW MEXICO BORDER. WILL KEEP FORECAST DRY. SATURDAY AND SUNDAY... THE SYSTEM TRACKS INLAND FRIDAY NIGHT THROUGH SUNDAY. A DRY COLD FRONT MOVES ACROSS OUR FORECAST AREA FRIDAY NIGHT AND SATURDAY. THERE MAY BE SOME SEMBLANCE OF A FRONTAL CLOUD BAND WITH IT BUT LIKELY THIS WILL BE SHALLOW. KEPT SLIGHT CHANCE FOR HIGHER TERRAIN SATURDAY DUE TO OROGRAPHIC LIFT AIDING THE FRONTAL LIFT. ALOFT...THERE LOOKS TO BE TWO MAIN SHORT WAVE/VORT MAXES WITH THE TROUGH THAT WILL AFFECT SOUTHERN CALIFORNIA AND ARIZONA THIS WEEKEND. THE FIRST ONE PASSES JUST NORTHWEST OF OUR AREA EARLY SATURDAY. THE SECOND ONE BRUSHES US LATER SATURDAY INTO SUNDAY. THE SECOND ONE LOOKS TO HAVE THE BEST POTENTIAL TO PRODUCE PRECIP AS QG FORCING WILL BE BETTER FOR OUR AREA AND THERE WILL BE COOLER AIR MAKING PRECIP PROCESSES MORE EFFICIENT. HOWEVER...PRECIP CHANCES WILL BE SLIGHT AND STILL CONFINED TO HIGHER TERRAIN AREAS. MAIN IMPACT WILL BE THE NICE COOL DOWN AND BREEZY CONDITIONS. OUR WESTERN AREAS WILL GET MOST OF THEIR COOLING ALL ON SATURDAY. OUR EASTERN AREAS INCLUDING PHOENIX METRO WILL DROP ABOUT 10 DEGREES SATURDAY THEN ANOTHER NOTABLE DROP FOR SUNDAY LEADING TO HIGHS IN THE LOW TO MID 70S ACROSS THE LOWER DESERTS. MONDAY THROUGH WEDNESDAY... A COUPLE OF TRAILING VORT MAXES ARE ADVERTISED TO CARVE OUT A PROMINENT SHORT WAVE TROUGH OVER THE AREA EARLY MONDAY INTO TUESDAY. THE ECMWF HAS RETURNED TO THE IDEA OF DEVELOPING A CLOSED LOW WITHIN THE BOTTOM OF THE TROUGH...CENTERED OVER PHOENIX BY 00Z TUESDAY...WHICH IS A DEEPER SOLUTION THAN THE GFS. THE GEM HAS A SIMILAR IDEA BUT IS FASTER WITH THE ARRIVAL AND DEPARTURE. HOWEVER...THE ECMWF LOOKS TO BE AN OUTLIER WITH RESPECT TO ITS ENSEMBLE...THE ECENS. ALSO...IT IS INDICATIVE OF LESS RUN TO RUN CONSISTENCY. THE GFS IS WELL SUPPORTED BY THE GEFS AND FORECASTS WERE WEIGHTED MORE HEAVILY TOWARD THAT SOLUTION. THUS MENTION OF PRECIP CHANCES ENDS SUNDAY NIGHT AND A WARMING TREND STARTS TUESDAY AS A RIDGE BEGINS BUILDING IN. && .AVIATION...
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SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA AND KSDL...SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH... THROUGH 20Z THURSDAY...SLOWLY INCREASING HIGH CLOUDS AOA 25 THSD FEET. LIGHT WIND UNDER 8 KNOTS. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
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&& .FIRE WEATHER...
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SATURDAY THROUGH WEDNESDAY... A SEASONABLY STRONG COLD FRONT WILL MOVE THROUGH THE REGION SATURDAY ALLOWING SLIGHTLY COOLER THAN NORMAL TEMPERATURES TO FILTER INTO THE DISTRICT THE FIRST HALF OF NEXT WEEK. BEHIND THIS FRONTAL PASSAGE...WIND SPEEDS WILL INCREASE AND BECOME OCCASIONALLY GUSTY DURING THE AFTERNOON HOURS...ESPECIALLY SATURDAY THROUGH MONDAY. GUSTS TO AROUND 30 MPH WILL BE POSSIBLE ALONG RIDGE TOPS AND THROUGH FAVORED RIVER VALLEY LOCATIONS. MINIMUM RELATIVE HUMIDITY VALUES WILL INITIALLY ONLY FALL INTO A 25-40 PERCENT RANGE OVER THE WEEKEND...BUT AS MUCH DRIER AIR MOVES INTO THE DISTRICT...HUMIDITIES WILL FALL INTO THE TEENS MONDAY AND TUESDAY POSSIBLY LEADING TO A SOMEWHAT LOCALIZED ELEVATED FIRE DANGER. OTHERWISE...OVERNIGHT RECOVERY WILL BE GOOD...AND CONDITIONS BECOMING MORE TRANQUIL TOWARDS THE MIDDLE OF NEXT WEEK.
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&& .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...AJ AVIATION...VASQUEZ FIRE WEATHER...MO

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