PHXAFDPSR (05/14/13 0411)
FXUS65 KPSR 141116
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
415 AM MST TUE MAY 14 2013
...UPDATED AVIATION AND FIRE WEATHER...
.SYNOPSIS...
HIGH PRESSURE WILL BEGIN TO EXIT THE REGION TODAY ALTHOUGH
TEMPERATURES WILL STILL REMAIN WELL ABOVE NORMAL. LINGERING MOISTURE
WILL MAINTAIN A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. ON WEDNESDAY...A WEAK
WEATHER SYSTEM PASSING MAINLY TO THE NORTH WILL LEAD TO SOME
SLIGHTLY COOLER HIGH TEMPERATURES AND AN END TO PRECIPITATION
CHANCES OVER SOUTH-CENTRAL ARIZONA. CONDITIONS WILL REMAIN DRY
THROUGH THE WEEKEND. ANTICIPATE SOME MODEST COOLING FRIDAY AND
SATURDAY BEFORE TEMPERATURES START TO WARM AGAIN EARLY NEXT WEEK.
&&
.DISCUSSION...
EARLY THIS MORNING...PLOT AND SATELLITE DATA SHOWED A STRONG UPPER
HIGH PERSISTING ACROSS THE DESERT SOUTHWEST...WITH A 588DM HIGH
CENTER OVER SRN NEVADA. MEANWHILE...A PESKY UPPER LOW CONTINUED TO
WOBBLE SLOWLY WESTWARD SOUTH OF THE ARIZONA/MEXICO BORDER WITH THE
CENTER LOCATED OVER CENTRAL BAJA CA. THESE TWO FEATURES HAVE KEPT
EASTERN ARIZONA UNDER A GENERAL EASTERLY FLOW ALOFT...ALLOWING MID
LEVEL MOISTURE TO REMAIN IN PLACE ACROSS OUR EASTERN ZONES. LATEST
00Z SOUNDINGS FROM TUS AND FLG SHOWED THE MID LEVEL MOISTURE AND
INSTABILITY...LIFTED INDEX WAS MINUS 2.6 ON THE FLG RAOB. PROGS
INDICATE MID LEVEL TEMPS WILL REMAIN SIMILAR OVER ZONE 24 THIS
AFTERNOON COMPARED TO YESTERDAY...AND GIVEN THE PERSISTENT MID LEVEL
MOISTURE AND STRONG SURFACE HEATING WE CAN EXPECT ANOTHER SLIGHT
CHANCE FOR ELEVATED...DRY AND HIGH BASED THUNDERSTORMS TO FORM THIS
AFTERNOON AND EVENING ACROSS HIGHER TERRAIN EAST OF PHOENIX...WITH
THE BEST THREAT ACTUALLY EAST OF GLOBE. IT DOES APPEAR THE THE LOW
TO OUR SOUTH WILL FINALLY BE NUDGED OFF AND TO THE EAST LATER TODAY
AND TONIGHT...KICKED OUT BY A SHORTWAVE NOW APPROACHING THE NRN CA
COAST. THIS KICKER FEATURE IS CLEARLY SEEN ON THE MORNING VAPOR LOOP.
WITH LITTLE CHANGE IN THICKNESS VALUES EXPECTED TODAY...AND UNDER
PLENTIFUL SUNSHINE...HIGH TEMPS WILL CHANGE LITTLE FROM YESTERDAY
AND WILL REMAIN WELL ABOVE SEASONAL NORMALS AND IN THE TRIPLE DIGITS
OVER MOST OF THE LOWER DESERT. THE PREVIOUSLY MENTIONED LOW
APPROACHING THE CA COAST WILL SCOOT EAST ACROSS THE AREA WEDNESDAY
BRINGING A DRIER WESTERLY FLOW ALOFT INTO THE AREA AND CAUSING HIGH
TEMPS TO FALL SEVERAL DEGREES OVER MUCH OF OUR WESTERN DESERT. IN
ADDITION...IT WILL KICK UP SOME AFTERNOON BREEZINESS AS INCREASED
MID LEVEL WINDS ARE MIXED TO THE SURFACE.
FOR THE REST OF THE FORECAST PERIOD...THURSDAY THROUGH MONDAY...THE
WESTERLIES WILL DROP FURTHER TO THE SOUTH AND IMPACT OUR
AREA...BRINGING INCREASED WIND DURING THE AFTERNOON AND EVENING
HOURS...AND DROPPING OUR HIGH TEMPERATURES BACK TO NEAR SEASONAL
NORMALS BY SATURDAY. OVERALL DRY WESTERLY FLOW ALOFT WILL DOMINATE
OUR WEATHER PATTERN EACH DAY AND MOSTLY SUNNY DAYS AND CLEAR NIGHTS
WILL BE THE GENERAL RULE. GUIDANCE...INCLUDING GFS ENSEMBLE
MEMBERS...REMAINS CONSISTENT IN CALLING FOR A PROGRESSIVE OPEN WAVE
TROF TO PUSH EAST ACROSS THE AREA FRIDAY INTO SATURDAY. ALTHOUGH IT
APPEARS THAT THE TROF WILL BE SLIGHTLY DEEPER THAN PREVIOUSLY
THOUGHT...THE TROF AXIS SHOULD REMAIN JUST NORTH OF OUR AREA AND WE
WILL REMAIN ON THE DRY SOUTHERN PERIPHERY. SUNDAY INTO NEXT
MONDAY...A DRIER MORE NORTHWEST FLOW WILL FOLLOW AS THE TROF EXITS
INTO THE CENTRAL CONUS...AND WE CAN EXPECT A WARMING TREND WITH
DESERT HIGH TEMPS REACHING BACK INTO THE TRIPLE DIGITS OVER THE
WARMEST LOCALES BY NEXT MONDAY.
&&
.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...KSDL...
FORECAST MODELS SUGGEST AN EARLIER AND MORE DEFINITIVE TRANSITION IN
SFC WIND DIRECTION THIS AFTERNOON VERSUS THE PAST SEVERAL DAYS. WITH
MODERATE CONFIDENCE HAVE THE SWITCH TO W/SW WINDS OCCURRING EARLY
AFTERNOON...AND SPEEDS AOA 10KT. WILL LIKELY SEE SOME OCCASIONAL
HIGHER GUSTS...BUT LIKELY NOT ABOVE 20KT AND VERY LIMITED IN TIME.
OTHERWISE...PERIODIC SCT/BKN CLOUDS AOA 15FT WILL DRIFT ACROSS CNTRL
ARIZONA...BECOMING CLEAR OVERNIGHT.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA...INCLUDING KIPL AND KBLH...
ONLY SOME HIGH CIRRUS WILL AFFECT SOUTHEAST CALIFORNIA...WITH THE
PRIMARY AVIATION IMPACT BEING GUSTY SFC WINDS. SPEEDS SHOULD
INCREASE MARKEDLY EARLY/MID AFTERNOON WITH FREQUENT HIGHER GUSTS
ABOVE 20KT FROM THE S/SW. GUSTINESS MAY CONTINUE THROUGH THE EVENING
HOURS BEFORE BETTER DECOUPLING OCCURS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
CONFIDENCE IS HIGH THAT ABNORMALLY WARM TEMPERATURES WILL PERSIST
THROUGH EARLY NEXT WEEK WITH LOWER ELEVATION HIGHS RANGING FROM THE
MID 90S TO JUST ABOVE 100F. NO PRECIPITATION IS EXPECTED THROUGH THE
ENTIRE PERIOD. MINIMUM HUMIDITY LEVELS WILL FALL BELOW 15
PERCENT...WITH MOST LOCATIONS INTO THE SINGLE DIGITS EACH DAY.
OVERNIGHT RECOVERY WILL GENERALLY BE FAIR. AFTERNOON WIND SPEEDS
SHOULD COMMONLY REACH 15-20 MPH THROUGH FRIDAY...RELAXING
SOMEWHAT DURING THE WEEKEND. FREQUENT HIGHER GUSTS CAN ALSO BE
EXPECTED...THOUGH REMAINING BELOW CRITICAL THRESHOLDS.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...CB
AVIATION...MO
FIRE WEATHER...VLM/MO
