000
FXUS65 KPSR 132215
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
315 PM MST MON MAY 13 2013

.SYNOPSIS...
HIGH PRESSURE WILL BEGIN TO EXIT THE REGION TUESDAY THOUGH
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...
REST OF TODAY THROUGH THURSDAY...SHALLOW MID LEVEL CLOUD CONVECTIVE
CLOUDS EVIDENT ON SATELLITE IMAGERY THIS AFTERNOON...MAINLY OVER THE
WHITE MOUNTAINS AND RIM COUNTRY. ASSOCIATED RADAR ECHOES ARE VERY
WEAK. TEMPS ON THE LOWER ELEVATIONS RUNNING NEAR OR ABOVE 100
DEGREES. THERE IS STILL SOME SURFACE HEATING YET TO OCCUR AND SO
DEEPER CONVECTION IS STILL A POSSIBILITY BUT IT WILL BE ISOLATED.
HELD ON TO THE SLIGHT CHANCE POPS FOR THIS EVENING OVER EASTERN
PORTIONS OF OUR SOUTHERN GILA COUNTY FORECAST ZONE. ON TUESDAY...THE
RIDGE CENTERED TO OUR NORTH AND THE LOW CENTERED TO OUR SOUTH WILL
BOTH BEGIN SHIFTING EASTWARD AS A SHORT WAVE APPROACHES FROM THE
WEST. THERE WILL BE LITTLE CHANGE IN THE TEMPERATURES AND MOISTURE
OVER OUR AREA. THUS ANTICIPATE TUESDAY TO LOOK SIMILAR TO TODAY.
HOWEVER...AN UPPER LEVEL DEFORMATION ZONE WILL BE IN PLACE OVER
NORTHERN ARIZONA AND THERE MAY BE A PERTURBATION/VORT MAX MOVING
ACROSS SOUTHEAST ARIZONA. ALSO...SOUTHEAST ARIZONA MAY HAVE A BIT
MORE MOISTURE TO WORK WITH THUS...CONVECTION MAY BE MORE PREVALENT
NEAR OUR BORDERS WHICH COULD SEND OUTFLOWS INTO SOUTH-CENTRAL
DESERTS. PROBABILITY OF THAT ALL COMING TOGETHER IS TOO LOW TO
INTRODUCE BLOWING DUST INTO THE FORECAST AT THIS TIME.
OTHERWISE...AFTERNOON/EVENING BREEZES WILL BE NOTICEABLY STRONGER.
ON WEDNESDAY...ANTICIPATE SLIGHTLY COOLER MAX TEMPS AS THE SHORT
WAVE PASSES BY...MAINLY OVER THE GREAT BASIN AND NORTHERN ARIZONA.
MODEST DYNAMICAL FORCING LOOKS TO TRACK TO OUR NORTH. FORECAST
SOUNDINGS SHOW THAT MID LEVEL MOISTURE DECLINES ON WEDNESDAY.
THUS...NO POPS FOR OUR AREA. CONDITIONS LOOK DRY ON THURSDAY AS A
LARGER TROUGH APPROACHES FROM THE WEST. NOT MUCH CHANGE TEMPERATURE
WISE...STILL ABOVE NORMAL.

RIDGE OF HIGH PRESSURE CENTERED
OVER THE NORTHERN GREAT BASIN IS DOMINATING THE WESTERN STATES.
MEANWHILE AN UPPER LOW REMAINS CENTERED NEAR CENTRAL BAJA MEXICO FOR
NORTHEASTERLY FLOW ALOFT ACROSS ARIZONA AND SOUTHEAST CALIFORNIA AND
A DEFORMATION ZONE OVER TEXAS. WATER VAPOR IMAGERY INDICATES A VORT
LOBE ON THE EASTERN SIDE OF THE LOW OVER CHIHUAHUA WITH SMALLER
PERTURBATIONS WITHIN THE CONFLUENT FLOW NEAR THE BORDERLANDS OF
SOUTHEAST ARIZONA AND NEW MEXICO. THE VORT LOBE IS ADVERTISED TO
BRUSH SOUTHEAST ARIZONA BY LATE THIS AFTERNOON. THIS COMBINED WITH
SLIGHTLY MORE MOISTURE COULD LEAD TO MORE HIGH BASED CONVECTION OVER
SOUTHEAST ARIZONA THAN YESTERDAY. WILL NEED TO SEE HOW CONVECTION
UNFOLDS LATER TODAY BUT IF ACTIVITY GETS CLOSE ENOUGH TO OUR
AREA...OUTFLOWS COULD BECOME AN ISSUE. MEANWHILE...ANTICIPATE
ISOLATED CONVECTION ONCE AGAIN OVER SOUTHERN GILA COUNTY AND THIS IS
WHERE THE POPS ARE. SOME ADDITIONAL WARMING CAN BE EXPECTED TODAY
AND THIS IS REFLECTED IN THE CURRENT FORECASTS. NO CHANGES AT THIS
TIME.

FRIDAY THROUGH MONDAY...GFS AND ECMWF ARE IN GOOD AGREEMENT AND BOTH
CALL FOR A PROGRESSIVE OPEN WAVE TROF TO PUSH EAST AND ACROSS THE
AREA FRIDAY AND SATURDAY WITH THE JET AXIS CUTTING ACROSS THE
ARIZONA/UTAH BORDER. AS IS COMMON FOR THIS TIME OF YEAR...A TROF
PASSAGE OF THIS CALIBER WILL DO NOTHING FOR OUR AREA WEATHER-WISE
OUTSIDE OF INCREASING AFTERNOON/EVENING BREEZINESS AND LOWERING HIGH
TEMPERATURES A HANDFUL OF DEGREES. IT WILL BE A DRY SYSTEM FOR US.
WE EXPECT HIGH TEMPS TO FALL INTO THE MID TO UPPER 90S OVER THE
LOWER DESERTS FRIDAY INTO SATURDAY... REMAINING NEAR OR SLIGHTLY
ABOVE SEASONAL NORMALS. DRY NORTHWEST FLOW ALOFT WILL FOLLOW ON
SUNDAY FOR CONTINUED SUNNY SKIES...ALONG WITH ANOTHER WARMING TREND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA AND SOUTHEAST CA...INCLUDING KPHX...KIWA...
KSDL...KBLH...AND KIPL...

SOME INCREASE IN HIGH CLOUDS (AOA 15K FT) CAN BE EXPECTED THROUGH
TUESDAY MORNING. OTHERWISE...ACROSS CNTRL ARIZONA LIGHT EASTERLY
FLOW SHOULD TRANSITION TO WESTERLY BY MID AFTERNOON...WITH SOME
INDICATIONS THAT DIRECTIONS MAY BE VARIABLE AT TIMES AFTER SUNSET.
SOUTHEAST CALIFORNIA TERMINALS SHOULD SEE A GENERAL SOUTHERLY
COMPONENT DURING THE DAYLIGHT HOURS BECOME WESTERLY AFTER SUNSET.
CONFIDENCE IN TIMING OF WIND SHIFTS IS MODERATE.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
CONFIDENCE IS HIGH THAT ABNORMALLY WARM TEMPERATURES WILL PERSIST
THROUGH THE WEEK WITH LOWER ELEVATION HIGHS ABOVE 100F ONLY COOLING
SLIGHTLY INTO THE MIDDLE/UPPER 90S BY THE WEEKEND. 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.

&&

$$

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DISCUSSION...AJ/CB
AVIATION...VLM/MO
FIRE WEATHER...VLM/MO