Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 300907
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
206 AM MST WED JUL 30 2014

.SYNOPSIS...
THERE WILL BE A BREAK IN THE MONSOON THROUGH THURSDAY...WITH
DECREASED CHANCES OF SHOWERS AND THUNDERSTORMS.
CONSEQUENTLY...TEMPERATURES WILL CONTINUE THEIR UPWARD TREND AND
HIGHS IN THE 110-115 RANGE WILL BE COMMON ACROSS THE DESERTS THROUGH
THURSDAY. A RETURN TO A MORE TYPICAL MONSOON REGIME IS EXPECTED LATE
FRIDAY INTO THE WEEKEND AS SHOWERS AND THUNDERSTORMS ARE ONCE AGAIN
EXPECTED ACROSS THE REGION.

&&

.DISCUSSION...
ANOTHER QUIET DAY CONVECTIVELY ON TUESDAY AS THERE WERE ONLY A FEW
SHOWERS AND ISOLATED THUNDERSTORMS TO CONTEND WITH ACROSS THE
REGION. AS A RESULT...SKIES WERE MOSTLY CLEAR THIS MORNING WITH ONLY
SOME LINGERING CLOUDS ACROSS NORTHERN ARIZONA. MEANWHILE TO THE
SOUTH...A WEAK COMPLEX OF STORMS WAS DISSIPATING ACROSS NORTHERN
SONORA. TEMPERATURES THIS MORNING AS OF 08Z WERE VERY SIMILAR TO
VALUES SEEN ON TUESDAY...GENERALLY IN THE UPPER 90S TO MID 90S. SKY
HARBOR WAS STILL HOLDING TOUGH AT 99.

TEMPERATURES REALLY OVERACHIEVED ON TUESDAY WITH MOST DESERT LOCALES
BREAKING THE 110 DEGREE MARK. LOOKING BACK AT THE 00Z SREF AND ECMWF
ANALYSIS AND COMPARING 850MB TEMPS FROM TUESDAY AFTERNOON TO
WEDNESDAY AFTERNOON...WE COULD ACTUALLY MANAGE ANOTHER 2-3 DEGREES
OF WARMING THIS AFTERNOON. CONSENSUS GUIDANCE IS STILL POINTING AT
110 DEGREES...BUT BASED ON WHAT HAPPENED TUESDAY IM GOING TO LEAN
ON THE WARM SIDE AND BUMP TEMPS UP A FEW MORE DEGREES. INEVITABLY
OUR LOWS THIS MORNING WILL BE IN THE UPPER 80S/LOWER 90S SO WELL
ALREADY BE STARTING OFF WELL ABOVE NORMAL. ONE FLY IN THE OINTMENT
IS THE LINGERING CLOUD COVER ACROSS NORTHERN SONORA. WITH WINDS
ALOFT EXPECTED TO REMAIN OUT OF THE SOUTHWEST...IT LOOKS LIKE THE
MAJORITY OF THAT CIRRUS WILL BE DEFLECTED INTO NEW MEXICO WITH SUNNY
SKIES PREVAILING ACROSS THE DESERTS. AS SUCH...IM GOING TO GO WITH
AN EXCESSIVE HEAT WARNING FOR THE LOWER DESERTS. EVEN WITH SOME
DEGREE OF COOLING EXPECTED ON THURSDAY AND THE POSSIBILITY OF SOME
INCREASING CLOUD COVER FROM DISTANT STORMS TO THE SOUTH...TEMPS WILL
REMAIN DANGEROUSLY WARM THROUGH THURSDAY EVENING AND THE EXCESSIVE
HEAT WARNING WILL RUN UNTIL 8 PM THURSDAY.

MONSOON MOISTURE IS EXPECTED TO CREEP BACK INTO THE AREA ON FRIDAY
AND BY AND LARGE THE FORECAST THINKING HAS NOT CHANGED FOR FRIDAY
THROUGH THE WEEKEND. DEEPER MOISTURE WILL LAG A BIT AND IS NOT
EXPECTED TO ARRIVE IN THE DESERTS UNTIL THIS WEEKEND. POPS WERE
INCREASED A BIT FOR FRIDAY /STILL GENERALLY LOOKING AT SLIGHT
CHANCES/ BUT HIGHER VALUES SEEM WARRANTED FOR SATURDAY AND SUNDAY.
BOTH THE GFS AND EUROPEAN INDICATE A TROUGH MOVING THROUGH THE AREA
AT 700-500MB SATURDAY AFTERNOON/EVENING WITH MID LEVEL WINDS AROUND
20KTS...MLCAPES AROUND 1000 J/KG AND MEAN BL MIXING RATIOS AROUND
8-10 G/KG. IF THOSE VALUES ACTUALLY COME TO PASS IT COULD END UP
BEING QUITE ACTIVE SATURDAY EVENING. SIMILAR CONDITIONS ARE EXPECTED
SUNDAY HOWEVER ITS TYPICALLY DIFFICULT TO GET BACK TO BACK ACTIVE
DAYS SO MY CONFIDENCE IN THE WEEKEND FORECAST IS LOW...ESPECIALLY
FOR SUNDAY.

LOOKING DOWN THE ROAD TO NEXT WEEK...SOUTHWEST FLOW IS EXPECTED TO
RETURN TO THE AREA MONDAY/TUESDAY...ADVECTING SOMEWHAT DRIER AIR
INTO THE REGION FROM THE WEST AND ONCE AGAIN RESULTING IN DECREASED
CHANCES OF PRECIP ALONG WITH INCREASED TEMPERATURES.

&&

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

NO AVIATION IMPACTS THROUGH WEDNESDAY AFTERNOON AS ONLY FEW/SCT MID
AND HIGH CLOUDS DEVELOP MAINLY OVER HIGH TERRAIN REMOVED FROM
TERMINAL SITES. LARGEST FORECAST CHALLENGE WILL BE TIMING OF WIND
SHIFTS...AND MUCH LIKE THE PAST 24 HOURS...TYPICAL DIRECTIONAL
CHANGES MAY BE DELAYED OR ABSENT. EVEN PROLONGED PERIODS OF VARIABLE
WINDS WILL BE POSSIBLE...WITH PEAK WINDS GENERALLY AOB 12KT.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
DRIER THAN NORMAL CONDITIONS CONTINUE THURSDAY. STORM CHANCES
WILL BE SLIGHT AND WILL BE LIMITED TO THE HIGHER TERRAIN OF EASTERN
ARIZONA. FRIDAY AND OVER THE WEEKEND WEEKEND...AN INCREASE IN
MOISTURE AND ASSOCIATED HUMIDITIES IS ANTICIPATED. THIS WILL LEAD TO
BETTER STORM CHANCES OVER THE HIGHER TERRAIN OF SOUTH-CENTRAL
ARIZONA AND STORM CHANCES...THOUGH SLIGHT...EXPANDING WESTWARD TO
THE LOWER ELEVATIONS. HIGH TEMPERATURES TREND DOWNWARD AS WELL.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...EXCESSIVE HEAT WARNING FROM 10 AM THIS MORNING TO 8 PM MST
     THURSDAY AZZ020>023-025>028.

CA...EXCESSIVE HEAT WARNING FROM 10 AM THIS MORNING TO 8 PM PDT
     THURSDAY CAZ031>033.

&&

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS
AVIATION...MO
FIRE WEATHER...AJ





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