280
FXUS65 KPSR 071735
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1035 AM MST SAT NOV 7 2009
SYNOPSIS
A WEAK PACIFIC LOW PRESSURE SYSTEM PASSING BY TO OUR SOUTH WILL
CONTINUE TO RESULT IN HIGH CLOUDINESS TODAY...BUT THE HIGH CLOUDS
WILL SLOWLY DECREASE FROM THE WEST DURING THE DAY. MORE SUNSHINE IS
EXPECTED TO RESULT IN SLIGHTLY HIGHER TEMPERATURES TODAY. DRY
WEATHER AND ABOVE AVERAGE TEMPERATURES FOR EARLY NOVEMBER WILL
CONTINUE AT LEAST THROUGH WEDNESDAY WITH PERIODS OF HIGH CLOUDINESS.
FOR THE LATTER PART OF NEXT WEEK...LOW PRESSURE WILL DEVELOP OVER
THE DESERT SOUTHWEST AND LEAD TO A COOLING TREND...WITH HIGH
TEMPERATURES TO DROP SEVERAL DEGREES BELOW SEASONAL NORMALS BY NEXT
FRIDAY. THIS WILL BE A DRY SYSTEM FOR OUR AREA...WITH JUST A SLIGHT
CHANCE FOR SHOWERS EXPECTED OVER THE HIGHER TERRAIN EAST OF PHOENIX
NEXT THURSDAY AND FRIDAY.
DISCUSSION
A NORTH TO SOUTH BAND OF HIGH CLOUDINESS OVER SOUTH-CENTRAL ARIZONA
WAS SLOWLY MOVING EAST OF PHOENIX LATE THIS MORNING. THIS HIGH
CLOUDINESS WAS RESULTING IN TEMPERATURES THAT WERE GENERALLY 5 TO 11
DEGREES COOLER COMPARED WITH THE SAME TIME YESTERDAY. EXPECT MORE
SUNSHINE IN THE SOUTH-CENTRAL DESERT AREAS INCLUDING THE GREATER
PHOENIX AREA BY THIS AFTERNOON AS THE HIGH CLOUDINESS MOVES EAST.
HOWEVER...IT MAY NOT BE ENOUGH TO GET TEMPERATURES TO THEIR FORECAST
VALUES...BUT EXPECT THE HIGHS WILL BE WITHIN A FEW DEGREES OF THOSE
FORECAST VALUES. SOME HIGH CLOUDS WERE MOVING EAST INTO SOUTHEAST
CALIFORNIA LATE THIS MORNING AS EXPECTED. NO UPDATES.
PREVIOUS DISCUSSION...
UPPER LEVEL CLOSED LOW CONTINUED TO TRACK EASTWARD ACROSS THE
CENTRAL GULF OF CA EARLY THIS MORNING...AND WAS MOVING INTO NWRN
MEXICO. IT WAS SPREADING MID/HI CLOUDS INTO MAINLY SERN AZ...BUT A
LOOK AT THE RECENT TUS SOUNDING SHOWED MOST OF THE MOISTURE WAS AT
AND ABOVE 500MB...WITH THE AIRMASS RATHER DRY BELOW. AT 2 AM SURFACE
DEWPOINTS OVER OUR LOWER DESERTS WERE A MIXED BAG RANGING FROM MID
20S TO THE MID 40S. PROGS AGREE THAT THE LOW WILL KEEP MOVING EAST
AND AWAY FROM OUR CWA TODAY...ALLOWING FOR SKIES TO CLEAR. WITH THE
INCREASED SUNSHINE...MAX TEMPS SHOULD RECOVER A FEW DEGREES TODAY
AND MOSTLY BE IN THE MID TO UPPER 80S OVER THE DESERTS.
FOR SUNDAY INTO EARLY NEXT WEEK...FLOW ALOFT FORECAST TO BE QUITE
ZONAL WITH A VERY FLAT AND SOMEWHAT DIRTY RIDGE TO MOVE INTO THE
DESERT SOUTHWEST. THERE WILL BE PERIODS OF HIGH CLOUDS...AND
TEMPERATURES WILL NOT CHANGE OVERMUCH...REMAINING WELL ABOVE
SEASONAL NORMALS. TEMPERATURES WILL LIKELY PEAK TUESDAY WITH MAX
READINGS REACH NEAR 90 OVER THE WARMEST LOWER DESERTS...UNDER PARTLY
SUNNY SKIES.
FOR THE LATTER PORTION OF THE WEEK...WEDNESDAY THROUGH FRIDAY...THE
WEATHER PATTERN WILL BE CHANGING...AS A BROAD UPPER LEVEL LOW
PRESSURE TROUGH DEVELOPS OVER THE WESTERN STATES. LATEST EUROPEAN
AND GFS ARE IN QUITE GOOD AGREEMENT THROUGH FRIDAY...WITH THE MAIN
DIFFERENCE BEING THE ECMWF IS A BIT DEEPER FRIDAY COMPARED TO THE
GFS. PROGS HAVE BEEN SUGGESTING THIS TRANSITION TO TROFFING FOR THE
PAST COUPLE OF DAYS...THUS CONFIDENCE IS MUCH HIGHER WITH THIS
SOLUTION. APPEARS THAT THIS WILL BE A RATHER DRY SYSTEM FOR
US...WITH WIND AND COOLING TO BE BIGGER FACTORS THAN PRECIPITATION.
LAST FEW MEX MOS RUNS HAVE CALLED FOR SINGLE DIGIT POPS THRU DAY
7...FOR THE MOST PART...AND MODEL QPFS FOR SOUTHERN AZ ARE MINIMAL.
GIVEN THE HIGH CONFIDENCE IN THE TROFFING SOLUTION...WILL GO WITH
CLIMO PLUS POPS FROM WEDNESDAY THRU FRIDAY...WITH SLIGHT CHANCES
MENTIONED IN THE HIGHER TERRAIN EAST OF PHOENIX. HAVE MADE SOME
ADJUSTMENTS TO THE MAX TEMPS GRIDS AS WELL...AND LOWERED MAX TEMPS
THURSDAY AND FRIDAY 2-3 DEGREES ACROSS THE CWA BETTER FIT THE
HEIGHT/THICKNESS FALLS BEING ADVERTISED BY THE ECMWF AND GFS. HIGHS
SHOULD FALL TO NEAR NORMAL NEXT THURSDAY...THEN SEVERAL DEGREES
BELOW NORMAL FRIDAY.
AVIATION
SOUTH-CENTRAL ARIZONA...SOUTHEAST CALIFORNIA...AND SOUTHWEST
AZ...INCLUDING KPHX...KIWA...KIPL...AND KBLH.
MID AND HIGH CLOUDS WILL CONTINUE TO DECREASE ACROSS SOUTH CENTRAL
AZ...WHILE MOSTLY CLEAR SKIES RULE SOUTHEAST CALIF TODAY/TONIGHT.
SFC WINDS WILL REMAIN ON THE LIGHT SIDE...LESS THAN 7 KTS...WITH A
GENTLE WEST BREEZE FORECAST AT SKY HARBOR AIRPORT AFT 19Z.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
FIRE WEATHER
MONDAY THROUGH FRIDAY...
ANOTHER WEAK LOW WILL DEVELOP ACROSS THE WESTERN STATES WEDNESDAY.
JUST ENOUGH MOISTURE WILL BE DRAWN INTO ARIZONA FOR A SLIGHT CHANCE
OF SHOWERS FOR ZONE 133 WEDNESDAY...THURSDAY AND FRIDAY. WINDS ARE
ALSO EXPECTED TO INCREASE ON WEDNESDAY...BUT SPEEDS WILL LIKELY
REMAIN BELOW CRITICAL FIRE WEATHER THRESHOLDS.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
WEATHER.GOV/PHOENIX
DISCUSSION...ELLIS/CB
AVIATION...SIPPLE
FIRE WEATHER...SIPPLE
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