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National Weather Service Tucson Arizona
HOME > Back to products page | Weather Glossary

AREA FORECAST DISCUSSION

 
 FXUS65 KPSR 231242 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
540 AM MST MON NOV 23 2009

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS

&&

.SYNOPSIS...
MOSTLY CLEAR NIGHTS AND SUNNY DAYS ARE EXPECTED TO CONTINUE THROUGH
AT LEAST FRIDAY. A RIDGE OF HIGH PRESSURE WILL SLOWLY BUILD OVER THE
WESTERN STATES THIS WEEK LEADING TO A GRADUAL WARMING TREND.
TEMPERATURES WILL RISE TO WELL ABOVE AVERAGE FOR LATE NOVEMBER BY
THANKSGIVING DAY...IN THE UPPER 70S TO NEAR 80 DEGREES ON THE LOW
DESERTS INCLUDING PHOENIX...YUMA...AND EL CENTRO. A LARGE COOLING
TREND IS ANTICIPATED SATURDAY AND SUNDAY AS A LOW PRESSURE SYSTEM
DEVELOPS OVER THE DESERT SOUTHWEST.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS A LOW PRESSURE SYSTEM MOVING THROUGH THE
WESTERN STATES...THE SOUTHERN END OF WHICH IS BRUSHING ARIZONA AND
SOUTHEAST CALIFORNIA. THIS SYSTEM WILL HAVE LITTLE EFFECT ON OUR
WEATHER EXCEPT FOR SOME MORE NOTICEABLE WINDS...WITH LOCALLY BREEZY
CONDITIONS THIS AFTERNOON OVER THE LOWER COLORADO RIVER VALLEY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BUILD IN FROM THE PACIFIC LEADING
TO A GRADUAL WARMING TREND. ANTICIPATE TEMPERATURES TO PEAK ON
THURSDAY. A STRONG NORTH AND NORTHEASTERLY ORIENTED PRESSURE
GRADIENT WILL DEVELOP LEADING TO LOCALLY BREEZY CONDITIONS AT TIMES
WEDNESDAY AND THURSDAY.

THE MODELS DEPICT THE RIDGE BEGINNING TO SHIFT EASTWARD FRIDAY AS A
TROUGH MOVES IN. THE GFS AND THE CANADIAN ARE FASTER WITH IT THAN
THE ECMWF. WITH TIME...THE ECMWF AND GFS SHOW THE FLOW PATTERN
AMPLIFYING LEADING TO A TROUGH DIGGING SOUTHWARD OVER THE INTERIOR
WEST SATURDAY...WITH THE GFS FASTER THAN THE ECMWF. THE OPERATIONAL
CANADIAN SHOWS A MORE PROGRESSIVE PATTERN HOWEVER THE CANADIAN
ENSEMBLE MEAN SUPPORTS THE IDEA OF AMPLIFICATION AND A DIGGING
TROUGH. ON THE OTHER HAND...THE OPERATIONAL GFS IS MORE AGGRESSIVE
WITH THE TROUGHING OVER ARIZONA AND SOUTHEAST CALIFORNIA THAN MOST
OF THE GFS ENSEMBLE MEMBERS. THOUGH ECMWF HAS A SLOWER ARRIVAL OF A
DIGGING TROUGH OVER OUR FORECAST AREA IT MAKES UP FOR IT BY RAPIDLY
INTENSIFYING THE UPPER TROUGH INTO A CLOSED LOW OVER ARIZONA ON
SUNDAY. THE ECMWF HAS BEEN SHOWING SHOWING A DEEP CLOSED LOW OVER
ARIZONA FOR THIS WEEKEND FOR AT LEAST 6 RUNS NOW BUT IT HAS HAD RUN
TO RUN INCONSISTENCIES IN THE EVOLUTION/TRACK. SO THE GFS IS NOW
COMING AROUND TO A SOLUTION MORE LIKE THE ECMWF.

THE SHORT OF ALL OF THIS IS MUCH COOLER AND BREEZY TO WINDY
CONDITIONS FOR THIS COMING WEEKEND. CONSERVATIVELY...THE MAX TEMPS
OVER THE LOW DESERTS SUNDAY WILL BE IN THE MID 60S...AFTER PEAKING
NEAR 80 THURSDAY AND FRIDAY. SOME ADDITIONAL COOLING IS ANTICIPATED
MONDAY OVER THE SOUTH-CENTRAL DESERTS WHILE OUR WESTERN AREAS
ACTUALLY START TO WARM UP. WINDS LOOK LIKE THEY WILL BE CONSIDERABLY
STRONGER SUNDAY THAN SATURDAY...MAINLY OVER SOUTHEAST CALIFORNIA AND
THE LOWER COLORADO RIVER VALLEY. GIVEN THE OVERLAND TRAJECTORY...THE
SYSTEM LOOKS TO BE MOISTURE STARVED AND THUS HAVE HELD OFF
INTRODUCING ANY MENTION OF PRECIP...BEST CHANCES LOOK TO BE OUTSIDE
OF OUR FORECAST AREA OVER THE WHITE MOUNTAINS.

&&

.AVIATION...
SOUTHEAST CA...SOUTHWEST AND SOUTH CENTRAL AZ...INCLUDING KIPL...
KBLH...KPHX...AND KIWA.

EXCEPT FOR OCCASIONAL THIN HI CIRRUS...AOA 20K FEET...SKIES TO BE
MOSTLY CLEAR NEXT 24 HOURS ALL AIRFIELDS. FOR THE MOST PART WINDS
WILL BE RATHER LIGHT AND DIURNAL...EXCEPT DOWN THE LOWER CO RIVER
VALLEY TODAY. SURFACE HIGH DEVELOPING TO OUR NORTH WILL TIGHTEN
GRADIENT DOWN THE RIVER...AND CAUSE BREEZY NORTH WINDS TO DEVELOP AT
KBLH AFTER ABOUT 18Z. EXPECT OCNL GUSTS BETWEEN 20-25KT STARTING
EARLY THIS AFTERNOON AND THEN TAPERING OFF SHORTLY AFTER SUNSET.
OTHERWISE NO AVIATION CONCERNS. VFR CONDITIONS EXPECTED ALL
AIRFIELDS NEXT 24 HOURS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
HIGH PRESSURE ALOFT WILL DOMINATE THE WEATHER PATTERN WEDNESDAY AND
THURSDAY...WITH MOSTLY CLEAR OR CLEAR SKIES EXPECTED EACH DAY...AND
RELATIVELY LIGHT WINDS. HIGH TEMPERATURES WILL CONTINUE WELL ABOVE
SEASONAL NORMALS...ALONG WITH VERY DRY AIR OVER THE DESERTS. MANY
LOCALES WILL SEE MINIMUM RH VALUES IN THE SINGLE DIGITS...WITH
MODEST RECOVERY AT NIGHT. FORECAST MODELS IN BETTER AGREEMENT
REGARDING A CHANGE IN THE WEATHER DEVELOPING OVER THE WEEKEND. A LOW
PRESSURE SYSTEM WILL BE SETTLING IN OVER THE DESERT SOUTHWEST...
LEADING TO A SUBSTANTIAL COOLING TREND FRIDAY THROUGH SUNDAY. HIGH
TEMPERATURES MAY FALL AROUND 15 DEGREES OVER THIS TIME FRAME WITH
HIGHS SUNDAY EXPECTED IN THE MID 60S OVER MOST OF THE LOWER DESERTS.
THIS WILL BE RATHER DRY SYSTEM FOR OUR AREA WITH NO PRECIPITATION IN
THE FORECAST AT THIS TIME. HOWEVER HUMIDITIES WILL BE ON THE
INCREASE...PARTLY DUE TO INCREASING LOW LEVEL MOISTURE AND ALSO
COOLING TEMPERATURES. BREEZY OR LOCALLY WINDY WEATHER IS LIKELY OVER
THE WEEKEND AS WELL.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&




NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...AJ
AVIATION...CB
FIRE WEATHER...CB
















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