739
FXUS65 KPSR 230958
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
258 AM MST THU MAY 23 2013
SYNOPSIS
A LOW PRESSURE CENTER OVER THE PACIFIC NORTHWEST IS EXPECTED TO KEEP
THE REGION UNDER DRY SOUTHWESTERLY FLOW ALOFT...WITH BREEZY TO WINDY
CONDITIONS AT TIMES THE REST OF THIS WEEK AND INTO EARLY NEXT WEEK.
ANTICIPATE SOME MODEST COOLING TODAY WITH TEMPERATURES REMAINING
NEAR SEASONAL NORMALS THROUGH THE WEEKEND. ADDITIONAL COOLING IS
LIKELY NEXT WEEK WITH HIGHS ACROSS THE LOWER DESERTS IN THE UPPER
80S TO MID 90S.
DISCUSSION
THE MAIN WEATHER FEATURE REMAINS FAR REMOVED FROM THE DESERT
SOUTHWEST...BUT WILL HAVE SOME MINOR IMPACTS OVER THE COMING DAYS.
BREEZY TO WINDY DAYTIME CONDITIONS REMAIN TO BE THE BIGGEST IMPACT
WITH SOME LOCATIONS YESTERDAY GUSTING TO NEAR 40 MPH. PRESSURE
GRADIENTS TODAY WILL STILL BE ON THE HIGHER SIDE...BUT NOT QUITE
LIKE YESTERDAY AND FRIDAY WILL BE LESSER THAN TODAY. STRONGEST WINDS
TODAY ARE EXPECTED TO BE ACROSS SOUTHERN GILA COUNTY WITH AFTERNOON
GUSTS APPROACHING 35 MPH. THE DRY AIRMASS IN PLACE WILL PERSIST INTO
THE WEEKEND...BUT AN INCREASE IN MID AND UPPER LEVEL MOISTURE BY
SATURDAY NIGHT SHOULD LEAD TO INCREASING HIGH CIRRUS. TEMPERATURES
OVER THE NEXT SEVERAL DAYS WILL CHANGE VERY LITTLE...BUT WILL BE 4-7
DEGREES OFF YESTERDAY/S HIGHS DUE TO THE SLIGHT COOLING INFLUENCE OF
THE DEEP CLOSED LOW OVER PACIFIC NORTHWEST. THE BLOCKING UPPER LEVEL
PATTERN WITH THE PACIFIC NORTHWEST LOW AND THE HIGH AMPLITUDE RIDGE
OVER THE PLAINS INTO SOUTHERN CANADA WILL START TO BREAK DOWN BY THE
WEEKEND. HOWEVER...REINFORCING SHORTWAVE IMPULSES DROPPING DOWN FROM
THE NORTHERN PACIFIC WILL KEEP A LARGE SCALE TROUGHING PATTERN
ACROSS THE WESTERN UNITED STATES FOR THE FORESEEABLE FUTURE. THIS
WILL KEEP THE DESERT SOUTHWEST UNDER A MODESTLY WARM SOUTHWESTERLY
FLOW THROUGH THE WEEKEND...WITH TEMPERATURES REMAINING AROUND OR
SLIGHTLY BELOW SEASONAL NORMALS.
UNCERTAINTY INCREASES AFTER THIS WEEKEND WITH PREVIOUS MODEL RUNS
DIFFERING IN THE PROGRESSION OF A STRONGER NORTHERN PACIFIC SYSTEM.
LATEST MODEL GUIDANCE IS SEEMS TO BE IN BETTER AGREEMENT...BUT
CONFIDENCE IS FAR FROM HIGH. A STRONG UPPER JET MAX IS FORECAST TO
APPROACH THE WEST COAST NEXT MONDAY...BUT WEAKENING AS IT DOES. EVEN
WITH THE DEPICTED WEAKENING...BOTH THE GFS AND EUROPEAN SHOW A
DEVELOPING 500MB LOW DIVING SOUTHEASTWARD INTO THE DESERT SOUTHWEST
MONDAY NIGHT INTO TUESDAY. BOTH MODELS GENERALLY AGREE WITH THE
INTENSITY OF THE SYSTEM WITH SLIGHT TIMING DIFFERENCES. BASED ON THE
OVERALL GOOD AGREEMENT NOW...FEEL THAT A COOLER FIRST HALF OF NEXT
WEEK SHOULD OCCUR. HAVE UPDATED TEMPERATURES FOR TUESDAY AND
WEDNESDAY NEXT WEEK...LOWERING HIGHS ANYWHERE FROM 3 TO 10 DEGREES.
A DECENT AMOUNT OF MID AND HIGH LEVEL MOISTURE SHOULD ACCOMPANY THE
SYSTEM...BUT FOR NOW ONLY EXPECTING A COUPLE DAYS OF PARTLY TO
MOSTLY CLOUDY SKIES WITH CHANCES FOR ANY PRECIPITATION LESS THAN 10
PERCENT.
AVIATION
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...KSDL...SOUTHEAST
CALIFORNIA/SOUTHWEST ARIZONA...INCLUDING KIPL AND KBLH...
DRY SOUTHWEST FLOW ALOFT WILL KEEP SKIES CLEAR TO MOSTLY CLEAR
THROUGH THE TAF PERIOD. GUSTY WINDS ARE EXPECTED TO REDEVELOP AT THE
TERMINALS THIS AFTERNOON...BUT WITH SPEEDS REMAINING LIGHTER THAN
WHAT WE SAW YESTERDAY. WINDS WILL THEN DIMINISH LATER THIS
EVENING...AND REVERT BACK TO THE USUAL DIURNAL TRENDS IN DIRECTION
AT THE PHX AREA TERMINALS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
FIRE WEATHER
SATURDAY THROUGH WEDNESDAY...
LOW PRESSURE IS EXPECTED TO REMAIN ALONG THE WEST COAST FROM
SATURDAY ONWARD INTO MONDAY...THEN MOVE INLAND ON TUESDAY AND
WEDNESDAY...KEEPING ARIZONA AND SOUTHEAST CALIFORNIA UNDER A DRY
SOUTHWEST TO WEST FLOW ALOFT THROUGH THE PERIOD. BREEZY TO WINDY
CONDITIONS WILL DEVELOP DURING THE AFTERNOON AND EVENING HOURS EACH
DAY...WITH PEAK WIND GUSTS IN EXCESS OF 25 MPH POSSIBLE. SINGLE
DIGIT MINIMUM HUMIDITIES WILL CONTINUE THROUGH MONDAY...WITH
SLIGHTLY HIGHER VALUES ON TUESDAY AND WEDNESDAY. OVERNIGHT RECOVERY
WILL BE POOR OVER SOUTH-CENTRAL ARIZONA AND POOR TO FAIR OVER
SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA. HIGH TEMPERATURES WILL
REMAIN NEAR OR A BIT BELOW SEASONAL NORMALS FROM SATURDAY ONWARD
INTO MONDAY...WITH SOMEWHAT COOLER TEMPERATURES POSSIBLE ON TUESDAY
AND WEDNESDAY AS THE LOW PRESSURE MOVES INLAND INTO THE DESERT
SOUTHWEST.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...KUHLMAN
AVIATION...PERCHA
FIRE WEATHER...PERCHA
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