Weather Service Report


837 
FXUS65 KPSR 210917
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
217 AM MST SUN SEP 21 2014

.SYNOPSIS...
DRIER AIR WILL GRADUALLY FILTER INTO THE REGION TODAY AND MONDAY 
LEADING TO DRASTIC DECLINE IN STORM CHANCES. SLIGHT CHANCES FOR 
SHOWERS AND THUNDERSTORMS WILL BE CONFINED TO THE HIGHER MOUNTAINS 
OF SOUTH-CENTRAL ARIZONA THROUGH MONDAY. SLIGHTLY ABOVE NORMAL 
TEMPERATURES ARE ANTICIPATED THROUGH THE MIDDLE OF THIS WEEK. AN 
APPROACHING PACIFIC WEATHER SYSTEM LIKELY AFFECTING THE DESERT 
SOUTHWEST ON FRIDAY AND SATURDAY WILL LEAD TO AN INCREASE IN STORM 
CHANCES AND COOLER TEMPERATURES. 

&&

.DISCUSSION...
AS THE UPPER LOW WHICH IS NOW CENTERED OVER CENTRAL CALIFORNIA 
CONTINUES TO LIFT NORTHWARD...DRIER SOUTHWESTERLY MID AND UPPER 
LEVEL FLOW IS TAKING OVER ACROSS SOUTHWEST AND MUCH OF SOUTH-CENTRAL 
ARIZONA. THIS DRIER AIR IS EXPECTED TO PUSH AS FAR EAST AS PHOENIX 
BY THIS AFTERNOON...ESSENTIALLY CUTTING OFF ANY RAIN CHANCES EXCEPT 
FOR HIGHER TERRAIN AREAS EAST OF PHOENIX. THE UPPER LOW IS FORECAST 
TO MOVE INTO THE GREAT BASIN BY THIS EVENING WITH THE UPPER RIDGE TO 
OUR SOUTH CREEPING NORTHWARD INTO ARIZONA. GOOD MODEL AGREEMENT 
SHOWS THE RIDGE BUILDING OVER THE DESERT SOUTHWEST THE NEXT FEW DAYS 
WITH HEIGHTS MAXING OUT IN THE 590-592DM RANGE ON TUESDAY AND 
WEDNESDAY. ANY LINGERING LOW LEVEL MOISTURE OVER EAST-CENTRAL 
ARIZONA WILL LIKELY GET PUSHED OUT OF THE AREA WHICH SHOULD END ANY 
SLIGHT CHANCES FOR RAIN ACROSS THE HIGHER TERRAIN ON TUESDAY AND 
WEDNESDAY. THE HIGH HEIGHTS AND DRIER AIR WILL ALLOW FOR SOME 
WARMING OVER THE NEXT FEW DAYS WITH LOWER DESERT LOCATIONS PEAKING 
OUT IN THE 100-105 RANGE...OR ROUGHLY 3-5 DEGREES ABOVE SEASONAL 
NORMALS.

BY LATE IN THE WEEK...THE NEXT WEATHER SYSTEM WILL SLOWLY MOVE 
SOUTHEASTWARD INTO THE PACIFIC NORTHWEST AND GREAT BASIN. A GOOD 
AMOUNT OF UNCERTAINTY REMAINS WITH THIS SYSTEM WITH LONG RANGE 
MODELS STRUGGLING A BIT WITH THE TIMING AND HOW FAR SOUTH THE MAIN 
SHORTWAVE WILL GO. LATEST RUNS SHOW A FASTER AND LESS DIGGING TROUGH 
FROM THE GFS WHILE THE EUROPEAN DIGS THE TROUGH AS FAR SOUTH AS 
SOUTHERN CALIFORNIA WHILE BRIEFLY CUTTING THE LOW OFF FROM THE POLAR 
JET STREAM. THE TIMING DOES SEEM TO BE PUSHED BACK FROM YESTERDAY/S 
MODEL RUNS...SO THE BEST RAIN CHANCES HAVE SHIFTED FROM FRIDAY TO 
SATURDAY. THIS IS REFLECTED IN THE FORECAST BY DECREASING POPS 
SLIGHTLY ON FRIDAY AND INCREASING POPS ON SATURDAY. THE AMOUNT OF 
MOISTURE THAT WILL GET DRAWN UP AHEAD OF THE SYSTEM IS ALSO 
PROBLEMATIC AS THE DEEPER EUROPEAN BRINGS IN SUBSTANTIALLY MORE 
MOISTURE THAN THE GFS. FOR NOW...KEEPING WITH A FAIRLY WIDESPREAD 
10-20 POPS ON BOTH DAYS. TEMPERATURES WILL BEGIN TO DECREASE 
STARTING FRIDAY WITH LOWER DESERT HIGHS LIKELY ONLY IN THE LOWER 90S 
FOR NEXT WEEKEND.    

&&

.AVIATION...
SOUTH-CENTRAL AND SOUTHWEST ARIZONA INCLUDING KPHX...KIWA...KSDL...  
CONVECTIVE CHANCES OVER THE GREATER PHOENIX AREA HAVE ENDED. SCT-BKN 
CLDS AOA 10 THSD AGL ARE EXPECTED THROUGH 08Z SUN...ALONG WITH LIGHT 
WIND UNDER 8 KNOTS.  FROM 08Z SUN TO 21Z SUN...MOSTLY CLEAR SKIES 
AND LIGHT WIND.

SOUTHEAST CALIFORNIA INCLUDING KIPL...AND KBLH...
THROUGH 21Z SUN...MOSTLY CLEAR SKIES AND LIGHT WIND.


AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
MOISTURE RETREAT DUE TO WESTERLY FLOW WILL KEEP STORM CHANCES 
MINIMAL THROUGH THURSDAY AND LIMITED TO THE HIGHER MOUNTAINS OF 
SOUTH-CENTRAL ARIZONA. MEANWHILE...TEMPERATURES NUDGE UPWARD A FEW 
DEGREES ABOVE NORMAL. HUMIDITIES ON THE LOWER DESERTS DROP BELOW 15 
PERCENT THOUGH MAX HUMIDITIES REMAIN FAIR. NO STRONG WINDS ARE 
EXPECTED DURING THIS TIME FRAME. ON FRIDAY...A PACIFIC WEATHER 
SYSTEM WILL PULL MOISTURE NORTHWARD OVER THE REGION FOR A RETURN OF 
STORM CHANCES INTO NEXT WEEKEND...MAINLY EAST OF THE LOWER COLORADO 
RIVER VALLEY. IN ADDITION...COOLER TEMPERATURES AND BREEZY TO 
LOCALLY WINDY CONDITIONS CAN BE EXPECTED AS WELL. 

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
AVIATION...VASQUEZ
FIRE WEATHER...MEYERS/AJ









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