242  
FXUS65 KPSR 051720  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
1020 AM MST FRI SEP 5 2025  
   
UPDATE  
UPDATED AVIATION DISCUSSION.  
 
 
   
KEY MESSAGES  
 
- CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS WILL REMAIN  
THROUGH SATURDAY BEFORE RAIN CHANCES END COMPLETELY STARTING  
SUNDAY.  
 
- TEMPERATURES WILL BE BELOW NORMAL THROUGH SUNDAY BEFORE WARMING  
BACK INTO THE NORMAL RANGE FOR AT LEAST SOUTH-CENTRAL AND  
EASTERN ARIZONA THROUGH THE MIDDLE OF NEXT WEEK.  
 
 
   
SHORT TERM /TODAY THROUGH SATURDAY/  
 
TODAY INTO SATURDAY WILL BRING A DIMINISHING THREAT OF STORMS AS  
DRIER AIR ALOFT BEGINS TO SPREAD OVER THE REGION AND INCREASED  
SUBSIDENCE LIKELY LIMITS AREAL COVERAGE. FOR THE REST OF THE  
OVERNIGHT HOURS, WE MAY SEE A FEW ISOLATED SHOWERS BUT MOST  
LOCATIONS WILL SEE CLEARING SKIES AND SOMEWHAT HUMID CONDITIONS.  
THE TROUGH AXIS THAT AIDED IN STORM DEVELOPMENT THE LAST COUPLE OF  
DAYS HAS NOW MOVED TO THE EAST OF THE AREA WITH WEAK RIDGING  
MOVING IN FROM THE WEST. MOISTURE IN THE LOW AND MID LEVELS WILL  
REMAIN QUITE HIGH TODAY, BUT ABOVE 600MB NORTHERLY DRY AIR WILL  
ACT TO LIMIT STORM ACTIVITY TODAY. HI-RES CAMS MOSTLY SHOWS  
ISOLATED SHOWERS AND WEAK STORMS ACROSS THE ARIZONA HIGH TERRAIN  
AND MAYBE AN ISOLATED SHOWER OR TWO OVER THE LOWER DESERTS. WE  
CAN'T RULE OUT SOME ISOLATED SHOWER ACTIVITY DURING THE OVERNIGHT  
HOURS TONIGHT, BUT THERE IS NO MODEL CONSENSUS FOR EXACTLY WHERE.  
POPS THROUGH TONIGHT HAVE BEEN LOWERED TO BETWEEN 10-20%.  
 
GOING INTO THE WEEKEND, THE LARGE PACIFIC TROUGH OFF THE WEST  
COAST WILL BEGIN TO INFLUENCE OUR REGION MORE BRINGING WESTERLY  
DRY FLOW ACROSS THE ENTIRE DESERT SOUTHWEST. THE DRIER AIR ALOFT  
WILL PERSIST AND GET EVEN DRIER, GRADUALLY MIXING OUT WHATS LEFT  
OF THE MID LEVEL MOISTURE THIS WEEKEND. MOISTURE LEVELS ON  
SATURDAY ARE LIKELY TO STILL BE ENOUGH FOR SOME ISOLATED SHOWERS  
AND MAYBE A FEW WEAK STORMS, BUT AS WITH TODAY THE FAVORED AREAS  
FOR THIS ACTIVITY WILL BE OVER THE ARIZONA HIGH TERRAIN.  
 
TEMPERATURES OVER THE NEXT COUPLE OF DAYS WILL BARELY BUDGE WITH  
DAYTIME HIGHS FROM THE MID 90S ACROSS THE SOUTH-CENTRAL ARIZONA  
LOWER DESERTS TO THE UPPER 90S ACROSS THE WESTERN DESERTS, OR  
AROUND FIVE DEGREES BELOW NORMALS.  
 
 
   
LONG TERM /SUNDAY THROUGH THURSDAY/  
 
OVERALL QUIET AND DRYING CONDITIONS ARE FORECAST FOR SUNDAY  
THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. THE PACIFIC TROUGH IS  
EXPECTED TO DEEPEN AND FULLY CLOSE OFF WEST OF NORTHWEST U.S.  
COAST THIS WEEKEND BEFORE MOVING ONSHORE ON MONDAY. AS IT DEEPENS  
STARTING SUNDAY, IT SHOULD PROMOTE AMPLIFIED UPPER LEVEL RIDGING  
CENTERED ALONG THE ARIZONA/NEW MEXICO BORDER NORTHWARD INTO  
WYOMING. THIS IS EXPECTED TO BRIEFLY BOOST H5 HEIGHTS OVER MUCH  
OF OUR REGION INTO A 590-593DM RANGE LEADING TO WARMER  
TEMPERATURES FOR AT LEAST SUNDAY AND MONDAY. NBM FORECAST HIGHS  
SHOW READINGS RIGHT AROUND 100 DEGREES FOR SUNDAY ACROSS THE LOWER  
DESERTS TO BETWEEN 101-104 DEGREES ON MONDAY AND TUESDAY. FURTHER  
DRYING THROUGH EARLY NEXT WEEK SHOULD COMPLETELY END RAIN CHANCES  
EVEN ACROSS THE HIGHER TERRAIN BY MONDAY AND EVENTUALLY LOWER  
SURFACE DEW POINTS INTO THE 40S BY NEXT TUESDAY OR WEDNESDAY.  
 
MODEL UNCERTAINTY INCREASES SOMEWHAT DURING THE MIDDLE TO LATTER  
PART OF NEXT WEEK AS THERE ARE DIFFERENCES WITHIN THE MODELS WITH  
THE EVENTUAL EVOLUTION OF THE PACIFIC TROUGH. THERE IS AT LEAST  
GOOD AGREEMENT WITH H5 HEIGHTS LOWERING OVER OUR REGION BY NEXT  
WEDNESDAY AS THE TROUGH MOVES FULLY OVER THE WESTERN U.S., BUT  
THERE ARE BIGGER DIFFERENCES LATE NEXT WEEK WITH HOW FAR SOUTH  
AND EAST THE BASE OF THE TROUGH WILL TRACK. FOR NOW, WE CAN SAFELY  
SAY THIS PATTERN SHOULD KEEP CONSIDERABLE DRY AIR OVER MOST IF  
NOT ALL OF OUR REGION THROUGH LATE NEXT WEEK. FORECAST  
TEMPERATURES SHOW HIGHER SPREAD LATER NEXT WEEK, BUT THE OVERALL  
CONSENSUS SHOWS A SLIGHT COOLING TREND AND READINGS STAYING AT OR  
JUST BELOW NORMALS DURING THE LATTER HALF OF NEXT WEEK.  
 
 
   
AVIATION  
UPDATED AT 1720Z.  
 
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:  
SHOWER AND STORM CHANCES ARE SHOWING SIGNS OF INCREASING ACROSS  
THE VALLEY TAF SITES INTO EARLY AFTERNOON. A COMPLEX OF SHOWERS  
AND STORMS CONTINUES TO DRIFT SOUTHEAST TOWARD THE AREA WITH GOOD  
INSTABILITY IN PLACE. THIS HAS RESULTED IN RENEWED DEVELOPMENT ON  
THE LEADING EDGE WITH ITS PROGRESSION TO THE SOUTHEAST. WHATEVER  
DOES DEVELOP, SHOULD BE A LATE MORNING AND EARLY AFTERNOON EVENT.  
HAVE INTRODUCED VCTS ON THE VALLEY TAFS THROUGH THE 21-22Z TIME  
FRAME. PRIMARY IMPACTS WOULD BE LIGHTNING AND BRIEF HEAVY  
RAINFALL. SOME SLIGHTLY ELEVATED GUSTY AND ERRATIC WINDS WITH  
NEARBY STORMS, BUT OTHERWISE AND OVERALL VARIABLE WIND IN FORECAST  
THROUGH THE TAF PERIOD WITH LOW CONFIDENCE WITH ANY EASTERLY  
DUIRNAL SHIFT.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
NO MAJOR AVIATION WEATHER CONCERNS ARE EXPECTED THROUGHOUT THE TAF  
PERIOD AT AT LEAST KIPL. THESE AREAS SHOULD SEE TYPICAL WIND  
PATTERNS WITH SPEEDS GENERALLY AOB 10 KTS. FEW TO SCT MID TO HIGH  
CLOUDS WILL PERSIST THROUGHOUT THE PERIOD.  
 
 
   
FIRE WEATHER  
 
HIGHER LOW LEVEL MOISTURE WILL CONTINUE INTO THE WEEKEND, BUT  
RAIN CHANCES WILL BE DIMINISHING AND ENDING ALTOGETHER BY SUNDAY.  
EXPECT PERIODS OF ISOLATED SHOWERS AND WEAK STORMS THROUGH  
SATURDAY, BUT WETTING RAIN CHANCES WILL MOSTLY RANGE BETWEEN  
10-20%. MINRHS ARE ONLY EXPECTED TO DROP INTO A 30-45% RANGE  
THROUGH THE WEEKEND AS TEMPERATURES STAY BELOW NORMAL. WINDS WILL  
TEND TO FAVOR DIURNAL PATTERNS ACROSS THE EASTERN DISTRICTS,  
WHILE FAVORING THE SOUTH ACROSS THE WESTERN DISTRICTS. THE  
GRADUAL DRYING CONDITIONS WILL CONTINUE DURING THE FIRST HALF OF  
NEXT WEEK KEEPING RAIN CHANCES NEAR ZERO AND EVENTUALLY LOWERING  
MINRHS BACK INTO THE TEENS BY NEXT TUESDAY.  
 
 
   
PSR WATCHES/WARNINGS/ADVISORIES  
 
AZ...NONE.  
CA...NONE.  
 
 
 
 
SHORT TERM...KUHLMAN  
LONG TERM...KUHLMAN  
AVIATION...FRIEDERS  
FIRE WEATHER...KUHLMAN  
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