178  
FXUS65 KPSR 100537  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
1037 PM MST FRI MAY 9 2025  
   
UPDATE  
UPDATED AVIATION DISCUSSION.  
 
 
   
SYNOPSIS  
 
HIGH PRESSURE IS STRENGTHENING OVER THE REGION LEADING TO  
TEMPERATURES IN THE TRIPLE DIGITS TODAY LASTING THROUGH THE  
WEEKEND, UP TO 105 DEGREES ON SUNDAY. THIS HAS LEAD TO WIDESPREAD  
MODERATE HEATRISK AND SOME LOCALIZED MAJOR HEATRISK IN THE  
WESTERN PORTIONS OF THE REGION. SKIES WILL REMAIN CLEAR THROUGH  
SATURDAY, AFTERWARDS HIGHER LEVEL CLOUD COVERAGE WILL BE COMMON.  
BREEZY CONDITIONS WILL ALSO START SATURDAY, CALMING DOWN SLIGHTLY  
ON SUNDAY BEFORE RAMPING BACK UP MONDAY AS A LOW PRESSURE SYSTEM  
APPROACHES. THIS SYSTEM WILL ALSO HELP BRING TEMPERATURES DOWN.  
 
 
   
DISCUSSION  
 
UPPER LEVEL RIDGING HAS BECOME DOMINATE OVER THE REGION AS  
TEMPERATURES ARE EXPECTED TO CLIMB JUST OVER 100 DEGREES TODAY AND  
CONTINUE TO RISE OVER THE WEEKEND AS THE RIDGE CONTINUES TO BUILD.  
PEAK H5 HEIGHTS LOOK TO BE BETWEEN 585-587DM, JUST INTO THE 90TH  
PERCENTILE OF CLIMATOLOGY FOR THIS TIME OF YEAR. THIS WILL VERY  
LIKELY (>90%) PUT HIGH TEMPERATURES BETWEEN 104-106 OVER THE  
WEEKEND. THESE TEMPERATURES HAVE ELEVATED THE HEATRISK TO MODERATE  
WIDESPREAD ACROSS A THE DESERT SW, WITH MAJOR HEATRISK IN VERY  
LOCALIZED AREAS IN THE WESTERN PORTIONS OF THE REGION STARTING  
SATURDAY. WHILE MOST OF THE REGION IS ANTICIPATED TO BE BACK UNDER  
MINOR HEATRISK THE PHOENIX METRO HOLDS ONTO MODERATE RISK INTO  
MONDAY BEFORE DIPPING BACK DOWN TO MINOR. CLEAR SKIES ARE EXPECTED  
THROUGH SATURDAY, WITH HIGHER LEVEL CLOUD COVERAGE STARTING SUNDAY,  
WHICH MAY LOWER THE MAX TEMPERATURE OUTPUT BY THE NBM.  
 
WINDS ARE FORECAST TO PICK UP SATURDAY MORNING FROM THE  
EAST/SOUTH-EAST ACROSS MUCH OF SOUTHERN AND CENTRAL ARIZONA, WITH  
GUSTS AROUND 25-35 MPH. THIS IS MAINLY DUE TO AN INCREASING  
GRADIENT BETWEEN OUR HIGH PRESSURE RIDGE AND A STRENGTHENING LOW  
OVER THE LOWER MS RIVER VALLEY. WINDS WILL RELAX BY THE AFTERNOON  
HOURS AND WILL SEE A SIMILAR TREND SUNDAY.  
 
MODELS SHOW THE RELATIVELY DEEP TROUGH OFF THE PACIFIC NW  
AFFECTING H5 HEIGHTS IN THE REGION BY SUNDAY. HOWEVER, TEMPERATURES  
ARE VERY UNLIKELY (<10%) TO BE AFFECTED ON SUNDAY. THIS SYSTEM  
LOOKS TO WEAKEN AS IT PUSHES FURTHER INLAND, BUT WILL STILL IMPACT  
THE REGION ONCE ITS SITUATED OVER THE GREAT BASIN BY MONDAY.  
DURING WHICH, AREA WIDE BREEZY CONDITIONS WILL PICK BACK UP.  
ENSEMBLES STILL AGREE THIS PACIFIC TROUGH WILL BE FAIRLY SLOW TO  
FULLY MOVE THROUGH THE REGION, NOT UNTIL NEXT TUESDAY OR  
WEDNESDAY. THERE IS STILL SOME UNCERTAINTY WITH THE EXACT TIMING  
AND THE DEPTH OF THE SYSTEM, WITH NBM TEMPERATURES SLOWING THE  
COOL DOWN EARLY NEXT WEEK, BUT WE COULD SEE HIGHS EVENTUALLY DROP  
INTO THE 80S BY WEDNESDAY.  
 
 
   
AVIATION  
UPDATED AT 0020Z.  
 
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, KDVT:  
EASTERLY WINDS WILL PREVAIL THROUGH THE TAF PERIOD. AN ENHANCED  
EASTERLY GRADIENT WIND WILL DEVELOP TONIGHT, SHORTLY AFTER  
MIDNIGHT. WINDS ABOVE THE SURFACE AS HIGH AS 30-35 KTS MAY LEAD  
LLWS MAGNITUDES UP TO 25-30 KTS BETWEEN 7-14Z, BUT MENTION WILL BE  
LEFT OUT OF THE TAF. THE ELEVATED WINDS WILL LEAD TO SURFACE WIND  
GUSTS TO AROUND 25-30 KTS SATURDAY, MAINLY BETWEEN 15-20Z. GUST  
MAGNITUDES WILL SUBSIDE GRADUALLY THROUGH SATURDAY AFTERNOON.  
SKIES WILL REMAIN MOSTLY CLEAR.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
LIGHT DIURNAL WINDS WILL PREVAIL AT BOTH TERMINALS THROUGH  
TONIGHT, WITH PERIODS OF LIGHT VARIABILITY AS WELL. AN INCREASED  
EASTERLY WIND GRADIENT WILL THEN TAKE HOLD BY LATE MORNING AT BOTH  
TERMINALS, WITH SURFACE SPEEDS INCREASING TO AROUND 8-13 KTS WITH  
GUSTS UP TO 15-25 KTS THAT WILL CONTINUE THROUGH EARLY AFTERNOON  
SATURDAY. MOSTLY CLEAR SKIES WILL PREVAIL, WITH FEW TO SCT HIGH  
CLOUDS MOVING IN LATE IN THE AFTERNOON AND EVENING SATURDAY.  
 
 
   
FIRE WEATHER  
 
HIGH PRESSURE WILL STRENGTHEN OVER THE REGION INTO THE WEEKEND  
LEADING TO HOT TEMPERATURES AND HIGHS TOPPING 100 DEGREES OVER  
THE MAJORITY OF THE LOWER DESERTS THROUGH SUNDAY. HUMIDITIES WILL  
DROP A BIT FURTHER TODAY WITH MINRHS AROUND 15% BEFORE DROPPING  
CLOSER TO 10% BY SUNDAY. AFTER LIGHT WINDS TODAY, WINDS WILL  
BECOME QUITE BREEZY OUT OF THE EAST ON SATURDAY WITH PEAK GUSTS  
OF 25-35 MPH DURING THE MORNING HOURS ACROSS PORTIONS OF SOUTHERN  
ARIZONA. EXPECT ANOTHER ROUND OF EASTERLY BREEZY CONDITIONS  
SUNDAY MORNING ACROSS EASTERN ARIZONA BEFORE BREEZY CONDITIONS  
EXPAND TO INCLUDE THE WESTERN DISTRICTS SUNDAY AFTERNOON. THESE  
CONDITIONS MAY LEAD TO A PERIOD OF ELEVATED FIRE DANGER IN SOME  
AREAS THIS WEEKEND. AN APPROACHING LOW PRESSURE SYSTEM EARLY NEXT  
WEEK WILL LEAD TO A COOLING TREND, BUT ALSO MORE BREEZY TO WINDY  
CONDITIONS WHICH WILL LIKELY BRING A CONTINUATION OF THE ELEVATED  
FIRE DANGER.  
 
 
   
PSR WATCHES/WARNINGS/ADVISORIES  
 
AZ...NONE.  
CA...NONE.  
 
 
 
 
DISCUSSION...KUHLMAN/RYAN  
AVIATION...BENEDICT  
FIRE WEATHER...KUHLMAN/RYAN  
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