399  
FXUS65 KPSR 122159  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
259 PM MST MON MAY 12 2025  
   
SYNOPSIS
 
 
GUSTY WINDS AND ELEVATED TO LOCALLY CRITICAL FIRE WEATHER CONDITIONS  
WILL BE THE MAIN WEATHER CONCERNS THROUGH TUESDAY, AS A LOW PRESSURE  
SYSTEM PASSES OVER THE GREAT BASIN. TEMPERATURES WILL ALSO COOL FROM  
THE UPPER NINETIES THIS AFTERNOON TO THE EIGHTIES ACROSS MUCH OF THE  
LOWER DESERTS BY TUESDAY. TRANQUIL CONDITIONS RETURN WEDNESDAY, WITH  
TYPICAL AFTERNOON BREEZES AND A GRADUAL WARMING TREND TO NEAR  
SEASONAL NORMALS DURING THE LATTER HALF OF THE WORKWEEK.  
 

 
   
DISCUSSION
 
 
EARLY AFTERNOON MID-LEVEL WV IMAGERY SHOWS A TROUGH MOVING ONSHORE  
OVER THE PACIFIC NORTHWEST, WITH NOTABLE HEIGHT PACKING EVIDENT IN  
500 MB RAP ANALYSIS TO ITS SOUTHEASTERN PERIPHERY. MOUNTAIN WAVE  
ACTIVITY IN THE LEE OF THE SIERRAS IS QUITE APPARENT, INDICATIVE OF  
THE STRONG SOUTHWESTERLY FLOW THAT IS EXPECTED TO SHIFT OVER THE  
FORECAST AREA OVER THE NEXT 12-24 HOURS AS THE TROUGH DIGS INTO THE  
GREAT BASIN. WHILE THE STRONGER FLOW ALOFT IS EXPECTED TO BRING  
BREEZY TO WINDY CONDITIONS ACROSS PORTIONS OF THE AREA AS EARLY AS  
THIS AFTERNOON, THE REGION STILL REMAINS UNDER THE INFLUENCE OF HIGH  
PRESSURE AND POSITIVE H5 HEIGHT ANOMALIES TODAY. ABUNDANT HIGH  
CLOUDS MAY LIMIT AFTERNOON HIGHS FROM REACHING THE CENTURY MARK  
ACROSS MUCH OF THE LOWER DESERTS, BUT TEMPERATURES WILL STILL RANGE  
FROM 4 TO 8 DEGREES ABOVE NORMAL THIS AFTERNOON, MOSTLY IN THE UPPER  
90S.  
 
AS MENTIONED ABOVE, STRONG WINDS WILL BE ONE OF THE PRIMARY IMPACTS  
FROM THE INCOMING DRY WEATHER SYSTEM THROUGH TUESDAY. WIND GUSTS  
OF 25-40 MPH ARE EXPECTED ACROSS THE AREA, MAINLY DURING THE  
AFTERNOONS AND EVENINGS. THE STRONGEST WINDS WILL BE FOCUSED  
ACROSS SOUTHEASTERN CA AND OVER THE AZ HIGH TERRAIN. A WIND  
ADVISORY REMAINS IN EFFECT FOR MUCH OF WESTERN IMPERIAL COUNTY  
THROUGH TUESDAY NIGHT, TO CAPTURE THE AREAS MOST PRONE TO MOUNTAIN  
ROTOR ACTIVITY AND DOWNSLOPING WINDS. THOUGH THERE WILL LIKELY BE  
A LULL IN STRONGER GUSTS EARLY TUESDAY MORNING, MOST GUIDANCE  
INCLUDING GFS/NAM MOS FOR IMPERIAL SHOW SUSTAINED WIND SPEEDS  
REMAINING AROUND 25 KTS, JUST UNDER THE ADVISORY THRESHOLD, SO  
HAVE OPTED TO MAINTAIN PREVIOUSLY ISSUED PRODUCT WITHOUT SPLITTING  
IT UP. STRONG WINDS COMBINED WITH LOW RELATIVE HUMIDITIES BETWEEN  
8-15% AND DRY FINE FUELS WILL LEAD TO ELEVATED TO LOCALLY  
CRITICAL FIRE WEATHER CONDITIONS AS WELL. THEREFORE, A RED FLAG  
WARNING REMAINS IN EFFECT FOR SOUTHERN GILA COUNTY AND THE HIGHER  
ELEVATIONS OF NORTHEASTERN PINAL AND EASTERN MARICOPA COUNTIES  
THROUGH 7 PM MST THIS EVENING AND AGAIN TUESDAY FROM THE LATE  
MORNING THROUGH EARLY EVENING.  
 
THE OTHER IMPACT OF THIS SYSTEM WILL BE COOLER TEMPERATURES. EXPECT  
LOWER DESERT HIGHS TO FALL SOLIDLY IN THE 80S OVER SE CA AND SW AZ  
TUESDAY AND CLOSE TO 90F FOR PORTIONS OF THE PHOENIX METRO AREA,  
THEN 80S AREAWIDE WEDNESDAY (70S FOR POPULATED HIGHER TERRAIN AREAS  
LIKE GLOBE/MIAMI, AND WESTERN JTNP.) THESE COOLER TEMPS ARE AROUND 3  
TO 6 DEGREES BELOW NORMALS FOR THE TIME OF YEAR.  
 
LATE WEEK, GLOBAL GUIDANCE STILL DEPICTS SOME MEASURE OF LONGWAVE  
TROUGHING/QUASI-ZONAL FLOW BEING MAINTAINED OVER THE WESTERN US,  
WITH H5 HEIGHTS GRADUALLY REBOUNDING TO AROUND 576-579 DM. LATEST  
NBM PROBABILISTIC GUIDANCE SHOWS A VERY NARROW IQR IN FORECAST  
TEMPERATURES, SO CONFIDENCE IS QUITE HIGH THAT TEMPS WILL RETURN TO  
NEAR SEASONAL LEVELS. THIS UPCOMING WEEKEND, ENSEMBLES STILL SHOW A  
SHORTWAVE CARVING OUT THE WESTERN SIDE OF THE LONGWAVE  
TROUGH/QUASI-ZONAL PATTERN OVER THE WESTERN CONUS. THOUGH THERE  
ARE NOTABLE DISCREPANCIES IN HOW FAR SOUTH THIS TROUGH WILL DIVE,  
IT WILL LIKELY RESULT IN ANOTHER COOLDOWN TO BELOW NORMAL AND  
BREEZY TO LOCALLY WINDY CONDITIONS THIS UPCOMING WEEKEND.  
 

 
   
AVIATION
 
UPDATED AT 1705Z.  
 
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, KDVT:  
A PERIOD OF SOUTHERLY CROSS RUNWAY WINDS FOLLOWED BY VEERING  
DIRECTIONS AND INCREASING AFTERNOON/EARLY EVENING GUSTS WILL BE THE  
MAIN WEATHER ISSUES THROUGH TUESDAY MORNING UNDER PERIODS OF  
MID/HIGH CIGS. CONFIDENCE IS GOOD THAT A FEW HOURS OF 150V210 WINDS  
WILL BE COMMON EARLY THIS AFTERNOON BEFORE COMPLETING THE W/SW  
SWITCH. GUSTS AROUND 25KT SHOULD AFFECT ALL TERMINALS INTO THE MID  
EVENING BEFORE RELAXING. CONFIDENCE IN WIND TRENDS OVERNIGHT IS LOW  
WITH THE TRADITIONAL EASTERLY SWITCH EITHER FAILING TO OCCUR, OR  
ONLY OCCURRING FOR A FEW HOURS BEFORE QUICKLY REVERTING BACK TO A SW  
DIRECTION.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
GUSTY WINDS AND THE POTENTIAL FOR LOCALIZED BLOWING DUST WILL BE THE  
PRIMARY WEATHER ISSUES UNDER MID/HIGH CLOUD DECKS. GUSTS WILL  
INCREASE THROUGH THE AFTERNOON WITH DIRECTIONS GENERALLY VEERING  
FROM SOUTHERLY TO SW. GUSTS MAY EXCEED 30KT AT KIPL THROUGH THE  
EVENING HOURS WITH SPEEDS PEAKING 25-30KT AT KBLH DURING THE EARLY  
EVENING BEFORE PARTIALLY RELAXING OVERNIGHT. THESE STRONG GUSTS MAY  
RESULT IN LOCAL SURFACE AND SLANTWISE VISIBILITY RESTRICTIONS DUE TO  
BLOWING DUST.  
 

 
   
FIRE WEATHER
 
 
ELEVATED FIRE DANGER WILL EXIST TODAY AND TUESDAY AS WARM  
TEMPERATURES, LOW HUMIDITY LEVELS, AND GUSTY WINDS BECOME  
JUXTAPOSED WITH RECEPTIVE, DRY FINE FUELS. MINRHS OF 8-15% WILL BE  
COMMON THROUGHOUT THE WEEK FOLLOWING POOR TO FAIR OVERNIGHT  
RECOVERY OF 20- 50%. WINDS WILL GUST TO BETWEEN 25-40 MPH DURING  
THE AFTERNOON AND EARLY EVENING TODAY AND TUESDAY, SOME HIGHER  
GUSTS ARE POSSIBLE IN WESTERN IMPERIAL COUNTY. GUSTS WILL LIKELY  
BE MOST PRONOUNCED ACROSS RIDGE TOPS AND IN THE TYPICAL  
DOWNSLOPING AREAS. SPEEDS SHOULD WEAKEN DURING THE LATTER HALF OF  
THE WEEK, THOUGH STILL WILL RETAIN THE USUAL AFTERNOON UPSLOPE  
GUSTINESS. TEMPERATURES WILL ALSO COOL DURING THE FIRST HALF OF  
THE WEEK AS THE WEATHER SYSTEM MOVES INTO THE REGION, HOWEVER  
SHOULD REBOUND CLOSER TO SEASONAL NORMALS BY THE END OF THE WEEK.  
 

 
   
PSR WATCHES/WARNINGS/ADVISORIES
 
 
AZ...RED FLAG WARNING UNTIL 7 PM MST THIS EVENING FOR AZZ133.  
 
RED FLAG WARNING FROM 10 AM TO 8 PM MST TUESDAY FOR AZZ133.  
 
CA...WIND ADVISORY UNTIL 5 AM PDT WEDNESDAY FOR CAZ562.  
 
WIND ADVISORY UNTIL 2 AM PDT WEDNESDAY FOR CAZ563-566-567.  
 

 
 

 
 
DISCUSSION...WHITTOCK  
AVIATION...18  
FIRE WEATHER...WHITTOCK/BERISLAVICH  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab AZ Page
The Nexlab CA Page Main Text Page