881  
FXUS65 KPSR 152342  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
442 PM MST THU MAY 15 2025  
   
UPDATE
 
UPDATED AVIATION DISCUSSION.  
 

 
   
KEY MESSAGES
 
 
1) GUSTY WINDS OVER THE WEEKEND RESULTING IN A LOCALLY ELEVATED  
FIRE DANGER  
 
2) INCREASED ODDS FOR ABOVE NORMAL TEMPERATURES AND WIDESPREAD  
MODERATE HEATRISK RETURNING LATE NEXT WEEK...  
   
DISCUSSION
 
 
WEATHER PATTERN OVERVIEW:  
 
BROAD, WEAKLY CYCLONIC FLOW LINGERS OVER THE SW CONUS AS A CLOSED,  
OCCLUDED LOW PRESSURE SYSTEM LIFTS INTO THE UPPER MIDWEST. THE  
WEAKNESS LEFT IN THE MIDTROPOSPHERIC FLOW OVER THE FORECAST AREA  
FROM THIS EXITING SYSTEM WILL QUICKLY BE FILLED OVER THE WEEKEND BY  
A SERIES OF PACIFIC NEGATIVE HEIGHT ANOMALIES INTENSIFYING INTO AN  
AMPLIFIED LONGWAVE WESTERN TROUGH. THE MAGNITUDE OF THE ATTENDANT  
PACIFIC JET DURING THIS MERIDIONAL TRANSITION WILL ENSURE ROBUST  
SHORTWAVE ENERGY AND NOTABLE HEIGHT FALLS MIGRATE INTO MUCH OF  
ARIZONA. THE TIMING AND JUXTAPOSITION OF HEIGHT FALLS AND JET CORE  
CARVING OUT THE TROUGH BASE WILL SUPPORT VERY GUSTY WINDS THROUGHOUT  
THE WEEKEND, BUT PARTICULARLY SATURDAY AFTERNOON/EVENING ACROSS SE  
CALIFORNIA WHERE PARAMETERS ALIGN NEARLY OPTIMALLY. AS SUCH,  
ADVISORIES WILL ALMOST CERTAINLY BE NECESSARY IN THE TYPICAL WIND  
PRONE LOCATIONS OF IMPERIAL COUNTY. THESE GUSTY WINDS COMBINED WITH  
SEASONALLY LOW HUMIDITY VALUES WILL ALSO RESULT IN AN ELEVATED FIRE  
DANGER, THOUGH MORE LIMITED WIND SPEEDS IN SOUTH-CENTRAL ARIZONA  
SATURDAY AND HIGHER MOISTURE SWEEPING THROUGH THE REGION SUNDAY MAY  
PRECLUDE MORE CRITICAL CONDITIONS.  
 
ENSEMBLE MEMBERSHIP REMAINS IN GOOD AGREEMENT DEPICTING SEVERAL  
VORTICITY CENTERS PIVOTING THROUGH THE LONGWAVE TROUGH WITH ONE  
NOTABLE AND FINAL TRAILING WAVE DIGGING INTO NORTHERN ARIZONA  
MONDAY. GIVEN THE INLAND TRAJECTORY OF THIS ENTIRE SERIES OF  
SHORTWAVES, MOISTURE WILL BE EXTREMELY LIMITED WITH BOUNDARY LAYER  
MIXING RATIOS NEVER EXCEEDING 5 G/KG. HOWEVER, GIVEN THE UNUSUAL  
DEPTH OF THE TROUGH AND MAGNITUDE OF THE COLD CORE, A FEW SHOWERS  
MAY BE SQUEEZED OUT OVER HIGHER TERRAIN AREAS. ON THE OTHER HAND,  
RECENT OPERATIONAL MODELS HAVE SHIFTED THE JET STREAK AND COLD CORE  
SLIGHTLY FURTHER NORTH RESULTING IN A FORECAST OF A LARGE MIDLEVEL  
CAPPING INVERSION LOCKED OVER THE SOUTHERN HALF OF ARIZONA. IF THIS  
MODEL TREND COMES TO FRUITION, IT WOULD BE ALL BUT IMPOSSIBLE FOR  
ANYTHING OTHER THAN OUTFLOW WINDS TO PROPAGATE INTO LOWER  
ELEVATIONS.  
 
WHILE SOME SUBTLE MIDLEVEL WEAKNESS IN THE HEIGHT FIELD MAY HOLD  
OVER THE SOUTHWEST DURING THE LATTER HALF OF THE WEEK, ENSEMBLES ARE  
FAR MORE RESOLUTE IN BUILDING STRONGER RIDGING OVER NORTHERN MEXICO  
AND SW CONUS. SOME OF THE MORE EXTREME MEMBERS HAVE BEEN  
HIGHLIGHTING H5 HEIGHTS AROUND 594DM, HOWEVER THE PREPONDERANCE OF  
OUTPUT SUGGESTS HEIGHTS CLOSER TO 588DM. AS A RESULT, WIDESPREAD  
MODERATE HEATRISK SHOULD EVOLVE TOWARDS THE END OF NEXT WEEK WITH  
TEMPERATURES NEARLY 10F ABOVE NORMAL. SHOULD ANY OF THE MORE  
ANOMALOUS SOLUTIONS BE REALIZED (AND IT COULD BE ARGUED THAT WOULD  
BE A LIKELY OUTCOME GIVEN THE PATTERN PROGRESSION), THIS COULD BE  
THE FIRST VESTIGES OF MAJOR HEATRISK WITH TEMPERATURES 15F ABOVE  
NORMAL YIELDING EXTREME HEATRISK OVER THE HOLIDAY WEEKEND.  
 
FORECAST CONFIDENCE & DEVIATIONS:  
 
GOOD CONFIDENCE IN TEMPERATURE FORECASTS EXISTS THE NEXT COUPLE  
DAYS, BUT THEN DETERIORATES SIGNIFICANTLY EARLY NEXT WEEK DEPENDING  
ON HOW FAR SOUTH THE COLD CORE MIGRATES. MANDATED NBM FORECASTS HAVE  
BUMPED WARMER BASED MAINLY ON CHANGES IN THE OPERATIONAL MEMBERS,  
BUT COULD FLIP FLOP BACK BASED ON FUTURE MODEL ITERATIONS. FEEL THE  
AUTOMATED NBM WINDS OVER THE WEEKEND ARE SOMEWHAT UNDERFORECAST AND  
HAVE MADE SOME MINOR INCREASES DURING PEAK MIXING HOURS. SPURIOUS  
POP AND QPF GRIDS WERE SUBSTANTIALLY REDUCED THIS CYCLE, HOWEVER DID  
HAVE TO MAKE SOME MINOR ADJUSTMENTS BASED ON UNREALISTIC MODEL  
ARTIFACTS. AVERAGE CONFIDENCE EXISTS WITH RESPECT TO TEMPERATURES  
TOWARDS THE END OF THIS FORECAST PERIOD, BUT WOULD NOT BE SURPRISED  
IF ACTUAL READINGS WERE EVEN WARMER THAN THE CURRENT AUTOMATED NBM  
OUTPUT.  
 

 
   
AVIATION
 
UPDATED AT 2341Z.  
 
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, KDVT;  
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
 
NO AVIATION IMPACTS ARE EXPECTED THROUGH THE NEXT 24 HOURS. WINDS  
AT ALL TERMINALS WILL FOLLOW TYPICAL DIURNAL TRENDS, WITH SPEEDS  
REMAINING AT OR BELOW 10 KTS THROUGH MOST OF THE TAF PERIOD.  
AFTERNOON GUSTINESS CAN BE EXPECTED IN THE PHOENIX AREA, WITH  
GUSTS UP TO 15-20 KTS AT TIMES. CLEAR SKIES WILL PREVAIL.  
 

 
   
FIRE WEATHER
 
 
WITH DRY CONDITIONS PREVAILING THROUGH NEXT WEEK, WINDS WILL  
INCREASE IN SPEED OVER THE WEEKEND YIELDING AN ELEVATED FIRE DANGER  
WITH LOCALLY NEAR CRITICAL CONDITIONS. MINRHS WILL MOSTLY FALL IN A  
10-15% RANGE THROUGH SATURDAY BEFORE A COOLER AND SOMEWHAT MORE  
MOIST AIRMASS KEEP MINIMUM READINGS IN A 15-25% RANGE SUNDAY AND  
MONDAY. POOR TO FAIR OVERNIGHT RECOVERY OF 20-50% WILL IMPROVE  
CLOSER TO A 35-60% RANGE EARLY NEXT WEEK. WINDS WILL BE MOST  
PRONOUNCED IN WESTERN DISTRICTS SATURDAY WITH GUSTS 30-40 MPH, THEN  
TRANSLATING INTO EASTERN DISTRICTS SUNDAY ALBEIT WITH SOMEWHAT  
WEAKER SPEEDS. VERY WARM AND DRY WEATHER WILL RETURN DURING THE  
MIDDLE OF NEXT WEEK, HOWEVER WIND SPEEDS WILL BE MUCH WEAKER AS HIGH  
PRESSURE STARTS BUILDING INTO THE REGION.  
 

 
   
PSR WATCHES/WARNINGS/ADVISORIES
 
 
AZ...NONE.  
CA...NONE.  

 
 

 
 
DISCUSSION...18  
AVIATION...BENEDICT  
FIRE WEATHER...18  
 
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