625  
FXUS65 KPSR 260045  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
545 PM MST MON OCT 25 2021  
   
UPDATE
 
UPDATED 00Z AVIATION DISCUSSION.  
 

 
   
SYNOPSIS
 
 
A WEATHER SYSTEM MOVING THROUGH THE REGION TODAY WILL BRING GUSTY  
WINDS, CHANCES FOR RAIN, AND COOLER TEMPERATURES. CHANCES FOR RAIN  
WILL MOSTLY REMAIN LIMITED TO HIGH TERRAIN LOCATIONS AS A COLD  
FRONT MOVES THROUGH LATE TONIGHT INTO TUESDAY. DRIER, COOLER  
WEATHER WILL SET IN FOR TUESDAY BEFORE QUICKLY WARMING UP AGAIN  
DURING THE SECOND HALF OF THE WEEK. INCREASING HIGH PRESSURE  
DURING THE LATTER HALF OF THE WEEK WILL PUSH TEMPERATURES BACK TO  
NEAR NORMAL READINGS WITH DRY CONDITIONS PREVAILING.  
 

 
   
DISCUSSION
 
 
WATER VAPOR IMAGERY SHOWS THE CENTER OF A ROBUST MID-LEVEL  
SHORTWAVE JUST OFF THE CENTRAL CALIFORNIA COAST WHILE AN  
ATMOSPHERIC RIVER CONTINUES TO BRING RAIN AND SNOW TO PARTS OF THE  
WEST. SHORT-TERM GUIDANCE TAKES THE WAVE ON A SOUTHEASTERLY  
TRAJECTORY TONIGHT THROUGH SOUTHERN CALIFORNIA AND ARIZONA BEFORE  
QUICKLY EJECTING INTO THE SOUTHERN ROCKIES TUESDAY. DESPITE ITS  
EXPEDITIOUSNESS, THIS SYSTEM WILL CAUSE NOTICEABLE CHANGES TO OUR  
MELLIFLUOUS WEATHER OF LATE.  
 
FIRST, BREEZY TO WINDY CONDITIONS ARE SPREADING THROUGHOUT  
SOUTHEASTERN CALIFORNIA AND SOUTHWESTERN ARIZONA WITH 25-35 MPH  
GUSTS BECOMING COMMON BY THIS EVENING. A PERIOD OF SLIGHTLY  
STRONGER GUSTS, PERHAPS AS STRONG AS 40-45 MPH, MAY OCCUR FOR A  
SHORT TIME AS A COLD FRONT PASSES THROUGH THAT AREA BETWEEN 5 AND  
8 PM. ASSESSING THE POTENTIAL FOR STRONGER GUSTS AND/OR WIDESPREAD  
40+ MPH GUSTS IS LESS CERTAIN. THE LATEST ECMWF EFI, A USEFUL  
TOOL TO ASSESS ANOMALOUS WIND GUSTS, SHOWS INDEX VALUES REACHING  
0.6 TO 0.7 FOR PARTS OF THE WESTERN CWA, SUGGESTING CONDITIONS  
WILL MOSTLY REFLECT THE CURRENT FORECAST. AS SUCH, A WIND ADVISORY  
REMAINS IN EFFECT ONLY FOR THE MOUNTAIN SPRINGS AREA OF IMPERIAL  
COUNTY THIS EVENING.  
 
THE COLD FRONT AND BREEZY CONDITIONS WILL SPREAD EAST INTO SOUTH-  
CENTRAL AZ LATER THIS EVENING. WIND GUSTS AROUND THE PHOENIX AREA  
ARE FORECAST TO REACH 20-30 MPH BUT A FEW EXPOSED RIDGETOPS  
AROUND THE AREA AND OVER IN GILA COUNTY COULD SEE A FEW BRIEF 40  
MPH GUSTS. WITH THESE KINDS OF SPEEDS AND RECENT DRY CONDITIONS,  
LOCALIZED BLOWING DUST CANNOT BE RULED ANYWHERE IN THE LOWER DESERT,  
ESPECIALLY AROUND PLACES MORE SUSCEPTIBLE TO BLOWING DUST. IF THE  
DUST DOES BLOW, SUSPENDED LOFTED DUST AND SUBSEQUENT HAZY SKIES  
COULD LINGER FOR A DAY OR TWO.  
 
BY TONIGHT, THE ASSOCIATED AR WILL ALSO TRANSITION SOUTHWARD WITH  
THE MID-LEVEL WAVE BUT MOST OF THE MOISTURE WILL HAVE BEEN  
DEPLETED OVER THE CALIFORNIA MOUNTAINS. NEITHER GUIDANCE NOR  
OBSERVATIONAL TRENDS SIGNAL MUCH CONFIDENCE FOR RAIN HERE EVEN  
THOUGH POPS REMAIN IN THE 20-40% RANGE ACROSS THE NORTHERN  
PORTIONS OF THE CWA. THE NBM QPF PROBABILITIES ARE TELLING WITH  
HARDLY ANY CHANCE FOR 0.10” OF TOTAL RAINFALL ANYWHERE IN THE  
LOWER DESERT. OUTSIDE OF A FEW PLACES THAT MIGHT SEE A COUPLE  
HUNDREDTHS, MOST PLACES SEEM POISED TO REMAIN DRY. THE BEST TIMING  
FOR RAIN POTENTIAL COINCIDES WITH THE AFOREMENTIONED FRONTAL  
PASSAGE.  
 
COOLER, DRIER WEATHER SETS IN FOR TUESDAY AS CLEAR SKIES PREVAIL AND  
AFTERNOON HIGHS ONLY TOP OUT IN THE UPPER 70S ACROSS THE LOWER  
DESERTS, WHICH IS AROUND 10 DEGREES BELOW SEASONAL NORMALS. THE  
BELOW NORMAL TEMPERATURES WON'T STICK AROUND FOR LONG AS HEIGHTS  
QUICKLY RISE IN RESPONSE TO UPPER LEVEL RIDGING BUILDING BACK INTO  
THE DESERT SOUTHWEST. TEMPERATURES ARE EXPECTED TO WARM BACK TO NEAR  
NORMAL VALUES BY THURSDAY AS THE NBM SHOWS HIGH TEMPERATURES  
CLIMBING INTO THE UPPER 80S FOR MOST LOWER ELEVATION LOCALES. NBM  
SHOWS TEMPERATURES FURTHER WARMING ON FRIDAY WITH HIGHS FLIRTING  
WITH 90 DEGREES. THE AVERAGE LAST 90 DEGREE DAY FOR PHOENIX IS  
OCTOBER 30TH.  
 

 
   
AVIATION
 
UPDATED AT 0044Z.  
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:  
 
WINDS WILL BECOME INCREASINGLY BREEZY OUT OF THE SW AHEAD OF A  
COLD FRONT, WITH GUSTS CLIMBING UP TO 20-25 KTS AND BREEZIEST  
CONDITIONS IN THE 3Z-8Z TIMEFRAME. A PRE-FRONTAL TROUGH SHOULD  
SHIFT WINDS MORE WESTERLY AROUND 5Z-8Z AND FRONTAL PASSAGE IS  
EXPECTED BETWEEN 8Z-11Z. WINDS SHOULD BEGIN SUBSIDING POST-FRONT,  
BUT REMAIN WESTERLY THROUGH TUESDAY. THERE IS A SLIGHT CHANCE  
(10-20%) ISOLATED LIGHT SHOWERS MAY ACCOMPANY THE FRONT, WITH  
GREATER CHANCES FAVORING THE HIGHER TERRAIN TO THE NORTH AND EAST.  
INCREASING CLOUDS JUST AHEAD OF THE FRONT IS EXPECTED. PRIMARY  
CIGS ARE FAVORED AROUND 7-8 KFT, BUT COULD FALL AS LOW AS 4-5 KFT.  
THE POTENTIAL FOR MVFR WILL MOSTLY BE BETWEEN 5Z-9Z, WITH CLOUDS  
RAPIDLY CLEARING POST- FRONT.  
 
STRONGER WINDS IN SOUTHEAST CA HAVE ALREADY GENERATED A LOT OF  
LOFTED DUST THIS AFTERNOON. THE LOFTED DUST MAY BE CARRIED INTO  
THE METRO AREA WITH THE COLD FRONT AND IMPACT SLANTWISE  
VISIBILITY TUESDAY, ESPECIALLY IN THE MORNING AND POSSIBLY THE  
EVENING.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
 
STRONG WIND GUSTS, UPWARDS OF 30-35 KTS, OUT OF THE WEST TO  
SOUTHWEST WILL CONTINUE THROUGH THE NEXT FEW HOURS BEFORE  
GRADUALLY FALLING FOLLOWING A COLD FRONT. THE STRONG WINDS ARE  
GENERATING BLOWING DUST WHICH COULD LOWER VISIBILITY DOWN TO 4-5  
SM AT TIMES, AS HAS BEEN OBSERVED AT KBLH. FRONTAL PASSAGE WILL  
BE BETWEEN 3Z TO 6Z. MODERATE LLWS IS POSSIBLE AT KIPL THIS  
EVENING POST- FRONT IF THE SURFACE IS ABLE TO DECOUPLE AND SURFACE  
SPEEDS FALL BELOW 10 KTS. THE GRADIENT ALOFT, WITH 30-40 KT WINDS  
ABOVE 1 KFT, SHOULD WEAKEN BY 12Z. BREEZY N TO NW WINDS STILL  
EXPECTED TUESDAY, BUT WITH NOTABLY LOWER SPEEDS THAN TODAY. FEW TO  
SCT MID AND HIGH CLOUDS SHOULD CLEAR RAPIDLY POST FRONT, BY  
MIDNIGHT.  
 

 
   
FIRE WEATHER
 
 
WEDNESDAY THROUGH SUNDAY:  
BELOW NORMAL TEMPERATURES ON WEDNESDAY WILL QUICKLY GIVE WAY TO A  
WARMING TREND ON THURSDAY AS HIGH PRESSURE BUILDS INTO THE REGION.  
BY FRIDAY, NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES ARE EXPECTED  
AS AFTERNOON HIGHS APPROACH 90 DEGREES. MINIMUM AFTERNOON RH  
VALUES WILL REMAIN IN THE TEENS THROUGH SATURDAY BEFORE INCREASING  
TO AROUND 20-25% ON SUNDAY. MAXIMUM RHS WILL GENERALLY REMAIN  
AROUND 40-50%. NORTH TO NORTHWESTERLY DAYTIME BREEZY CONDITIONS  
ARE EXPECTED THROUGH THE MIDDLE PART OF THE WEEK BEFORE LIGHT AND  
DIURNAL WINDS ARE SEEN STARTING ON FRIDAY.  
 

 
   
SPOTTER INFORMATION STATEMENT
 
 
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.  
 

 
   
PSR WATCHES/WARNINGS/ADVISORIES
 
 
AZ...NONE.  
CA...WIND ADVISORY UNTIL 2 AM PDT TUESDAY FOR CAZ562.  
 
BLOWING DUST ADVISORY UNTIL 9 PM PDT THIS EVENING FOR CAZ563>567.  
 
WIND ADVISORY UNTIL 7 PM PDT THIS EVENING FOR CAZ563-566-567.  
 

 
 

 
 
DISCUSSION...12/SMITH  
AVIATION...BENEDICT  
FIRE WEATHER...SMITH/KUHLMAN  
 
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