390  
FXUS65 KPSR 162350  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
450 PM MST SAT OCT 16 2021  
   
UPDATE
 
00Z AVIATION DISCUSSION.  
 

 
   
SYNOPSIS
 
 
HIGH PRESSURE OVER THE REGION WILL YIELD MOSTLY CLEAR SKIES AND  
QUITE SEASONABLE TEMPERATURES THIS WEEKEND THOUGH PERIODICALLY  
BREEZY CONDITIONS WILL BE COMMON THROUGH SOUTH-CENTRAL ARIZONA. A  
WEAK COLD FRONT WILL RESULT IN SOMEWHAT COOLER TEMPERATURES MONDAY  
AND TUESDAY, HOWEVER SUBTLE WARMING WILL RESUME WEDNESDAY AND  
THURSDAY. DRY WEATHER IS EXPECTED THROUGH THE END OF NEXT WEEK.  
 

 
   
DISCUSSION
 
 
PRONOUNCED RIDGING REMAINS POSITIONED OVER THE SW CONUS THIS  
AFTERNOON WITHIN A PROGRESSIVE HEMISPHERIC FLOW PATTERN, ALBEIT WITH  
WEATHER DISTURBANCES PRIMARILY DEFLECTED NORTH OF THE FORECAST AREA  
AND THROUGH THE NORTHERN HALF OF THE CONUS. OBJECTIVE ANALYSIS AND  
REGIONAL SOUNDINGS EXHIBIT LITTLE CHANGE IN HEIGHTS/THERMAL PROFILES  
ALOFT OVER ARIZONA, HOWEVER DO REVEAL SUBSTANTIAL WARMING IN THE SFC-  
H7 LAYER RESULTING IN FORECAST TEMPERATURES FINALLY REBOUNDING TO  
THE SEASONAL AVERAGE THROUGH SUNDAY (I.E. LOWER ELEVATION  
COMMUNITIES AROUND THE 90F THRESHOLD). DUE TO THE CONFIGURATION OF  
THE RIDGE AXIS, SURFACE PRESSURE RISES HAVE BEEN FAVORED OVER THE  
ROCKIES RESULTING IN A STEEP GRADIENT OVER THE ELEVATION TRANSITION  
IN THE EASTERN CWA. MECHANICAL MIXING HAS TRANSLATED A PORTION OF  
THE HIGHER MOMENTUM AIR TOWARDS THE SURFACE, AND WIDESPREAD GUSTS 20-  
25 MPH HAVE BEEN COMMON ACROSS THE PHOENIX METRO AND SURROUNDING  
AREAS. A SUBTLE RECONFIGURATION OF THE RIDGE WITH MODEST HEIGHT  
FALLS BEGINNING TO ENTER THE REGION WILL ALLOW THE PRESSURE GRADIENT  
TO RELAX SUNDAY YIELDING FAR LESS GUSTINESS.  
 
DURING THE FIRST PART OF NEXT WEEK, A MORE SIGNIFICANT TROUGH WILL  
MOVE ACROSS NORTHERN/CENTRAL CALIFORNIA INTO THE GREAT BASIN  
STRENGTHENING THE MID-LEVEL TROPOSPHERIC FLOW ACROSS THE SOUTHWEST.  
GIVEN THE ANTECEDENT DRY AIRMASS IN PLACE AND WESTERLY LOW LEVEL  
TRAJECTORIES ACCOMPANYING THIS SYSTEM, BETTER QUALITY MOISTURE  
SHOULD REMAIN FAR REMOVED FROM THE FORECAST AREA WITH THE BEST  
PRECIPITATION CHANCES CONFINED TO COASTAL SOUTHERN CALIFORNIA.  
PERIODS OF HIGH CIRRUS CLOUD COVER AND LOCALLY BREEZY CONDITIONS ARE  
REALLY THE ONLY WEATHER IMPACTS OF CONSEQUENCE ACROSS SOUTHEAST  
CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY ON MONDAY. AT THIS  
TIME, MORE NOTABLE WIND ANOMALIES PER NAEFS OUTPUT SHOULD REMAIN  
NORTH OF THE FORECAST AREA WITH THE MORE TYPICAL DOWNSLOPING GUSTS  
IN SW IMPERIAL COUNTY.  
 
MIDTROPOSPHERIC HEIGHT RISES WILL AGAIN ENVELOP THE REGION DURING THE  
LATTER HALF OF NEXT WEEK WITH H5 HEIGHTS POTENTIALLY REBOUNDING BACK  
ABOVE 588DM. WHILE DIURNAL MIXING DEPTHS ARE MORE SHALLOW THIS TIME  
OF YEAR, THERE IS AT LEAST A 50% CHANCE HIGH TEMPERATURES AT THE END  
OF THE WEEK REACH INTO THE LOWER 90S (THOUGH STILL WELL SHORT OF  
RECORD TERRITORY). WHERE AS FORECAST CONFIDENCE IS EXCELLENT THROUGH  
MUCH OF NEXT WEEK, UNCERTAINTY GROWS MORE SUBSTANTIALLY NEXT WEEKEND  
(AND BEYOND) AS A DOWNSTREAM BLOCKING PATTERN RETROGRADES BACK INTO  
NORTH AMERICA. ENSEMBLE TRENDS SUGGEST A SOMEWHAT LESS CHANCE FOR  
SHARP TROUGHING TO ENTER THE SOUTHWEST, BUT RATHER A PREPONDERANCE  
OF GUIDANCE INDICATES NEGATIVE HEIGHT ANOMALIES BECOMING QUASI-  
STATIONARY ALONG THE PACIFIC NW COAST WHILE STRONGER ZONAL FLOW  
PREDOMINATES THE LOCAL FORECAST AREA. THIS CONFIGURATION WOULD  
SUPPORT CONTINUED DRY WEATHER WITH TEMPERATURE NOT FAR FROM  
CLIMATOLOGY.  
 

 
   
AVIATION
 
UPDATED AT 2350Z.  
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:  
EASTERLY FLOW WILL PERSIST INTO EARLY SUNDAY AFTERNOON. BREEZY  
CONDITIONS ARE ALSO LIKELY EARLY THIS AFTERNOON BEFORE WINDS  
SUBSIDE SOMEWHAT EARLY THIS EVENING. LATER TONIGHT (PRIMARILY  
AFTER 5Z), LOCALIZED POCKETS OF LLWS WILL LIKELY DEVELOP AROUND  
THE VALLEY. WHERE WINDS DROP OFF AT THE SURFACE, 25 KT OF SHEAR IS  
POSSIBLE. THESE WINDS WILL THEN MIX DOWN TO THE SURFACE RESULTING  
IN AREAS WITH SUSTAINED WINDS OF 10-15 KTS. DUE TO ELEVATED WIND  
SPEEDS, THERE MAY BE BLOWING DUST (MORE LIKELY AT KIWA). WINDS  
WILL REMAIN ELEVATED NEAR 10 KTS IN THE AFTERNOON ON SUNDAY,  
BEFORE SUBSIDING A BIT SUNDAY EVENING. SKIES WILL BE MOSTLY CLEAR  
BEFORE THICKER MID AND HIGH-LEVEL CLOUDS MOVE INTO THE REGION LATE  
TOMORROW MORNING AND PERSIST THROUGH THE AFTERNOON.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
WINDS WILL RETAIN NORTHERLY AND WESTERLY COMPONENTS THROUGH  
SUNDAY MORNING WITH SPEEDS GENERALLY LESS THAN 15 KT. SUNDAY  
AFTERNOON, A SHIFT TO SOUTHWESTERLY FLOW IS LIKELY WITH SPEEDS  
REMAINING ELEVATED AROUND 10-15 KTS. AT KBLH, GUSTS TO 20 KTS WILL  
ALSO BE POSSIBLE TOMORROW AFTERNOON.  
 

 
   
FIRE WEATHER
 
 
MONDAY THROUGH FRIDAY:  
BREEZY CONDITIONS ARE ANTICIPATED ON MONDAY ACROSS SOUTHEAST  
CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY AS A DRY LOW PRESSURE  
SYSTEM ADVANCES ACROSS THE SOUTHWEST. TEMPERATURES WILL BE A FEW  
DEGREES BELOW NORMAL MONDAY THROUGH WEDNESDAY IN ASSOCIATION WITH  
THIS SYSTEM AND PERIODIC UPPER-LEVEL CLOUD COVER. WINDS WILL WEAKEN  
DURING THE MIDDLE PART OF THE WEEK AS HIGH PRESSURE REBUILDS, AND  
TEMPERATURES CLIMB BACK INTO THE UPPER 80S TO NEAR 90 THURSDAY AND  
FRIDAY. MIN AFTERNOON RH VALUES WILL MOSTLY FALL BETWEEN 15-20%  
ACROSS THE LOWER DESERTS TO 20-25% ACROSS THE HIGH TERRAIN.  
OVERNIGHT RECOVERIES WILL MOSTLY REACH BETWEEN 30-50% THROUGH THE  
PERIOD.  
 

 
   
SPOTTER INFORMATION STATEMENT
 
 
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.  
 

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

 
 

 
 
DISCUSSION...18/ROGERS  
AVIATION...FELDY/HIRSCH  
FIRE WEATHER...ROGERS  
 
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