747  
FXUS65 KPSR 131752  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
1052 AM MST THU AUG 13 2020  
   
UPDATE
 
UPDATED AVIATION DISCUSSION.  
 

 
   
SYNOPSIS
 
 
STRONG HIGH PRESSURE WILL REMAIN SITUATED ACROSS THE SOUTHWESTERN  
U.S. INTO NEXT WEEK BRINGING CONTINUED HOT CONDITIONS. HIGH  
TEMPERATURES ACROSS THE LOWER DESERTS WILL APPROACH OR EXCEED 115  
DEGREES STARTING TODAY AND LASTING THROUGH AT LEAST EARLY NEXT  
WEEK. ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE TODAY BEFORE  
CHANCES DECREASE TOMORROW. POTENTIAL FOR A SLIGHTLY BETTER  
MONSOON SET-UP THIS WEEKEND OR EARLY NEXT WEEK.  
 

 
   
DISCUSSION
 
 
STRONG HIGH PRESSURE OVER SOUTHERN NEW MEXICO WILL CONTINUE TO  
STRENGTHEN AND PROGRESS NORTHWESTWARD, POSITIONING ITSELF OVER US  
FRIDAY AND NEAR THE NEVADA/UTAH BORDER BY SUNDAY. THE CENTER OF  
THE HIGH THEN APPEARS TO SLOWLY DRIFT BACK SOUTH TOWARDS THE  
MIDDLE OF NEXT WEEK. THIS WILL KEEP VERY WARM TEMPERATURES IN  
PLACE, WITH HIGHS APPROACHING OR EXCEEDING 115 DEGREES EACH DAY.  
THE EXCESSIVE HEAT WARNING WILL EXPAND AND COVER THE ENTIRE  
FORECAST AREA BY TOMORROW AND WILL REMAIN IN EFFECT THROUGH  
MONDAY.  
 
IN TERMS OF MOISTURE, SOUTH-SOUTHWEST FLOW ON THE WESTERN  
PERIPHERY OF THE HIGH IS CURRENTLY STREAMING IN THICKER MID- AND  
UPPER-LEVEL MOISTURE. THIS IS ADVECTING THICKER CLOUDS, EMBEDDED  
WITH ISOLATED VIRGA, INTO OUR FORECAST AREA. THESE THICKER CLOUDS  
WILL LIKELY PROHIBIT TEMPERATURES FROM DROPPING TOO MUCH  
OVERNIGHT, WITH PHOENIX LIKELY ADDING ANOTHER 90 DEGREE OR ABOVE  
LOW TEMPERATURE TO THE TALLY. 1 INCH OR GREATER PWS WILL BE LIKELY  
AGAIN TODAY, WITH THE GREATEST VALUES ACROSS THE WESTERN PORTIONS  
OF MARICOPA & PINAL COUNTIES WESTWARD INTO THE COLORADO RIVER  
VALLEY. BEST STORM COVERAGE WILL BE IN THIS AREA, AS WELL AS  
ACROSS THE MOUNTAINOUS TERRAIN NORTH, SOUTH, AND EAST OF PHOENIX.  
ANY SHOWER OR STORM THAT MANAGES TO DEVELOP WILL BE BRIEF AND BE  
CAPABLE OF PRODUCING LIGHTING, GUSTY ERRATIC WINDS, HEAVY RAIN,  
AND BLOWING DUST.  
 
AS HIGH PRESSURE MOVES OVERHEAD TOMORROW, STORM CHANCES WILL  
DECREASE A BIT DUE TO A MORE STABLE AIRMASS A LOFT. HOWEVER, IT  
DOES APPEAR THAT ONCE THE CENTER OF THE HIGH IS NORTH OF US,  
PRETTY MUCH SATURDAY ONWARD, THERE WILL BE A MORE FAVORABLE  
PATTERN ALOFT THAT COULD POTENTIALLY DRIVE SOME STORMS INTO THE  
LOWER DESERTS, ESPECIALLY ON SUNDAY. ON SUNDAY, THERE CURRENTLY APPEARS  
TO BE BETTER POTENTIAL FOR A STRONGER OUTFLOW TO PUSH IN FROM THE  
EAST AND INTERACT WITH A MOIST AND UNSTABLE ATMOSPHERE IN THE  
LOWER DESERTS AND POSSIBLY REGENERATE NEW STORMS. DUE TO THIS  
POTENTIAL FOR STORMS ON SUNDAY, THE NBM IS SHOWING A DECENT SPREAD  
IN THE HIGH TEMPERATURE FORECAST. WE WILL CONTINUE TO MONITOR THE  
SITUATION, ANY LITTLE CHANGE IN THE FORECASTED POSITION OF THE  
HIGH, COULD LEAD TO STORM CHANCES SHIFTING TO ANOTHER DAY. DUE TO  
THE UNCERTAINTIES, THE EXCESSIVE HEAT WARNING WAS NOT EXTENDED  
INTO THE MIDDLE OF NEXT WEEK AT THIS TIME. HOWEVER, IF  
TEMPERATURES CONTINUE TO TREND AS WARM AS THEY HAVE BEEN TRENDING,  
THE WARNING MAY NEED TO BE EXTENDED.  
 

 
   
AVIATION
 
UPDATED AT 1750Z.  
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:  
WINDS WILL REMAIN VERY LIGHT AND OFTEN VARIABLE FOR THE NEXT FEW  
HOURS BEFORE BECOMING PREDOMINANTLY WESTERLY BETWEEN 19-21Z. WINDS  
ARE LIKELY TO REMAIN WESTERLY THROUGH THE EVENING WITH THE  
NIGHTLY EASTERLY WINDS OCCURRING A FEW HOURS AFTER SUNSET.  
OCCASIONAL AFTERNOON BREEZES OF 15-20 KTS ARE POSSIBLE. AFTERNOON  
THUNDERSTORMS ARE FAVORED TO REMAIN SOUTH AND NORTH OF THE  
TERMINAL AREA. HOWEVER, THERE IS A 20-30% CHANCE ISOLATED  
THUNDERSTORMS COULD FORM OVER WESTERN MARICOPA COUNTY, INCLUDING  
THE WESTERN HALF OF THE PHOENIX AREA. FOR NOW, CONFIDENCE IN  
STORMS DIRECTLY IMPACTING ANY PARTICULAR TERMINAL IS TOO LOW TO  
MENTION IN THE TAFS, BUT OF ALL THE SITES, KDVT AND KSDL SEEM THE  
MOST LIKELY TO SEE STORMS (LESS THAN 20% CHANCE). IF THESE STORMS  
DO DEVELOP, ANY OUTFLOWS WOULD LIKELY REINFORCE THE WESTERLY WINDS  
AT STRONGER SPEEDS THAN WHAT IS CURRENTLY IN THE TAFS.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
FOR KIPL, WINDS ARE EXPECTED TO FOLLOW TYPICAL DIURNAL TRENDS AT  
SPEEDS MOSTLY AOB 10 KTS. AT KBLH, WINDS WILL BECOME WESTERLY BY  
THE LATE AFTERNOON AND THEN SOUTHERLY DURING THE OVERNIGHT HOURS,  
ESPECIALLY IF OUTFLOWS FROM DISTANT THUNDERSTORMS CAN REACH THE  
AREA. OTHERWISE, THERE MAY ALSO BE EXTENDED PERIODS OF A  
LIGHT/VARIABLE WIND AT BOTH SITES.  
 

 
   
FIRE WEATHER
 
 
SATURDAY THROUGH WEDNESDAY:  
VERY HOT TEMPERATURES AND OVERALL DRY CONDITIONS WILL PERSIST  
THROUGH THE MIDDLE OF NEXT WEEK. MINIMUM HUMIDITIES THROUGH THE  
PERIOD WILL DROP INTO THE TEENS EACH DAY WITH OVERNIGHT RECOVERIES  
GENERALLY BETWEEN 25-50%. WINDS WILL GENERALLY FOLLOW TYPICAL  
DIURNAL/TERRAIN INFLUENCES WITH SPEEDS REMAINING LIGHT ASIDE FROM  
SOME TYPICAL AFTERNOON BREEZES. THUNDERSTORM ACTIVITY WILL BE  
LIMITED WITH ISOLATED STORMS POSSIBLE BUT FAVORING THE HIGH  
TERRAIN.  
 

 
   
CLIMATE
 
 
RECORD HIGH TEMPERATURES:  
 
DATE PHOENIX YUMA EL CENTRO  
---- ------- ---- ---------  
8/13 115 IN 2012 117 IN 2012 116 IN 2012  
8/14 117 IN 2015 115 IN 2019 116 IN 2015  
8/15 115 IN 2015 117 IN 2015 118 IN 2019  
8/16 113 IN 2013 115 IN 1992 117 IN 2016  
8/17 114 IN 2013 114 IN 1992 115 IN 2015  
8/18 112 IN 2011 116 IN 1960 115 IN 2015  
 

 
   
SPOTTER INFORMATION STATEMENT
 
 
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.  
 

 
   
PSR WATCHES/WARNINGS/ADVISORIES
 
 
AZ...EXCESSIVE HEAT WARNING UNTIL 8 PM MST MONDAY FOR AZZ530>556-  
559>562.  
 
HEAT ADVISORY UNTIL 8 PM MST MONDAY FOR AZZ557-558-563.  
 
CA...EXCESSIVE HEAT WARNING UNTIL 8 PM PDT MONDAY FOR CAZ565>567-569-  
570.  
 
EXCESSIVE HEAT WARNING FROM 10 AM FRIDAY TO 8 PM PDT MONDAY FOR  
CAZ560>564-568.  
 

 
 

 
 
DISCUSSION...FELDKIRCHER  
AVIATION...ROGERS/MO  
FIRE WEATHER...FELDKIRCHER  
CLIMATE...MO  
 
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