536  
FXUS65 KPSR 120508  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
1008 PM MST SUN APR 11 2021  
   
UPDATE
 
UPDATED AVIATION DISCUSSION.  
 

 
   
SYNOPSIS
 
 
WITH HIGH PRESSURE SLOWLY BEING REPLACED BY THE INFLUENCE OF A  
WEATHER DISTURBANCE NORTH OF THE AREA, TEMPERATURES WILL STEADILY  
COOL BACK NEAR THE SEASONAL NORMAL BY THE MIDDLE OF THE WEEK.  
THIS PATTERN WILL ENSURE DRY WEATHER CONTINUES WITH LOCALLY BREEZY  
CONDITIONS DURING THE MIDDLE OF THE WEEK. TEMPERATURES SHOULD  
GRADUALLY MODERATE SOMEWHAT WARMER HEADING INTO NEXT WEEKEND.  
 

 
   
DISCUSSION
 
 
OBJECTIVE ANALYSIS THIS AFTERNOON SHOWS A WEAK SYNOPTIC FLOW  
PATTERN OVER THE REGION WITH A WEAK LOW AMPLITUDE SHORTWAVE TROUGH  
ALONG THE WESTERN COASTLINE. SCATTERED TO BROKEN CIRRUS ARE SEEN  
SPREADING EASTWARD OVER THE AREA DOWNSTREAM OF THIS SHORTWAVE.  
FORECAST SOUNDINGS INDICATE THE HIGH CLOUDS MAY STILL BECOME A  
LITTLE THICKER THROUGH THE REST OF THE AFTERNOON, BUT IT DOES NOT  
APPEAR THEY WILL HAVE TOO MUCH INFLUENCE ON THE MAX TEMPERATURES  
EXPECTED IN THE LOW 90S AS NBM MAINTAINS ONLY A 2-3 DEGREE  
SPREAD.  
 
BY SUNRISE MONDAY MORNING THE SHORTWAVE SHOULD MOSTLY BE EAST OF  
THE AREA WITH SKIES CLEARING UP IN ITS WAKE. HOWEVER, A GENERAL  
CYCLONIC FLOW SHOULD PERSIST ACROSS THE REGION AS A BROAD TROUGH  
PATTERN IS ESTABLISHED ACROSS THE WESTERN CONUS. WITHIN THIS BROAD  
TROUGH PATTERN, A SHORTWAVE TROUGH ON THE WESTERN FLANK IS  
EXPECTED TO DIG INTO THE PACIFIC NORTHWEST BY THE END OF MONDAY.  
THIS SHORTWAVE WILL EVENTUALLY BECOME CUT OFF TUESDAY INTO  
WEDNESDAY AS A SIGNIFICANT BLOCKING PATTERN SETS UP ACROSS THE  
EASTERN PACIFIC AND THE ENTIRE CONUS. ALTHOUGH THE DEVELOPING CUT-  
OFF LOW WILL LARGELY REMAIN WELL TO OUR NORTH, IT WILL LEAD TO  
INCREASING WESTERLY FLOW TUESDAY INTO WEDNESDAY AND BREEZY TO  
LOCALLY WINDY DAYTIME CONDITIONS. WIND GUSTS BOTH DAYS OF 20-30  
MPH ARE LIKELY FOR THE BULK OF THE AREA WITH NEAR ADVISORY LEVEL  
WINDS POSSIBLE ACROSS SOUTHEAST CALIFORNIA. THE INCREASED WINDS  
AND LOW DAYTIME RHS SHOULD AGAIN BRING ANOTHER PERIOD OF ELEVATED  
FIRE WEATHER CONCERNS. TEMPERATURES WILL SLOWLY RETREAT STARTING  
TUESDAY AS UPPER LEVEL HEIGHTS GET SUPPRESSED FROM THE LOW TO OUR  
NORTH. BY WEDNESDAY, HIGH TEMPERATURES ARE FORECAST TO FALL BACK  
TO NEAR NORMAL READINGS, THE FIRST TIME IN OVER TWO WEEKS.  
 
THE BLOCKING PATTERN SHOULD LAST THROUGH LATE WEEK KEEPING MOSTLY  
ZONAL DRY WESTERLY FLOW OVER OUR REGION. THE LOW TO OUR NORTH WILL  
GRADUALLY WEAKEN BEFORE LIKELY BECOMING AN OPEN WAVE BY THURSDAY OR  
FRIDAY ALLOWING HEIGHTS ALOFT TO SLOWLY RISE OVER OUR REGION. THIS  
SHOULD MARK THE BEGINNING OF A SLOW UPWARD CLIMB IN TEMPERATURES,  
BUT SUB 90 DEGREE READINGS ARE LIKELY TO STAY THROUGH AT LEAST  
FRIDAY AND NEAR 90 BY SATURDAY. MODEL ENSEMBLES SHOW OBVIOUS  
DISAGREEMENT AND LARGER SPREAD IN A TRANSITION PERIOD FOR NEXT  
WEEKEND, BUT A BUILDING RIDGE TO OUR WEST AND A SLOW WARMING TREND  
LOOKS TO BE SLIGHTLY FAVORED. HOWEVER, LATEST ENSEMBLE CLUSTERS  
SHOW AROUND 60% OF GLOBAL MEMBERS SUPPORT A TRAILING SHORTWAVE  
INTO THE WEEKEND, BUT THIS MAY JUST LIMIT HOW QUICKLY TEMPERATURES  
WARM BACK UP.  
 

 
   
AVIATION
 
UPDATED AT 0510Z.  
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:  
A WEAK UPPER LEVEL LOW PRESSURE SYSTEM WILL MOVE THROUGH THE  
DESERT SOUTHWEST OVERNIGHT. MID AND HIGH CLOUDS ASSOCIATED WITH  
THIS SYSTEM WILL PERSIST TONIGHT, BEFORE CLEARING OUT MONDAY  
MORNING. OTHERWISE, WINDS WILL GENERALLY REMAIN DIURNAL AT ALL  
TAF SITES. THERE WILL LIKELY BE A PERIOD OF SOUTHERLY CROSSWINDS  
AT KPHX EARLY MONDAY AFTERNOON, THOUGH SPEEDS WILL GENERALLY  
REMAIN BELOW 12 KT.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
NO AVIATION WEATHER IMPACTS ANTICIPATED. MID AND HIGH CLOUDS  
ASSOCIATED WITH A WEAK UPPER LEVEL LOW PRESSURE SYSTEM WILL  
PERSIST EARLY TONIGHT, BEFORE CLEARING OUT EARLY MONDAY MORNING.  
OCCASIONAL BREEZINESS IS LIKELY MONDAY AFTERNOON, PARTICULARLY AT  
KBLH WHERE SOUTHERLY WINDS WILL LIKELY REACH 12 KT.  
 

 
   
FIRE WEATHER
 
 
WEDNESDAY THROUGH SUNDAY:  
NEAR NORMAL TEMPERATURES ARE EXPECTED DURING THE MIDDLE OF THE  
WEEK, BUT SHOULD GRADUALLY WARM BACK UP DURING THE WEEKEND, WITH  
HIGHS RETURNING TO THE LOW 90S AREA WIDE BY SUNDAY. AFTERNOON  
BREEZINESS WILL BE COMMON WITH THE TYPICAL UPSLOPE FAVORED AREAS  
EXPERIENCING THE STRONGEST GUSTS. STRONGER WINDS WILL BE LIKELY  
DURING THE MIDDLE OF THE WEEK YIELDING A PERIOD OF ELEVATED FIRE  
DANGER, PRIMARILY WEDNESDAY. DRY CONDITIONS WILL ALSO PREVAIL  
THROUGH THE WEEK WITH AFTERNOON MINIMUM HUMIDITY VALUES FALLING TO  
NEAR 10% WHILE OVERNIGHT RECOVERY WILL BE POOR ONLY BOUNCING BACK  
TO A 25-40% RANGE. THE WEATHER CONDITIONS MUCH OF NEXT WEEK WILL  
PROVIDE AN EXCELLENT OPPORTUNITY FOR PRESCRIBED BURNING OPERATIONS  
DURING THE MORNING AND EARLY AFTERNOON HOURS.  
 

 
   
SPOTTER INFORMATION STATEMENT
 
 
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.  
 

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

 
 

 
 
DISCUSSION...BENEDICT/KUHLMAN  
AVIATION...HIRSCH  
FIRE WEATHER...BENEDICT/MO/KUHLMAN  
 
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