820  
FXUS65 KPSR 282148  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
248 PM MST SUN FEB 28 2021  
   
SYNOPSIS
 
 
COOLER AND WINDY CONDITIONS TODAY AS A DRY SYSTEM PASSES THROUGH.  
A COLD MORNING IS EXPECTED TO START THE WEEK WITH SOME LOWER  
DESERT SPOTS FALLING TO FREEZING. WARMER CONDITIONS ARE  
ANTICIPATED HEADING INTO MIDWEEK AS HIGH PRESSURE MOVES THROUGH  
THE INTERMOUNTAIN WEST. A LOW PRESSURE SYSTEM WILL BRING A CHANCE  
OF RAIN TO THE AREA DURING THE WEDNESDAY INTO THURSDAY TIMEFRAME.  
THEREAFTER, A RETURN TO ABOVE NORMAL NORMAL TEMPERATURES IS  
LIKELY BY FRIDAY AND INTO NEXT WEEKEND.  
 

 
   
DISCUSSION
 
 
IT IS PRETTY EASY TO PICK OUT WHERE THE SHORTWAVE TROUGH IS AND  
ITS ORIENTATION ON SATELLITE THIS AFTERNOON. SCATTERED CUMULUS,  
CLOSELY TIED TO THE TROUGH, HAS DEVELOPED WITH WHAT LITTLE MID  
LEVEL MOISTURE EXISTS AND ARE PUSHING SOUTHEAST THROUGH CENTRAL  
AND EASTERN AZ. THERE ARE EVEN A FEW WEEK ECHOES WITH SOME OF THE  
CUMULUS, BUT WITH THE VERY DRY SURFACE CONDITIONS IT WILL LIKELY  
BE AN INSURMOUNTABLE TASK FOR A RAIN DROP TO REACH THE SURFACE  
BEFORE EVAPORATING. THE BIGGEST AND MOST NOTICABLE IMPACT FROM  
THIS PASSING TROUGH TODAY HAS BEEN THE WINDS AND VERY DRY AIR. IT  
HAS BEEN BREEZY FROM THE GET-GO TODAY WITH GUSTS GENERALLY UP TO  
25-35 MPH, AND SOME LOCALIZED GUSTS UP TO 40 MPH, ACROSS OUR CWA.  
GUST MAGNITUDES IN SOUTHEAST CA AND SOUTHWEST AZ, WHERE A WIND  
ADVISORY IS STILL IN EFFECT, SHOULD GENERALLY LET UP OVER THE FEW  
HOURS. WINDS MOST LOCATIONS SHOULD SUBSIDE LATE THIS EVENING.  
WINDS ARE EXPECTED TO INCREASE ALOFT OUT OF THE NORTHEAST TONIGHT,  
AS THE TROUGH PUSHES AWAY, BUT THESE STRONGER WINDS ARE UNLIKELY  
TO DESERT FLOOR LOCATIONS GIVEN THE OVERNIGHT TIME PERIOD.  
 
ANOTHER SENSIBLE IMPACT FROM THIS TROUGH HAS BEEN MUCH COOLER  
CONDITIONS. TEMPERATURES EARLY THIS AFTERNOON ARE ROUGHLY 10  
DEGREES COOLER THAN THIS TIME YESTERDAY. MOST LOWER DESERT  
LOCATIONS ARE STRUGGLING TO EVEN REACH THE MID 60S. WE WILL SEE  
THE ABNORMALLY COOL CONDITIONS EXTEND THROUGH MONDAY MORNING.  
POTENTIALLY THE COLDEST TEMPERATURES IN ABOUT A MONTH ARE EXPECTED  
TOMORROW MORNING. NBM IS PROJECTING LOWS ACROSS THE LOWER DESERTS  
GENERALLY IN THE 35-40 DEGREE RANGE, WITH SOME OF THE TYPICAL COLD  
SPOTS, LIKE PINAL COUNTY, LIKELY FALLING NEAR OR BELOW FREEZING.  
ELEVATED WINDS THROUGH THE NIGHT COULD CERTAINLY KEEP TEMPERATURES  
LOCALLY A LITTLE WARMER THAN ANTICIPATED, BUT ON THE FLIP SIDE  
LIGHT WINDS PAIRED WITH THE VERY DRY CONDITIONS AND CLEAR SKIES  
COULD ALSO PUSH TEMPERATURES EVEN A DEGREE OR TWO COOLER THAN  
CURRENTLY FORECASTED. A FREEZE WARNING HAS BEEN ISSUED FOR  
PORTIONS OF PINAL COUNTY FOR TOMORROW MORNING.  
 
TEMPERATURES WILL REBOUND QUICKLY INTO THE AFTERNOON MONDAY AND  
INTO MIDWEEK AS A RIDGE MIGRATES SWIFTLY ACROSS THE INTERMOUNTAIN  
WEST. THE 80 DEGREE MARK IS NOT OUT OF THE QUESTION FOR PHOENIX  
TUESDAY WITH AN EVEN BETTER CHANCE WEDNESDAY NOW WITH POTENTIAL  
WARM AIR ADVECTION AHEAD OF OUR NEXT SYSTEM. THE NBM SUGGESTS  
ROUGHLY A 20 PERCENT CHANCE OF REACHING 80 TUESDAY AND 65 PERCENT  
CHANCE WEDNESDAY, WHICH IS STILL WELL BELOW THE DAILY RECORDS THAT  
ARE NEAR 90 DEGREES.  
 
BY MIDWEEK, FOCUS WILL SHIFT TO A PACIFIC LOW PRESSURE SYSTEM AND  
THE POTENTIAL FOR RAINFALL ACROSS THE DESERT SOUTHWEST. ENSEMBLE  
SYSTEMS HAVE GENERALLY COME INTO BETTER AGREEMENT AND THIS IS  
REFLECTED IN THE POPS, WHICH CONTINUE TO INCREASE. THE 12Z NBM IS  
NOW SHOWING A 75% PROBABILITY OF 24-HR QPF GREATER THAN 0.01"  
ACROSS CENTRAL PORTIONS OF AZ. MAIN SOURCE OF UNCERTAINTY SEEMS TO  
BE WITH THE AMPLITUDE OF THE WAVE. THE TRACK HAS TRENDED A LITTLE  
FURTHER NORTHWEST, BUT EPS AND NAEFS STILL SUPPORT A MODERATE IVT  
PLUME INTO AZ. RIGHT NOW, BEST CHANCE FOR RAIN APPEARS TO BE  
WEDNESDAY NIGHT INTO THURSDAY MORNING, THOUGH SOME GEFS MEMBERS  
SUGGEST SHOWERS COULD DEVELOP AS EARLY AS WEDNESDAY AFTERNOON.  
GREATEST QPF WILL FAVOR THE HIGHER TERRAIN NORTH AND EAST OF  
PHOENIX.  
 
NCEP CLUSTER ANALYSIS REVEALS THAT NEARLY THREE QUARTERS OF THE  
MEMBERS RESULT IN A SCENARIO THAT WOULD PRODUCE A WIDESPREAD TENTH  
OF AN INCH OF PRECIPITATION FROM MARICOPA COUNTY NORTH AND  
EASTWARD AND EVEN UP TO A QUARTER OF AN INCH CLOSER TO THE  
MOGOLLON RIM. A FEW GEFS AND A COUPLE EPS MEMBERS EVEN SUGGEST  
RAINFALL AMOUNTS NEAR HALF AN INCH IN PHOENIX, THOUGH THE  
PROBABILITY OF THIS OCCURRING IS LESS THAN 5 PERCENT. THE WPC  
FORECAST HAS GENERALLY BEEN IN LINE WITH MOST ENSEMBLE MEANS WITH  
AROUND 0.1" IN THE PHOENIX AREA TO UP TO 0.25"-0.50" TO THE NORTH  
AND EAST.  
 
IN THE WAKE OF THE LOW PRESSURE SYSTEM, LATEST GEFS/EPS MEANS  
INDICATE AN ANOMALOUSLY STRONG RIDGE WILL BUILD ACROSS THE  
INTERMOUNTAIN WEST. PROBABILITIES ARE HIGH THAT WE WILL SEE THE  
WARMEST CONDITIONS OF THE YEAR SO FAR BY NEXT WEEKEND. HIGH  
TEMPERATURES IN PHOENIX WILL LIKELY REACH THE LOWER 80S BY FRIDAY  
AND PERHAPS EVEN THE MID 80S BY SATURDAY.  
 

 
   
AVIATION
 
UPDATED AT 1650Z.  
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:  
 
WINDS WILL CONTINUE TO BE THE MAIN WEATHER CONCERN THROUGH EARLY  
EVENING UNDER MOSTLY CLEAR SKIES. NORTHWESTERLY WINDS WILL REMAIN  
GUSTY TO AROUND 25 KTS THROUGH MUCH OF THE AFTERNOON. A GUSTY NNW  
HEADING MAY BE ENOUGH OF A CROSS RUNWAY COMPONENT TO IMPACT  
ARRIVAL RATES. GUSTS SHOULD QUICKLY DIMINISH WITH SUNSET WHILE  
DIRECTIONS WILL TREND MORE TOWARDS A NE DIRECTION PROGRESSING  
THROUGH TONIGHT. WINDS SHOULD EVENTUALLY SHIFT DIRECTLY OUT OF THE  
EAST FOR AT LEAST KPHX AND KIWA AFTER SUNRISE MONDAY MORNING,  
LIKELY STAYING EASTERLY ALL DAY MONDAY.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
 
GUSTY NORTHERLY WINDS WILL CONTINUE FOR MUCH OF TODAY UNDER CLEAR  
SKIES. GUSTY WINDS TO AROUND 30KTS ARE EXPECTED FOR KBLH THROUGH  
THIS AFTERNOON. WINDS WILL EVENTUALLY DIMINISH, BUT STAY OUT OF  
THE NORTH THROUGH MONDAY MORNING. FOR KIPL, LOOK FOR NORTHERLY  
WINDS TO BE GUSTY AT TIMES THROUGH THIS AFTERNOON WITH SPEEDS TO  
AROUND 20 KTS. WINDS WILL EVENTUALLY RELAX AND TURN MORE OF THE  
THE WEST THIS EVENING, LASTING THROUGH THE REST OF THE PERIOD.  
 

 
   
FIRE WEATHER
 
 
TUESDAY THROUGH SATURDAY:  
RELATIVELY WARM AND DRY CONDITIONS ARE LIKELY TUESDAY. BREEZY  
CONDITIONS ARE THEN EXPECTED TO DEVELOP AHEAD OF A PACIFIC LOW  
PRESSURE SYSTEM WEDNESDAY. THIS SYSTEM WILL ALSO BRING A CHANCE OF  
RAIN TO THE DESERT SOUTHWEST WEDNESDAY NIGHT. HIGHEST RAIN TOTALS  
ARE LIKELY IN THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX,  
HOWEVER WETTING RAINS WILL STILL BE POSSIBLE ACROSS THE LOWER  
DESERTS. IN THE WAKE OF THE LOW PRESSURE SYSTEM, A WARMING TREND  
IS ANTICIPATED ALONG WITH A RETURN TO ABOVE NORMAL TEMPERATURES  
AND SEASONABLY DRY CONDITIONS BY FRIDAY.  
 

 
   
SPOTTER INFORMATION STATEMENT
 
 
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.  
 

 
   
PSR WATCHES/WARNINGS/ADVISORIES
 
 
AZ...FREEZE WARNING FROM 2 AM TO 9 AM MST MONDAY FOR AZZ553.  
 
WIND ADVISORY UNTIL 4 PM MST THIS AFTERNOON FOR AZZ530>533-535-  
536.  
 
CA...WIND ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR CAZ560-564-565-  
568>570.  
 

 
 

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