787  
FXUS65 KPSR 260420  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
920 PM MST SAT MAR 25 2017  
   
SYNOPSIS
 
 
A WEAK UPPER LEVEL DISTURBANCE WILL EXIT THE AREA TONIGHT WITH  
HIGH PRESSURE MOVING IN FOR SUNDAY AND EARLY MONDAY. ANOTHER  
PACIFIC LOW PRESSURE SYSTEM WILL THEN AFFECT THE REGION LATE  
MONDAY THROUGH TUESDAY BRINGING CHANCES OF SHOWERS MAINLY TO THE  
HIGHER TERRAIN NORTH AND EAST OF PHOENIX. DRY AND WARMER WEATHER  
WILL RETURN FOR WEDNESDAY AND THURSDAY, BUT FOLLOWED BY YET  
ANOTHER PACIFIC STORM FRIDAY AND NEXT SATURDAY.  
 

 
   
DISCUSSION
 
 
UPPER LEVEL OPEN WAVE TROF CONTINUED TO PUSH EAST/SOUTHEAST ACROSS  
THE DESERT SOUTHWEST THIS EVENING; 500MB PLOT DATA DEPICTED SOME OF  
THE MOST SIGNIFICANT HEIGHT FALLS ACROSS FAR NORTHERN AZ WITH 110M  
SEEN AT FLAGSTAFF. COLDEST TEMPS ALOFT - MINUS 20C OR LOWER - WERE  
ALSO WELL TO THE NORTH OF THE PHOENIX AREA AND THIS PROVED TO BE A  
DRY SYSTEM FOR SOUTHERN ARIZONA. FOR THE MOST PART SKIES WERE SUNNY  
TODAY WITH JUST A BIT OF HIGH BASED CUMULUS DEVELOPING OVER NRN  
MARICOPA AND SOUTHERN GILA COUNTY AND AFTER SUNSET THE LOWER CLOUDS  
QUICKLY DISSIPATED. AS THE SYSTEM QUICKLY PUSHES OFF TO THE EAST  
TONIGHT, SKIES WILL CONTINUE TO CLEAR AS STRONGER DVV/SUBSIDENCE/Q  
DIVERGENCE MOVES IN BEHIND THE EXITING SYSTEM. AT 9 PM IR IMAGERY  
SHOWED GENLY CLEAR SKIES FROM PHOENIX WESTWARD. MAIN IMPACT OF THE  
PASSING SYSTEM TODAY WAS INCREASED WIND; A FEW LOCATIONS OVER THE  
CENTRAL DESERTS REPORTED PEAK GUSTS OVER 30 MPH INCLUDING PHOENIX  
AND IMPERIAL SAW SIMILAR GUSTS EARLIER IN THE EVENING BUT FOR THE  
MOST PART WINDS HAVE TAPERED OFF FOLLOWING SUNSET AND LACK OF  
MIXING. FORECASTS LOOK TO BE IN DECENT SHAPE AND NO UPDATES ARE  
NEEDED AT THIS TIME.  
   
PREVIOUS DISCUSSION
 
 
A WEAK SHORTWAVE TROUGH CONTINUES TO TRACK EASTWARD THROUGH  
ARIZONA EARLY THIS AFTERNOON WITH THE MAIN CIRCULATION CENTER  
MOVING THROUGH SOUTHWEST UTAH AND A WEAKER SECONDARY VORT MAX NEAR  
FLAGSTAFF. SKIES HAVE MOSTLY CLEARED ACROSS SOUTHERN ARIZONA AND  
SOUTHEAST CALIFORNIA ASIDE FROM A FEW HIGH BASED CU ACROSS LA PAZ  
AND NORTHERN MARICOPA COUNTIES. ANY SHOWER ACTIVITY REMAINS WELL  
NORTH OF OUR CWA NEAR THE VORT MAX AND EXPECT THIS ACTIVITY TO  
STAY OUT OF OUR AREA THROUGH THE REST OF TODAY.  
 
WEAK RIDGING ALOFT RETURNS STARTING TONIGHT LASTING THROUGH  
SUNDAY NIGHT, BUT TEMPERATURES WILL CHANGE VERY LITTLE THROUGH  
MONDAY. THE ACTIVE WEATHER PATTERN CONTINUES INTO NEXT WEEK AS  
ANOTHER QUICK MOVING PACIFIC LOW IS SET TO MOVE SOUTHEASTWARD INTO  
NORTHERN CALIFORNIA EARLY MONDAY AND THEN INTO NORTHWEST ARIZONA  
BY MONDAY AFTERNOON. AS WITH THE PREVIOUS SYSTEM, THIS ONE WILL  
AGAIN BE FAIRLY MOISTURE STARVED. HOWEVER, MODELS AGREE THIS  
SYSTEM WILL BE STRONGER AS IT DEEPENS AND CLOSE OFF OVER NORTHERN  
ARIZONA MONDAY NIGHT INTO EARLY TUESDAY. THE LATEST MODEL FORECAST  
HAS THE LOW TRACKING INTO CENTRAL ARIZONA TUESDAY MORNING BEFORE  
TURNING EASTWARD INTO NEW MEXICO TUESDAY NIGHT. SHOWER ACTIVITY  
WILL LIKELY BE SCATTERED AND MAINLY CONFINED TO HIGHER TERRAIN  
AREAS ON TUESDAY, BUT CAN'T RULE OUT A FEW SHOWERS INTO THE  
PHOENIX AREA. QPF AMOUNTS WILL BE ON THE LIGHT SIDE WITH MOST  
AREAS SEEING LESS THAN A TENTH OF AN INCH. WINDS WILL LIKELY BE AN  
ISSUE STARTING MONDAY AFTERNOON ACROSS SOUTHEAST CALIFORNIA AHEAD  
OF THE COLD FRONT AND AGAIN BEHIND THE FRONT ON TUESDAY. GUSTS  
APPROACHING 40 MPH WILL BE POSSIBLE AND A WIND ADVISORY MAY BE  
NEEDED FOR OUR WESTERN ZONES.  
 
SOME MODEL DISAGREEMENT EXISTS WITH THE EXIT TIMING OF THE  
TUESDAY SYSTEM, BUT GENERAL MODEL CONSENSUS SHOWS INCREASING  
SUBSIDENCE AND BUILDING HEIGHTS BY WEDNESDAY MORNING. THIS SHOULD  
LEAD TO A QUICK REBOUND IN TEMPERATURES BY WEDNESDAY AS HIGHS  
SHOULD EASILY CLIMB BACK INTO THE 80S OVER THE LOWER DESERTS FOR  
BOTH WEDNESDAY AND THURSDAY.  
 
FRIDAY AND SATURDAY...  
 
ALL MODELS ARE IN GENERAL AGREEMENT IN DEVELOPING YET ANOTHER  
PACIFIC TROF OVER AZ THIS PERIOD. MODELS HOWEVER ARE STILL  
CONFLICTED IN THE EVENTUAL TRACK OF THIS SYSTEM, WHICH HAS POTENTIAL  
TO BE THE STRONGEST, COLDEST, AND WETTEST SYSTEM IN THE SERIES.  
HOWEVER BIG DISPARITIES EXIST WITH THE MODEL GUIDANCE, WITH THE  
EUROPEAN SUGGESTING A MORE PROGRESSIVE TROF THROUGH AZ FRIDAY AND  
INTO NEW MEXICO FRIDAY NIGHT. THE GFS ON THE OTHER HAND FORECASTS A  
DEEP COLD CUTOFF LOW TO BECOME NEARLY STATIONARY OVER CENTRAL AZ  
FRIDAY AND SATURDAY. FORECAST CONFIDENCE IS VERY LOW THIS FAR OUT,  
SO PRECIP PROBABILITIES WILL BE SHADED TOWARD A SLIGHT CHANCE IN  
SOUTH CENTRAL AZ.  
 

 
   
AVIATION
 
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, AND KSDL:  
 
WEATHER SYSTEM CONTINUES TO PUSH OFF TO THE EAST AND FOLLOWING  
SUNSET SKIES HAVE CLEARED NICELY. EXPECT GENLY CLEAR SKIES INTO  
SUNDAY MORNING WITH SOME HIGH CIRRUS MOVING IN DURING THE DAY  
TOMORROW. WINDS WILL REMAIN FROM THE WEST PAST MIDNIGHT BUT SHOULD  
EVENTUALLY TURN EAST AFTER 08Z AND REMAIN THERE INTO THE EARLY  
AFTERNOON ON MONDAY. SINCE THE GUSTINESS HAS PRETTY MUCH ENDED WE DO  
NOT EXPECT ANY AVIATION CONCERNS FOR THE NEXT 24 HOURS AT LEAST.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
 
WEATHER SYSTEM CONTINUES TO PUSH OFF WELL TO THE EAST AND GRADIENTS  
HAVE RELAXED, AS SUCH WINDS HAVE TAPERED OFF AND THE GUSTINESS AT  
KIPL HAS SUBSIDED. EXPECT WEST WINDS TO CONTINUE INTO MID MORNING  
MONDAY BUT STAY MOSTLY BELOW 15KT. WINDS HAVE BEEN LESS AT KBLH AND  
SHOULD CONTINUE TO FAVOR THE NORTHWEST THROUGH NORTH INTO MONDAY  
MORNING WITH SPEEDS LESS THAN 12KT. SKIES TO BE CLEAR FOR THE MOST  
PART WITH POSSIBLY SOME THIN HIGH CLOUDS MOVING INTO THE AREA DURING  
THE DAY ON MONDAY. NOW THAT THE WINDS HAVE DIED OFF THERE ARE NO  
AVIATION CONCERNS FOR THE NEXT 24 HOURS AT LEAST.  
 
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.  
 

 
   
FIRE WEATHER
 
 
MONDAY THROUGH FRIDAY...  
ACTIVE STORM PATTERN WILL REMAIN OVER THE INTERMOUNTAIN WEST AT  
LEAST THROUGH THE END OF THE MONTH AND POSSIBLY INTO EARLY APRIL  
AS A SERIES OF PACIFIC STORMS PASS THROUGH. BREEZY WEATHER WILL  
REMAIN A COMMON FEATURE OF MOST AFTERNOONS/EARLY EVENINGS FOR THE  
DISTRICTS WITH DAYTIME HUMIDITY LEVELS RANGING 10-25 PERCENT AT  
THEIR DRIEST. MOST OF THE PACIFIC STORMS WILL TRAVEL THROUGH THE  
GREAT BASIN BEFORE SWEEPING INTO ARIZONA, ALLOWING FOR ABOVE  
NORMAL CHANCES OF PRECIPITATION FOR THE ARIZONA DISTRICTS BUT NEAR  
TO BELOW NORMAL CHANCES FOR PRECIP ALONG AND WEST OF THE COLORADO  
RIVER VALLEY. WITH AN ACTIVE STORM TRACK OVER THE AREA,  
TEMPERATURES WILL TREND MORE TOWARDS SEASONAL AVERAGES. PERIODS OF  
STRONGER WINDS MAY LEAD TO A LOCALLY ELEVATED FIRE DANGER AT  
TIMES THAT MAY TURN INTO CRITICAL FIRE WEATHER CONDITIONS FOR SOME  
LOCALES. A FAIR BIT OF UNCERTAINTY REMAINS WITH THE TRACK OF THE  
NEXT FEW SYSTEMS TO MOVE THROUGH THE REGION IN THE FAR EXTENDED  
PERIOD THAT MAY RAMP UP OR BACK OFF CONCERNS FOR  
ELEVATED/CRITICAL FIRE DANGER.  
 

 
   
SPOTTER INFORMATION STATEMENT
 
 
SPOTTER REPORTS WILL NOT BE NEEDED THROUGH THE WEEKEND.  
 

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

 
 

 
 
VISIT US ON FACEBOOK, TWITTER, AND AT WEATHER.GOV/PHOENIX  
 
DISCUSSION...CB  
PREVIOUS DISCUSSION...KUHLMAN/VASQUEZ  
AVIATION...CB  
FIRE WEATHER...NOLTE  
 
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