757  
FXUS65 KPSR 270544 AAA  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
1045 PM MST WED APR 26 2017  
   
UPDATE
 
UPDATED AVIATION DISCUSSION.  
   
SYNOPSIS
 
 
A SERIES OF MAINLY DRY PACIFIC WEATHER DISTURBANCES WILL MOVE ACROSS  
THE WESTERN STATES THROUGH EARLY NEXT WEEK. THESE SYSTEMS WILL KEEP  
AFTERNOON TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL, ALONG WITH  
BREEZY AFTERNOONS AND EVENINGS. A STRONGER DISTURBANCE IS EXPECTED  
TO MOVE ACROSS NORTHERN ARIZONA ON FRIDAY, BRINGING WINDY  
CONDITIONS, AND THE POTENTIAL FOR SHOWERS TO THE EASTERN ARIZONA  
MOUNTAINS.  
 

 
   
DISCUSSION
 
 
A BIT OF A CALMER EVENING WHEN COMPARED TO LAST NIGHT, WHICH SOME  
WIDESPREAD STRONG WINDS AND EVEN SOME LOFTED BLOWING DUST ACROSS THE  
REGION. WEAK SHORTWAVE RIDGING PASSING OVER THE REGION HAS REDUCED  
WINDS THROUGH THE COLUMN QUITE A BIT, WITH SUSTAINED WINDS REMAINING  
MAINLY AOB 25 MPH. RELATIVELY LIGHT WINDS ARE EXPECTED TO CONTINUE  
THROUGH THURSDAY BEFORE ANOTHER RATHER STRONG UPPER LOW DROPPING  
INTO THE 4-CORNERS REGIONS BRINGS ANOTHER ROUND OF STRONG WINDS AND  
HIGH FIRE DANGER LEVELS ON FRIDAY. AS FAR AS THE SHORT TERM IS  
CONCERNED, OTHER THAN SOME VERY MINOR EDITS TO THE HOURLY GRIDS,  
INHERITED FORECASTS STILL LOOK GOOD.  
 

 
   
PREVIOUS DISCUSSION
 
 
TONIGHT AND THURSDAY...  
 
DRY NORTHWEST FLOW ALOFT WILL CONTINUE TO PROVIDE MOSTLY CLEAR SKIES  
AND WARMER TEMPERATURES THROUGH THURSDAY. AFTERNOON WESTERLY BREEZES  
IN THE 10 TO 20 MPH ARE ALSO FORECAST.  
 
FRIDAY AND FRIDAY NIGHT...  
 
ANOTHER BUT STRONGER DISTURBANCE, UNDER NORTHWESTERLY FLOW ALOFT, IS  
FORECAST TO DEEPEN ACROSS AZ FRIDAY AFTERNOON AND NIGHT. STRONG  
HEIGHT FALLS SWEEPING IN FROM NORTHWEST AZ FRIDAY AFTERNOON, THEN  
INTO EAST CENTRAL AZ FRIDAY EVENING PORTEND ANOTHER WINDY EPISODE.  
A FIRE WEATHER WATCH HAS ALSO BEEN POSTED FRIDAY FOR THE COLORADO  
RIVER VALLEY EAST TO PHOENIX AND POINTS EAST OVER OUR SOUTHERN GILA  
COUNTY MOUNTAINS.  
 
ADDITIONALLY, MODELS HAVE BEEN FORECASTING A MODERATE SURGE OF LOW  
LEVEL MOISTURE FROM MEXICO FRIDAY AFTERNOON INTO SOUTH CENTRAL AND  
SOUTHEAST AZ. HOWEVER THE LACK OF MORNING WEATHER BALLOON DATA FROM  
NORTHWEST MEXICO MAY HAVE CAUSED THE 12Z MODELS TO FORECAST MORE  
MOISTURE THAN PREVIOUS MODEL RUNS. NONE THE LESS, AN INCREASINGLY  
STRONG DYNAMICAL PATTERN WITH ENHANCED VERTICAL MOTION FIELDS OVER  
EAST CENTRAL AZ FRIDAY, INCLUDING PARTS OF OUR ZONE 24, STILL  
WARRANT A SLIGHT CHANCE SHOWERS OR THUNDERSTORMS.  
 
CLEARING SKIES WITH A DRIER AIRMASS IS EXPECTED LATER FRIDAY NIGHT  
ALONG WITH DIMINISHING BREEZES.  
 
SATURDAY AND SATURDAY NIGHT...  
 
SATURDAY WILL BE THE COOLEST DAY AFTER FRIDAYS FRONTAL PASSAGE.  
BREEZY TO WINDY CONDITIONS ARE ALSO EXPECTED. THE WINDIEST AREAS  
SATURDAY AFTERNOON WILL OCCUR DOWN THE COLORADO RIVER VALLEY WHERE  
NORTHERLY GUSTS TO 40 MPH ARE POSSIBLE.  
 
SUNDAY THROUGH WEDNESDAY...  
 
DRY NORTHWEST FLOW ALOFT ALONG WITH NEAR NORMAL TEMPERATURES ARE  
FORECAST. NORMAL HIGH TEMPERATURES FOR THE LOWER DESERTS ARE IN THE  
LOWER 90S FOR THE FIRST WEEK OF MAY. MOSTLY CLEAR SKIES ARE ALSO  
FORECAST THIS PERIOD.  
 

 
   
AVIATION
 
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, AND KSDL:  
 
ONCE THEY DEVELOP (AT OR SHORTLY AFTER MIDNIGHT), TYPICAL EASTERLY  
DIURNAL WINDS (IN THE 7-10 KT RANGE) ARE EXPECTED TO PERSIST  
THROUGH MIDDAY ON THURSDAY, THEN SWITCH TO WESTERLY ON THURSDAY  
AFTERNOON, WITH SUSTAINED WINDS RISING INTO THE 10-12 KNOT RANGE  
DURING THE LATE AFTERNOON/EARLY EVENING HOURS. LIGHTER WESTERLY  
WINDS TO PERSIST WELL INTO THU NIGHT. SCT-BKN DECKS MAINLY AOA 25  
KFT TO PERSIST THROUGH THE TAF PERIOD.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
 
WESTERLY TO NORTHWESTERLY WINDS TO PERSIST THROUGH THE TAF PERIOD AT  
BOTH SE CA TAF SITES, WITH SPEEDS REMAINING MAINLY IN THE 7-10 KT  
RANGE. SCT TO BKN DECKS PRIMARILY AOA 25 KFT PERSIST THROUGH THE  
TAF PERIOD AS WELL  
 
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.  
 

 
   
FIRE WEATHER
 
 
SATURDAY THROUGH WEDNESDAY:  
 
A SHARP COOLING TREND WILL SETTLE INTO THE REGION AS A MOSTLY DRY  
STORM SYSTEM SWEEPS THROUGH THE GREAT BASIN AND DOWN THROUGH THE  
SOUTHWEST FRIDAY INTO SATURDAY. ON SATURDAY, BREEZY CONDITIONS FROM  
THE NORTH WILL PERSIST OVER THE WESTERN DESERTS AND WITH MINIMUM RH  
VALUES TO STAY MOSTLY BELOW 10 PERCENT AREA-WIDE, WE CAN EXPECT  
CONTINUED DANGEROUS FIRE WEATHER CONDITIONS OUT WEST DURING THE  
AFTERNOON HOURS.  
 
DRY AND WARMER CONDITIONS ARE EXPECTED SUNDAY INTO MONDAY  
 
LESS WIND IS EXPECTED TODAY AS COMPARED TO YESTERDAY WITH SPEEDS  
MOSTLY BELOW 12 KTS OVER THE NEXT 24 HOURS AT BOTH TAF SITES. AT  
KIPL, LIGHT AND VARIABLE WINDS WILL PERSIST UNTIL ABOUT 20Z WHEN  
THE WINDS WILL THEN SHIFT TO SOUTHEAST. AFTER SUNSET, NEAR 02Z,  
WINDS WILL SHIFT BACK TO THE WEST-NORTHWEST. AT KBLH, LIGHT AND  
VARIABLE WINDS WILL CONTINUE THIS MORNING BEFORE SHIFTING TO THE  
WEST EARLY THIS AFTERNOON NEAR 20Z. AS HIGH  
PRESSURE BUILDS INTO THE AREA FROM THE WEST. BY MONDAY HIGH  
TEMPERATURES OVER THE DESERTS WILL CLIMB INTO THE MID 90S FOR THE  
MOST PART WITH MINIMUM RH VALUES TO STAY MOSTLY IN THE SINGLE  
DIGITS. LESS WIND IS EXPECTED ALTHOUGH WE SHOULD SEE CONTINUED  
AFTERNOON AND EARLY EVENING BREEZES ACROSS MUCH OF THE AREA,  
FAVORING THE WEST. ANOTHER WEATHER SYSTEM WILL PUSH ACROSS THE  
REGION TUESDAY/WEDNESDAY, BRINGING BREEZY CONDITIONS BACK TO THE  
AREA AND A VERY VERY SLIGHT CHANCE OF RAIN ON WEDNESDAY TO THE  
HIGHER TERRAIN OF SOUTHERN GILA COUNTY.  
 

 
   
SPOTTER INFORMATION STATEMENT
 
 
SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH THE MIDDLE OF NEXT  
WEEK.  
 

 
   
PSR WATCHES/WARNINGS/ADVISORIES
 
 
AZ...FIRE WEATHER WATCH FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING  
FOR AZZ132-133  
 
FIRE WEATHER WATCH FROM FRIDAY MORNING THROUGH FRIDAY AFTERNOON  
FOR AZZ131.  
 
CA...FIRE WEATHER WATCH FROM FRIDAY MORNING THROUGH FRIDAY AFTERNOON  
FOR CAZ231  
 

 
 

 
 
VISIT US ON FACEBOOK, TWITTER, AND AT WEATHER.GOV/PHOENIX  
 
DISCUSSION...PERCHA/VASQUEZ  
AVIATION...PERCHA  
FIRE WEATHER...HERNANDEZ/CB  
 
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