239  
FXUS65 KTWC 211605  
AFDTWC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TUCSON AZ  
905 AM MST SUN JAN 21 2018  
   
SYNOPSIS
 
SUNNY SKIES TODAY WITH THE EXCEPTION OF THE WHITE  
MOUNTAINS WHERE CLOUDS WILL GIVE WAY TO SOME SUNSHINE LATER TODAY.  
MUCH COOLER TEMPERATURES CONTINUE TODAY, WITH A WIDESPREAD FREEZE  
MONDAY MORNING. DRY CONDITIONS WITH WARMER TEMPERATURES MOST OF THE  
WEEK, BEFORE A TROUGH BRINGS COOLER AIR AND GUSTY WINDS LATE IN THE  
WEEK.  
 

 
   
DISCUSSION
 
THE UPPER LOW IS CURRENTLY NEAR THE COLORADO/NEW  
MEXICO BORDER AND CONTINUES TO PUSH EASTWARD. THIS HAS LEFT  
SOUTHEAST ARIZONA UNDER A MUCH COLDER AIRMASS WITH NORTHWESTERLY  
FLOW ALOFT. SKIES HAVE CLEARED OUT WITH THE EXCEPTION OF THE WHITE  
MOUNTAINS WHERE SOME RESIDUAL WRAPAROUND MOISTURE REMAINS WHICH  
COULD PRODUCE A COUPLE OF SNOW SHOWERS. OTHERWISE, THE MAIN STORY  
FOR TODAY WILL BE THE BELOW NORMAL TEMPERATURES WITH HIGHS IN THE  
50'S FOR VALLEY LOCATIONS. GIVEN THE FAVORABLE NORTHWEST FLOW IN THE  
UPPER GILA RIVER VALLEY, THIS AREA WILL SEE GUSTY WINDS UP TO 30  
MPH. WITH A COLD AIR MASS IN PLACE, THIS WILL SET THE STAGE FOR THE  
COLDEST OVERNIGHT/EARLY MORNING WE'VE HAD IN SOME TIME WITH A FREEZE  
FOR JUST ABOUT ALL OF OUR FORECAST AREA AND AN EASY HARD FREEZE FOR  
LOCALES SOUTH AND EAST OF TUCSON. THE ONLY FLY IN THE OINTMENT IS  
SOME INCREASING CIRROFORM CLOUDS OVERNIGHT WHICH COULD PREVENT  
TEMPERATURES FROM REACHING THEIR LOWEST POTENTIAL.  
 
A WARMING TREND WILL COMMENCE MONDAY, THOUGH HIGH TEMPERATURES WILL  
STILL REMAIN ABOUT 5 DEGREES BELOW NORMAL. AS A WEAK DISTURBANCE  
ALOFT APPROACHES, CONSIDERABLE CIRROFORM CLOUDINESS WILL CONTINUE ON  
MONDAY. WEAK RIDGING IS EXPECTED TUESDAY AND WEDNESDAY WITH  
CONTINUED WARMING DAYTIME TEMPERATURES BEFORE A TROUGH SKIRTS BY TO  
OUR NORTH FOR THE END OF THE WEEK. THIS TROUGH WILL RESULT IN  
PERHAPS A FEW INCREASED BREEZES AND DROP OUR TEMPERATURES BACK TO  
NEAR NORMAL LEVELS. NO PRECIPITATION AGAIN IN SIGHT FOR AT LEAST THE  
NEXT 7 DAYS.  
 

 
   
AVIATION
 
VALID THRU 22/18Z.  
CLEAR SKIES WITH THE EXCEPTION OF THE WHITE MOUNTAINS WHERE BKN-OVC  
CLOUD COVERAGE 3-7K FT AGL WILL QUICKLY DECREASE AS THE DAY  
PROGRESSES. SCT-BKN CIRRUS RETURN AFTER 22/06Z. WLY/NWLY SFC WINDS  
AT 10-15 KTS THIS MORNING WILL INCREASE THIS AFTERNOON TO 12-20 KTS,  
ESPECIALLY E OF KTUS. A FEW GUSTS TO AROUND 30 KTS MAY OCCUR NEAR  
KSAD. LESS WIND WILL OCCUR THIS EVENING INTO MONDAY MORNING.  
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.  
 

 
   
FIRE WEATHER
 
OTHER THAN A FEW SNOW SHOWERS ACROSS THE WHITE  
MOUNTAINS THIS MORNING, DRY CONDITIONS WILL PREVAIL OVER THE NEXT  
WEEK. GUSTY NORTHWEST WINDS AT 15-20 MPH WILL FAVOR THE UPPER GILA  
RIVER VALLEY INCLUDING SAFFORD TODAY, WITH EAST WINDS RETURNING FOR  
TUESDAY AND WEDNESDAY. BREEZY WEST WINDS MAY RETURN LATE IN THE  
WORK WEEK.  
 

 
   
CLIMATE
 
THE CURRENT FORECAST HIGH FOR TUCSON TODAY IS 54  
DEGREES, WHICH IS 12 DEGREES BELOW AVERAGE. IF THIS OCCURS IT  
WOULD MARK THE FIRST DOUBLE DIGIT BELOW AVERAGE HIGH TEMPERATURE  
SINCE LATE JULY LAST YEAR.  
 

 
   
TWC WATCHES/WARNINGS/ADVISORIES
 
 
FREEZE WARNING FROM 1 AM TO 9 AM MST MONDAY FOR AZZ502-504-505.  
 

 
 

 
 
GL  
 
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