Weather Service Report


340 
FXUS65 KTWC 200437
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
935 PM MST FRI DEC 19 2014

.SYNOPSIS...A DRY NORTHWEST FLOW PATTERN WILL RESULT IN SOME PASSING 
HIGH LEVEL CLOUDS AND NEAR TO SLIGHTLY BELOW TEMPERATURES THIS 
WEEKEND. SOME AREAS OF FOG AND FREEZING FOG ARE EXPECTED AGAIN EARLY 
SATURDAY MORNING MAINLY ACROSS THE VALLEYS OF COCHISE AND GRAHAM 
COUNTY.   FOR EARLY TO MID NEXT WEEK...TEMPERATURES WILL RISE TO 
ABOVE NORMAL LEVELS DUE TO A PASSING UPPER LEVEL RIDGE. UNSETTLED 
AND COOLER WEATHER LOOKS LIKELY FOR THE END OF NEXT WEEK.  

&&

.DISCUSSION...MAIN FORECAST CONCERN TONIGHT IS DEVELOPMENT OF FOG 
AGAIN MAINLY E OF TUCSON. COULD SEE AREAS OF DENSE FOG AGAIN BUT AT 
THIS TIME DON'T BELIEVE THAT IT WILL BE WIDESPREAD ENOUGH FOR AN 
ADVISORY BUT OBS WILL BE MONITORED CLOSELY OVERNIGHT INTO SATURDAY 
MORNING. OTHERWISE SATELLITE IMAGERY SHOWED HIGH CLOUDS OVER WRN AZ 
MOVING E. PARTLY CLOUDY FORECAST FOR TONIGHT RIGHT ON TRACK. CLOUDS 
MAY TAKE AN EDGE OFF LOW TEMPERATURES BUT OVERALL IT WILL STILL BE 
CHILLY TO COLD WITH AREAS OF FROST. CHECK PREVIOUS DISCUSSION BELOW 
FOR ADDITIONAL FORECAST DETAILS FOR THE WEEKEND INTO NEXT WEEK.

&&

.AVIATION...VALID THRU 21/00Z.
EASTERN AREAS COULD SEE DEVELOPMENT OF PATCHY FOG OR FREEZING FOG 
AFTER 20/09Z THROUGH 20/17Z. SCT TO LCLY BKN HIGH CLOUDS THRU 
SATURDAY AFTERNOON. SURFACE WIND LESS THAN 10 KTS WILL PREVAIL 
THROUGH THE PERIOD. AVIATION DISCUSSION NOT UPDATED FOR TAF 
AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WILL PREVAIL TODAY THROUGH WEDNESDAY. 
20-FT WINDS WILL GENERALLY BE LIGHT AND TERRAIN DRIVEN THROUGH THE 
MIDDLE OF NEXT WEEK. HOWEVER...SOME NORTHWEST BREEZES WILL OCCUR 
MONDAY AFTERNOON ACROSS THE UPPER GILA RIVER VALLEY INCLUDING 
SAFFORD. AT THIS TIME CONFIDENCE IS LOW CONCERNING THE TIMING AND 
IMPACTS OF THE NEXT SIGNIFICANT WEATHER MAKER WHICH MAY AFFECT THE 
REGION LATE NEXT WEEK. GUSTY WINDS AND ANOTHER CHANCE FOR VALLEY 
RAIN AND MOUNTAIN SNOW ARE POSSIBLE.

&&

.PREVIOUS DISCUSSION...
IN THE LARGER SCALE...WEAK SHORTWAVE RIDGING ALOFT IS CENTERED JUST 
WEST OF US AT THIS TIME WITH SOME THIN CIRROFORM CLOUDS ACROSS 
WESTERN ARIZONA AND MORE EXTENSIVE MID AND HIGH LEVEL CLOUDS ACROSS 
THE EASTERN PACIFIC PUSHING INTO SOUTHERN CALIFORNIA. CONSIDERING 
AMPLE LOW LEVEL MOISTURE REMAINS TONIGHT WE THINK THERE WILL BE SOME 
AREAS OF FOG AND FREEZING FOG AGAIN EARLY SATURDAY MORNING ACROSS 
THE VALLEYS OF GRAHAM AND COCHISE COUNTY. THE UPPER GILA RIVER 
VALLEY WILL AGAIN HAVE THE BEST CHANCE OF SEEING FOG AND FREEZING 
FOG. SOME AREAS OF FROST WILL BE POSSIBLE AS WELL FOR SOME OF THE 
OUTLYING AREAS OF THE TUCSON METRO. THERE WILL BE SOME THIN 
CIRROFORM CLOUDS OVERNIGHT WHICH COULD HELP MITIGATE LOW 
TEMPERATURES AND FOG SLIGHTLY BUT CONFIDENCE IS HIGH ENOUGH TO PUT 
AREAS OF FOG IN THE FORECAST FOR THE VALLEYS EAST OF TUCSON. 

A WEAK SHORTWAVE TROUGH WILL SKIRT ACROSS MAINLY EASTERN SECTIONS OF 
THE FORECAST AREA ON SATURDAY WITH LITTLE SENSIBLE WEATHER IMPACT 
OTHER THEN SOME MAINLY HIGH LEVEL CLOUDS. TEMPERATURES WILL WARM A 
FEW DEGREES ON SATURDAY COMPARED TO TODAY.

THEREAFTER...DRY NORTHWESTERLY FLOW ALOFT IS EXPECTED FROM SUNDAY 
THROUGH THE MIDDLE OF NEXT WEEK AS RIDGING ALOFT IS CENTERED ACROSS 
THE EASTERN PACIFIC AND TROUGHINESS IS LOCATED OVER THE PLAINS. 
TEMPERATURES WILL BE NEAR NORMAL SUNDAY AND ABOUT 5 DEGREES ABOVE 
NORMAL MONDAY. THERE WILL BE A WEAK COLD FRONT MOVING THROUGH FROM 
THE NORTH-NORTHEAST EARLY TUESDAY BUT THIS WILL HAVE LITTLE IMPACT 
ON TEMPERATURES FROM TUCSON WESTWARD WITH PERHAPS SLIGHT COOLING FOR 
EASTERN AREAS TUESDAY INTO WEDNESDAY. 

BY LATE NEXT WEEK...THERE REMAINS CONSIDERABLE DIFFERENCES IN THE 
GLOBAL MODEL GUIDANCE AS ANOTHER TROUGH MOVES INTO THE WESTERN US. 
THE 12Z GFS KEEPS MAINLY ZONAL WESTERLY FLOW THIS FAR SOUTH WITH THE 
12Z CANADIAN AND ECMWF MORE AMPLIFIED WITH THE TROUGH LATE NEXT 
WEEK. WILL TAKE A MIDDLE OF THE ROAD APPROACH CLOSE TO 12Z GEFS AND 
ECMWF ENSEMBLE MEANS. THUS...HAVE ONLY MADE MINOR TWEAKS TO THE 
ONGOING FORECAST WITH SLIGHT CHANCE POPS NORTHEAST OF TUCSON AND 
ESPECIALLY IN THE WHITE MOUNTAINS THURSDAY AND FRIDAY. TEMPERATURES 
WILL DROP BACK DOWN TO NEAR NORMAL VALUES LATE NEXT WEEK. 


.TWC WATCHES/WARNINGS/ADVISORIES...NONE. 

&&

$$

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON




Return to Home page


Western Regional Climate Center, wrcc@dri.edu