Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 192134
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
234 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...SKIES ARE NOW MOSTLY SUNNY THIS AFTERNOON ACROSS
SOUTHEAST ARIZONA WITH BELOW NORMAL TEMPERATURES. A STEEP INVERSION
THIS MORNING WITH EXTENSIVE AREAS OF CLOUDS AND FOG IN THE VALLEYS
FROM TUCSON SOUTH AND EASTWARD HAVE FINALLY DISSIPATED WITH THE LAST
VESTIGES OF CLOUDS CLEARING AROUND 1 PM NEAR SAFFORD. 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.


&&

.AVIATION...VALID THRU 21/00Z.
GENERALLY SKC WITH PERIODS OF SCT HIGH CLOUDS MOVING THROUGH EARLY
TONIGHT. EASTERN AREAS COULD SEE DEVELOPMENT OF PATCHY FOG OR
FREEZING FOG AFTER 20/09Z THROUGH 20/17Z. OTHERWISE CLEAR SKIES AND
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.

&&

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

&&

$$

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

DISCUSSION...GL
AVIATION/FIRE WEATHER...RH










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