Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 180915
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
215 AM MST THU DEC 18 2014

.SYNOPSIS...THE FINAL WEATHER SYSTEM IN THIS LATEST SERIES WILL MOVE
ACROSS THE REGION TODAY WITH ANOTHER ROUND OF SHOWERS DEVELOPING
LATER THIS MORNING AND CONTINUING INTO THE AFTERNOON.  THE SHOWERS
WILL END THIS EVENING WITH AREAS OF FOG DEVELOPING FOR FRIDAY
MORNING.  DRY CONDITIONS ARE THEN EXPECTED INTO THE MIDDLE OF NEXT
WEEK WITH TEMPERATURES GRADUALLY WARMING TO SLIGHTLY ABOVE NORMAL
LEVELS BY WEDNESDAY.

&&

.DISCUSSION...JUST A FEW ISOLATED SHOWERS AROUND THIS HOUR WITH
SOME FOG DEVELOPING HERE AND THERE.  THIS WILL CHANGE AS THE MORNING
PROGRESSES...ESPECIALLY AFTER SUNRISE.  FINAL SHORTWAVE CURRENTLY
ROTATING AROUND THE BOTTOM OF THE LONGWAVE TROUGH WILL MOVE ACROSS
THE REGION THROUGH THE DAY RESULTING IN PRECIPITATION BLOSSOMING
OVER THE CENTRAL PART OF THE CWA LATER THIS MORNING THEN EXPANDING
AS IT MOVES OFF TO THE EAST THROUGH THE AFTERNOON.  AROUND MID
AFTERNOON EXPECT SHOWERS TO BE OCCURRING FROM THE TUCSON AREA
EASTWARD WITH SNOW FALLING ABOVE ABOUT 6500-7000 FT.  BY
SUNSET...SHOWERS WILL BE CONFINED TO COCHISE...GRAHAM AND GREENLEE
COUNTIES AS IT PUSHES EAST AND ENDING ALL AREAS BY/AROUND MIDNIGHT.

I RAISED THE QPF A BIT FROM WHAT WAS IN THE GRIDS EARLIER WITH THE
FOCUS SOUTH AND EAST OF TUCSON FOR A GENERAL 0.10-0.30 OVER THE
VALLEY AREAS AND AND 0.25-0.50 OVER THE MOUNTAINS.  FOR SNOWFALL...I
WOULD EXPECT AN ADDITIONAL 2-4 INCHES OVER MOST OF THE MOUNTAIN
AREAS WITH LOCAL ACCUMULATIONS PUSHING 6 INCHES TODAY INTO THE
EVENING.

AFTER THE PRECIPITATION ENDS LATER TONIGHT THE SKIES WILL BEGIN TO
CLEAR OUT WHICH AFTER 48 HOURS OF WETNESS...SHOULD ALLOW FOR AREAS
OF FOG TO FORM LATE TONIGHT INTO FRIDAY MORNING SO I TWEAKED THE
GRIDS FROM PATCHY VALLEY FOG TO AREAS OF VALLEY FOG.  POTENTIAL FOR
SOME LOCALLY DENSE FOG IN THE FAVORED COLDER VALLEYS EAST OF TUCSON
SO TOSSED IN PATCHY DENSE FOG AMONGST THE AREAS OF FOG.  WITH THE
FOG AND COLD AIR MASS STILL IN PLACE FRIDAY WILL HAVE BELOW NORMAL
HIGH TEMPERATURES FOR ANOTHER DAY.

THEN SATURDAY A RATHER WEAK SHORTWAVE WILL DROP SE ACROSS THE AREA
BUT THIS FEATURE SHOULD ONLY PRODUCE A FEW MID AND HIGH CLOUDS AS IT
PASSES.  HOWEVER...THIS WILL TRANSITION THE FLOW ALOFT TO NW FROM
SUNDAY THROUGH WEDNESDAY WITH HEIGHTS RISING RESULTING IN MOSTLY
CLEAR SKIES AND WARMING TEMPERATURES REACHING A FEW DEGREES WARMER
THAN NORMAL BY TUESDAY AND WEDNESDAY.

BEYOND THAT...LONG RANGE MODELS BEGINNING TO ADVERTISE THE POTENTIAL
FOR ANOTHER DECENT TROUGH TO MOVE THROUGH OR NEARBY THE AREA NEXT
THURSDAY AND/OR FRIDAY FOR ANOTHER CHANCE OF PRECIPITATION.
CERNIGLIA

&&

.AVIATION...VALID THRU 19/12Z.
ISOLATED TO SCATTERED VALLEY RAIN/MOUNTAIN SNOW SHOWERS WILL OCCUR
MAINLY EAST OF KTUS THRU MID-MORNING. SCATTERED TO NUMEROUS VALLEY
RAIN/MOUNTAIN SNOW SHOWERS WILL THEN DEVELOP AROUND 15Z-17Z TODAY
AND CONTINUE INTO THIS AFTERNOON. AREAS OF MVFR CONDITIONS WILL
OCCUR ESPECIALLY ACROSS THE HIGHER TERRAIN AND WITH HEAVIER PRECIP.
THEREAFTER...VALLEY RAIN/MOUNTAIN SNOW WILL DECREASE FROM WEST TO
EAST THIS EVENING FOLLOWED BY DRY CONDITIONS LATE TONIGHT INTO EARLY
FRIDAY MORNING. CLOUD DECKS TODAY WILL GENERALLY RANGE FROM 3-6K FT
AGL...THOUGH BASES LESS THAN 1K FT AGL WILL OCCUR. EXPECT OCCASIONAL
VSBYS REDUCED TO LESS THAN 1SM IN FOG THRU THIS AFTERNOON. GRADUAL
CLEARING WILL OCCUR THIS EVENING INTO EARLY FRIDAY MORNING. SURFACE
WIND WILL MOSTLY BE LESS THAN 10 KTS. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.  FRANCIS

&&

.FIRE WEATHER...UNSETTLED WEATHER WILL CONTINUE TODAY IN THE FORM OF
VALLEY RAIN AND MOUNTAIN SNOW. SNOW LEVELS WILL BE AS LOW AS 6000 FT
WITH SEVERAL INCHES OF SNOW ACCUMULATIONS ABOVE 7000 FEET. THE
VALLEY RAIN AND MOUNTAIN SNOW WILL DECREASE FROM WEST TO EAST THIS
EVENING...THEN DRY CONDITIONS WILL PREVAIL LATE TONIGHT THROUGH NEXT
WEDNESDAY. EXPECT GENERALLY LIGHT TERRAIN DRIVEN WINDS DURING MUCH
OF THE PERIOD INTO THE MIDDLE OF NEXT WEEK. HOWEVER...SOME NORTHWEST
BREEZES MAY OCCUR MONDAY AFTERNOON ACROSS THE UPPER GILA RIVER
VALLEY INCLUDING SAFFORD. DAYTIME TEMPERATURES WILL BE WELL BELOW
NORMAL TODAY FOLLOWED BY A GRADUAL WARMING TREND FRIDAY INTO THE
MIDDLE OF NEXT WEEK.  FRANCIS
&&

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

&&

$$

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