Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 172109
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
209 PM MST WED DEC 17 2014

.SYNOPSIS...TROUGH OF LOW PRESSURE WILL CONTINUE TO BRING VALLEY
RAIN AND MOUNTAIN SNOW TO THE AREA THROUGH TOMORROW NIGHT. THEN
EXPECT DRY CONDITIONS WITH A GRADUAL WARMING TREND INTO CHRISTMAS
EVE.

&&

.DISCUSSION...BEGINNING TO SEE SOME ENHANCEMENT IN PRECIPITATION
THANKS TO AN IMPULSE IN THE FLOW. THE ENERGY WITH THIS IMPULSE
WILL GENERALLY STAY NORTH OF TUCSON...SO BULK OF PRECIPITATION
WILL BE THERE. THAT BEING SAID THERE IS ENOUGH MOISTURE IN PLACE
FOR CONTINUAL OFF AND ON SHOWERS THROUGHOUT THE EVENING.

AFTER THIS IMPULSE MOVES THROUGH THIS EVENING EXPECT TO SEE
ANOTHER LULL IN SHOWERS AFTER MIDNIGHT. THEREFORE...HAVE CONTINUED
THE LOWER POP FROM PREVIOUS PACKAGE...THOUGH HAVE SLIGHTLY
INCREASED POPS ACROSS THE NORTHERN THIRD OF THE FORECAST AREA FOR
THIS PERIOD. THIS IS TO ACCOUNT FOR THE ADDITIONAL MOISTURE EXPECT
NORTH OF TUCSON AND ANY LINGERING ENERGY. HAVE ALSO ADDED SOME FOG
MENTION FOR PINAL COUNTY DURING THIS TIME. NOT EXPECTING MUCH IN
THE WAY OF DENSE OR MAJOR VISIBILITY REDUCTION AS RADIATIVE
COOLING WILL BE LIMITED.

THEN TOMORROW MORNING ANOTHER IMPULSE WILL SLIDE THROUGH THE AREA.
THIS TIME THE BULK OF THE ENERGY WILL BE ACROSS NORTHERN SONORA
MEXICO. THIS WILL KEEP THE BEST QPF VALUES ACROSS THE SOUTHERN
HALF OF THE AREA TOMORROW. AS THIS IMPULSE EXITS THE REGION SO
DOES THE MOISTURE...THOUGH GRADUALLY. BY MIDNIGHT FRIDAY MOST OF
THE SHOWER ACTIVITY WILL BE GONE THOUGH HAVE REINTRODUCED LOW END
SLIGHT CHANCE POPS TO THE HIGHER ELEVATIONS OUT EAST.

FRIDAY THE UPPER RIDGE AXIS SHIFT OVER HEAD ALLOWING FOR THE AREA
TO DRY OUT AND WARM UP. THOUGH...THE WARM UP WILL BE GRADUAL. WITH
THE LOCATION OF THE UPPER HIGH LATE WEEK AND INTO THE WEEKEND
SHOULD KEEP MOSTLY NORTHWEST FLOW IN PLACE. GUIDANCE HAS TRENDED
AWAY FROM THE WEEKEND SHORTWAVE ENERGY HAVING ANY IMPACT ON THE
AREA AS THEY KEEP TRENDING FURTHER EAST WITH IT. THERE IS SOME
INDICATION THAT THE RIDGE MAY BEGIN TO BREAK DOWN OVER THE AREA
AROUND CHRISTMAS AS A PACIFIC TROUGH BEGINS TO DIG ACROSS THE
WESTERN STATES. STAY TUNED.


&&

.AVIATION...VALID THRU 19/00Z.
ISOLATED TO SCATTERED VALLEY RAIN/MOUNTAIN SNOW SHOWERS WILL
CONTINUE THRU THIS EVENING WITH PERHAPS AN ISOLATED RUMBLE OF
THUNDER. BKN-OVC CLOUDS AT 4-6K FT AGL WITH MULTIPLE BKN-OVC LAYERS
ABOVE. EXPECT LOCAL MVFR CONDITIONS AT GENERALLY 2-3K FT ESP IN THE
VICINITY OF SHOWERS THRU THIS EVE. SFC WINDS WILL BE GENERALLY
WLY/SWLY AT 8-15 KTS WITH A FEW GUSTS UP TO AROUND 20 KTS POSSIBLE
IN FAR SRN AREAS THIS AFTERNOON. WINDS THEN BECOMING DIURNAL AND
TERRAIN DRIVEN FROM LATE THIS EVENING THROUGH TOMORROW AFTERNOON.
ANOTHER ROUND OF ISOLATED TO SCATTERED VALLEY RAIN/MOUNTAIN SNOW
SHOWERS WILL OCCUR THURSDAY WITH SKY CONDITIONS QUITE SIMILAR TO
TODAY. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...UNSETTLED WEATHER WILL CONTINUE THROUGH THURSDAY IN
THE FORM OF VALLEY RAIN AND MOUNTAIN SNOW WITH SOMEWHAT OF A BREAK
IN THE PRECIPITATION TONIGHT. SNOW LEVELS WILL BE AS LOW AS 6000 FT
WITH ACCUMULATING SNOWS OCCURRING GENERALLY ABOVE 7000 FT AND
SEVERAL INCHES POSSIBLE. BREEZY SOUTHWESTERLY WINDS NEAR THE
INTERNATIONAL BORDER THIS AFTERNOON SHOULD TAPER OFF DURING THE
EARLY EVENING HOURS WITH LIGHTER WESTERLY WINDS OCCURRING THURSDAY.
MOSTLY DRY CONDITIONS ARE EXPECTED THROUGH THE COMING WEEKEND WITH
PLENTY OF PASSING HIGHER CLOUDS AND FAIRLY LIGHT NORTH TO NORTHWEST
WINDS.

&&

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

&&

$$

DISCUSSION...MEADOWS
FIRE WEATHER...81

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