Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 132205
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
305 PM MST SAT DEC 13 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL CONTINUE TO RESULT IN VALLEY
RAIN AND MOUNTAIN SNOW...AS WELL AS COLDER TEMPERATURES AND GUSTY
WINDS ACROSS THE EASTERN HALF OF SOUTHEAST ARIZONA THROUGH THE EARLY
EVENING HOURS TONIGHT...BEFORE PUSHING EAST OF THE REGION BY
MIDNIGHT. SOME PATCHY DENSE FOG IS EXPECTED TO DEVELOP LATE TONIGHT
AND EARLY SUNDAY MORNING IN THOSE AREAS THAT RECEIVED RAINFALL.
TEMPERATURES WILL REMAIN ON THE COOL SIDE SUNDAY...WITH SOME DRYING
MONDAY AND TUESDAY. ANOTHER STORM SYSTEM IS THEN EXPECTED TO MOVE
INTO THE REGION WEDNESDAY AND THURSDAY...RESULTING IN ANOTHER CHANCE
OF VALLEY RAIN AND MOUNTAIN SNOW.

&&

.DISCUSSION...SATELLITE AND MODEL DATA INDICATE THE UPPER LOW WAS
BEGINNING TO PUSH EASTWARD ALONG THE UTAH/ARIZONA BORDER. THE
ASSOCIATED FRONTAL/PRECIPITATION BAND HAS SLOWLY SHIFTED EAST
THROUGH THE DAY...WITH THIS BAND OVER CENTRAL PIMA COUNTY AT 15Z
THIS MORNING...THE TUCSON METRO AREA AT 18Z AND NOW EAST OF THE
TUCSON AREA AT 21Z. EXPECT THIS BAND TO CONTINUE TO SLOWLY PUSH EAST
ACROSS COCHISE...GRAHAM AND GREENLEE COUNTIES THROUGH THE REMAINDER
OF THE AFTERNOON AND EARLY EVENING HOURS...BEFORE MOVING EAST OF THE
STATE BY MIDNIGHT. TOTAL PRECIPITATION AMOUNTS ALONG THIS BAND HAVE
RANGED FROM 0.25 TO 0.50 INCHES IN VALLEY LOCATIONS...TO BETWEEN
0.75 AND 1.3 INCHES IN THE MOUNTAINS. TEMPERATURES HAVE GENERALLY
BEEN TO WARM FOR SNOWFALL IN THE HIGHER TERRAIN...EXPECT AT THE
HIGHEST ELEVATIONS ABOVE 8500 FEET. HOWEVER...EXPECT SNOWFALL LEVELS
TO FALL THIS AFTERNOON/EVENING ACROSS THE EASTERN ZONES AS THE COLD
POOL PUSHES ACROSS THE STATE. IN FACT...THUNDERSTORMS ARE CURRENTLY
ONGOING OVER THE NORTHWESTERN PART OF THE STATE IN THIS COLD POOL.
AT THIS TIME...EXPECT ANY THUNDERSTORM CHANCES TO STAY NORTH OF THE
FORECAST AREA ACROSS THE NORTHERN HALF OF THE STATE. AS THE SYSTEM
PUSHES EAST OF THE STATE TONIGHT...WITH CLEARING SKIES AND COLDER
AIR OVERSPREADING THE FORECAST AREA...EXPECT SOME AREAS OF PATCHY
DENSE FOG DEVELOPMENT IN AREAS THAT RECEIVED RAINFALL. MAIN TIMING
FOR ANY FOG DEVELOPMENT WILL BE AFTER MIDNIGHT...THROUGH EARLY
SUNDAY MORNING.

BEHIND THE SYSTEM...READINGS WILL REMAIN ON THE COOL SIDE SUNDAY...
WITH AFTERNOON HIGH TEMPERATURES ABOUT 5-8 DEGREES BELOW SEASONAL
AVERAGES. A SLOW WARMUP WILL THEN TAKE PLACE MONDAY AND TUESDAY AS
SHORT WAVE RIDGING OCCURS ACROSS THE DESERT SOUTHWEST IN ADVANCE OF
THE NEXT SYSTEM TO IMPACT THE REGION WEDNESDAY AND THURSDAY.
ALTHOUGH THERE ARE SOME SIGNIFICANT DIFFERENCES BETWEEN THE MODELS
IN THE MEDIUM/LONG RANGE...THERE IS INCREASING CONFIDENCE THAT A
SYSTEM WILL IMPACT THE REGION MID TO LATE WEEK. THE EXACT
TRACK/TIMING HAS YET TO BE NARROWED DOWN...BUT HAVE INCREASED
PRECIPITATION CHANCES FOR THE WEDNESDAY/THURSDAY TIME FRAME ACROSS
SOUTHERN ARIZONA INTO THE CHANCE CATEGORY FOR MOST VALLEY LOCATIONS
AND LIKELY POPS IN THE MOUNTAINS. WITH COLDER AIR IN PLACE...EXPECT
LOWER SNOW LEVELS WITH THIS NEXT SYSTEM. BEYOND THIS SYSTEM...MODELS
ARE INDICATING THE POSSIBILITY OF YET ANOTHER SYSTEM LATE NEXT
WEEKEND. STAY TUNED...AS THE UNSETTLED WEATHER PATTERN IS EXPECTED
TO CONTINUE THROUGH THE NEXT WEEK.

&&

.AVIATION...VALID THRU 15/00Z.
A COLD FRONT WILL CONTINUE TO MOVE EAST ACROSS SOUTHEAST ARIZONA
TONIGHT RESULTING IN WIDESPREAD VALLEY SHRA AND HIGHER TERRAIN SHSN.
ALONG THE FRONT ITSELF...EXPECT VISIBILITIES 2-3SM WITH -SHRA BR AND
CLOUD CEILINGS BKN005-015 AGL WITH MOUNTAINS OBSCURED. ELSEWHERE...
MVFR CONDITIONS SHOULD OCCUR INTO THE EVENING...ESPECIALLY ACROSS
THE HIGHER TERRAIN DUE TO SHRA/SHSN. CONDITIONS WILL IMPROVE FROM
WEST-TO-EAST THIS EVENING...FOLLOWED BY THE POSSIBILITY OF PATCHY
DENSE FOG OVERNIGHT TONIGHT INTO SUNDAY MORNING.

SURFACE WIND INTO THIS EVENING WILL BE SWLY TO NWLY AT 10-20 KTS
WITH GUSTS TO NEAR 30 KTS. THE STRONGEST WIND WILL BE ALONG AND
AHEAD OF THE FRONT EAST OF KTUS. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...A COLD FRONT TRACKING THROUGH SOUTHEAST ARIZONA
TODAY WILL CONTINUE TO BRING WIDESPREAD VALLEY RAIN AND MOUNTAIN
SNOW INTO THIS EVENING. GUSTY SOUTHWEST TO NORTHWEST WINDS WILL
PREVAIL...ESPECIALLY ALONG AND AHEAD OF THE FRONT EAST OF TUCSON.
SHOWERS WILL THEN TAPER OFF THIS EVENING...FOLLOWED BY PATCHY DENSE
FOG OVERNIGHT INTO SUNDAY MORNING.

ANOTHER PACIFIC LOW PRESSURE SYSTEM WILL BRING A CHANCE OF SHOWERS
THE MIDDLE OF THE UPCOMING WEEK. EXPECT SCATTERED TO NUMEROUS VALLEY
RAIN AND MOUNTAIN SNOW SHOWERS WEDNESDAY AND THURSDAY.

&&

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

&&

$$

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