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000
FXUS65 KTWC 302158
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
300 PM MST SAT NOV 30 2013

.SYNOPSIS...MOSTLY CLOUDY CONDITIONS WILL CONTINUE INTO SUNDAY UNDER
SOUTHWEST FLOW ALOFT. OTHERWISE MILD AND DRY CONDITIONS FOR THE
REMAINDER OF THE WEEKEND INTO EARLY NEXT WEEK. AN AREA OF LOW
PRESSURE IN SOUTHEAST ALASKA THIS AFTERNOON WILL DIVE INTO THE
PACIFIC NORTHWEST BY MONDAY AND THEN MOVE SLOWLY THROUGH THE WESTERN
STATES FOR MUCH OF NEXT WEEK. THIS SYSTEM WILL BRING A CHANCE OF
VALLEY RAIN AND MOUNTAIN SNOW TO SOUTHEAST ARIZONA LATE TUESDAY
NIGHT THROUGH FRIDAY MORNING. THIS SYSTEM WILL ALSO BRING LOWER SNOW
LEVELS...GUSTY WINDS AND MUCH COOLER TEMPERATURES. THE FIRST
WIDESPREAD FREEZE FOR THE LOWER DESERTS IS POSSIBLE FRIDAY MORNING.

&&

.DISCUSSION...THE LAST DAY OF NOVEMBER HAS BEEN A CLOUDY ONE ACROSS
MOST OF SOUTHEAST ARIZONA AS STREAM OF MAINLY HIGH CLOUDS CONTINUES
ACROSS THE AREA UNDER SW FLOW ALOFT. THESE CLOUDS ARE ASSOCIATED
WITH A SLOWLY SW RETROGRADING UPPER LOW THAT WAS WELL WEST OF THE
BAJA CALIFORNIA COAST. WILL MAINTAIN A MOSTLY CLOUDY TO CLOUDY SKY
TONIGHT WITH MILD OVERNIGHT LOWS SIMILAR TO WHAT OCCURRED THIS
MORNING.

THE FIRST DAY OF DECEMBER WILL BE MOSTLY CLOUDY WITH HIGHS CLOSE TO
TODAY. ABOVE NORMAL TEMPERATURES WILL CONTINUE ON MONDAY AND TUESDAY
BEFORE A SIGNIFICANT CHANGE IN THE WEATHER OCCURS...STARTING
WEDNESDAY AND CONTINUING THROUGH NEXT WEEKEND. OUTSIDE OF A CHANCE
OF PRECIPITATION ON LATE TUESDAY NIGHT THROUGH FRIDAY MORNING...THE
MAIN WEATHER CONCERN WILL BE THE MUCH MUCH COLDER TEMPERATURES AS AN
ARCTIC AIR MASS SETTLES IN OVER THE AREA. CONFIDENCE IS GROWING FOR
A WIDESPREAD HARD FREEZE FRIDAY MORNING WHICH INCLUDES THE LOWER
DESERTS. BELOW NORMAL TEMPERATURES CONTINUING THROUGH DECEMBER 9TH.

MORNING PLOTS UP IN ALASKA PLACE A VERY COLD 514DM LOW NEAR
YAKUTAT...WHICH IS THE PRIME SPOT FOR REALLY COLD TEMPERATURES
ACROSS THE EASTERN INTERIOR OF ALASKA. THIS ARCTIC AIR MASS WILL
WORK ITS WAY SOUTH SUNDAY AND MONDAY AS THE UPPER LOW MOVES TO NEAR
SEATTLE MONDAY MORNING.

ON TUESDAY...UPPER TROF DEEPENS TO OUR NW WITH PRESSURE GRADIENT
STARTING TO TIGHTEN...THUS BRINGING SOME AFTERNOON BREEZES TO THE
AREA. WILL SEE AN INCREASE IN MID-LEVEL MOISTURE LATE TUESDAY NIGHT
THAT A FEW LIGHT VALLEY RAIN/MOUNTAIN SNOW SHOWERS COULD DEVELOP.

WEDNESDAY...BREEZY TO LOCALLY WINDY AS UPPER TROF/ASSOCIATED COLD
FRONT EDGES CLOSER TO THE AREA. PRECIPITATION CHANCES IN THE VALLEYS
LESS THAN 30 PERCENT WITH 30%-50% IN THE MOUNTAINS. SNOW LEVEL WILL
BE LOWERING TO 6000 FEET NORTH AND WEST TO 7500 FEET SOUTHEAST.
HIGHS WILL BE 5-12 DEGREES COOLER THAN TUESDAY WITH THE LEAST AMOUNT
OF CHANGE OCCURRING EAST OF TUCSON.

WEDNESDAY NIGHT INTO THURSDAY...SNOW LEVEL CONTINUE TO SLOWLY FALL
AS TROF AXIS PUSHES THROUGH THE STATE. STILL SOME TIMING ISSUES
BETWEEN MODELS WHICH WILL BE RESOLVED OVER THE COMING DAYS. HIGHS ON
THURSDAY 6-10 DEGREES COOLER THAN WEDNESDAY.

THURSDAY NIGHT INTO FRIDAY...AS MENTIONED ABOVE THERE ARE TIMING
DIFFERENCES BETWEEN THE MODELS WITH THE GFS BEING DRY WHILE ECMWF
HOLDING ON TO A BIT MORE MOISTURE AND COMBINED WITH LOWER SNOW
LEVELS...COULD SEE SOME FLAKES AT THE LOWEST ELEVATIONS EAST OF
TUCSON. DEPENDING ON WHICH MODEL IS CORRECT IT WILL BE COLD AS THE
MODIFIED ARCTIC AIR MASS SETTLES IN OVER THE AREA. LOWERED FORECAST
LOWS FOR FRIDAY MORNING SIGNIFICANTLY FROM WHAT I INHERITED AND HAVE
ALL OF SOUTHEAST ARIZONA BELOW FREEZING WITH THE FIRST WIDESPREAD
HARD FREEZE FOR THE LOWER DESERTS POSSIBLE. SOME OF THE HIGHEST
MOUNTAIN SPOTS WILL SEE LOWS IN THE SINGLE DIGITS. HIGHS ON FRIDAY
WILL BE RATHER CHILLY...MAINLY IN THE 50S.

SATURDAY...DRY AND WARMER.

&&

.AVIATION...CONSIDERABLE CLOUDS ABOVE 15KFT WILL CONTINUE ACROSS THE
AREA THROUGH SUNDAY AFTERNOON...OR 01/22Z...AS LOW PRESSURE REMAINS
WELL WEST OF BAJA CALIFORNIA. WINDS GENERALLY LESS THAN 10 KTS
THROUGH 01/22Z. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A NEARLY STATIONARY LOW WELL WEST OF THE BAJA
CALIFORNIA COAST WILL PROVIDE DRY CONDITIONS AND CONSIDERABLE CLOUDS
INTO EARLY NEXT WEEK. BY THE MIDDLE OF NEXT WEEK A STRONG TROUGH
WILL DEVELOP ALONG THE WEST COAST. THIS TROUGH WILL CONTINUE TO
DEEPEN INTO THE LATTER PART OF NEXT WEEK FOR A SIGNIFICANT CHANGE
TOWARDS COLD TEMPERATURES AND INCREASED SHOWER ACTIVITY. A SLIGHT
CHANCE OF SHOWERS STARTING LATE TUESDAY WITH INCREASING COVERING
STARTING LATE WEDNESDAY INTO THURSDAY. DECREASING SHOWER COVERAGE ON
FRIDAY AS SNOW LEVELS DROP TO AROUND 4000 FEET. ANTICIPATING THE
STRONGEST SOUTHWEST WINDS OF 15-30 MPH TO OCCUR AHEAD OF THIS TROUGH
AROUND MID WEEK.

&&

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

&&

$$

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