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000
FXUS65 KTWC 021332 AAA
AFDTWC

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TUCSON AZ
632 AM MST MON DEC 2 2013

.SYNOPSIS...PARTLY TO MOSTLY CLOUDY CONDITIONS WILL CONTINUE TODAY
UNDER SOUTHWEST FLOW ALOFT. OTHERWISE MILD AND DRY CONDITIONS WILL
CONTINUE INTO TUESDAY. A STRONG STORM NEAR THE COAST OF BRITISH
COLUMBIA THIS MORNING WILL DIVE INTO THE PACIFIC NORTHWEST TODAY
AND THEN MOVE SLOWLY THROUGH THE WESTERN STATES FOR MUCH OF THE
COMING WEEK. THIS SYSTEM WILL BRING A CHANCE OF VALLEY RAIN AND
MOUNTAIN SNOW TO SOUTHEAST ARIZONA LATE TUESDAY NIGHT THROUGH
THURSDAY NIGHT OR 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.

&&

.UPDATE...ADJUSTED CLOUD COVER FOR TODAY TO REFLECT THE MOST RECENT
SATELLITE TRENDS. THIS MEANS MORE SUN TODAY THAN PREVIOUSLY
EXPECTED. STILL SOME HIGH CLOUDS SPILLING IN FROM TIME TO TIME FROM
THE WEST AND SOUTHWEST.

WITH A VERY DRY SOUNDING THIS MORNING...THE DEWPOINT TEMPERATURES
WERE ALSO ADJUSTED FOR TODAY.

&&

.DISCUSSION...WATER VAPOR IMAGERY SHOWS A WEAK SHORTWAVE TROUGH
SLIDING SOUTH AND EAST THROUGH SOUTHERN ARIZONA WITH THE ASSOCIATED
VORT LOBE EXTENDING FROM CENTRAL TEXAS THROUGH SOUTHERN NEW MEXICO
AND SOUTHERN ARIZONA AND THEN WEST THROUGH SOUTHERN CALIFORNIA AND
NORTHERN BAJA WITH NEARLY ZONAL FLOW ACROSS THE DESERT SOUTHWEST.

MEANWHILE...A PACIFIC LOW PRESSURE SYSTEM CONTINUES TO SPIN WELL
WEST OF THE SOUTHERN BAJA PENINSULA. THIS LOW HAS RETROGRADED FROM
THIS TIME YESTERDAY WITH PLENTY OF MID AND HIGH LEVEL MOISTURE
CONTINUING TO SPILL ACROSS MUCH OF MEXICO AND INTO SOUTHERN PARTS OF
THE DESERT SOUTHWEST FOR PARTLY TO MOSTLY CLOUDY SKIES.

THE LOW PRESSURE SYSTEM OVER THE BRITISH COLUMBIA COAST WILL
CONTINUE TO DIVE SOUTHEAST AND INTO THE PACIFIC NORTHWEST TODAY AND
INTO NORTHERN CALIFORNIA BY TUESDAY. THIS WILL RESULT IN ZONAL FLOW
ACROSS THE DESERT SOUTHWEST WITH TEMPERATURES REMAINING MILD TODAY
AND TUESDAY.

DURING THE DAY ON WEDNESDAY THIS SYSTEM WILL CONTINUE TO STRENGTHEN
WITH AN INFLUX OF MOISTURE OUT AHEAD OF THE TROUGH AXIS WHICH WILL
EXTEND FROM THE NORTHERN ROCKIES THROUGH CENTRAL CALIFORNIA.
PRECIPITABLE WATER VALUES ARE EXPECTED TO INCREASE WITH A RANGE FROM
A HALF INCH TO NEAR THREE QUARTERS OF AN INCH WEDNESDAY THROUGH
EARLY THURSDAY...WHICH IS AT OR EVEN ABOVE SATURATION WITH THE
1000-500MB THICKNESS VALUES THAT ARE EXPECTED AT THAT TIME.
THAT SAID...I INCREASED PRECIPITATION CHANCES MAINLY FOR THE
WEDNESDAY NIGHT/EARLY THURSDAY TIME FRAME WITH SOLID 50 PERCENT POPS
FOR CENTRAL AND EASTERN ZONES AND LIKELY POPS FOR THE MOUNTAINS.
HOWEVER...MY POPS ARE STILL JUST A BLEND BETWEEN THE DRIER GFS...
WHICH HAS 33% POPS FOR TUCSON WEDNESDAY NIGHT AND THE WETTER ECMWF
WHICH HAS 68 PERCENT.

MUCH COLDER AIR IS EXPECTED WITH THIS SYSTEM WITH SNOW LEVELS
STARTING OUT EARLY WEDNESDAY AT ABOUT 8500-9000 FEET...BUT FALLING
INTO THE 5000-5500 FOOT RANGE BY EARLY THURSDAY MORNING. SNOW LEVELS
WILL BOTTOM OUT AT ABOUT 3500-4000 FEET LATE THURSDAY...BUT BY THEN
PRECIPITATION CHANCES WILL BE FAIRLY LOW...SO ONLY THE MOUNTAIN
ZONES FOR AREAS NEAR THE NEW MEXICO BORDER EXPECTED TO SEE
ADDITIONAL SNOW.

ONCE THIS SYSTEM EXITS THE REGION...BROAD TROUGHINESS WILL COVER THE
WESTERN STATES WITH ANOTHER SYSTEM MOVING BY WELL TO OUR NORTH THIS
WEEKEND. I ONLY HAVE SLIGHT CHANCE POPS FOR FRIDAY THROUGH THE
WEEKEND ACROSS THE WHITE MOUNTAINS OF GRAHAM AND GREENLEE COUNTIES
AND BEYOND THAT TIME THE MODELS HAVE SERIOUS DISCREPANCIES.

HIGH TEMPERATURES GENERALLY 6 TO 8 DEGS ABOVE NORMAL TODAY AND
TUESDAY...THEN ABOUT 2 TO 4 DEGS BELOW NORMAL WEDNESDAY.
THEREAFTER...HIGHS WELL BELOW NORMAL WITH THE COLDEST DAY OCCURRING
ON FRIDAY WHEN HIGHS WILL BE 10 TO 15 DEGS BELOW NORMAL. LOWS WILL
BE RANGE FROM 8 TO 12 DEGS ABOVE NORMAL TUESDAY THROUGH THURSDAY
MORNINGS...THEN 5 TO 8 DEGS BELOW NORMAL THEREAFTER...WITH THE
COLDEST MORNING ON FRIDAY.

&&

.AVIATION...VALID THRU 03/12Z.  WAVES OF HIGH LEVEL CLOUDS AOB 20K
FT WILL CONTINUE TO SPREAD ACROSS SRN AZ THRU MONDAY NIGHT.  NORMAL
DIURNAL WINDS AOB 10 KT ANTICIPATED THROUGH THE NEXT 24 HOURS.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WILL PREVAIL THROUGH TUESDAY WITH
TEMPERATURES REMAINING ABOVE NORMAL AND WINDS REMAINING LIGHT WITH
THE EXCEPTION OF A BIT OF A SOUTHWEST BREEZE TUESDAY AFTERNOON.
THEN A DEEP AND COLD STORM SYSTEM WILL DROP OVER THE REGION FOR THE
LATTER HALF OF THE WEEK.  THIS WILL RESULT IN BREEZY CONDITIONS
WEDNESDAY AND THURSDAY WITH A CHANCE OF SHOWERS THROUGH THURSDAY
NIGHT.  THE BIGGEST CHANGE WILL BE IN THE TEMPERATURES WHICH WILL BE
ROUGHLY 15 DEGREES COLDER THAN NORMAL THURSDAY THROUGH WEEKEND.
CERNIGLIA

&&

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

&&

$$

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AVIATION/FIRE WEATHER...CERNIGLIA