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000
FXUS65 KTWC 091630
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
930 AM MST MON DEC 9 2013

.SYNOPSIS...COOLER AIR WILL ACCOMPANY A SYSTEM TODAY...WITH MORE
FREEZING TEMPERATURES TUESDAY MORNING IN THE LOWER ELEVATION VALLEYS
AROUND TUCSON AND WEST. OTHERWISE...DRY CONDITIONS WITH A WARMING
TREND IN DAYTIME TEMPERATURES CAN BE ANTICIPATED TUESDAY THROUGH
SATURDAY.

&&

.DISCUSSION...THE MAIN FORECAST CONCERN OR CHALLENGE WILL BE RELATED
TO LOW TEMPERATURES FOR TUESDAY MORNING. THE ADDITIONAL SHOT OF
COOLER AIR THAT WAS EXPECTED TO HELP SET THE STAGE FOR A HARD FREEZE
ACROSS PARTS OF THE LOWER DESERTS OF PIMA AND PINAL COUNTIES DOES NOT
APPEAR TO BE THE CASE NOW. LATEST MODEL GUIDANCE SUGGESTED THAT LOW
TEMPERATURES TONIGHT WILL BE A ABOUT 2 TO 5 DEGREES WARMER THAN
PREVIOUSLY PROJECTED. AT ANY RATE...STILL LOOKING AT FREEZING OR
NEAR FREEZING TEMPERATURES IN THE LOWER DESERTS TONIGHT BUT POSSIBLY
NOT AS COLD AS CURRENTLY FORECAST. FOR NOW...NOT GOING TO MAKE ANY
ADJUSTMENTS FOR A MORNING UPDATE AND TAKE A CLOSING LOOK AT THE
FORECAST FOR TONIGHT IN THE AFTERNOON PACKAGE. OTHERWISE...THE
FORECAST LOOKED IN GOOD SHAPE OVERALL.

&&

.AVIATION...VALID THRU 10/12Z. VFR CONDITIONS AND LIGHT WINDS WILL
PREVAIL THRU THE PERIOD...WITH DECREASING LOW/MID CLOUDS THROUGH THE
DAY. HOWEVER...HIGH CLOUD COVER WILL BE ON THE RISE AS SHORTWAVE LOW
CUTS OFF FROM MEAN FLOW WEST OF BAJA TODAY. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...CLOUDS WILL CLEAR OUT TODAY AS COLDER AND DRIER AIR
MOVES IN. THE COLD AIR WILL BE IN PLACE THRU TUESDAY MORNING...WITH
WARMING TREND TUESDAY AFTERNOON INTO THE LATTER HALF OF THE WEEK.
WINDS AND HUMIDITY LEVELS ARE EXPECTED TO REMAIN WITHIN SEASONALLY
NORMAL RANGES INTO NEXT WEEKEND.

&&

.PREV DISCUSSION...INITIAL FOCUS IS ON THE COLD AIR SLIDING DOWN THE
WRN STATES THIS MORNING. AS THIS COLD/DRY AIR MOVES IN TODAY MOST OF
THE CLOUD COVER WILL CLEAR OUT. CURRENT FORECAST HAS FROPA DURING
THE AFTERNOON HOURS TODAY...WITH A CONTINUAL PUSH OF COLD AIR BEHIND
AS SURFACE RIDGE BUILDS OF THE WRN CONUS. EARLY TUESDAY AS THE RIDGE
SLIDES SE-WARD RIDGING WILL BACKDOOR THE COLD AIR INTO THE AREA. ALL
IN ALL TUESDAY LOOKS TO BE THE COLDEST DAY. FREEZE WATCH IN PLACE
THOUGH MOST LOCATIONS HAVE ALREADY HIT FREEZING THIS YEAR.
NEVERTHELESS...WILL LEAVE IT FOR THE NEXT SHIFT.

THE AREA WILL WARMING UP AFTER TUESDAY MORNING AS THE LONG WAVE TROF
FINALLY SLIDES EAST. HOWEVER...ONE LAST PIECE OF SHORTWAVE ENERGY
WILL GET CUT OFF AND LINGER WEST OF BAJA BEFORE EJECTING WEDNESDAY
OVER SRN AZ. THE ONLY ISSUE WITH THIS WILL BE HOW MUCH MOISTURE CAN
GET RAPPED UP IN THE LOW AND BROUGHT INTO THE AREA. HAVE UPPED POPS
FOR THURSDAY TO ACCOUNT FOR THIS.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
  FREEZE WATCH FROM LATE TONIGHT THROUGH TUESDAY MORNING FOR
   PINAL AND PIMA COUNTIES ZONES AZZ501>506.

&&

$$

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