FXUS65 KTWC 061627
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
925 AM MST SUN DEC 6 2009

.SYNOPSIS...ISOLATED SNOW SHOWERS ACROSS THE WHITE MOUNTAINS 
OTHERWISE DRY CONDITIONS WILL PREVAIL TODAY. A STRONG WINTER STORM 
SYSTEM WILL APPROACH THE AREA FROM THE NORTHWEST ON MONDAY. THIS 
SYSTEM WILL BRING WIDESPREAD VALLEY RAIN AND SIGNIFICANT MOUNTAIN 
SNOW TO SOUTHEAST ARIZONA PARTICULARLY MONDAY NIGHT INTO MIDDAY 
TUESDAY. DRIER CONDITIONS WEDNESDAY FOLLOWED BY ANOTHER CHANCE OF 
VALLEY RAIN AND MOUNTAIN SNOW THURSDAY INTO FRIDAY.

&&

.DISCUSSION...SATELLITE IMAGERY INDICATED CLEAR SKIES ACROSS SERN 
SECTIONS THOUGH ARC OF LOWER AND MID-LEVEL CLOUDINESS EXTENDED FROM 
WRN/CENTRAL PIMA COUNTY NEWD TO THE WHITE MOUNTAINS. HANNAGAN MEADOW 
OBSERVER REPORTED LIGHT SNOW OCCURRING AT 15Z. WILL OPT FOR ISOLATED 
SNOW SHOWERS ACROSS NRN GREENLEE COUNTY TODAY WITH PRECIP-FREE 
CONDITIONS ELSEWHERE. A FEW GUSTS ALREADY THIS MORNING AROUND 18-25 
KTS VIA THE KFHU/KOLS OBSERVATIONS. SOME BREEZES THIS AFTERNOON 
MAINLY ACROSS THE HIGHER TERRAIN EAST AND SOUTH OF TUCSON. STILL A 
SLIGHT CHANCE OF SNOW SHOWERS ACROSS THE WHITE MOUNTAINS TONIGHT 
THOUGH DRY ELSEWHERE.

WRN CONUS TROUGH TO CONTINUE TO DEEPEN MON. MID-LEVEL GRADIENT TO BE 
SUFFICIENTLY TIGHT FOR BREEZY TO WINDY CONDITIONS STARTING MON 
AFTERNOON...AS WELL AS MON NIGHT AND TUE. MAY EVENTUALLY NEED A WIND 
ADVISORY FROM THE TUCSON METRO AREA EWD/SWD FOR SOME PORTION OF MON 
AFTERNOON-TUE. ALSO...MOISTURE WILL INCREASE ACROSS THE AREA TO 
SUPPORT A CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW MAINLY IN THE 
AFTERNOON MON. HAVE NOTED THAT THE 06/12Z NAM POPS WERE LOWER-SINGLE
DIGITS FOR KTUS MON. THUS...MAY TRIM POPS FROM TUCSON SWD/EWD 
IN THE AFTERNOON PACKAGE AFTER BASED ON RECEIPT OF 06/12Z GFS. 

06/00Z GFS/ECMWF SOLUTIONS DEPICT DEEPER-LAYER MOISTURE ACROSS SE AZ 
MON NIGHT-TUE MORNING. THIS PERIOD IS ALSO COINCIDENT WITH SYNOPTIC- 
SCALE ASCENT AS PER 700-300 MB NEGATIVE DIV-Q FIELDS. PRECIP SHOULD 
TAPER FROM WEST-EAST TUE AS DEEPER MOISTURE IS SHUNTED WELL NEWD. 
WINTER STORM WATCH TO CONTINUE FOR MONDAY AFTERNOON THRU TUE 
AFTERNOON FROM TUCSON EWD/SWD ABOVE 6000 FEET. SNOW ACCUMULATIONS OF 
6-12 INCHES BETWEEN 6000-7000 FEET ARE EXPECTED BY TUE EVENING... 
WITH THE POTENTIAL FOR 12-18 INCHES ABOVE 7000 FEET. BELIEVE THIS IS 
TOO EARLY TO UPGRADE TO WINTER STORM WARNING...THOUGH WILL DISCUSS 
THIS NOTION WITH WFO/S PSR/FGZ DURING THE 18Z COORD CALL.

SHORTWAVE RIDGE ALONG THE CALIFORNIA COAST WED WILL FLATTEN AND MOVE 
EWD ACROSS THE AREA WED NIGHT. RIDGE TO BE FAIRLY DIRTY WITH MID AND 
HIGH-LEVEL MOISTURE TO MOVE ACROSS THE AREA. THE NEXT SIGNIFICANT 
SHORTWAVE TROUGH CONTINUES TO BE PROGGED TO MOVE ACROSS THE GREAT 
BASIN REGION LATE THUR AND FRI. THIS SYSTEM WILL BRING ANOTHER 
CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW SHOWERS PARTICULARLY FROM 
TUCSON EWD. ENOUGH MOISTURE TO JUSTIFY LOW-GRADE POPS AREAWIDE SAT. 

NEAR-NORMAL DAYTIME TEMPS TODAY AND MON. QUITE COOL TUE THEN WARMER 
WED WITH HIGH TEMPS THUR-SAT TRENDING EITHER CLOSE TO NORMAL OR 
PERHAPS A FEW DEGS BELOW NORMAL.

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL INTO MONDAY MORNING. 
SCATTERED TO OCCASIONALLY BROKEN CLOUDS WITH BASES AROUND 5-8K FT 
AGL TODAY BECOMING BROKEN-OVERCAST DECKS AFTER 00Z AND CONTINUING 
INTO MONDAY MORNING. SURFACE WINDS DURING THE 18Z-23Z PERIOD TODAY 
SLY/SWLY 10-20 KTS AND GUSTY...OTHERWISE SURFACE WINDS GENERALLY 
LESS THAN 10 KTS INTO MONDAY MORNING. DETERIORATING CONDITIONS WITH 
SHRA/HIGHER TERRAIN SHSN AND GUSTY SLY/SWLY WINDS AFTER 18Z MONDAY 
AND CONTINUING INTO TUESDAY MORNING. AVIATION DISCUSSION NOT UPDATED 
FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A FEW SNOW SHOWERS ACROSS THE WHITE MOUNTAINS 
OTHERWISE DRY CONDITIONS TODAY. ALSO...SOME AFTERNOON BREEZES 
PARTICULARLY SOUTH AND EAST OF TUCSON ARE EXPECTED. A STRONG STORM 
SYSTEM WILL APPROACH SOUTHEAST ARIZONA FROM THE NORTHWEST MONDAY. 
THIS SYSTEM WILL BRING WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW 
PARTICULARLY MONDAY NIGHT THROUGH MIDDAY TUESDAY. BREEZY TO WINDY 
CONDITIONS WILL ALSO ACCOMPANY THIS SYSTEM. DRIER CONDITIONS WILL 
OCCUR WEDNESDAY. ENOUGH MOISTURE FOR A CHANCE OF RAIN AND MOUNTAIN 
SNOW THURSDAY INTO SATURDAY AS A SERIES OF DISTURBANCES MOVE ACROSS 
THE AREA. BREEZY TO OCCASIONALLY WINDY CONDITIONS MAY ALSO ACCOMPANY 
THESE SYSTEMS.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...WINTER STORM WATCH MONDAY 
      AFTERNOON THROUGH TUESDAY AFTERNOON (08/00Z - 09/00Z) 
      AZZ019-030-033>035 ABOVE 6000 FEET.

$$

BF

WEATHER.GOV/TUCSON