FXUS65 KTWC 222103
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
200 PM MST TUE DEC 22 2009

.SYNOPSIS...A STRONG STORM SYSTEM WILL PASS THROUGH THE SOUTHERN 
ROCKIES TONIGHT INTO WEDNESDAY. AHEAD OF THIS STORM...STRONG WINDS 
WITH AREAS OF BLOWING DUST PREVAILED ACROSS SOUTHEAST ARIZONA. WINDS 
WILL DIMINISH AS VALLEY RAIN AND MOUNTAIN SNOW DEVELOP THIS EVENING 
INTO WEDNESDAY MORNING. DECREASING CLOUDS AND MUCH COOLER WEDNESDAY 
THEN WIDESPREAD FREEZING TEMPERATURES WEDNESDAY NIGHT AND THURSDAY 
MORNING. EXPECT DRY CONDITIONS CHRISTMAS EVE INTO THIS WEEKEND 
THOUGH DAYTIME TEMPERATURES REMAINING BELOW NORMAL.

&&

.DISCUSSION...WIND AND BLOWING DUST HAVE BEEN THE MAIN WEATHER 
CONCERN TODAY AS A STORM SYSTEM CONTINUES TO APPROACH THE AREA. 
SATELLITE IMAGERY SHOWED MOST OF SOUTHEAST ARIZONA UNDER THE DRY 
SLOT AHEAD OF THE SURFACE FRONT WHICH EXTENDED SOUTH THROUGH GILA 
BEND TO AJO AND ORGAN PIPE AT 1 PM MST. SHOWERS WERE STARTING TO 
DEVELOP ALONG THIS FRONTAL BAND WITH THUNDERSTORMS NEAR PHOENIX. AS 
THE FRONT TRACKS EASTWARD THIS AFTERNOON AND THIS EVENING THE CHANCE 
OF SHOWERS WILL BE ON THE INCREASE. JUST AHEAD AND ALONG THE FRONT 
WINDS WILL PEAK IN SPEED...WITH WINDS DIMINISHING NOTICEABLY BEHIND 
THE FRONT. EXPECT THE FRONT TO PASS THROUGH COCHISE COUNTY LATE THIS 
EVENING INTO EARLY WEDNESDAY SO WILL KEEP THE WIND ADVISORY GOING 
THERE THROUGH 3 AM MST WED. OTHERWISE...WIND SPEEDS SHOULD BE 
DIMINISHING THROUGH THE EVENING HOURS ELSEWHERE. SATELLITE IMAGERY 
DEPICTED A NARROW BAND OF BLOWING DUST EXTENDING FROM MEXICO 
NORTHWARD THROUGH THE TOHONO OODHAM NATION INTO PINAL COUNTY. 
VISIBILITIES FROM SELLS TO NEAR COVERED WELLS ON STATE HIGHWAY 86 
COULD BE BELOW 1/4 OF A MILE. REPORTS OF AT LEAST TWO SEPARATE 
MULTIPLE CAR COLLISIONS ON INTERSTATE 10 NEAR CASA GRANDE AND NORTH 
OF PICACHO PEAK HAVE BEEN RECEIVED. THEREFORE...WILL KEEP THE DUST 
WARNING FOR THIS AREA GOING UNTIL 5 PM MST.

THE FOCUS WILL SHIFT TO SNOWFALL AMOUNTS LATE THIS EVENING INTO 
EARLY WEDNESDAY IN THE MOUNTAINS AS THE BRUNT OF THE SYSTEM IMPACTS 
THE AREA. STRONG UPSLOPE FLOW IN THE WHITE MOUNTAINS AND A SLIGHTLY 
DELAYED ENDING IN PRECIPITATION CHANCES SHOULD GIVE THIS AREA A 
SIGNIFICANT AMOUNT OF SNOW BY WEDNESDAY AFTERNOON. THUS...WILL BE 
UPGRADING TO A WINTER STORM WARNING FOR THE WHITE MOUNTAINS AS 8 TO 
12 INCHES OF SNOWFALL WILL BE POSSIBLE THERE. WILL KEEP THE WINTER 
WEATHER ADVISORY FOR GRAHAM COUNTY ABOVE 6000 FEET AS LIGHTER SNOW 
AMOUNTS WERE STILL ANTICIPATED. 

SYSTEM EXITS THE REGION WEDNESDAY AFTERNOON WITH IMPROVING 
CONDITIONS. CLEAR SKIES WEDNESDAY NIGHT WILL LEAD TO WIDESPREAD 
FREEZING TEMPERATURES THURSDAY MORNING...INCLUDING THE GREATER 
TUCSON AREA. RIDGE OF HIGH PRESSURE IN PLACE FOR DRY AND SLIGHTLY 
WARMER WEATHER INTO THE WEEKEND.  

&&

.AVIATION...OVC CIRRUS DECKS WILL YIELD TO SCT-BKN CLOUDS WITH BASES 
OF 3-7 KFT ABOVE VALLEY FLOORS TIL 03Z TIME PERIOD. EXPECT 
SCT-NUMEROUS SHRA/HIGHER TERRAIN SHSN RESULTING IN WIDESPREAD MVFR 
CONDITIONS TONIGHT WITH MOUNTAIN OBSCURATIONS...ESPECIALLY NE OF 
KTUS. SURFACE WINDS SWLY/WLY INCREASING 20-30 KTS THIS AFTN WITH 
GUSTS TO 35-45 KTS INTO TONIGHT. EXPECT DECREASING CLOUDS AND PRECIP 
AND DIMINISHING WIND FROM WEST TO EAST FROM LATE TONIGHT THROUGH WED 
MORNING. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...STRONG SW WINDS WILL CONTINUE THROUGH THE 
NIGHT...BECOMING MORE WESTERLY. SOME GUSTS OF 40 TO 50 MPH WILL 
OCCUR...WITH A FEW HIGHER GUSTS ON RIDGE TOPS.  HOWEVER...HUMIDITY 
VALUES WILL REMAIN WELL ABOVE CRITICAL VALUES. THE SYSTEM 
RESPONSIBLE FOR THE WIND WILL ALSO PRODUCE WIDESPREAD RAIN AND SNOW 
NORTHEAST OF TUCSON...AND A FEW LIGHTNING STRIKES MAY ACCOMPANY THIS 
PRECIPITATION. NO OTHER FIRE WEATHER CONCERNS ARE ANTICIPATED 
THROUGH THE CHRISTMAS WEEKEND.
 
&&

.TWC WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 5 PM MST THIS EVENING UNTIL 3 PM MST 
WEDNESDAY ABOVE 6000 FEET FOR AZZ019

WINTER WEATHER ADVISORY IN EFFECT AZZ030 FROM 5 PM THIS          
EVENING TO 6 AM MST WEDNESDAY ABOVE 6000 FEET

WIND ADVISORY TIL 8 PM MST THIS EVENING AZZ032>034

WIND ADVISORY TIL 3 AM MST WEDNESDAY AZZ035

$$

WEATHER.GOV/TUCSON