FXUS65 KTWC 111554
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
900 AM MST FRI DEC 11 2009

.SYNOPSIS...A SERIES OF WEAK DISTURBANCES WILL BRING PERIODS OF HIGH 
CLOUDS TO SOUTHEAST ARIZONA TODAY AND SATURDAY...WITH ONLY A FEW 
LIGHT SHOWERS NEAR THE WHITE MOUNTAINS. A STRONGER STORM SYSTEM WILL 
BRING A CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW LATE SUNDAY AND 
MONDAY. HIGH PRESSURE BUILDING OVER THE DESERT SOUTHWEST IS EXPECTED 
TO BRING A WARMING TREND THE REST OF NEXT WEEK.

&&

.DISCUSSION...A FEW PATCHES OF MID AND HIGH CLOUD WITH A WEAK 
INFLECTION IN OUR ZONAL WESTERLY FLOW PASSING OVERHEAD. COULD SEE 
SOME LIGHT SHOWERS NORTH OF OUR AREA. ANOTHER IN A SERIES OF WEAK 
IMPULSES EARLY SATURDAY WITH A THIRD LATE SATURDAY...AGAIN MAINLY 
SOME CLOUDS WITH THAT...VIRGA OR SPRINKLES NOT OUT OF THE QUESTION 
WITH A FEW LIGHT MOUNTAIN SHOWERS.

MAIN TROUGH PUSHING INTO ARIZONA SUNDAY...AND INTO OUR AREA LATE 
SUNDAY INTO MONDAY. NEW NAM12 CONTINUING TREND OF DEEPER TRAJECTORY 
AND THUS SLOWER TIMING...WHILE ALSO ALLOWING BETTER DYNAMICS AND 
MOISTURE FOR SOUTHEAST ARIZONA. STILL NOT A TERRIBLY COLD OR STRONG 
SYSTEM BUT EXPECT SCATTERED VALLEY RAIN AND LIKELY MOUNTAIN SNOW. 
BEST CONDITIONS COMING TOGETHER FOR 03Z TO 12Z MONDAY WITH INITIAL 
PIECE OF ENERGY...THEN REINFORCING SHOT 18Z TO 21Z MONDAY. WE WILL 
ADJUST OUR CHANCE OF PRECIP UP WITH THE AFTERNOON FORECAST PACKAGE 
AND ISSUE A HAZARDOUS WEATHER OUTLOOK TO GIVE A HEADS-UP FOR A 
SYSTEM THAT COULD END UP BRINGING ADVISORY LEVEL SNOWS ABOVE 6K FEET 
OR SO.

DIRTY RIDGE WILL LIKELY BRING A WARMING TREND THE REMAINDER OF NEXT 
WEEK IN A CHANGE OVER TO A BLOCKING PATTERN.

&&

.AVIATION...SCATTERED TO BROKEN DECKS OF MID AND HIGH 
CLOUDS...MOSTLY ABOVE 15K FEET AGL. WINDS LIGHT AT LESS THAN 10 KTS 
AND DIURNALLY/TERRAIN DRIVEN THROUGH FRIDAY. AVIATION DISCUSSION NOT 
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...NO FIRE WEATHER CONCERNS AT THIS TIME.
 
&&

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

$$

WEATHER.GOV/TUCSON