FXUS65 KTWC 071051
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
350 AM PM MST MON DEC 7 2009

.SYNOPSIS...A STRONG WINTER STORM SYSTEM WILL APPROACH THE AREA FROM 
THE NORTHWEST TODAY. THIS SYSTEM WILL BRING WIDESPREAD VALLEY RAIN 
AND SIGNIFICANT MOUNTAIN SNOW TO SOUTHEAST ARIZONA TONIGHT INTO 
MIDDAY TUESDAY. DRIER CONDITIONS WEDNESDAY FOLLOWED BY ANOTHER 
CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW THURSDAY INTO FRIDAY.

&&

.DISCUSSION...LOTS OF THINGS TO CONSIDER THIS MORNING WHICH LED TO 
THE DISCUSSION BEING LATE. SATELLITE IMAGERY SHOWED MAINLY MID-HI 
LEVEL MOISTURE STREAMING ACROSS THE AREA FROM THE WEST IN ADVANCE OF 
THE UPPER LOW OVER NORTHERN CALIFORNIA. DEEPER MOISTURE WITH 
PRECIPITABLE WATER VALUES OVER ONE INCH WAS APPROACHING SOUTHERN 
CALIFORNIA COAST. PRESSURE GRADIENTS WILL BE ON THE INCREASE TODAY 
AS THE UPPER LOW DROPS SSE INTO CENTRAL CALIFORNIA. GOES DERIVED 
HIGH DENSITY WINDS DEPICTED WIND SPEEDS UP TO 45 KNOTS AROUND 700 MB 
APPROACHING SOCAL. THESE STRONG WINDS WILL BE SPREADING OVER THE 
AREA THIS AFTERNOON INTO EARLY TUESDAY MORNING. MORE LATER ON HOW 
THIS CHANGED OUR FORECAST. WITH THE MOISTURE INCREASING LATER TODAY 
EXPECT TO SEE SHOWERS DEVELOPING WEST AND NORTH OF TUCSON. AS THE 
UPPER TROF GETS CLOSER THIS EVENING...EXPECT SHOWERS TO INCREASE IN 
AREAL COVERAGE. SNOW LEVEL WILL BE AROUND 6000 FEET AND WITH 
EXCELLENT UPSLOPE FLOW...MODERATE TO LOCALLY HEAVY SNOW WILL BE 
OCCURRING IN THE MOUNTAINS...ESPECIALLY FROM EASTERN PIMA COUNTY 
NORTHEAST INTO THE WHITES. PRIMETIME FOR THE HEAVIEST SNOWS WILL BE 
BETWEEN 8 PM TONIGHT INTO 5 AM TUESDAY. EARLIER I MENTIONED ABOUT 
STRONGER WINDS TONIGHT WHERE THE MODELS ARE INDICATING THAT GUSTS UP 
TO 60 MPH ARE POSSIBLE ABOVE 8000 FEET. THAT COMBINED WITH THE 
FALLING SNOW...WHICH COULD BE AS MUCH AS 2 INCHES PER HOUR AT 
TIMES...WILL DEVELOP BLIZZARD LIKE CONDITIONS IN THE 
CATALINA/PINALENO AND WHITE MOUNTAINS. THUS HAVE DECIDED TO HOIST A 
RARE BLIZZARD WARNING FOR THESE MOUNTAIN RANGES. WILL CONTINUE 
WINTER STORM WARNING FROM 8000 FEET DOWN TO 6000 FEET WITH THE 
SOUTHERN MOUNTAINS RECEIVING THE LESSER SNOW AMOUNTS. CURRENTLY 
GOING WITH UP TO 18 INCHES IN THE WHITES...12-14 INCHES IN THE 
PINALENOS...UP TO A FOOT IN THE CATALINA/RINCONS...AND UP TO 10 
INCHES IN THE MOUNTAINS OF COCHISE/SANTA CRUZ COUNTIES. WOULDN'T BE 
SURPRISE IF THE AMOUNTS WERE HIGHER IN THE WHITES WHEN THE EVENT IN 
FINALLY DONE. WITH PEAK GRADIENT OCCURRING TONIGHT...WE HAVE DECIDED 
TO ALSO HOIST A WIND ADVISORY ACROSS GRAHAM/GREENLEE/COCHISE AND 
SANTA CRUZ COUNTIES TONIGHT INTO TUESDAY MORNING. RAINFALL AMOUNTS 
COULD BE AS HIGH AS AN INCH NORTH OF TUCSON...OTHERWISE VALUES WILL 
BE LESS THAN HALF AN INCH. THIS WILL DEFINITELY HELP IN EASING 
CURRENT SEVERE DROUGHT CONDITIONS. 

TROF AXIS TO PUSH THROUGH ON TUESDAY WITH ACTIVITY ENDING FROM WEST 
TO EAST. DRY WEDNESDAY THEN THERE WILL BE A SLIGHT CHANCE OF VALLEY 
SHOWERS/MOUNTAIN SNOW SHOWERS THURSDAY INTO THE WEEKEND AS SEVERAL 
WEATHER SYSTEMS OFF THE EASTERN PACIFIC MOVE THROUGH THE DESERT 
SOUTHWEST UNDER FAST ZONAL FLOW ALOFT.

COOL TEMPERATURES TO START THE WEEK WITH THE COLDEST READINGS ON 
TUESDAY THEN A SLOW WARMUP INTO THE WEEKEND. 

&&

.AVIATION...CONSIDERABLE LAYERED CLOUDS ABOVE 12K FT THROUGH THE 
MORNING HOURS. EXPECT BASES TO LOWER TO AROUND 8KFT AGL DURING THE 
AFTERNOON HOURS WITH SCT -SHRA DEVELOPING...MAINLY WEST AND NORTH OF 
TUCSON. THESE CONDITIONS WILL SPREAD EAST ACROSS THE REMAINDER OF 
SOUTHEAST ARIZONA TONIGHT WITH BASES LOWERING DOWN TO AROUND 6KFT 
AGL. AREAS OF MVFR CONDITIONS DUE TO SHRA/HIGHER TERRAIN SHSN 
TONIGHT INTO TUESDAY MORNING. SURFACE WINDS GENERALLY SLY/SWLY 8-18 
INCREASING 15-25 KTS AND GUSTY TONIGHT. AVIATION DISCUSSION NOT 
UPDATED FOR TAF AMENDMENTS.

&&

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

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
  WINTER STORM WARNING IN EFFECT FROM 5 PM MST TODAY TO 12 NOON MST 
   TUESDAY BETWEEN 6000 AND 8000 FEET FOR ZONES 019-030

  BLIZZARD WARNING IN EFFECT FROM 5 PM TODAY TO 12 NOON MST TUESDAY
   ABOVE 8000 FEET FOR ZONES 019-030.

  WINTER STORM WARNING IN EFFECT FROM 5 PM MST TODAY TO 12 NOON MST
   TUESDAY ABOVE 6000 FEET FOR ZONES 033>035.
  
  WIND ADVISORY IN EFFECT FROM 11 PM MST TONIGHT TO 12 NOON MST 
   TUESDAY FOR ZONES 019-030-034>035.

$$

WEATHER.GOV/TUCSON