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000
FXUS65 KTWC 091545
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
845 AM MST TUE FEB 9 2010

.SYNOPSIS...DRY WITH A BRIEF DAYTIME WARMING TREND BEFORE ANOTHER
WINTER STORM BRINGS VALLEY RAIN AND MOUNTAIN SNOW BY LATE WEDNESDAY
INTO THURSDAY. THIS NEXT STORM WILL BE COLDER THAN RECENT ONES...SO
THE SNOW LEVEL WILL BE MUCH LOWER WEDNESDAY NIGHT AND EARLY THURSDAY
WITH SIGNIFICANT ACCUMULATIONS POSSIBLE ABOVE 4000 FEET OR EVEN
LOWER. DRY AND WARMER FRIDAY INTO THE WEEKEND UNDER HIGH PRESSURE.

&&

.DISCUSSION...WATER VAPOR IMAGERY SHOWS A STRONG LOW JUST OFF THE
CENTRAL CALIFORNIA COAST WITH CLOUDINESS JUST AHEAD OF THE LOW OVER
MOST OF CALIFORNIA...NEVADA AND SPREADING INTO PORTIONS OF ARIZONA
AND UTAH.

OVER THE SOUTHEAST PACIFIC A LARGE BATCH OF MID AND HIGH LEVEL
CLOUDS WILL LIKELY HEAD TOWARD THE DESERT SOUTHWEST DURING THE NEXT
12 TO 24 HOURS AS A STRONG 300MB JET DEVELOPS TO OUR SOUTH AND
WEST.

SO FAR THE FORECAST FOR THIS AFTERNOON SEEMS TO BE ON TRACK WITH
RESPECT TO BOTH HIGH TEMPS AND THE ANTICIPATED INCREASE IN HIGH
CLOUDS LATE IN THE DAY. THEREFORE...NO CHANGES ARE PLANNED FOR THE
SHORT TERM...HOWEVER WILL CONTINUE TO MONITOR OBSERVATIONS...AS WELL
AS SATELLITE TRENDS AND WILL MAKE ADJUSTMENTS IF NEEDED.

FOR MORE DETAILS REGARDING THE UPCOMING SYSTEM WEDNESDAY NIGHT AND
EARLY THURSDAY...SEE THE PREVIOUS DISCUSSION SECTION BELOW. IN
ADDITION...MORE INFORMATION ABOUT THIS SYSTEM WILL BE FORTHCOMING ON
THE AFTERNOON DISCUSSION SINCE THE 12Z MODEL DATA WILL SHED MORE
LIGHT ON THIS STORM.

&&

.AVIATION...INCREASING HIGH CLOUDS FROM THE SOUTHWEST TODAY. SURFACE
WINDS ARE EXPECTED TO BE LESS THAN 15 KTS AND ADHERE TO TYPICAL
DIURNAL PATTERNS. HIGH PRESSURE WILL GIVE WAY TO A STRONG STORM
MOVING IN FROM THE WEST BY LATE WEDNESDAY. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

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

&&

.PREV DISCUSSION...SHORTWAVE RIDGE PHASING EASTWARD AHEAD OF A
STRONG LOW WINDING UP NEAR SAN FRANCISCO AS IT DIGS DOWN THE
CALIFORNIA COAST. IT IS EXPECTED TO TURN THE CORNER AND KICK
EASTWARD LATE TONIGHT AND EARLY WEDNESDAY MORNING ON A TRACK ACROSS
SOUTHERN CALIFORNIA AND NORTHERN BAJA TOWARD SOUTHERN ARIZONA.
TIMING IS STILL SHAKY WITH SOME MODEL RESOLUTIONS LIKELY A BIT
EARLY. EXPECT AN EXTRA WOBBLE AS INERTIA AND BRIEF RECONSOLIDATION
FROM LAST PIECE OF REINFORCING ENERGY ULTIMATELY BRINGS THE STORM
ACROSS THE AREA LATE WEDNESDAY AND WEDNESDAY NIGHT INTO THURSDAY
MORNING. THIS IS EXPECTED TO ALSO ALLOW A BETTER MOISTURE TAP
EARLIER AND FURTHER WEST FOR WIDESPREAD PRECIPITATION (WITH THE
SUBTROPICAL MOISTURE PLUME NOW REACHING TOWARD CENTRAL BAJA COMING
INTO PLAY). A COLDER AND STRONGER SYSTEM THAN MOST RECENT
STORMS...SNOW LEVELS WILL FALL TOWARD VALLEY FLOORS ESPECIALLY IN
EASTERN ZONES. SIGNIFICANT ACCUMULATIONS APPEAR LIKELY ABOVE 4000
FEET WITH SNOW LEVELS AS LOW AS 3000 FEET...PERHAPS LOCALLY A BIT
LOWER NEAR CONVECTION. BEST MOISTURE...DYNAMICS AND COLD AIR COME
TOGETHER WEDNESDAY EVENING INTO THURSDAY MORNING.

WE THINK THE ECMWF MIGHT BE A TAD TOO AGGRESSIVE WITH THE
TIMING...AND EXPECT SOME WRAP AROUND STILL ROTATING THROUGH THE
SOUTHEAST CORNER OF THE STATE THURSDAY MORNING.

RIDGING WILL DOMINATE WESTERN STATES IN THE PATTERN SETTING UP FOR
THE END OF THE WEEK AND NEXT WEEKEND. EXPECT A STRONG WARMING TREND
TO BACK ABOVE CLIMO AFTER THE COLD AND WET PERIOD.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...WINTER STORM WATCH FROM
     WEDNESDAY 3 PM THROUGH THURSDAY 11 AM ABOVE 4000
     FEET AZZ019-029-030-032>035.

$$

WEATHER.GOV/TUCSON