FXUS65 KTWC 101025
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
325 AM MST THU DEC 10 2009
.SYNOPSIS...A SERIES OF WEAK DISTURBANCES IN THE WESTERLY FLOW ALOFT
WILL BRING PERIODS OF HIGH CLOUDS TO SOUTHEAST ARIZONA THROUGH
SATURDAY. THE LAST DISTURBANCE IN THIS SERIES WILL BRING A SLIGHT
CHANCE OF SHOWERS MAINLY NORTH OF TUCSON AND NEAR THE WHITE
MOUNTAINS ON SUNDAY...WITH MOST LOCATIONS REMAINING DRY. A STRONG
RIDGE OF HIGH PRESSURE WILL BRING A STRONG WARMING TREND BY THE
MIDDLE OF NEXT WEEK.
&&
.DISCUSSION...CLEAR SKIES ACROSS SOUTHEAST ARIZONA AND RATHER CRISP
WITH KTUS ALREADY ACHIEVING OUR FORECASTED LOW OF 35 AS OF 3 AM.
DESPITE THE COLD START...AFTERNOON TEMPERATURES SHOULD EDGE A LITTLE
CLOSER TO MID DECEMBER NORMS TODAY WITH LOWER ELEVATIONS CLIMBING
INTO THE LOWER 60S. CLEAR SKIES AT SUNRISE...BUT HIGH CLOUDS WILL BE
INCREASING AGAIN TODAY AS THE NEXT WEAK DISTURBANCE ARRIVES IN THE
FAST WESTERLY FLOW ALOFT. THIS WEAK SHORTWAVE ACTUALLY SHOWS UP BEST
ON WATER VAPOR IMAGERY NEAR 30N/120W. SKY GRIDS SHOW PARTLY CLOUDY
THIS MORNING BECOMING MOSTLY CLOUDY THIS AFTERNOON.
OCCASIONAL HIGH CLOUDS WILL BE THE NAME OF THE GAME THROUGH FRIDAY
AND SATURDAY AS A PARADE OF UNIMPRESSIVE DISTURBANCES ZIP THROUGH
ARIZONA. 00Z GFS SHOWS THE NEXT WAVE ARRIVING FRIDAY WITH ANY
SIGNIFICANT PRECIP RELEGATED TO NORTHERN ARIZONA AND THE GREAT
BASIN. YET ANOTHER WAVE VERY SIMILARLY TRACKS THROUGH SATURDAY WITH
MORE HIGH CLOUDS FOR US...AND AGAIN ANY PRECIP REMAINING IN NORTHERN
ARIZONA. AS THESE WAVES PASS FRIDAY AND SATURDAY...OUR MOUNTAIN TOPS
COULD CERTAINLY SEE A PASSING STRAY SHOWER...ESPECIALLY THE WHITES.
HOWEVER...THE VAST MAJORITY OF THE CWA WILL REMAIN DRY. A SLIGHTLY
STRONGER SHORTWAVE STILL EXPECTED TO ARRIVE IN CALIFORNIA SUNDAY
MORNING. GFS AND ECMWF NOW AGREE THIS WAVE WILL HAVE LESS AMPLITUDE
AND BE WEAKER THAN THOUGHT EARLIER. AGAIN...IT BASICALLY ZIPS
THROUGH ARIZONA SUNDAY WITH CLOUDS AND MOST PRECIP CONFINED TO AREAS
NORTH OF OUR CWA. REDUCED INHERITED POPS SUBSTANTIALLY ON SUNDAY AND
MONDAY...ESPECIALLY SOUTH OF TUCSON. THE PHOENIX AND FLAGSTAFF CWAS
STAND A BETTER CHANCE OF SQUEEZING OUT SOME QPF SUNDAY...AND TRIED
TO BLEND IN WITH THEIR POP FIELDS. DROPPED THE TUCSON METRO AREA TO
10% POPS FOR SUNDAY...AND HELD ONTO SOME 20% POPS FOR THE NORTHERN
CWA/WHITES. WITH THE LESSER AMPLITUDE OF THE WAVE...ALSO DROPPED SKY
GRIDS TO PARTLY CLOUDY MAINLY SOUTH OF TUCSON DURING SUNDAY AS THE
WAVE PASSES.
THE DISTURBANCE THAT GIVES US A GLANCING BLOW ON SUNDAY WILL BE THE
LAST OF THE SERIES...WITH A SIGNIFICANT PATTERN CHANGE EXPECTED NEXT
WEEK. 00Z GFS AND ESPECIALLY THE 00Z ECMWF SHOW A STRONG RIDGE OF
HIGH PRESSURE BUILDING OVER THE DESERT SOUTHWEST TUESDAY THROUGH
THURSDAY. ECMWF IS MOST AGGRESSIVE...WITH 582 DM 500 MB HEIGHTS
APPROACHING SOUTHWEST ARIZONA WEDNESDAY...AND MOST OF ARIZONA WITH
GREATER THAN 582 DM HEIGHTS BY THURSDAY. ECMWF SUGGESTS HIGHS IN THE
UPPER 70S IN THE LOWER DESERTS BY NEXT THURSDAY...WITH A FEW LOWER
80S IN THE TYPICAL WARMEST LOCALES. DIDN'T GO THAT FAR YET...BUT DID
INCREASE MAX TEMPS INTO THE LOWER 70S FOR THE LOWER DESERTS TUESDAY
THROUGH THURSDAY. NEXT WEEK IS STARTING TO LOOK VERY NICE INDEED.
&&
.AVIATION...A WEAK DISTURBANCE IN ZONAL FLOW ALOFT WILL MOVE ACROSS
THE AREA TODAY. THIS FEATURE WILL BRING SCATTERED TO OCCASIONAL
BROKEN LAYERS OF MID TO HIGH LEVEL CLOUDS WITH CEILINGS BEING ABOVE
12KFT AGL. WILL ALSO SEE A FEW CUMULUS CLOUDS AROUND 7-9KFT AGL.
NORMAL DIURNAL WIND TRENDS DURING THE NEXT 24 HOURS. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
&&
.FIRE WEATHER...NO FIRE WEATHER CONCERNS AT THIS TIME.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...NONE.
$$
TURNER
WEATHER.GOV/TUCSON
