000
FXUS65 KTWC 280233
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
720 PM MST MON DEC 27 2010
.SYNOPSIS...A WEAK DISTURBANCE MAY BRING A FEW FLURRIES TO THE
MOUNTAINS EAST OF TUCSON TONIGHT. DRY CONDITIONS WITH NEAR NORMAL
DAYTIME TEMPERATURES TUESDAY. A STRONG STORM SYSTEM IS THEN EXPECTED
TO BRING VALLEY RAIN AND MOUNTAIN SNOW WEDNESDAY AFTERNOON INTO
THURSDAY...FOLLOWED BY MUCH COLDER TEMPERATURES FRIDAY AND NEW YEARS
DAY.
&&
.DISCUSSION...CURRENT SATELLITE IR IMAGERY SHOWS THE BULK OF THE
HEAVIER CLOUDINESS MOVING ON TO THE EAST. MUCH OF THE CWA STILL
UNDER PARTLY CLOUDY CONDTIONS DUE TO SOME LINGERING CIRRUS THAT WILL
LIKELY STICK AROUND INTO THE OVERNIGHT HOURS. ZOOMING OUT TO LOOK AT
THE SOUTHWEST IN TOTAL...SKIES MAY START OFF PARTLY TO MOSTLY SUNNY
TOMORROW MORNING BEFORE ANOTHER WAVE OF CLOUDS STARTS TO PUSH IN FOR
THE AFTERNOON. MOVING OVER TO THE RADAR IMAGERY...STILL SEEING A FEW
LIGHT ECHOES OUT THERE. ONE PATCH...AT THE TIME OF THIS WRITING OVER
EASTERN PIMA COUNTY...IS LIKELY VIRGA. THE OTHER...OVER NORTHERN
GRAHAM COUNTY...AGAIN AT THE TIME OF THIS WRITING...GIVEN THE
ELEVATIONS THERE...MAY BE PRODUCING SOME LIGHT SNOW FLURRIES.
MODEL SOLUTIONS STILL ON TRACK FOR UPCOMING WEATHER SYSTEM WEDNESDAY
NIGHT INTO FRIDAY. PLEASE REFER TO PREV DISCUSSION SECTION...THE
HAZARDOUS WEATHER OUTLOOK LOCATED AT AWIPS PIL PSRHWOTWC...AND THE
SPECIAL WEATHER STATEMENT LOCATED AT AWIPS PIL PSRSPSTWC FOR FURTHER
DETAILS. INHERITED FORECAST CONTINUES TO DEPICT MODEL SOLUTIONS
WELL...SO NO CHANGES OR UPDATES PLANNED.
&&
.AVIATION...FOR LOCATIONS EAST OF A KSAD-KDUG LINE...FEW-SCT CLOUDS
8-12K FT AGL AND BKN-OVC CLOUDS AT OR ABOVE 15K FT AGL THRU 28/12Z
WITH A SLIGHT CHANCE OF -SHRA AND HIGHER TERRAIN -SHSN. FOR
LOCATIONS WEST OF KSAD-KDUG LINE...INCLUDING KTUS AND KOLS...EXPECT
FEW-SCT CLOUDS 8-10K FT WITH SCT CLOUDS AT OR ABOVE 15K FT AGL. FOR
ALL SOUTHEAST ARIZONA 13Z-23Z TUESDAY FEW-SCT CLOUDS MOSTLY AT OR
ABOVE 15K FT AGL. SURFACE WIND GENERALLY LESS THAN 10 KTS THRU
TUESDAY AFTERNOON. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.
&&
.CLIMATE...AS THE WEDS-FRI STORM APPROACHES...LOOKING BACK INTO THE
CLIMATE DATABASE THE LAST TIME SNOWFALL WAS REPORTED AT TUCSON
INTERNATIONAL AIRPORT WAS A TRACE ON FEB 10 2009...WHILE THE LAST
MEASURABLE SNOWFALL THERE WAS 0.6 OF AN INCH BACK ON JAN 30 2002.
&&
.FIRE WEATHER...NO FIRE WEATHER CONCERNS.
&&
.PREV DISCUSSION...SHORTWAVE TROUGH AXIS EXTENDING FROM THE GRAND
CANYON SWWD TO EAST OF YUMA THIS AFTERNOON. PERHAPS SOME SNOW
FLURRIES ACROSS MOUNTAIN PEAKS EAST OF TUCSON TONIGHT.
OTHERWISE...MOSTLY CLEAR SKIES ACROSS WRN/CENTRAL PIMA COUNTY AND
DECREASING CLOUDS BY DAYBREAK ACROSS ERN SECTIONS. SUNNY TO PARTLY
CLOUDY SKIES TUE BEHIND THE DEPARTING SHORTWAVE TROUGH. PRECIP-FREE
CONDITIONS UNDER PARTLY CLOUDY SKIES AREA WIDE TUE NIGHT.
THEREAFTER...27/12Z NAM/GFS/ECMWF CONTINUED TO BE IN GOOD AGREEMENT
WITH REGARD TO DEPICTING A DEEPENING TROUGH OVER THE WRN CONUS WED.
WILL MAINTAIN PRECIP-FREE CONDITIONS ACROSS THIS FORECAST AREA WED
MORNING. THE OFFICIAL FORECAST PRESENTLY INDICATES CHANCE-CATEGORY
POPS ACROSS MUCH OF SE AZ WED AFTERNOON. BASED PRIMARILY ON THE
27/15Z SREF AS WELL AS THE AFOREMENTIONED NAM/GFS/ECMWF...POPS WERE
INCREASED TO NEAR 100 PERCENT MOST SECTIONS. BREEZY TO WINDY
CONDITIONS MAY CREATE LOCALIZED BLIZZARD CONDITIONS ACROSS THE
HIGHER TERRAIN NE OF TUCSON WED NIGHT.
523 DM UPPER LOW PROGGED TO BE CENTERED OVER UTAH THUR...THEN VERY
DEEP UPPER LOW TO EJECT NEWD INTO SRN SOUTH DAKOTA BY MIDDAY FRI.
CERTAINLY ENOUGH MOISTURE TO JUSTIFY CHANCE-CATEGORY POPS FROM
TUCSON EWD THUR...AND A SLIGHT CHANCE OF POPS ACROSS WRN PIMA COUNTY.
SNOW LEVELS MIDDAY WED FORECAST TO BE AROUND 6000-6500 FEET...THEN
SNOW LEVELS ARE EXPECTED TO LOWER TO 2500 NORTH TO 3500 FEET SOUTH
MIDDAY THUR. THUS A SLIGHT CHANCE OF SNOW SHOWERS TO THE VALLEY
FLOORS IS JUSTIFIED THUR NIGHT...THEN PRECIP IS FORECAST TO END FROM
WEST-EAST FRI. DRY CONDITIONS TO OCCUR AREA WIDE FRI NIGHT-MON.
THE BEST ESTIMATE PRESENTLY FOR STORM TOTAL QPF/S IN THE VALLEYS
WILL RANGE FROM 0.25-0.75 INCH...WITH 0.50-1.50 INCHES LIQUID
AMOUNTS IN THE MOUNTAINS. HAVE INCREASED THE STORM TOTAL SNOW
ACCUMULATIONS TO RANGE UP TO 20 INCHES IN THE WHITE MOUNTAINS...
WITH 10-15 INCHES ACROSS THE SOUTHERN MOUNTAINS IN GRAHAM COUNTY
INCLUDING MOUNT GRAHAM...AS WELL AS THE CATALINA AND RINCON
MOUNTAINS ADJACENT THE TUCSON METRO AREA. ALTHOUGH NOT DEPICTED AT
THIS TIME...WOULD NOT BE SURPRISED TO SEE PERHAPS UP TO 2 INCHES OR
SO OF SNOWFALL IN THE TUCSON METRO AREA BY THUR NIGHT. THESE
FORECAST SNOW ACCUMULATIONS WILL BE SUBJECT TO CHANGE AS THE EVENT
DRAWS CLOSER.
THE OTHER SIGNIFICANT IMPACT FROM THIS SYSTEM WILL BE MUCH COLDER
TEMPS BY THUR NIGHT AND FRI. FOR INSTANCE...THE OFFICIAL FORECAST
WILL CONTINUE TO DEPICT MIN TEMPS ACROSS MUCH OF THE TUCSON METRO
AREA TO BE IN THE UPPER 20S F THUR NIGHT/FRI MORNING...WITH MIN
TEMPS TO BE EVEN A FEW DEGS F COLDER FRI NIGHT/SAT MORNING. DAYTIME
TEMPS FRI TO AVERAGE NEARLY 20 DEGS F BELOW NORMAL. HIGH TEMPS NEW
YEARS DAY TO BE ABOUT 10-15 DEGS F BELOW NORMAL. SLIGHTLY WARMER
SUN-MON THOUGH HIGH TEMPS REMAINING BELOW NORMAL.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...NONE.
$$
SMR/BF
WEATHER.GOV/TUCSON
