Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 250341
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
840 PM MST WED DEC 24 2014

.SYNOPSIS...THERE IS A WIND ADVISORY IN EFFECT FROM 10 AM UNTIL 9 PM
CHRISTMAS DAY FOR MUCH OF COCHISE...EASTERN SANTA CRUZ...AND EXTREME
SOUTHEASTERN PIMA COUNTIES. A STORM SYSTEM WILL DIG INTO THE DESERT
SOUTHWEST ON CHRISTMAS DAY WITH BREEZY TO WINDY CONDITIONS AND A
CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW THURSDAY NIGHT. THIS SHOULD
BE A QUICK SHOT OF PRECIPITATION...ENDING IN THE EASTERN AREAS
FRIDAY MORNING. COOL AND DRY WEATHER WILL THEN RETURN THIS WEEKEND.

&&

.DISCUSSION...HIGH CLOUDS HAD SPREAD INTO THE AREA THIS EVENING IN
ADVANCE OF A SYSTEM THAT WILL PASS THROUGH THE REGION TOMORROW.
STRONG AND GUSTY WINDS CAN BE ANTICIPATED TOMORROW AS THE SYSTEM
ENTERS THE STATE. A WIND ADVISORY HAS ALREADY BEEN POSTED FOR MAINLY
COCHISE AND PARTS OF SANTA CRUZ AND EXTREME SOUTHEAST PIMA COUNTIES
TOMORROW FROM 10 AM MST TO 9 PM MST. THE SYSTEM WILL ALSO BRING A
FEW SHOWERS TO THE AREA LATE THURSDAY. CURRENT FORECAST LOOKED ON
TRACK...SO NO UPDATES NECESSARY.

&&

.AVIATION...VALID THRU 26/00Z.
BKN-OVC ABOVE 20 KFT AGL. AFTER 25/16Z...SCT-BKN CLOUDS AT 5-10K FT
AGL MAINLY FROM KTUS WWD/NWD...WITH A SLIGHT CHANCE OF VALLEY
SHRA/MOUNTAIN SHSN. SURFACE WIND SLY/SELY AT 5-15 KNOTS THRU
25/15Z...THEN SURFACE WIND LATE THURSDAY MORNING AND THURSDAY
AFTERNOON WILL BE SWLY/WLY AT 18-30 KTS AND GUSTS TO 30-45 KTS. THE
STRONGEST SURFACE WIND WILL BE EAST OF KTUS AND KOLS...IN THE
VICINITY OF KDUG. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A STRONG STORM SYSTEM WILL MOVE INTO THE FOUR
CORNERS AREA ON THURSDAY...AND CONTINUE EASTWARD INTO NEW MEXICO
FRIDAY. AS THIS SYSTEM APPROACHES THE REGION EXPECT DRY CONDITIONS
THROUGH CHRISTMAS MORNING...THEN INCREASING PRECIPITATION CHANCES
THURSDAY AFTERNOON AND EVENING...ESPECIALLY ACROSS THE EASTERN HALF
OF SOUTHEAST ARIZONA. A SLIGHT CHANCE OF PRECIPITATION WILL PERSIST
ALONG THE NEW MEXICO BORDER ON FRIDAY. THIS AREA OF LOW PRESSURE
WILL ALSO RESULT IN A SUBSTANTIAL INCREASE IN WINDS ON THURSDAY...
WITH THE HIGHEST WIND SPEEDS ACROSS COCHISE...EASTERN SANTA CRUZ AND
FAR SOUTHEASTERN PIMA COUNTIES...WHERE A WIND ADVISORY IS IN EFFECT
FROM 10 AM TO 9 PM THURSDAY. WIND GUSTS MAY APPROACH 55 MPH AT THE
HIGHEST ELEVATIONS AND 30 TO 40 MPH IN VALLEY LOCATIONS. DRY
CONDITIONS WILL THEN RETURN AREAWIDE ON SATURDAY AND PERSIST THROUGH
EARLY NEXT WEEK.

&&

.PREV DISCUSSION...VISIBLE SATELLITE IMAGERY WAS SHOWING A BATCH OF
CIRRUS STREAMING INTO AZ THIS AFTERNOON FROM THE NORTHWEST AHEAD OF
THE NEXT WEATHER DISTURBANCE. 24/18Z GFS 500 MB HEIGHTS AND WV
IMAGERY ARE SHOWING THIS TROUGH JUST ONSHORE IN THE PACIFIC
NORTHWEST WITH RIDGING OVER THE WRN CONUS BEGINNING TO FLATTEN OUT.
THIS SYSTEM WILL QUICKLY DIVE SOUTHEAST THROUGH THE GREAT BASIN
OVERNIGHT BEFORE IMPACTING THE SOUTHWESTERN STATES ON CHRISTMAS DAY.

BOTH THE 24/12Z OPERATIONAL GFS AND ECMWF HAVE SPED UP THE
PROGRESSION OF THIS SYSTEM AS COMPARED TO THE LAST SEVERAL RUNS. AS
SUCH...HAVE INCREASED POPS TO INCLUDE ISOLATED RAIN SHOWERS AS EARLY
AS TOMORROW AFTERNOON FOR AREAS MAINLY TO THE NORTH AND WEST OF
TUCSON. ADDITIONALLY...SOLUTIONS INCLUDING THE CMC HAVE BECOME
INCREASINGLY WET. THEREFORE...DECIDED TO INCREASE POPS AREA WIDE
AFTER 26/00Z BUT ESPECIALLY FOR HIGHER ELEVATIONS AND TO THE SOUTH
AND EAST OF TUCSON. CONFIDENCE CONTINUES TO INCREASE IN THE
LIKELIHOOD OF STORM TOTAL QPF AMOUNTS BETWEEN ONE TENTH AND ONE
THIRD OF AN INCH WITH 2 TO 4 INCHES OF SNOW LIKELY ABOVE 7000 FT.

WIND WILL ALSO BE AN ISSUE TOMORROW WITH BREEZY TO WINDY
CONDITIONS...AS SLY/SWLY WINDS WILL LIKELY REACH UP TO 30 MPH
SUSTAINED WITH GUSTS TO AROUND 40 MPH IN SOME VALLEY LOCATIONS. ONCE
HERE...THIS TROUGH WILL HANG AROUND FOR A LITTLE WHILE AFTER PRECIP
HAS ENDED. LOWERED HEIGHTS COUPLED WITH CLEARING SKIES AND CALM
WINDS WILL MAKE FREEZING TEMPERATURES LIKELY FOR THE EASTERN TWO
THIRDS OF THE CWA SATURDAY MORNING. THE POTENTIAL EXISTS FOR A HARD
FREEZE TO OCCUR FOR THE TUCSON METRO AREA...PERHAPS FOR A FEW HOURS
OR SO. THEREAFTER...THE TROUGH WILL ELONGATE AND EJECT TOWARD THE
EAST WITH THE SECOND HALF OF THE WEEKEND THRU THE BEGINNING OF NEXT
WEEK LOOKING FAIRLY PLEASANT.

DRY CONDITIONS WILL PREVAIL SATURDAY THROUGH TUESDAY AS THE NEXT
WEATHER SYSTEM IS PRETTY FAR OUT IN THE EXTENDED. OPERATIONAL MODELS
ARE BEGINNING TO COME INTO SLIGHTLY BETTER ALIGNMENT WITH THE
TIMING...DEPTH...AND PRECIPITATION ASSOCIATED WITH THIS TROUGH...BUT
PLENTY OF DISCREPANCIES STILL EXIST. FOR NOW...HAVE DECIDED TO GO
WITH A SLIGHT CHANCE OF SHOWERS ADJACENT TO THE NEW MEXICO BORDER
WEDNESDAY AND WEDNESDAY NIGHT...AS THE GFS IS CONSIDERABLY WETTER
THAN THE ECMWF.

TEMPERATURES WILL FALL FOLLOWING THE CHRISTMAS DAY SYSTEM...LASTING
THROUGH THE WEEKEND. THEN...A SLIGHT UPTICK IN TEMPERATURES WILL
OCCUR EARLY NEXT WEEK...ALTHOUGH WE WILL STILL REMAIN BELOW NORMAL
VALUES.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...WIND ADVISORY FROM 10 AM TO 9 PM
      MST THURSDAY FOR AZZ503-507-508-512-513.

&&

$$

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON

PREV DISCUSSION...FRENCH
AVIATION/FIRE WEATHER...ZELL






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