Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 230913
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
213 AM MST TUE DEC 23 2014

.SYNOPSIS...DRY WITH MOSTLY CLEAR SKIES TO START THE WEEK. A WEAK
COLD FRONT WILL MOVE THROUGH EARLY THIS MORNING...BRINGING COOLER
TEMPERATURES ESPECIALLY EAST OF TUCSON. A STORM SYSTEM DIGGING INTO
THE FOUR CORNERS AREA LATE IN THE WEEK WILL BRING A FEW SHOWERS...
ESPECIALLY NEAR THE EASTERN MOUNTAINS THURSDAY NIGHT INTO FRIDAY.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 23/00Z UPPER-AIR PLOTS SHOW A
LARGE UPPER LOW CURRENTLY SPINNING OVER EASTERN NEBRASKA WITH AN
ELONGATED VORT LOBE ON THE BACK SIDE OF THIS LOW DROPPING TO THE
SOUTH ACROSS THE FOUR CORNERS REGION AND INTO NEW MEXICO. ANY
MOISTURE WITH THIS SYSTEM...ALBEIT LIMITED...WILL REMAIN TO OUR EAST
AS THIS SYSTEM MOVES THROUGH NEW MEXICO TODAY AND BEGINS TO SHUNT
TOWARD THE EAST LATE TONIGHT INTO WEDNESDAY. MEANWHILE...A RIDGE
CENTERED OVER THE EASTERN PACIFIC WATERS WILL RESULT IN THE
AMPLIFIED RIDGE AXIS EXTENDING ACROSS CALIFORNIA INTO THE GREAT
BASIN AND INTO THE NORTHERN ROCKIES BY EARLY WEDNESDAY. THE RIDGE
AXIS WILL CONTINUE TO PUSH EAST AND WEAKEN IN RESPONSE TO ANOTHER
PACIFIC TROUGH MAKING ITS WAY INTO THE PACIFIC NORTHWEST WEDNESDAY.
THIS SYSTEM WILL THEN DIVE TO THE SOUTHEAST TO THE GREAT BASIN LATE
WEDNESDAY INTO EARLY THURSDAY. DURING THE DAY ON THURSDAY THE TAIL
END OF THE TROUGH AXIS AND ASSOCIATED VORT LOBE WILL BE SWINGING
THROUGH THE BASE OF THE TROUGH BEFORE EJECTING TO THE NORTHEAST
ACROSS THE PLAINS STATES EARLY FRIDAY. MEANWHILE...A SECONDARY
IMPULSE WILL CARVE THROUGH THE TROUGH AXIS FRIDAY INTO SATURDAY
ACROSS MUCH OF ARIZONA. THE BULK OF THE MOISTURE AND PRECIPITATION
THREAT WITH THIS SYSTEM WILL BE MOSTLY THURSDAY NIGHT INTO FRIDAY
WITH THE PRECIPITATION THREAT DECREASING CONSIDERABLY BY FRIDAY
NIGHT. THAT SAID...THE CHANCE FOR SHOWERS WITH THIS SYSTEM ARE NOT
EXPECTED TO BE MUCH...GENERALLY SLIGHT CHANCES OVER THE
DESERTS/VALLEYS AND LOW END CHANCE CATEGORY POPS FOR MOUNTAIN TOPS.
THIS SYSTEM WILL ALSO BRING MUCH COOLER TEMPERATURES TO THE REGION
AS WELL...BUT EVEN THROUGH SNOW LEVELS WILL FALL TO AROUND 6000-7000
FEET WITH THIS STORM...SNOW AMOUNTS ARE NOT EXPECTED TO BE MUCH MORE
THAN A DUSTING WITH THE BEST THREAT FOR SNOW IN THE WHITE MOUNTAINS
OF NORTHERN GREENLEE COUNTY. A SIGNIFICANT INCREASE IN WINDS IS ALSO
EXPECTED TO ACCOMPANY THIS SYSTEM WITH BREEZY TO WINDY CONDITIONS
CHRISTMAS DAY.

A DRY FORECAST IS EXPECTED THIS WEEKEND THROUGH EARLY NEXT WEEK.
MODELS ARE INDICATING THAT ANOTHER PACIFIC SYSTEM WILL DEVELOP OVER
THE PACIFIC NORTHWEST DURING THE WEEKEND AND WILL DIVE SOUTHEAST
REACHING THE GREAT BASIN AND NORTHERN CALIFORNIA BY LATE MONDAY.
MOISTURE WITH THIS SYSTEM THROUGH THAT TIME WILL REMAIN WELL TO OUR
NORTH...BUT WE WILL SEE AN INCREASE IN WINDS EARLY NEXT WEEK AS THIS
SYSTEM APPROACHES THE SOUTHWEST TOWARD THE MIDDLE OF NEXT WEEK.

FOR TUCSON...HIGH TEMPERATURES WILL GENERALLY RANGE FROM 2 TO 4 DEGS
BELOW NORMAL TODAY AND WEDNESDAY...THEN AROUND 2 TO 4 DEGS ABOVE
NORMAL FOR CHRISTMAS DAY. HIGHS 6 TO 8 DEGS BELOW NORMAL FRIDAY AND
SATURDAY...THEN ONLY SLIGHTLY BELOW NORMAL FOR SUNDAY AND MONDAY.
LOW TEMPS AROUND 3 TO 5 DEGS BELOW NORMAL TODAY...THEN NEAR NORMAL
THURSDAY AND FRIDAY...FOLLOWED BY 4 TO 6 DEGS BELOW NORMAL FOR
SATURDAY...THEN 1 TO 3 DEGS BELOW NORMAL FOR SUNDAY AND MONDAY.

&&

.AVIATION...VALID THRU 24/12Z.
MAINLY CLEAR SKIES THROUGH THE FORECAST PERIOD. WINDS WILL BEGIN TO
INCREASE OUT OF THE NORTH-NORTHEAST AFTER SUNRISE TODAY WITH THE
PASSAGE OF A DRY COLD FRONT FROM THE NORTH. SUSTAINED WINDS OF 10 TO
20 KTS WITH HIGHER GUSTS. THEN...A SURFACE GRADIENT WILL SET UP
TONIGHT WHICH WILL RESULT IN ENHANCED EASTERLY/NORTHEASTERLY WINDS
OF 10 TO 20 KTS DEVELOPING EARLY WEDNESDAY MORNING...ESPECIALLY IN
THE VICINITY OF THE KTUS TERMINAL. AVIATION DISCUSSION NOT UPDATED
FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WILL PREVAIL THROUGH WEDNESDAY WITH A
SLIGHT CHANCE OF A FEW RAIN AND SNOW SHOWERS OVER THE WHITE
MOUNTAINS LATE CHRISTMAS DAY THROUGH FRIDAY. BREEZY TO LOCALLY WINDY
NORTHERLY/NORTHEASTERLY WINDS WILL DEVELOP TODAY SHORTLY AFTER
SUNRISE. ADDITIONALLY...DEW POINTS WILL DROP SIGNIFICANTLY FOLLOWING
A DRY FRONTAL PASSAGE RESULTING IN LOWERING HUMIDITY LEVELS. A
TIGHTENING SURFACE PRESSURE GRADIENT WILL DEVELOP OVERNIGHT TUESDAY
RESULTING IN INCREASING EASTERLY WINDS WEDNESDAY MORNING BEFORE
RELAXING DURING THE AFTERNOON. ANOTHER SYSTEM PASSING TO OUR
NORTHEAST WILL ONCE AGAIN BRING BREEZY TO LOCALLY WINDY CONDITIONS
TO THE REGION ON THURSDAY.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

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

PUBLIC...MOLLERE
AVIATION/FIRE WEATHER...CARLAW/MEADOWS






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