Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 221531
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
830 AM MST MON DEC 22 2014

.SYNOPSIS...A DRY NORTHWEST FLOW WILL RESULT IN PATCHES OF HIGH
LEVEL CLOUDS WITH TEMPERATURES NEAR NORMAL TO START THE WEEK. A WEAK
COLD FRONT WILL MOVE THROUGH MONDAY NIGHT BRINGING SLIGHTLY COOLER
TEMPERATURES ESPECIALLY EAST OF TUCSON TUESDAY. A STORM SYSTEM WILL
STAY MAINLY TO OUR NORTH FOR THE END OF THE WEEK WITH A FEW SNOW
SHOWERS FOR THE WHITE MOUNTAINS.

&&

.DISCUSSION...WATER VAPOR SATELLITE IMAGERY AND MODEL DATA SHOW A
RIDGE OF HIGH PRESSURE PARKED JUST OFF THE WESTERN U.S. COAST. SOME
THIN HIGH CLOUDS CURRENTLY STREAMING IN FROM THE NORTHWEST THIS
MORNING. CLEARING IS EXPECTED AS THE RIDGE AXIS BEGINS TO TILT EAST
LATER TODAY. WITH STRONG NORTHWEST FLOW ALOFT TODAY DAYTIME MIXING
WILL LEAD TO SOME BREEZY CONDITIONS MAINLY EAST OF
TUCSON...ESPECIALLY THROUGH THE GILA VALLEY WHERE WINDS WILL REMAIN
ELEVATED INTO TONIGHT. HAVE A VERY SLIGHT CHANCE OF PRECIP CONFINED
TO THE WHITE MOUNTAINS TODAY AS A SHORTWAVE BRUSHES THE EASTERN
PORTION OF THE STATE. TEMPERATURES TODAY WILL GENERALLY BE WITHIN A
FEW DEGREES OF NORMAL...WITH MOST PLACES SEEING HIGH TEMPERATURES ON
THE ABOVE NORMAL SIDE.

FOR ADDITIONAL INFORMATION SEE THE PREVIOUS DISCUSSION BELOW.

&&

.AVIATION...VALID THRU 23/12Z.
SCT TO BKN CIRRUS GENERALLY ABOVE 20 KFT WITH SOME CLEARING EXPECTED
THROUGH THE AFTERNOON. SURFACE WINDS LIGHT...GENERALLY LESS THAN 10
KTS...AND TERRAIN DRIVEN UNTIL 22/18Z. WINDS INCREASING OUT OF THE
NORTHWEST 10 TO 15 KTS WITH AN OCCASIONAL GUST TO 20 KTS THEREAFTER
MAINLY SOUTH AND EAST OF KTUS. NORMAL DIURNAL WIND TRENDS RETURNING
TONIGHT. 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 CHRISTMAS DAY THROUGH FRIDAY. A SYSTEM PASSING TO THE
NORTH WILL BRING BREEZY NORTHWEST WINDS TO THE REGION THIS
AFTERNOON...PRIMARILY ACROSS AREAS EAST OF TUCSON. THE WINDS WILL
RELAX DURING THE EVENING EXCEPT ACROSS THE HIGHER TERRAIN AND THE
GILA VALLEY WHERE THEY WILL CONTINUE THROUGH MUCH OF TONIGHT. BREEZY
TO LOCALLY WINDY CONDITIONS AGAIN ON TUESDAY...WITH WINDS FROM A
MORE NLY/NELY DIRECTION. DEW POINTS WILL DROP SIGNIFICANTLY
FOLLOWING A FRONTAL PASSAGE FROM THE NORTH ON TUESDAY RESULTING IN
LOWERING HUMIDITY LEVELS. GUSTY WINDS WILL RETURN AGAIN ON THURSDAY.

&&

.PREVIOUS DISCUSSION...WATER VAPOR IMAGERY AND 22/00Z UPPER-AIR
PLOTS SHOW A RIDGE PARKED OVER THE EASTERN PACIFIC WATERS WITH
NORTHWEST FLOW ON THE TOP OF THE RIDGE SPILLING EXTENSIVE CLOUDINESS
SOUTHWARD ACROSS PARTS OF THE GREAT BASIN AND INTO THE DESERT
SOUTHWEST...WITH THE CLOUDS OVER MY FORECAST AREA MOSTLY HIGH LEVEL
CIRRUS CLOUDS.

MODELS INDICATE THAT AN UPPER LOW WILL CONTINUE TO DEVELOP ACROSS
THE NORTHERN ROCKIES/PLAINS STATES TODAY WITH A VORT LOBE ASSOCIATED
WITH THIS SYSTEM DROPPING SOUTH FROM THE NORTHERN ROCKIES THROUGH
THE GREAT BASIN AND THE FOUR CORNERS REGION TODAY...THEN INTO NEW
MEXICO AND WEST TEXAS TONIGHT AND TUESDAY. ANY MOISTURE ASSOCIATED
WITH THIS SYSTEM SHOULD REMAIN TO OUR EAST. HOWEVER...I DO SHOW
`SILENT` SINGLE DIGIT POPS FOR MAINLY THE WHITE MOUNTAINS TODAY AND
TONIGHT AS THIS SYSTEM BRUSHES BY TO OUR EAST TODAY THROUGH EARLY
TUESDAY. THIS WILL BE SOMETHING TO KEEP AN EYE ON TODAY. I THINK THE
BEST FORCING WITH THIS SYSTEM WILL STAY TO OUR EAST...THEREFORE NOT
EXPECTING ANY REAL THREAT FOR PRECIPITATION...BUT SOMETHING TO
WATCH.

BY LATE TUESDAY THE SYSTEM WILL BE WELL TO THE EAST OF ARIZONA WITH
RIDGING EXTENDING FROM THE EASTERN PACIFIC WATERS ACROSS CALIFORNIA
AND INTO THE GREAT BASIN AND NORTHERN ROCKIES. BY WEDNESDAY THE
RIDGE AXIS WILL PUSH FARTHER EAST AND WEAKEN AS ANOTHER PACIFIC
SYSTEM BEGINS TO MOVE TOWARD THE PACIFIC NORTHWEST. THIS SYSTEM WILL
MOVE ACROSS THE GREAT BASIN WEDNESDAY NIGHT AND INTO NORTHERN
ARIZONA ON THURSDAY. THIS SYSTEM WILL LINGER ACROSS THE REGION
THROUGH AROUND EARLY SATURDAY BEFORE EJECTING TO THE EAST. THIS
SYSTEM WILL HAVE LIMITED MOISTURE ASSOCIATED WITH IT...ESPECIALLY
THIS FAR SOUTH. THAT SAID...I ONLY MADE MINOR TWEAKS TO THE POP
GRIDS. WE SHOULD SEE MOSTLY ISOLATED SHOWERS FOR THE MOUNTAIN TOPS
THURSDAY NIGHT AND FRIDAY. AFTER THIS SYSTEM MOVES EAST...SHORTWAVE
RIDGING WILL BUILD IN BEHIND THIS SYSTEM...BUT WILL BE SHORT LIVED
AS ANOTHER PACIFIC SYSTEM MOVES ACROSS THE PACIFIC NORTHWEST AND
THROUGH THE CENTRAL ROCKIES AND REMAINING MAINLY TO OUR NORTH
THROUGH THE REST OF THE FORECAST PERIOD. FOR NOW I KEEP A DRY
FORECAST THROUGH THE WEEKEND.

FOR TUCSON...HIGH AND LOW TEMPS GENERALLY WITHIN A FEW DEGREES
EITHER SIDE OF NORMAL...BUT THE WARMEST DAY WILL OCCUR ON THURSDAY
WHEN HIGHS WILL BE AROUND 4 TO 6 DEGS ABOVE NORMAL. THE COOLEST DAYS
WILL BE FRIDAY AND SATURDAY WHEN HIGHS WILL BE A COUPLE OF DEGREES
BELOW NORMAL. LOW TEMPS WILL BE THE WARMEST ON FRIDAY...GENERALLY A
COUPLE OF DEGREES ABOVE NORMAL. THE COOLEST MORNINGS WILL OCCUR
WEDNESDAY AND AGAIN SATURDAY MORNING WHEN LOWS WILL BE ABOUT 3 TO 4
DEGS BELOW NORMAL.

&&

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

&&

$$

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