Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 210913
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
213 AM MST SUN DEC 21 2014

.SYNOPSIS...A DRY NORTHWEST FLOW PATTERN WILL RESULT IN SOME PASSING
HIGH LEVEL CLOUDS WITH TEMPERATURES NEAR NORMAL TODAY AND SLIGHTLY
ABOVE NORMAL MONDAY. 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 SLIGHT CHANCE OF PRECIPITATION FOR THE WHITE
MOUNTAINS.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 21/00Z UPPER-AIR PLOTS SHOW A
TROUGH THAT EXTENDS FROM THE CENTRAL PLAINS THROUGH WEST TEXAS.
MEANWHILE...A RIDGE RESIDES OVER THE PACIFIC WATERS WITH NORTH TO
NORTHWEST FLOW ALOFT OVER ARIZONA BETWEEN THESE TWO SYSTEMS AS
EVIDENCED BY THE WIND PROFILE FROM LAST EVENINGS KTWC 21/00Z
SOUNDING. IR SATELLITE IMAGERY SHOWS PERIODS OF MOSTLY HIGH CLOUDS
SPILLING OVER THE TOP OF THE RIDGE ACROSS THE GREAT BASIN AND INTO
PORTIONS OF THE DESERT SOUTHWEST...RESULTING IN PARTLY CLOUDY SKIES
AS A RESULT OF INTERMITTENT BATCHES OF CLOUDS THAT ARE EXPECTED TO
MOVE BY FROM TIME TO TIME TODAY.

MODELS CONTINUE TO SHOW THIS DRY NORTHERLY FLOW ACROSS ARIZONA
THROUGH MONDAY WITH A VORT LOBE MOVING ACROSS THE FOUR CORNERS
REGION AND WESTERN NEW MEXICO LATE MONDAY THROUGH EARLY TUESDAY AS
THE PARENT LOW ASSOCIATED WITH THIS FEATURE SLOWLY MOVES THROUGH THE
MIDWEST AND GREAT LAKES REGION. AS THIS OCCURS THE BULK OF THE
MOISTURE ASSOCIATED WITH THE SYSTEM WILL REMAIN NORTH AND EAST OF
ARIZONA FOR A CONTINUED DRY FORECAST...ALTHOUGH SOME INCREASE IN
WINDS IS EXPECTED MONDAY AFTERNOON...ESPECIALLY BETWEEN TUCSON AND
THE NEW MEXICO BORDER. TEMPERATURES WILL DROP SEVERAL DEGREES ON
TUESDAY WITH THE PASSAGE OF THIS SYSTEM. ONCE THIS SYSTEM MOVES TO
THE EAST LATE TUESDAY AND EARLY WEDNESDAY...STRONG PACIFIC RIDGING
BEHIND THIS SYSTEM WILL REMAIN OVER THE PACIFIC WATERS WELL WEST OF
THE BAJA PENINSULA...BUT WITH THE RIDGE AXIS EXTENDING NORTHEAST
ACROSS CALIFORNIA INTO THE GREAT BASIN AND NORTHERN ROCKIES ON
WEDNESDAY.

BY LATE WEDNESDAY INTO THURSDAY A PACIFIC SYSTEM IS PROGGED TO MOVE
THROUGH THE PACIFIC NORTHWEST...THEN MAKE ITS WAY INTO THE CENTRAL
ROCKIES BY LATE IN THE DAY ON THURSDAY. THIS SYSTEM WAS PROGGED TO
BE DEEPER AND A BIT WETTER ACCORDING TO EARLIER MODEL RUNS OF THE
ECMWF...BUT IT HAS BACKED OFF ON THIS SCENARIO AND IS NOW MORE IN
LINE WITH THE GFS...WHICH SHOWS THE SYSTEM BRUSHING BY TO OUR NORTH
LATE IN THE WEEK. ONCE AGAIN...MOISTURE WITH THIS SYSTEM IS EXPECTED
TO BE LIMITED AND MOSTLY RESIDING TO THE NORTHEAST OF ARIZONA. THAT
SAID...I MADE SOME MINOR TWEAKS TO THE POP GRIDS FOR THE THURSDAY
THROUGH FRIDAY TIME FRAME...BUT IT STILL LOOKS LIKE JUST A SLIGHT
CHANCE OF SHOWERS OVER THE WHITE MOUNTAINS FOR THAT PERIOD OF TIME.

FOR TUCSON...HIGH TEMPERATURES GENERALLY NEAR TO SLIGHTLY ABOVE
NORMAL TODAY... THEN 3 TO 5 DEGS ABOVE NORMAL FOR MONDAY. NEAR
NORMAL FOR TUESDAY...THEN 3 TO 5 DEGS ABOVE NORMAL AGAIN FOR
WEDNESDAY AND THURSDAY. THEREAFTER...HIGHS NEAR NORMAL. LOW
TEMPERATURES 2 TO 3 DEGS ABOVE NORMAL MONDAY AND TUESDAY
MORNINGS...THEN NEAR NORMAL WEDNESDAY MORNING. SLIGHTLY ABOVE NORMAL
THURSDAY AND FRIDAY...THEN SLIGHTLY BELOW NORMAL FOR SATURDAY
MORNING.

&&

.AVIATION...VALID THRU 22/126Z.
VFR CONDITIONS AT ALL TERMINALS WITH SCT TO BKN HIGH CLOUDS ABOVE
20K FT.  SURFACE WIND WILL BE DIURNAL AND GENERALLY LESS THAN 10 KTS
THROUGH THE PERIOD.  AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WILL PREVAIL THROUGH WEDNESDAY WITH A
SLIGHT CHANCE OF SOME RAIN AND SNOW SHOWERS OVER THE WHITE MOUNTAINS
CHRISTMAS DAY THROUGH FRIDAY.  A PASSING WEATHER SYSTEM WILL KICK UP
A NORTHWEST BREEZE MONDAY AFTERNOON ACROSS EASTERN AREAS ESPECIALLY
THE GILA VALLEY.  THE WINDS WILL SETTLE DURING THE EVENING EXCEPT
ACROSS THE HIGHER TERRAIN AND THE GILA VALLEY WHERE THEY WILL
CONTINUE THROUGH MUCH OF MONDAY NIGHT.  THIS WILL BE FOLLOWED BY A
NORTHERLY BREEZE ON TUESDAY AND A LIGHTER EAST BREEZE WEDNESDAY.
THEN THE SYSTEM ARRIVING LATE IN THE WEEK WILL GENERATE A SOUTHWEST
TO WEST BREEZE THURSDAY AND FRIDAY AFTERNOONS.  DEW POINTS WILL DROP
FOLLOWING THE LATE MONDAY SYSTEM THEN DROP FURTHER AFTER THE SYSTEM
LATE IN THE WEEK RESULTING IN LOWERING HUMIDITY LEVELS FROM WHAT WE
HAVE SEEN LATELY. CERNIGLIA

&&

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

&&

$$

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

PUBLIC...MOLLERE
AVIATION/FIRE WEATHER...CERNIGLIA





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