Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 210343
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
845 PM MST TUE JAN 20 2015

.SYNOPSIS...A COUPLE OF DISTURBANCES WILL BRING A CHANCE OF SHOWERS
MAINLY TO THE WHITE MOUNTAINS WEDNESDAY AFTERNOON AND WEDNESDAY
NIGHT...AND NEAR THE NEW MEXICO BORDER THURSDAY. MUCH COOLER
TEMPERATURES WILL OCCUR ON THURSDAY FOLLOWED BY A WARMING TREND
SATURDAY INTO MONDAY.

&&

.DISCUSSION...PACIFIC IMPULSE PUSHING FROM CALIFORNIA INTO NORTHWEST
ARIZONA THIS EVENING. INITIAL MOISTURE INCREASE AND SHOWER ACTIVITY
ACROSS NORTHERN ARIZONA. AS FAR AS SOUTHEAST ARIZONA IS CONCERNED
WE`RE STILL FOCUSING ON BEST CHANCE FOR SHOWERS NORTHEAST OF TUCSON
NEAR HIGHER TERRAIN...ESPECIALLY THE EAST CENTRAL MOUNTAINS LATER
WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT. MINOR FIRST 48 HOUR
ADJUSTMENTS WERE MADE BLENDING IN SOME EARLY 00Z MODEL DATA
INCLUDING HRRR AND NAMDNG5. PRIMARILY THIS BUMPED POPS UP ON OUR
BORDER WITH NEW MEXICO WITH THE SECOND IMPULSE FROM THE NORTH
THURSDAY. PLEASE SEE THE PREVIOUS DISCUSSION BELOW FOR ADDITIONAL
DETAILS.

&&

.AVIATION...VALID THRU 22/06Z.
VFR THROUGH THE PERIOD WITH INCREASING CLOUDS ABOVE 20K FT AGL THIS
EVENING INTO WEDNESDAY MORNING. CHANCE OF SHOWERS DEVELOPING NE OF
KSAD AFTER 21/20Z WITH MTNS OBSCD. WINDS WILL REMAIN LESS THAN 10
KTS THROUGH 21/17Z. THEREAFTER...INCREASING SW WIND 10 TO 15
KTS...BECOMING WEST WEDNESDAY AFTERNOON. STRONGEST WINDS SOUTH AND
EAST OF KTUS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A CHANCE OF MAINLY MOUNTAIN SHOWERS NORTH AND EAST
OF TUCSON WEDNESDAY INTO THURSDAY AS A WEAK SYSTEM MOVES ACROSS THE
AREA. MUCH COOLER TEMPERATURES THURSDAY FOLLOWED BY A WARMING TREND.
THEREAFTER...DRY CONDITIONS RETURNING THIS WEEKEND. SOME BREEZY
WINDS SOUTH AND EAST OF TUCSON WEDNESDAY...THEN LOCALLY GUSTY WINDS
THURSDAY AND FRIDAY. INCREASED EAST WINDS MAY LINGER INTO THIS
WEEKEND WITH A PERSISTENT EAST-WEST GRADIENT IN PLACE.

&&

.PREV DISCUSSION...A WEAK SHORTWAVE TROUGH PASSING THROUGH
CALIFORNIA TODAY WILL CONTINUE TO SPREAD CLOUDS OVER THE AREA THIS
EVENING AND TONIGHT. LATEST MODELS TRACK THIS FEATURE INTO ARIZONA
TOMORROW WITH THE BEST CHANCE OF PRECIPITATION DEVELOPING ACROSS
NORTHERN ARIZONA WEDNESDAY AFTERNOON. A SECONDARY SYSTEM WAS PROGGED
TO DIVE SOUTH THROUGH THE FOUR CORNERS AREA WEDNESDAY EVENING AND
NIGHT. THIS SYSTEM WILL HELP INCREASE THE CHANCES OF PRECIPITATION
IN THE WHITE MOUNTAINS AND ALONG THE NEW MEXICO AND ARIZONA STATE
LINE THROUGH THURSDAY AFTERNOON. THE SECOND SYSTEM WILL ALSO USHER
IN MUCH COLDER AIR ON THURSDAY...WITH HIGH TEMPERATURES PROJECTED TO
BE ABOUT 8 TO 10 DEGREES COLDER THAN COMPARED TO FORECAST READINGS
FOR TOMORROW. THEREAFTER...MODELS SHOWED A RIDGE OF HIGH PRESSURE
BUILDING INTO THE WEST COAST WITH THE STORM TRACK REMAINING NORTH
AND EAST OF THE AREA FRIDAY INTO THE WEEKEND. THIS WILL RESULT IN A
WARMING TREND FRIDAY THROUGH THE WEEKEND. MEDIUM RANGE MODELS HINT
AT A LOW PRESSURE SYSTEM DEVELOPING OFF THE WEST COAST OF BAJA
CALIFORNIA AND TRACKING INTO THE DESERT SOUTHWEST EARLY NEXT WEEK.
FOR NOW...WILL JUST SHOW AN INCREASE IN CLOUDINESS IN THE GRIDDED
FORECAST.

&&

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

&&

$$

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MEYER




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