Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 170405
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
905 PM MST TUE DEC 16 2014

.SYNOPSIS...A PACIFIC STORM SYSTEM WILL BRING VALLEY RAIN...
MOUNTAIN SNOW AND COOLER TEMPERATURES WEDNESDAY THROUGH THURSDAY.
DRY CONDITIONS WILL THEN PREVAIL FRIDAY INTO EARLY NEXT WEEK.

&&

.DISCUSSION...UPPER TROF AND ASSOCIATED COLD FRONT OVER FAR SRN
CA/NRN CA THIS EVENING. SCATTERED SHOWERS HAVE BEEN OCCURRING ACROSS
YUMA COUNTY WEST INTO IMPERIAL COUNTY CA. SAN DIEGO AND YUMA RADARS
SHOWED THAT THESE SHOWERS EXTENDED SOUTH ACROSS NRN BAJA AND FAR NW
SONORA MEX. UPDATED THE FORECAST EARLIER THIS EVENING TO INCREASE
POPS ACROSS WRN PIMA COUNTY.

WATER VAPOR IMAGERY THIS EVENING SHOWED A VORT MAX ROUNDING THE BASE
OF THE SRN CA/NRN BAJA TROF ALONG WITH KICKER TROF ALONG CNTRL/NRN
CA COAST. THE FIRST TROF WILL MOVE ACROSS THE AREA OVERNIGHT
INCREASING THE CHANCES OF VALLEY SHOWERS/MTN SNOW SHOWERS AFTER
MIDNIGHT. SNOW LEVELS WILL LOWER TO AROUND 6500 FEET WITH UP TO 1"
OF SNOW POSSIBLE IN THE CATALINA/SANTA RITA/GALIURO MOUNTAINS WITH
LESS AN INCH IN THE WHITES. THE KICKER TROF WILL QUICKLY FOLLOW ON
THE HEELS OF THE FIRST ONE AND BRING WIDESPREAD SHOWERS TO THE
AREA...ESPECIALLY ACROSS THE NORTHERN SECTIONS...ON WEDNESDAY. SNOW
LEVEL AROUND 6500 FEET WITH 1-4" POSSIBLE FOR MOUNTAIN RANGES FROM
TUCSON NE TOWARD THE WHITES.

RUNNING OUT ANOTHER UPDATE AS WE MADE SOME TWEAKS TO THE POP/QPF
FIELDS THRU WEDNESDAY AFTERNOON INCLUDING THE HIGHS FOR WEDNESDAY.

BASED ON 00Z RUNS OF NAM/GFS...WE MIGHT HAVE A BIT TOO MUCH POP
GOING LATE WEDNESDAY NIGHT AS THE AREA WILL BE BETWEEN SYSTEM WITH
TROF AXIS MOVING IN ON THURSDAY FOR ANOTHER ROUND OF VALLEY SHOWERS
AND MOUNTAIN SNOW. WE MAY EVENTUALLY NEED A WINTER WEATHER ADVISORY
FOR SOME OF OUR MOUNTAINS BEFORE THIS EVENT IS THROUGH.

&&

.AVIATION...VALID THRU 18/06Z.
CLOUDS WILL LOWER ACROSS SE AZ OVERNIGHT. -SHRA/MT -SHSN WILL BECOME
MORE PREVALENT OVERNIGHT...THEN BECOME SCT-NMRS WITH MT OBSCURATIONS
AND ISOLD MVFR CIGS BETWEEN 17/12Z AND 18/00Z. THERE SHOULD BE A
DECREASE IN PRECIPITATION COVERAGE WED NIGHT BEFORE ANOTHER BATCH OF
-SHRA/-SHSN MOVES INTO SE AZ THURSDAY. SFC WINDS WILL BE LESS THAN
15 KTS THROUGH THE PERIOD. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...A COUPLE OF STORM SYSTEMS WILL BRING A FEW PERIODS
OF VALLEY RAIN AND MOUNTAIN SNOW WEDNESDAY THROUGH THURSDAY. BREEZY
SOUTHERLY WINDS ARE EXPECTED WEDNESDAY AT 10 TO 20 MPH EASING AND
BECOMING WESTERLY THURSDAY. THEREAFTER...MOSTLY DRY WEATHER IS
EXPECTED THROUGH THE COMING WEEKEND WITH PLENTY OF PASSING HIGHER
CLOUDS.

&&

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

&&

$$

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