Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 142135

Area Forecast Discussion
National Weather Service Tucson AZ
235 PM MST Thu Dec 14 2017

.SYNOPSIS...Sunny and dry conditions will prevail across southeast
Arizona Friday and Saturday. A cold but quick moving weather
system will bring colder temperatures, valley rain and mountain
snow showers Saturday night and Sunday. Warmer temperatures and
dry weather will return early next week.


.DISCUSSION...Upper trough crossing the area has produced a few
showers and even an isolated thunderstorm or two in far southeast
AZ this afternoon. Will keep small chances this evening in that
area, but clearing is then expected overnight with mild
temperatures and dry weather Friday and Saturday.

Models have come into somewhat better agreement with the next
system moving into our area the latter half of the weekend, and
the consensus is now for wetter and cooler weather for Sunday.
Significant changes were made to the forecast to increase
precipitation chances Saturday night into Sunday night. While
chances have increased, amounts of precipitation are somewhat
uncertain due to the quick movement of this weather system into
and through our area. At this time, valley rainfall amounts of
less than a quarter inch are predicted snow showers in the
mountains. Snow levels could drop to between 4000 and 4500 feet
on Sunday although accumulations will be hard to come by during
the middle of the day at those levels, especially given recent
mild weather. Higher elevations could see some snow accumulations
though. Current thinking is for one to maybe two inches between
5000 and 6000 feet with 2-5" above 6000 feet. Best chances for
accumulating snows will be north and east of Tucson. Would not be
surprised to see 5-8 inches along the Rim and on Mt. Graham.

Temperatures will struggle to climb on Sunday as cold air settles
in under cloud cover. We are only looking at the 50s for Tucson.
Depending on how quickly skies clear Sunday night, wet roads
could turn slick across in eastern counties as temperatures drop
below freezing there. Lows Monday morning are currently forecast
to remain above freezing in the Tucson Metro.

Temperatures should return to above normal by Tuesday in moderate
westerly flow aloft.


.AVIATION...Valid thru 16/00Z.
Isold -SHRA/-TSRA possible southeast of KDUG through 15/01z with
clearing expected thereafter. Surface winds will become easterly
tonight 12-16 kts with gusts to 25 kts at times, and continue into
Friday. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Easterly 20 foot winds will develop overnight and
persist into Friday with speeds of 10 to 20 mph and gusts to 30
mph at times. Otherwise, mild and dry weather will prevail Friday
and Saturday. A stronger weather system will bring cooler
temperatures, valley rain and mountain snow to the area Sunday. Drier
air and warmer temperatures will then return next week.






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