Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 232215

Area Forecast Discussion
National Weather Service Tucson AZ
315 PM MST Mon Jan 23 2017

.SYNOPSIS...Valley rain and mountain snow showers will increase in
coverage late today followed by widespread valley rain and
mountain snow tonight. Precipitation chances decrease Tuesday with
much cooler temperatures and a widespread freeze Tuesday night.
Dry conditions with below average temperatures will then prevail
Wednesday into next weekend.


.DISCUSSION...Our next pacific storm system is almost here, with
the associated cold front pushing slowly through western Arizona
this afternoon. Showers increasing west and northwest of Tucson
this afternoon, with the area of development shifting into our
area over the next few hours. Breezy to windy conditions, but
generally below advisory levels. We should still see our best
period for moisture and dynamics ahead of and with the front
between sunset tonight and sunrise tomorrow morning, with an
emphasis on the 10PM to 3AM time frame.

Valley rain ranging from .1 to .5 inches tonight. Snow levels
around 8500 feet right now, falling to 7500 feet early this
evening, 5500 feet around midnight, and bottoming out at 4000-4500
feet around sunrise tomorrow. Most of the precip will be east of
the area by then however. It should work out to around 5 to 9
inches in the mountains, with an emphasis on the southern White
Mountains of northern Graham and Greenlee counties, the Mt Graham
area, and the Mt Lemmon area.

Partial clearing from the west tomorrow, with a dry and cold
northerly to northwesterly flow by Tuesday night and Wednesday.
Widespread freezing conditions Wednesday morning including Tucson
Metro, with upper teens to lower 20s in coldest valley locations
south and east of Tucson.

Another (dry) system brushing by north of the area will bring a
weak reinforcement for the cool air late in the week. That should
help keep our temperatures below average for late January through
next weekend.


.AVIATION...Valid through 25/00Z.
Scattered -SHRA mainly west and northwest of KTUS this afternoon,
then widespread valley -SHRA and mountain -SHSN tonight.
Precipitation decreasing rapidly in coverage Tuesday morning.
SCT-BKN clouds this afternoon around 6k-8k ft AGL, then cloud
decks 3k-5k ft AGL with patchy BR to 3SM this evening into
Tuesday morning. Surface wind at the KTUS/KOLS/KDUG terminals
swly/wly 12-25 kts with gusts to 35 kts, slowly diminishing after
24/09Z. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Valley rain and mountain snow will increase
in coverage late this afternoon and become widespread tonight.
Valley rain and mountain snow will decrease Tuesday followed by
dry conditions Wednesday into next weekend. 20-foot winds will be
gusty from the southwest to west this afternoon and tonight.
Otherwise, 20-foot winds will mainly be terrain driven less than
15 mph into the upcoming weekend.


Winter Weather Advisory until 5 AM MST Tuesday for AZZ510-511-

Freeze Watch from late Tuesday night through Wednesday morning
for AZZ502-504>506.




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