Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 240348

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

.SYNOPSIS...Scattered valley rain and mountain snow showers will
move across the area tonight with the precipitation most areas
ending by Tuesday morning.  Then much cooler temperatures are in
store for the region with a widespread freeze Tuesday night.
Dry conditions with below average temperatures will then prevail
Wednesday into next weekend.


.DISCUSSION...Shower activity has pushed across Pinal and most of
Pima counties this evening and will continue to push to the east
through the night. This won`t be a steady rain event for the valleys
but rather passing showers with up to a quarter of an inch expected.
For the mountains the upslope flow will help the precipitation to be
a bit steadier and heavier for a third to three quarters of an inch
liquid equivalent or roughly 3-8 inches of snow above the snow
level. Basically just enough for the snow advisory to remain in
effect so no significant changes there.  I did adjust the next 12-18
hours of the forecast to narrow up the time of precipitation, both
on the front end and on the backside as the precipitation should be
over by sunup all but the most eastern areas.  I also trimmed the
QPF a bit and adjusted cloud cover and temps.

Expecting clearing from west to east Tuesday with temperatures
roughly 10-15 degrees colder than average. That with a bit of a
breeze and a jacket will be a nice addition to the days wardrobe.
Late Tuesday night into Wednesday morning will be cold with sub-
freezing temperatures most areas by sunup Wednesday including teens
and 20s in the coldest valleys south and east of Tucson. A freeze
watch is in effect for portions of the area that have not seen a
freeze in awhile, basically Tucson west to nearly Ajo.

Dry conditions are then expected through at least next weekend with
below average temperatures continuing.  Cerniglia


.AVIATION...Valid through 25/00Z.
Widespread valley -SHRA and mountain -SHSN moving across the region
tonight. Precipitation decreasing rapidly in coverage early Tuesday
morning. Expect cloud decks 4k-6k ft AGL with patchy BR to 3SM
Tuesday morning tonight then diminishing from the west aft 24/12Z.
Surface wind at the KTUS/KOLS/KDUG terminals wly 12-20 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 become
somewhat widespread tonight then diminish rapidly early Tuesday
morning with clearing from the west. This will be followed by dry
conditions Wednesday through next weekend and likely well into
next week. 20-foot winds will be gusty from the southwest to west
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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