Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 230402
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
900 PM MST Sun Jan 22 2017

.SYNOPSIS...Variable cloudiness, then valley rain and mountain
snow will increase Monday afternoon and become widespread Monday
night as a storm system moves through the area. Precipitation
chances decrease Tuesday along with much cooler temperatures and a
widespread freeze Tuesday night. Expect dry conditions with a modest
warming trend Wednesday into next weekend, however temperatures will
remain below average for late January.

&&

.DISCUSSION...Skies cleared nicely this evening thanks to short wave
ridging out in advance of the next system approaching the region.
The clear skies will linger awhile then clouds will increase from
the west later tonight into tomorrow.  I adjusted the first 12 hours
of the forecast to tweak the clouds/weather and temperature fields
to account for the current conditions and expected short term
trends. The remainder of the forecast looks good and is described
well below. Cerniglia

From previous discussion...A strong low currently near the Oregon
coast will kick a weaker impulse (currently near southern
California) eastward over the next 36 hours. Another solid chance of
valley rain and mountain snow Monday afternoon into Tuesday morning.
Rainfall in valley locations should be around 1/4 to 1/2 inch with
higher amounts focused through eastern Pinal and northern Graham
counties. Snow levels will start around 8000 feet Monday before
falling to around 4000 feet north and 5000 feet south Tuesday
morning. Advisory level accumulations around 5 to 8 inches expected
above 6000 feet for Eastern Pima, Eastern Pinal, Graham and Greenlee
counties. Little or no accumulation below 5000 feet. Less for
southern mountains...around 1 to 4 inches.

A dry and cold northerly to northwesterly flow by Tuesday night
and Wednesday. Widespread freezing conditions Wednesday morning
including Tucson Metro, with lower to middle 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 24/00Z.
VFR with patchy mid and high cloud overnight. Increasing chance of
-SHRA and higher terrain -SHSN after 23/20Z with brief MVFR
conditions possible. Surface wind variable in direction less than
12 kts through tonight...increasing from the southwest after
23/18z. Aviation discussion not updated for TAF amendments.

&&

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

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon Monday to 5 AM MST Tuesday for
AZZ510-511-514.

&&

$$

Cerniglia/Meyer/Rasmussen

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