Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 222142
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
242 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
chance 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...Boundary layer moisture has dropped a bit with
surface dew points down 1 to 4 degrees in interior locations compared
to 24 hours ago, but by as much as 15 degrees near the
international border. Periods of mainly mid and high cloud
tonight, which will help moderate overnight temperatures a couple
of degrees compared to this morning.

The strong low currently near the Oregon and Northern California
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...A few showers may occur this afternoon and tonight
west-to-north of Tucson. 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.

&&

$$

Meyer/Rasmussen

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