Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 202150

Area Forecast Discussion
National Weather Service Tucson AZ
250 PM MST Sat Jan 20 2018

.SYNOPSIS...A cold front moving east across the area will bring
valley rain and mountain snow, with the best chances continuing
through this evening. Showers will end east of Tucson early by early
Sunday morning. Much cooler temperatures will result in a freeze in
the lower deserts, including Tucson, tonight and again Sunday night.
Southern and eastern valleys will be much colder. Dry conditions
with warmer temperatures next week.


.DISCUSSION...A cold front continued to pass through the state today
with radar only detecting a few areas of light rain and mountaintop
flurries in the vicinity of the frontal band. Most of the
precipitation has been located across central and northern Arizona
closer to the upper low tracking into Utah this afternoon. Latest
models showed very limit shower activity the farther south from the
upper low. Thus, there will be a brief opportunity for light
precipitation through this evening with skies clearing from west to
east tonight. Clearing skies and colder air ushering in behind the
front will set the stage for a freeze in the lower desert
elevations, including the greater Tucson metro area, tonight/Sunday
morning. The colder air mass will give way to high temperatures
about 8 to 10 degrees below normal Sunday with more freezing
temperatures Sunday/Monday morning. This cool down will be brief
though, as high temperatures rebound to near and slightly above
normal readings by Tuesday. The main storm track will remain north
of the area much of next week for dry and warmer weather.


.AVIATION...Valid thru 22/00Z.
SCT-OVC at 5-10k ft AGL this afternoon and this evening with
clearing Sunday morning. Expect scattered -SHRA and higher terrain
-SHSN in vicinity of the frontal boundary with MVFR conditions
possible with ceilings as low as 2k ft AGL . Best timing of lower
ceilings and vsbys at KTUS/KOLS terminals is through 21/00Z, with -
SHRA reaching KDUG this afternoon/evening. Improving conditions KTUS
vicinity westward this evening. Sfc wind swly-nwly 12-22 kts with
gusts to 35 kts this afternoon. Highest speeds likely at
KDUG/KALK/KFHU. Elevated wly winds will continue this evening,
briefly tapering off early Sunday morning before increasing again to
10-20 kts with a few spots up to around 25 kts near KSAD. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER... Scattered valley rain and mountain snow showers
associated with a cold front will then move eastward across the area
this afternoon and evening. Precipitation will end east of Tucson
tonight and Sunday morning, then dry conditions will prevail Sunday
afternoon into next Friday. Gusty southwest to northwest 20-foot
winds at 20 mph with gusts up to 30 mph this afternoon and evening,
especially across the southern portion of fire weather zones 151 and
152. Gusty northwest winds will favor the Upper Gila River Valley
including Safford on Sunday. Otherwise, 20-foot winds will be
terrain driven mainly less than 15 mph at other times through
Wednesday. Breezy west winds may return late next week.


Freeze Warning from 1 AM to 9 AM MST Sunday for AZZ502-504-505.

Freeze Warning from 1 AM to 9 AM MST Monday for AZZ502-504-505.



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