Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 271010

Area Forecast Discussion
National Weather Service Tucson AZ
310 AM MST Sun Nov 27 2016

.SYNOPSIS...Cooler temperatures today, then a fast moving storm
system will bring a good chance of valley rain and mountain snow
mainly tonight, followed by colder temperatures Monday. Expect
the coldest overnight lows of the season so far Tuesday night and
Wednesday night. Temperatures will remain below average through
the week, with another storm system bringing a chance of valley
rain and mountain snow Friday into next weekend.


.DISCUSSION...A trough is pushing into the Great Basin area from
the west this morning, with the first impulse bringing light
valley rain and mountain snow flurries to a few spots. Gusty
winds and cloud cover are moderating overnight temperatures, with
some eastern locations 10 to 20 degrees warmer than this time
yesterday morning. We won`t see much precip with this first one,
generally less than .05 with most valley locations only seeing a
trace. Snow levels are around 8000 feet north to 10000 feet south,
with Hannagan Meadows SNOTEL in the lower 30s. Colder air is
already pushing into western Arizona so snow levels will fall
during the day, and daytime highs will look a lot like current
values in many locations.

The second and strongest impulse will dig quickly in from the
northwest late this afternoon and tonight. Stronger dynamics,
cooler air and gusty upslope will squeeze more precip out of the
atmosphere this evening for much of our area. Valley rainfall
amounts won`t be that impressive, with storm total amounts around
.1 to .3 or so. Snow levels will fall as low as 4000 or 4500 feet
early Monday morning. Only a dusting of snow around 4500 feet,
with 1 to 3 inches between 5000 and 7000 feet and 3 to 6 inches
for most locations above 7000 feet. The mountains of northern
Graham and Greenlee counties will see the longest chance of snow
and the lowest early snow levels as the main portion of the storm
moves down from the northwest, so we are joining the Flagstaff
office with a Winter Weather Advisory tonight for the mountains
north of Safford.

A partial clearing trend Monday before the third impulse carving
down the back side of the trough pushes briefly into our area
Monday night into Tuesday morning. Not as much chance of precip
with this one, but it should help keep early morning low
temperatures from crashing.

Clearing skies, light winds and a cold airmass will bring the
coldest overnight lows of the season Tuesday night and Wednesday
night. Areas east and south of Tucson will see temperatures well
below hard freeze levels, and some other locations (including
Tucson Metro) may see their first freeze.

Some warming the second half of the week, but still below average.
Another storm system will dig down toward our area by late Friday
into next weekend, bringing another shot of cool air along with a
chance of valley rain and mountain snow. This one may completely
cut off however, so a tough timing and trajectory forecast.


.AVIATION...Valid through 28/12Z.
FEW-SCT clouds at 8-12k ft agl with SCT-BKN clouds at 15-20k ft agl.
ISOLD-SCT valley -SHRA/mountain -SHSN developing this evening,
becoming SCT-NUM early Monday morning. WLY/SWLY sfc wind at 12-16
kts with occasional gusts to 25 kts. Aviation discussion not updated
for TAF amendments.


.FIRE WEATHER...Considerably cooler temperatures will prevail this
week. A few rain and snow showers are possible mainly north and
northeast of Tucson today. More widespread valley rain and mountain
snow will occur tonight into Monday morning, with lingering
precipitation mainly east of Tucson Monday afternoon into Tuesday.
Expect breezy west to southwest winds around 15 to 20 mph with
higher gusts to continue today. Some residual westerly or
northwesterly gustiness is possible mainly across eastern zones
Monday and Tuesday. A strong low pressure system will bring another
round of wintry weather and gusty east winds to the region late in
the work week.


Winter Weather Advisory from 6 PM this evening to 6 AM MST
Monday for AZZ510.




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