Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 281022
Area Forecast Discussion
National Weather Service Tucson AZ
322 AM MST Mon Nov 28 2016
.SYNOPSIS...Some clearing from the west today before one final
impulse brings a few light valley rain and mountain snow showers
to the area tonight into Tuesday morning. Much cooler temperatures
with the coldest overnight lows of the season so far Tuesday
night and Wednesday night, with widespread freeze or hard freeze
conditions for Southeast Arizona. Temperatures will remain below
average through the week, with another storm system possibly
bringing a chance of valley rain and mountain snow Friday into
.DISCUSSION...Valley shower activity is clearing out as the main
portion of the storm shifts east of our area this morning. Still
seeing a few snow flurries in the mountains with snow levels as
low as 4500 feet this morning (Ft Huachuca was reporting snow in
their observation last hour). SNOTEL suggests 5-7 inches for
Hannagan Meadows, and a quick guesstimate from pre-sunrise cameras
are showing about 2 to 3 inches around Mt Lemmon, maybe a little
more on Mt Graham. No precip around most of today, but a third and
final impulse will carve down the back side of the trough and into
our area this evening. Not as strong, but still enough for a few
valley rain and mountain snow showers.
Our main story now will shift to the cold air. The final impulse
tonight should keep things mixed up enough to prevent temperatures
from crashing. However, clear skies and light winds will allow the
full potential of the colder airmass to be realized Tuesday night
into Wednesday morning. We have elected to issue a Freeze Watch
for the first potential freeze of the season for Southeast to
Eastern Pinal county, Eastern Pima county, Santa Cruz county, and
the Tohono O`Odham Nation late tomorrow night. Colder eastern
valleys in Greenlee, Graham, and Cochise counties have already had
several nights of widespread well below freezing temperatures.
They see this so often in the winter that we do not issue any
headlines after their first occurrence (unless there is an
extended warm spell). However, it should be noted that coldest
eastern valley locations are expected to drop into the teens
Tuesday night. Santa Cruz county is also handled this way, however
their near freezing temperatures have been spottier so far this
Wednesday night will again be well below average, similar to or
perhaps a degree or two warmer than Tuesday night.
Another system will dig toward us from the north Friday into early
Saturday, however the ECMWF no longer completely cuts it off, and
the GFS` cut-off point is now well south of Arizona. We will keep
a chance of valley rain and mountain snow showers in the forecast,
however these types of systems (unlike our current weather makers)
are notoriously difficult to pin down.
.AVIATION...Valid through 29/12Z.
FEW-SCT clouds at 3-5k ft agl becoming occasionally BKN near the
Int`l border clearing out by daybreak. Then, FEW-SCT clouds at 8-12k
ft agl through the day today. ISOLD-SCT valley
-SHRA/mountain -SHSN developing again this evening through early
Tuesday with brief MVFR conditions and mtn obscurations. WLY/SWLY
sfc wind at 10-15 kts with occasional gusts to around 25 kts.
Strongest wind near the KSAD/KDUG/KALK/KFHU terminals. Aviation
discussion not updated for TAF amendments.
.FIRE WEATHER...Considerably cooler temperatures will prevail this
week. A few rain and snow showers are possible again this evening
and lingering mainly east of Tucson through Tuesday morning.
Expect breezy west to southwest winds around 15 to 20 mph with
higher gusts once again today. Some residual westerly or
northwesterly gustiness is possible mainly across eastern zones
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 into this weekend.
Winter Weather Advisory until 6 AM MST early this morning for
Freeze Watch from late Tuesday night through Wednesday morning
Hard Freeze Watch from late Tuesday night through Wednesday
morning for AZZ503.
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