Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 062102

Area Forecast Discussion
National Weather Service Tucson AZ
202 PM MST Wed Dec 6 2017

.SYNOPSIS...Clouds and a few showers will linger southeast of
Tucson into Thursday. Gusty northeast winds will usher much
cooler temperatures into southeast Arizona Thursday, and a
widespread freeze from Tucson eastward Thursday night. Expect
warmer temperatures to return by the weekend.


.DISCUSSION...The upper trough axis continues to slowly shift
south across southeast Arizona but another system will pass
through our area Thursday. While the second system will have even
less moisture to work with, the colder air associated with it
could help squeeze out a few showers. Thus have left in small
chances for showers southeast of Tucson into Thursday, but have
lowered probabilities.

The main weather event this week will be the colder air that will
move into the area behind the second system aboard brisk northeast
winds. This will be the coldest air thus far this season and
freezing temperatures are a good bet east of Tucson. However, a
number of short range ensemble members are now indicating much
colder air than standard numerical guidance for the Tucson and
Nogales area. Thus, have opted to expand the freeze watch westward
for Thursday night/Friday morning. Locations farther east will
likely experience several hours below 28 degrees. a.k.a. a hard
freeze. The one tricky factor with Thursday night temperatures
concerns how quickly those northeast winds drop off overnight, and
will have to be monitored.

Temperatures will recover marginally Friday but Friday night
should also be fairly chilly before temperatures return to above
normal daytime highs over the weekend.

Longer range models are indicating another weak low in the SW U.S.
next week, but they are not consistent with the details. Given the
timing issues and the lack of moisture available for this low,
have opted to leave the forecast dry at this point.


.AVIATION...Valid thru 08/00Z. Isolated -SHRA are still possible
southeast of KTUS into Thursday. An increase in NE surface winds
to 15-20 kts with higher gusts will occur between 07/12z and
07/18z and continue until about 08/03z. Until then, surface winds
will mainly be less than 10 kts. Aviation discussion not updated
for TAF amendments.


.FIRE WEATHER...A Red Flag Warning is in effect Thursday for Fire
Weather Zone 150, particularly the area west of Sells. The
combination of strong and gusty northeast winds, low relative
humidity and a high fire danger may create critical fire
conditions, especially taking into the account that the current
fuel dryness levels are more representative of April than early

Otherwise, isolated showers remain possible east to south of
Tucson into Thursday. Dry conditions will prevail Thursday night
into early next week. Gusty northeast to east 20-foot winds occur
Thursday and usher in the coldest air of the season. After that,
20-foot winds will generally be 5-15 mph with an easterly
component Friday into early next week.


.CLIMATE...The official forecast high temperature for KTUS Thursday
is 59 degrees. The last occurrence of a recorded high temperature at
KTUS of under 60 degrees was February 19, 2017 when the high
temperature was 58 degrees.


Freeze Watch from Thursday evening through Friday morning for

Red Flag Warning Thursday for AZZ150 west of Sells.




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