Area Forecast Discussion
Issued by NWS Tucson, AZ

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455
FXUS65 KTWC 072139
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
239 PM MST Thu Dec 7 2017

.SYNOPSIS...Clear skies, diminishing wind, and much cooler air
will set the stage for freezing and subfreezing temperatures across
much of the area tonight. Otherwise, dry conditions with above
normal temperatures will prevail this weekend into next week.

&&

.DISCUSSION...Recent surface observations indicated that wind speeds
continued to diminish across the area this afternoon. The Blowing
Dust Advisory for Pinal county was allowed to expire at 1 PM MST.
Based on the trends in wind speed, will let the Red Flag Warning
expire on time at 4 PM MST as well. A much cooler air mass in place
combined with clear skies and diminishing wind speeds will lead to
freezing and subfreezing temperatures tonight through after daybreak
Friday. Latest model guidance still supported the Freeze Warning for
tonight. A widespread hard freeze, readings below 28 degrees, can be
expected for the valleys in Santa Cruz and Cochise counties as well
as the upper Gila river valley around Safford. Thereafter, models
maintain a very amplified ridge of high pressure over the western
United States which will keep the storm track well north and east of
the area. The only caveat was the possibility of a weak upper low
undercutting the ridge and approaching the Desert Southwest early
next week. Such a scenario was more pronounced in the ECMWF
solutions than the GFS model. Regardless, this feature would not
have much of an influence on the forecast.

&&

.AVIATION...Valid thru 09/00Z.
Clear skies KTUS vicinity westward into Friday morning. Far
southeast corner of AZ, scattered to overcast clouds generally 5k-
10k ft AGL through this evening, then clear or mostly clear skies by
daybreak Friday. Surface wind northeast to east 12-25 kts with gusts
upward to 35 kts through 08/03Z, then 5-12 kts through Friday.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...A Red Flag Warning will expire at 4 PM MST this
afternoon as wind speeds diminish further. Otherwise, dry conditions
tonight into next Thursday. 20-foot winds will generally be easterly
under 15 mph Friday into next Wednesday. Daytime temperatures will
warm this weekend to readings about 4 to 8 degrees above normal.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 10 PM this evening to 9 AM MST Friday morning
for AZZ503-504-506>509.

&&

$$

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