Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 191001
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
300 AM MST Tue Sep 19 2017

.SYNOPSIS...Dry conditions across much of the area with seasonably
warm temperatures through Wednesday. A strong low pressure trough
will then bring isolated showers and thunderstorms, gusty winds and
a cooling trend Thursday into Friday. Expect dry conditions with
below normal temperatures this weekend.

&&

.DISCUSSION...Despite a drier westerly flow aloft, models showed
enough moisture near the International Border to support a slight
chance of showers and thunderstorms southeast of Tucson through
Wednesday. Thereafter, models deepen a system over the Intermountain
West Thursday into the weekend with varying amounts of moisture
advecting into southeast Arizona in advance of it. The latest GFS
solution suggested that the bulk of this moisture will remain east
of the area. This solution differed from the ECMWF model which
showed deeper moisture increasing east through south of Tucson
Thursday into Friday. Given the wide spectrum of solutions, will
keep the trend of increasing rain chances for Thursday and Friday in
the forecast for now. Otherwise, the system will bring strong and
gusty winds, especially Thursday and Friday, along with noticeably
cooler temperatures.

&&

.AVIATION...Valid thru 20/12Z.
A few -TSRA/-SHRA may occur near the international border southeast
of KTUS and perhaps near KDUG this afternoon. Forecast confidence is
too low to include VCTS or -TSRA in the KDUG TAF. Otherwise, clear
skies will prevail west-to-north of KTUS. A few to scattered clouds
around 8k-12k ft AGL will occur southeast of KTUS this afternoon and
evening. Surface wind late this morning through the early evening
hours will be swly to nwly at 13-20 kts with gusts to near 30 kts.
Surface wind mainly less than 12 kts at other times. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...There will continue to be a slight chance of
afternoon and evening showers and thunderstorms mainly east and
south of Tucson through Friday, before a drying trend takes place
this weekend. A deepening upper trough over the western United
States will result in gusty southwest winds, especially during the
afternoon and evening hours through Saturday. The strongest winds
are expected on Thursday and Friday. Near normal high temperatures
will continue through Thursday, cooling to below normal levels this
weekend.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

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