172 
FXUS65 KTWC 111022
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
321 AM MST Thu Oct 11 2018

.SYNOPSIS...Increasing moisture from tropical system Sergio along
with influences from a Pacific storm system will bring showers 
and thunderstorms to the forecast for much of the region Thursday 
night into early next week. Temperatures will continue to be below
average.

&&

.DISCUSSION...Not a lot of changes have been made to the forecast as 
tropical moisture from remnants of Sergio was still on the way. 
Latest guidance showed that the bulk of this deep moisture will 
arrive late tonight and Friday with widespread rain commencing 
during this time frame. The increase in moisture will prime the air 
mass for more wet weather as an upper low drops south along the 
California coast through Saturday. Both the GEFS and ECMWF models 
track this upper low through southern California/northern Baja late 
Saturday through early Monday. Thereafter, a slight chance in 
afternoon showers and thundertorms will remain in the forecast for 
mainly the mountains.

&&

.AVIATION...Valid through 12/12Z.
SCT-BKN clouds 4-8k ft AGL with and SCT-BKN clouds above 20k ft AGL 
today. Increasing cloudiness after 12/00Z with BKN-OVC layered 
clouds generally above 4k ft AGL due to the moisture in advance of 
Tropical Storm Sergio. Some -SHRA will start to develop mainly after 
12/00Z and become more prevalent overnight. Surface wind variable in 
direction and mainly less than 12 kts this morning, then becoming 
SWLY/SLY 10-20 kts this afternoon before tapering off to less than 
12 kts again this evening. Aviation discussion not updated for TAF 
amendments.

&&

.FIRE WEATHER...Increasing moisture associated with tropical system 
Sergio is expected to result in areas of showers and thunderstorms 
as early as this afternoon and continuing through Friday night, with 
an emphasis on locations southeast of Tucson through Friday night. A 
secondary weather system will keep unsettled weather continuing 
through the weekend and perhaps into early next week with isolated 
to scattered showers and thunderstorms each day. 20-foot winds will 
be southwesterly around 15 to 20 mph this afternoon, then becoming 
easterly on Friday around 10 to 20 mph. A more typical terrain 
driven wind generally less than 15 mph is expected this weekend 
before more easterly winds kick in early next week.
.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

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