Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 181704

Area Forecast Discussion
National Weather Service Tucson AZ
1004 AM MST Sun Nov 18 2018

.SYNOPSIS...Dry conditions with seasonably mild daytime
temperatures during most of the upcoming week. A passing weather
system on Thanksgiving Day should produce a few showers mainly
near the mountains.


.DISCUSSION...We continue with a ridge near the west coast today,
accompanied by mild and dry conditions for SE Arizona. Just some
mid and high cloud with precipitable water values near 1/3 of an
inch and surface dew points in the teens and 20s.

We`re already seeing the first stage of our pattern change with a
significant split off the California coast. This will fill quite a
bit as it translates into the base of the ridge early in the
week, with just some patchy cloudiness to note it`s passing late

A deeper trough with higher latitude support will push through the
region the second half of the week. It has the potential to
generate a stronger moisture and dynamics couplet through much of
the state with a chance of valley rain and mountain snow showers.
Our corner of the state is on the periphery of this action, with
subtle differences in the operational, ensemble and ensemble mean
trajectories creating very different sensible weather results.
Translation: it might rain, it might not. It will be interesting
to see if the ECMWF continues a deeper trough inflection with the
Thursday system as the 12Z GFS remains a little more zonal.


.AVIATION...Valid through 19/18Z.
Mostly broken clouds above 20k ft AGL into this afternoon then
few to scattered cirrus this evening into Monday morning. Surface
wind variable in direction mainly under 12 kts. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions across much of southeast Arizona
this week. However, isolated showers should occur on Thanksgiving
Day mainly north of Tucson. 20-foot winds will be terrain driven
and generally under 10 mph. The exception is Monday into Tuesday
morning when east to southeast gusts near 20 mph may occur at






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