Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 130441
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
937 PM MST Tue Dec 12 2017

.SYNOPSIS...Considerable cloudiness brought on by an area of low
pressure over the Gulf of California will gradually decrease
tonight into Wednesday. Another area of low pressure will move south
across New Mexico Thursday and Friday bringing breezy conditions to
parts of southeast Arizona. While some cooling could occur Friday as
this system passes, above average temperatures will prevail through
the weekend.

&&

.DISCUSSION...Cloudiness associated with an upper low spinning south
of the area will diminish in coverage tonight. The gusty easterly
winds will also decrease in speed tonight most areas. Current
forecast appeared to handle things well, so no updates necessary.

&&

.AVIATION...Valid thru 14/06Z.
SCT-BKN clouds above 15k ft AGL decreasing in coverage tonight. East
to southeast surface winds 15-20 kts diminishing in most areas to 10
kts or less this evening but increasing to around 15 kts again
overnight in favored locations such as KTUS. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...Dry air will remain in place over the region through
the forecast period. Sustained 20-foot winds will be east-southeast
and at 15-20 mph will generally diminish but could increase in
favored gap wind locations again overnight. Expect 20-foot winds to
be less than 15 mph and follow typical diurnal trends Wednesday
before a storm system tracking across the New Mexico brings
northwest breezes Thursday afternoon and easterly winds again
Friday. Another storm system could pass to the east of our area
again Sunday.

&&

.DISCUSSION...A disturbance rotating around low pressure centered
over the Gulf of California has produced thick cloud cover and
easterly breezes to southeast Arizona today. These clouds will be
shifting westward tonight into Wednesday but a few sprinkles could
occur mainly west of Tucson this evening. The easterly winds
should die down this evening but could spike up again in favored
locations as the easterly flow aloft will continue. Those areas
where winds stay up will remain the most mild overnight. This
includes part of the Tucson metro.

The low to our south will get kicked south as as system topping
the western U.S. ridge dives south along the eastern Rockies.
Models are stronger with this system than previous runs as it
passes to the east of AZ. If it is indeed stronger, it should
bring moderate northwest winds to southeast Arizona Thursday, and
cooler air Friday and Saturday. Therefore have trimmed
temperatures for that period, but even so, the forecast daytime
highs are still above normal.

Both the ECMWF and GFS bring yet another trough of low pressure
across the Rockies this weekend but differ on where it ends up by
next week. The EC is more progressive while the GFS spins up a
closed low over the SW/SC. Numerous GFS ensemble members are
depicting precipitation over southeast Arizona, but confidence is
still too low in this scenario to introduce rain chances to the
seven day forecast.

&&

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

&&

$$

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