Area Forecast Discussion
Issued by NWS Tucson, AZ

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609
FXUS65 KTWC 140450
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
950 PM MST Sat Jan 13 2018

.SYNOPSIS...Very warm afternoon temperatures will continue through
the weekend along with a mixture of sunshine and high clouds and a
few easterly breezes. Mainly dry through the upcoming week with
temperatures well above average. A pattern change by next weekend
should bring much cooler temperatures and the chance of valley
rain and mountain snow Friday night and Saturday.

&&

.DISCUSSION...No surprises, with the strong ridge building in
from the west bringing warm daytime temperatures and dry
conditions. The 00Z KTWC sounding was down to 1/5 of an inch
precipitable water, and surface dew points in the teens to lower
20s. We will dirty up with a little cirrus level moisture, but not
much more. No updates. Please see the previous discussion below
for additional details.

&&

.AVIATION...Valid thru 15/06Z.
FEW-SCT cirrus clouds around 25k ft will persist into Sunday.
Gusty ELY/SELY SFC winds will continue to decrease to less than
12kts this evening. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Expect another round of easterly winds Tuesday;
otherwise, 20-foot winds will remain terrain driven at less than
15 mph. Warm and dry conditions will persist through the coming
week before slightly cooler temperatures and a chance of rain will
be possible next weekend.

&&

.PREV DISCUSSION...A chamber of commerce approved January weekend
for Southeast Arizona with temperatures in the 70`s from Tucson
westward and in the 60`s across the eastern valleys. Flow pattern
aloft consists of northwesterly flow on the east side of a ridge
axis near the west coast. Easterly breezes continue this afternoon
especially in the normally prone areas such as Tucson with a few
gusts up to about 25 mph. These will gradually weaken as the
afternoon progresses. More of the same on Sunday with less wind
and similar temperatures to today and continued mostly clear
skies.

Heading into the upcoming work week, benign weather will continue
much of the time. An area of high pressure at the surface will build
to our northeast with another bout of breezy easterly winds on
Tuesday. We did go ahead and knock down high temperatures especially
for the eastern valleys Tuesday as cooler air seeps west past the
Continental Divide into Eastern Arizona. Even as such, still near
normal for eastern areas and about 5 to 7 degrees above normal from
Tucson westward. Meanwhile, a weak shortwave trough will pass
through Tuesday night with some increased clouds. We have introduced
slight chance of rain and snow showers for the White Mountains
during this time as well. Ridging aloft will build back in for
Wednesday and Thursday with temperatures still remaining above
normal, though perhaps not quite as warm as we were previously
thinking.

A more profound change in our weather pattern by next weekend as
troughing moves into the Southwestern US. Friday will still be mild
with perhaps some breezy afternoon winds. 12Z GFS/ECMWF along with
GEFS and EPS ensembles are overall fairly consistent for days 6-7 on
this trough with just some minor differences in the amplitude,
strength and timing. The ECMWF is the slightly deeper model with
better precipitation chances and lower snow levels. Our initial
thinking is a strong cold front pushes through the region Friday
night into Saturday morning with a chance of valley rain and
mountain snow showers for much of the CWA. Depending on the strength
of the trough and resulting snow levels, couldn`t rule out some snow
flakes down to the valley floors above 4000 feet especially in
Cochise County Saturday morning. Still plenty of time to watch this
and no matter what exact precipitation scenario ultimately unfolds,
it will be much cooler next weekend as we experience another taste
of winter.

&&

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

&&

$$

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