Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 050425

Area Forecast Discussion
National Weather Service Tucson AZ
924 PM MST Sun Dec 4 2016

.SYNOPSIS...Dry conditions will occur through Tuesday. A system
moving northeast of the area may then bring a few rain and snow
showers mainly to the White Mountains Tuesday night and Wednesday.
Dry conditions with above normal daytime temperatures will then
prevail during the latter part of the week and next weekend.


.DISCUSSION...Satellite imagery was showing some high clouds
approaching the area from southeast California. These high clouds
will spread across the area overnight. Current forecast handled
these trends well, so no updates necessary this evening. Please
refer to the additional sections for more details.


.AVIATION...Valid through 06/06Z.
FEW-SCT cirrus AOA 20k ft AGL developing into Monday morning. SFC
wind speeds less than 10 kts overnight becoming W/SW 8-12 kts with
gusts to around 20 kts possible Monday afternoon. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...There is a slight chance of rain and snow showers
across the White Mountains Tuesday night and Wednesday. Otherwise,
dry conditions will continue into the upcoming weekend. 20-ft winds
will be gusty around 15 to 20 mph from the southwest on Tuesday,
with winds becoming easterly on Thursday and Friday. 20-foot winds
will mainly follow terrain at less than 15 mph at other times.


.PREV DISCUSSION...Upper level ridge axis extending from
central Arizona westward to west of the southern California coast
has resulted in clear skies across southeast Arizona today. Clear
skies will continue through at least this evening, and perhaps
during the overnight hours as well, as the upper ridge axis moves
south of the area. Some cirriform clouds are expected to move across
this forecast area Monday ahead of a deepening upper trough over the
Pacific Northwest/northern Rockies.

Clouds should continue to increase sufficiently for partly cloudy
skies Monday night and Tuesday as a broad upper trough develops
across the western/central CONUS. The 04/12Z deterministic GFS/
ECMWF/CMC agree that precip-free conditions will persist Monday
night and Tuesday. However, the 04/18Z NAM depicted the potential
for a few hundredths of an inch of rainfall across far western Pima
County Tuesday. This NAM depiction was discounted for Tuesday.

A shortwave trough embedded within the southwestern periphery of the
broad upper trough is progged to move southeastward across the Four
Corners region Tuesday night, then eastward into the central CONUS
plains Wednesday. This system should provide enough upward forcing
to produce at least a few rain/snow showers mostly across the White
Mountains Tuesday night and Wednesday.

Have noted that the 04/18Z NAM was similar to the 04/12Z NAM with
respect to generating measurable precip further west, or across the
Tohono O`odham Nation and western Pima County, Tuesday night and
Wednesday. However, the 04/12Z deterministic ECMWF is preferred
versus the wetter NAM, and the considerably drier GFS. At any rate,
no significant impact is expected from this passing system. Dry
conditions will then return area-wide Wednesday night and continue
into next weekend under wly/nwly flow aloft.

High temps Monday will generally be about 2-5 degs warmer versus
temps achieved this afternoon, then no significant change in high
temps will occur Tuesday. Cooler temps are on tap Wednesday as the
shortwave trough passes northeast of the area. A warming trend will
then prevail Thur-Fri followed by only very minor daytime temp
changes next weekend. High temps Fri-Sun will average about 2-5 degs
or so above normal depending upon location.






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