Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 131654

Area Forecast Discussion
National Weather Service Tucson AZ
954 AM MST Fri Jan 13 2017

.SYNOPSIS...Mild temperatures today with increasing clouds. A
few sprinkles possible later today, then a low pressure system will
bring a good chance of valley rain and mountain snow over the
weekend into early Monday along with cooler temperatures. A few
showers near the mountains early next week, then another storm
system may impact the area later next week.


.DISCUSSION...Increasing moisture over the next 36 hours as a
strong low currently near the southern California coast tracks
into northern Baja before pushing eastward across southern Arizona
and northern Sonora over the weekend. Best valley rain and
mountain snow time with the main low will be Saturday afternoon
through Sunday morning, and that`s where we have our Winter
Weather Advisory above 6500 feet.

A second, weaker piece of energy will carve into the back side of
the trough position as the main low exits into the southern and
central plains Sunday night and Monday, keeping things showery
and cool around Southeast Arizona.

That system we`ve been talking about for the second half of next
week could be a stronger and colder storm for our area.

Please see the previous discussion below for additional details.


.AVIATION...Valid through 14/18Z.
VFR with SCT-BKN clouds at 8-13k ft AGL and BKN-OVC clouds above
15k ft AGL. A few showers with clouds increasing after 14/15z.
Surface wind from KTUS westward generally less than 12 kts.
Surface wind east to south of KTUS (including the KOLS/KDUG
terminals) sly/sely surface wind at 12-18 kts with gusts to 25
kts. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Relatively mild temperatures with increasing
cloudiness through late tonight. A low pressure system will then
move into the region this weekend, resulting in a good chance of
valley rain and mountain snow by Saturday afternoon and Sunday.
Some showers lingering into Monday. Dry conditions are expected
to return areawide Tuesday and Wednesday before another storm
system brings more precipitation the second half of next week.
Outside of some elevated southerly 20-foot winds at 10-20 mph
today and Saturday, 20-foot winds are expected to be terrain
driven and generally less than 15 mph.


.PREV DISCUSSION...A low pressure system will continue to drop
south along the southern California coast today before turning
east and tracking through Sonora Mexico on Saturday. Ahead of the
storm system, clouds will continue to increase and thickening over
southeast Arizona today. Enough mid-level moisture was expected to
spread into the area for some light sprinkles this afternoon and
tonight, especially in the mountains. As the system approaches the
Baja Spur tonight, precipitation chances will be on the increase.
The bulk of the precipitation will be Saturday afternoon and night
as the storm system passes through Sonora Mexico. Snow levels will
start out rather high tonight and Saturday, generally above 7,500
feet, then drop to around 5,500 feet by daybreak Sunday. A winter
weather advisory has already been posted for total snow
accumulations of 6 to 12 inches above 6500 feet Saturday into
Sunday morning. Models eject the system northeast into the west
Texas Sunday evening, with some wrap around precipitation possible
through early Monday. Otherwise, improving weather conditions can
be expected through the middle of next week. Thereafter, models
track another system through the central Rockies with the tail end
bringing more precipitation to the area around Thursday and Friday
of next week.


Winter Weather Advisory from 11 AM Saturday to 11 AM MST Sunday
for AZZ510>514.




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