Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 110351
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
850 PM MST Tue Jan 10 2017

.SYNOPSIS...Expect dry conditions with modestly cooler daytime
temperatures through Thursday. A low pressure system will then
bring a chance of valley rain and mountain snow mainly Friday
night into Sunday. Dry conditions with warmer temperatures will
return early next week.

&&

.DISCUSSION...Much of the southwest part of the country including
the local area was treated to a beautiful sunset this evening thanks
to plenty of high level clouds streaming across the area. Another
fairly dense batch of high clouds will drift across the area in the
strong westerly flow over the next few hours then thin out later
tonight. Variable high clouds with seasonal temperatures will be the
rule through Thursday. The current forecast has the short term
period covered well so no updates planned at this time. The
remainder is from the previous discussion and covers the later
period well.  Cerniglia

The split off the Eastern Pacific that we have been monitoring
looks a little deeper and slower as it tries to shed energy and
fill a bit over southern California Friday, and then Arizona and
northern Sonora over the weekend. Increasing moisture and upslope
from the southwest will probably bring some very light precip or
virga as early as Friday due to terrain influences and the warm
sector ahead of the low.

The best moisture and dynamics couplet for our part of the state
looks to be Saturday into Sunday, with periods of showers
spreading in from the west and southwest. We still need to monitor
timing trends closely as the track gets further and further from
significant higher latitude influences and may try to cut off for
a bit in our general vicinity early Sunday.

Initially high snow levels Friday night, falling as low as 5k-6k
feet Saturday night, subject to change with the track and timing
issues. Preliminary total QPF values around .2 to .5 inches for
valleys and .4 to 1 inch in the mountains over the weekend. That
would give us 6 to 10 inches or so above 7k feet.

Plenty of cool air with this system as a northerly flow behind the
low keeps temperatures below average early in the new week. Watch
for a chilly overnight low or two Sunday night and Monday night,
again depending on the progressive nature of the system and
clearing trends behind it.  Meyer

&&

.AVIATION...Valid through 12/00Z.
FEW-SCT clouds at 11-14k ft AGL and BKN-OVC clouds AOA 20k ft AGL
thru the forecast period. Surface wind generally less than 12 kts.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Dry conditions with a gradual daily cooling trend
expected through Thursday. A low pressure system will then move
into the region late in the week, resulting in a chance of valley
rain and mountain snow starting Friday night and continuing into
early Sunday. Dry conditions are expected to return late Sunday
through Tuesday of next week. 20-foot winds through much of the
forecast period will be terrain driven and less than 15 mph.

&&

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

&&

$$

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