Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 142200 CCA

Area Forecast Discussion...correction
National Weather Service Tucson AZ
300 PM MST Sun Jan 14 2018

.SYNOPSIS...Very warm mid-January afternoon temperatures and dry
conditions will continue through the upcoming week. A pattern
change late in the week into next weekend should bring much
cooler temperatures and the chance of valley rain and mountain
snow Friday night and Saturday.


.DISCUSSION...Another rather warm Sunday across southeast Arizona
with a few spots near record highs. High clouds across the area this
afternoon will continue into evening hours as high pressure aloft
weakens over the state. The weakening is occurring due to two
weather systems, one impacting the Pacific NW and the other
impacting the upper midwest and the Great Lakes. Both features will
have an impact on our weather Tuesday and Wednesday.

Remaining warm on MLK day under a mostly sunny to partly cloudy
sky with highs running 9-11 degrees above mid-January normals.

On Tuesday a back door cold front, associated with the Great
Lakes upper low, will push into the eastern areas bringing much
cooler high temperatures. Highs across Graham, Cochise and
Greenlee counties will run about 7-15 degrees cooler than Monday
while across SE Pinal, eastern Pima and Santa Cruz counties it
will be 2-8 degrees cooler than Monday with biggest change in the
mountains. Gusty east winds will also be around in the morning and
afternoon hours.

A fast moving upper level trof, breaking off the system impacting
the Pac NW, will quickly move thru the Great Basin and the four
corners area late Tuesday night into Wednesday. The feature will
bring a chance of valley rain and mountain snow showers mainly NE
of Tucson. Snow levels will drop down to around 7000 feet with
little accumulation expected. Highs on Wednesday will rebound
about 2-7 degrees across the eastern areas while being at or
slightly cooler than Tuesday from Tucson west.

Short wave ridging on Thursday will bring warmer daytime
temperatures area wide with biggest change occurring across the
eastern areas.

Still rather warm on Friday with gusty southwest winds developing
in advance of a strong/cold/rather moisture starved storm system
that will move across the area late Friday night into Saturday.
There continues to be timing/depth/moisture differences between
GFS/EC/CMC. At this time going with cold front moving across the
area late Friday night into Saturday morning with snow level
crashing to as low as 3500 feet on Saturday. Still plenty of time
to work out the finer details as the week progresses. What is
certain is that it will be much colder on Saturday with the high
temperature for most of the area occurring just after midnight.
Daytime temperatures will be 10-20 degrees colder than Friday.
Could end up colder than what we currently are forecasting. With
the passage of this system, overnight lows will be colder both
Sunday and Monday mornings with freezing temperatures returning
to Tucson.


.AVIATION...Valid thru 16/00Z.
SCT-BKN clouds around 25k ft will persist into Monday. Expect SFC
winds to remain ELY/SELY at less than 12 kts through the period.
Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Warm and dry conditions will continue for Monday.
A passing disturbance will create gusty easterly winds on
Tuesday, as well as a slight chance of showers mainly in the White
Mountains Tuesday night into Wednesday. Things will dry out for
Thursday before another system moves through Friday night into
Saturday bringing with it cooler temperatures, increased
westerly/southwesterly winds, and a chance for valley rain and
mountain snow showers.





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