Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 160448

Area Forecast Discussion
National Weather Service Tucson AZ
948 PM MST Mon Jan 15 2018

.SYNOPSIS...Gusty winds and several degrees of cooling Tuesday,
otherwise very warm mid-January afternoon temperatures and
generally dry conditions will persist most of the 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 late Friday night into Saturday.


.DISCUSSION...Gusty east winds will develop overnight into Tuesday
as a strong surface high builds through a large portion of the
Central and Southern Plains and the front range of the Rockies. A
backdoor cold front will push in from New Mexico with much cooler
temperatures and about 6 to 10 degrees of cooling from Tucson
eastward. We may need to watch for areas of blowing dust in dust
prone locations (such as near I-10). The direction isn`t favorable
for problems between Tucson and the New Mexico border, but we may
see some dust develop between Tucson and Phoenix mainly in Pinal
county. We are putting in a mention of patchy blowing dust in the
weather grids after collaboration initiated by Phoenix (thanks

Otherwise, the current forecast handles things well, so please see
the previous discussion below for details.


.AVIATION...Valid thru 17/06Z.
SCT- BKN clouds tonight and Tuesday briefly down as low as 12k ft
AGL. Expect SFC winds to become ELY/SELY 15-20 kts from Tucson
eastward after 16/09Z. Aviation discussion not updated for TAF


.FIRE WEATHER...Dry with light winds through this evening. A passing
disturbance will create gusty easterly winds Tuesday, as well as a
slight chance of light showers mainly in the White Mountains late
Tuesday night into Wednesday. Things will dry out for Thursday
before another system moves through late Friday night and Saturday.
This will result in cooler temperatures, increased
westerly/southwesterly winds, and a better chance of valley rain and
mountain snow showers.


.PREV DISCUSSION...The cirrus level cloud cover that was around
this morning continues to push east into New Mexico this afternoon
leaving behind it plenty of sunshine with daytime temperatures
running at or a few degrees cooler than Sunday. For tonight will
start the evening mostly clear but will see an increase in mainly
high level cloud cover overnight into Tuesday. At the surface
there is a back door cold front pushing west through New Mexico
which will move into southeast Arizona on Tuesday. Big question is
how far west will this front push before washing out on Tuesday.
There are differences in the MOS temperature guidance with NAM
cooler than GFS and ECMWF in the middle. Made some slight downward
adjustments by a few degrees on the highs for Tuesday from Tucson
east. Overall it will be much cooler east of Tucson where highs
will run about 15 to 20 degrees colder than today. Gusty east
winds will be on the increase later tonight into Tuesday.

A fast moving weak upper level trof, breaking off the larger
system impacting the Pac NW, will move across the four corners
area Tuesday night into Wednesday. This feature will bring a
slight chance of light snow showers/flurries to the White

Short wave ridging over the state Wednesday night into early
Friday in advance of next Pacific weather system to impact the
area. High temperatures return to well above normal readings
Thursday and Friday before turning sharply colder on Saturday.
Gusty southwest winds will also be on the increase on Friday.

The sharply colder temperatures on Saturday are associated with an
upper level trof and associated cold front that will sweep across
the area on Saturday. Latest model runs are a bit slower than
previous solution thus delayed the onset of any light
precipitation in this moisture starved system to late Friday into
Saturday. Most areas will record their high temperature on
Saturday during the early morning hours with afternoon readings 15
to 20 degrees colder than Friday afternoon. Not expecting much in
liquid and solid precipitation amounts with this moisture starved
system with snow levels as low as 4000 feet on Saturday.

Trailing weak disturbance aloft on back side of system Saturday
will keep a slight chance of snow showers/flurries in the Whites.

With colder air in place, overnight lows Sunday and Monday
mornings will be much colder with readings running 5 to 10
degrees below normal and freezing temperatures returning to the
Tucson metro area.






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