Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 170357

Area Forecast Discussion
National Weather Service Tucson AZ
855 PM MST Thu Feb 16 2017

.SYNOPSIS...Dry with warmer conditions are expected for one
more day Friday. Then a strong Pacific storm system will bring a
very good chance of valley rain, mountain snow, cooler temperatures
and gusty winds this weekend.


.DISCUSSION...Another mild evening tonight with yet another
warmer than normal day expected tomorrow.  With a warmer start,
afternoon temperatures will still end up pretty close to today`s
highs despite an increase in cloud cover.

Then our attention turns to the developing storm that is currently
well out over the eastern Pacific.  This system will rapidly move to
the coast Friday as it deepens then shift inland into Saturday. As
it approaches the coast Friday southerly breezes will begin to pick
up across southern Arizona but nothing significant expected.

It becomes more interesting Saturday as the storm draws closer and
the moisture rapidly deepens.  There is a chance for some showers as
early as before dawn Saturday mainly west of Tucson, however the
bulk of the precipitation is expected later Saturday through Sunday.
It will also be quite breezy Saturday across the region with
sustained winds in the 20-25 mph range and gusts quite a bit higher.
Some of the normally windier locations could see wind advisory
criteria for a period of time.

This system will be quite a bit wetter than the last one and total
valley rainfall should end up between 1/3 of an inch and 1 inch.  As
is typical, the snow levels will start out fairly high, near 8,000
feet early Saturday and steadily fall to near 6,000 feet Sunday.
Also in typical fashion, the bulk of the precipitation will fall
before the coolest air arrives limiting the amount of accumulation
at the lower elevations.  So at this time the expectation is for 10-
16 inches of snow possible above 7,500 feet where a Winter Storm
Watch is in effect for our mountain areas.

The precipitation will wind down fairly quickly late Sunday with dry
conditions expected through at least the middle of next week.
Temperatures will start out rather cool with a steady warming trend
thereafter.  A slight hiccup in that is a system passing by to our
north late Wednesday into Thursday which should bring a decent
breeze and cooler temperatures.  A few model solutions also hint at
some scattered showers northern areas so we will need to watch for


.AVIATION...Valid through 18/00Z.
SCT clouds above 20k ft AGL mainly west of KTUS into this evening,
then FEW-SCT clouds at 12k-15k ft AGL and BKN clouds above 20k ft
AGL late tonight into Friday afternoon. Surface wind mostly less
than 12 kts thru tonight, then sly/swly 12-18 kts with gusts to near
25 kts after 15Z Friday and continuing Friday afternoon. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions will continue into Friday followed by
a very good chance of valley rain and mountain snow this weekend as a
strong Pacific storm system moves across the region. Expect gusty
south to southwest winds Friday afternoon through Saturday with
winds diminishing Sunday. 20-foot winds will generally be less than
15 mph through much of next week. Dry and warmer conditions will
prevail Tuesday into next Thursday.


Winter Storm Watch above 7500 feet from Saturday afternoon
through Sunday afternoon for AZZ510>514.


FIRE WEATHER...Francis/Meyer


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