Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 262102

Area Forecast Discussion
National Weather Service Tucson AZ
202 PM MST Wed Apr 26 2017

.SYNOPSIS...Another system north of our area will bring increasing
winds Thursday afternoon followed by a return of strong and gusty
winds Friday into Saturday. A few showers or thunderstorms
possible northeast of Tucson. Cooler Saturday followed by dry
conditions with a warming trend next week. Another round of strong
winds possible next Tuesday or Wednesday.


.DISCUSSION...A spring pattern with enhanced winds will continue
into early next week. We`re keeping a brisk northwesterly flow
aloft in an amplified pattern between major features. A very
strong ridge just off the west coast with a mean trough position
through much of the Great Basin and Front Range. As systems slide
down and reinforce the back side of the trough, we go from breezy
to windy. That will start to happen again Thursday afternoon, with
Friday another day of particular concern for dust, fire weather,
and advisory level winds.

This next system will likely dig just bit further south as the
ridge amplifies offshore. This should bring a few showers or
thunderstorms to mainly higher terrain areas northeast of Tucson
late Friday into Saturday. Plenty of cooler air behind a late
April frontal passage Saturday with daytime temperatures dropping
from upper 80s to lower 90s tomorrow to 70s on Saturday. Saturday
night will be the coolest we`ve seen in about 3 weeks, with 30s in
valleys east and south of Tucson, and 40s from Tucson westward. A
few spots will probably freeze Sunday morning in colder Cochise
county valley locations.

The eastern flank of the ridge will start to assert itself into
our area early next week with a slow pattern shift. We still may
see another batch of strong gusty winds Tuesday and/or Wednesday
with systems digging sharply immediately downstream to our east.
Otherwise dry and warmer.


.AVIATION...Valid through 28/00Z.
SKC to SCT clouds above 20k ft AGL thru fcst pd. SFC wind W/NW 10-20
kts with gusts to 25 kts through 27/02z then becoming light and
variable at less than 10 kts. SFC wind increasing again Thursday
afternoon to 15-20 kts with gusts to 30 kts. The strongest speeds
will be E of KTUS. Aviation discussion not updated for TAF


.FIRE WEATHER...Interesting few days coming up, at least through
Saturday.  Due to the fire behavior noted with the very dry fuels we
have leaned toward the side of caution with RFWs.  For Thursday,
winds will pick up in the afternoon and are expected reach Red Flag
criteria across much of zone 152 and some parts of SE zone 151
including the higher terrain of Whetstone Mtns near the Sawmill
Fire.  Feedback from the fire indicates that the Empire RAWS wind
speeds are lighter than the wind in the open (partly sheltered), so
based on that and coordinating with onsite IMET will include the
fire area in the Red Flag warning for Thursday for a marginal event.

Then the attention turns to Friday where winds will be stronger and
likely very similar to what we saw Tuesday.  RH levels will be
elevated again like Tuesday and generally a bit above criteria, but
based on how the very dry fuels reacted to the wind, and
coordination with IMET, opted to issue a Fire Weather Watch for much
of zones 151 and 152.  Actually RH levels will be lower from Tucson
westward which will meet criteria based on the current forecast.

Winds will remain rather elevated again Saturday coupled with lower
humidity levels on the back side of the passing system with a good
chance we will see Critical fire weather conditions again across
much of zone 152 and SE 151, but will let that go for now and focus
on the near term.

Beyond that the wind generally settles down some but the air mass
will remain very dry with single digit min RHs each afternoon
into next week (and another round of gusty winds possible


Red Flag Warning from noon to 7 PM MST Thursday for AZZ151-152.

Fire Weather Watch from Friday morning through Friday evening
for AZZ150>152.




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