Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 271646

Area Forecast Discussion
National Weather Service Tucson AZ
946 AM MST Thu Apr 27 2017

.SYNOPSIS...Another system north of our area will bring increasing
winds this afternoon followed by a return of strong and gusty winds
Friday into Saturday. Blowing dust may be an issue, especially in
the vicinity of Interstate 10. A few showers or thunderstorms are
possible northeast of Tucson on Friday. Cooler on Saturday
followed by dry conditions with a warming trend next week.


.DISCUSSION...Winds will be increasing over the next 48 hours as
a strong ridge amplifies off the west coast and a system digs
through the intermountain west and front range of the rockies. We
currently have a red flag warning for today and Friday. Taking a
look at things for wind and blowing dust advisories for Friday as
well. Saturday will be cooler but also much drier behind the
front, and the winds will probably still be there much of the

Current forecast handles all of this pretty well. Please see the
previous discussion below for additional details.


.AVIATION....AVIATION...Valid through 28/18Z.
SCT-BKN clouds above 20k ft AGL. SFC wind light and variable at
less than 10 kts this morning, then increasing this afternoon to
15-20 kts with gusts to 30 kts. The strongest speeds will be east
of KTUS. Looking into Friday afternoon stronger winds will be
impacting all terminal sites. Aviation discussion not updated for
TAF amendments.


.FIRE WEATHER...Strong and gusty winds will continue to be a concern
the next several days. Today, the wind will pick up again during
the afternoon. Latest models were still showing Red Flag
conditions across much of zone 152 and parts of southeast zone
151. This includes the higher elevations of Whetstone Mountains
near the Sawmill wildfire.

Even stronger winds can be anticipated Friday, but models continued
to show an increase in relative humidity values. However, given the
very dry fuels went ahead and upgraded Fire Weather Watch to Red
Flag Warning. The wind will remain elevated in speed Saturday across
eastern sections on the back side of an exiting system to the north.
Humidity values will also lower on Saturday, so critical fire
weather conditions will once again be a concern. For now, will focus
on today and Friday with the expectation of a watch or warning being
posted for Saturday as the weekend draws closer. The wind settles
down next week, but very dry conditions will remain in place.


.PREV DISCUSSION...Today`s winds associated with short wave
moving across WY/UT into CO which tightens up the pressure
gradient. Further tightening of the gradient will occur on Friday
as a follow-up system, currently in the Gulf of Alaska this
morning, dives into the Great Basin with a cut-off low developing
near the 4-corners late Friday afternoon into Friday evening. This
system will also bring an increase in moisture with a chance of
showers or thunderstorms for mainly the White mountains at this
time. Can`t rule out a stray shower getting close to the Safford
area late Friday afternoon into Friday night.

Warmer today with highs running 2-6 degrees above late April
normals. Cooler Friday with highs similar to what occurred on

Closed low moving across New Mexico on Saturday with tight pressure
gradient remaining over the area. Fire weather concerns are
addressed below. Much cooler on Saturday with highs about 10 degrees
below normal. Enjoy it. Just a hint for what may come by the end of
next week. With colder air mass over the area overnight lows
Saturday night into Sunday morning could get quite chilly especially
for the normally colder sheltered areas east and south of Tucson. A
few hours of freezing temperatures not out of the question.

Dry NW flow aloft Sunday thru Tuesday results in a warming trend
area wide. Upper ridge amplifying up the west coast on Wednesday
will move east over the state next Thursday and east of the state
next Friday. Although outside of this forecast package it is of
interest as both the GFS and ECMWF forecast low-level thickness
values suggest Tucson will make another run at the first triple
digit high of 2017 on Cinco de Mayo.


Red Flag Warning until 7 PM MST this evening for AZZ151-152.

Red Flag Warning from 10 AM to 8 PM MST Friday for AZZ150>152.




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