Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 222255

Area Forecast Discussion
National Weather Service Tucson AZ
355 PM MST Mon May 22 2017

.SYNOPSIS...Strong high pressure aloft will bring well above average
daytime temperatures through midweek. The high pressure system will
weaken Thursday into Friday, allowing for a cooling trend with
afternoon breeziness. Strengthening high pressure next weekend will
maintain dry conditions and another warming trend.


.DISCUSSION...Clear skies west of Tucson with scattered cumuloform
clouds east of Tucson at this time. Lightning strikes were noted
earlier this afternoon just east of this forecast area adjacent the
White Mountains (AZZ510). Any measurable rainfall and lightning
strikes should remain just east of this forecast into early this
evening as a shortwave trough moves southeastward into central New

Thus, expect clearing skies and decreasing wind this evening due to
the loss of daytime heating, then clear skies or perhaps a few thin
cirriform clouds may occur late tonight into Tuesday. Gusty
northwest afternoon winds will prevail Tuesday and Wednesday,
especially east of Tucson.

A vigorous low pressure system over the Pacific Northwest Wednesday
is progged to move into the northern Rockies Thursday. This will
flatten the upper ridge over the area, and the mid-level gradient
will tighten accordingly. The flow aloft will become increasingly
southwesterly Friday, and the mid-level gradient will remain fairly
tight. Although precip-free conditions will continue, the main
result from this pattern will be gusty southwest to west afternon
winds and a cooling trend.

The upper ridge is then progged to amplify near the West Coast
Saturday, then move eastward into the Great Basin region Sunday.
Meanwhile, a baggy trough is depicted via the 22/12Z GFS/ECMWF to be
southwest of the area this weekend. The deterministic GFS/ECMWF were
very similar with depicting a very dry regime capable of yielding
clear skies.

Thereafter, there were stark differences between the GFS/ECMWF for
next Monday. The GFS maintained a very dry environment, but the
ECMWF produced fairly substantial rainfall amounts across eastern
sections of this forecast area. At this time have leaned toward the
GFS and have opted for mostly clear skies next Monday with the
belief that deeper moisture will remain east of this forecast area.

The warming trend will continue Tuesday and Wednesday, with daytime
temperatures to average about mostly 5-10 degrees above normal.
Cooler temperatures will then prevail Thursday through Saturday
followed by another warming trend early next week.


.AVIATION...Valid thru 24/00Z.
FEW-SCT clouds around 8k-12k ft AGL east of KTUS early this evening
then SKC to FEW clouds above 20k ft AGL late tonight into Tuesday.
Surface wind east of KTUS early this evening and Tuesday afternoon
nwly 12-25 kts with gusts to 35 kts. Otherwise and elsewhere,
surface wind terrain driven mainly less than 12 kts. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions will prevail into next weekend.
Expect afternoon 20-foot wind gusts through Wednesday to around 25
mph. Stronger winds are forecast to occur Thursday and Friday as a
weak system approaches from the west. The combination of strong and
gusty southwest to west winds, low relative humidity and a high to
very high fire danger may create critical fire conditions Thursday
and Friday, especially across higher terrain east to south of
Tucson. Less wind will then mitigate critical fire conditions next






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