Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 230410

Area Forecast Discussion
National Weather Service Tucson AZ
910 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...Latest IR satellite imagery shows a batch of high
clouds making its way southeastward across the southern half of the
state this evening. These clouds will dissipate during the early
overnight period. A ridge of high pressure continues to build
overhead paving the way for even warmer temperatures for the next
couple of days. Expect Wednesday to be the warmest as the ridge axis
passes through the region. Gusty west to northwest afternoon winds
will once again be prevalent through midweek with the strongest
winds occurring east of Tucson. The breakdown of the high pressure
ridge along with a trough dropping through the Great Basin region
will combine to bring an even greater uptick in wind gusts for
Thursday and Friday. In addition, temperatures will return to near
normal values through the weekend. No updates are needed to the
current forecast. Please see the previous discussion for more


.AVIATION...Valid thru 24/06Z.
SKC to FEW clouds above 20k ft AGL tonight into Tuesday morning,
then mainly SKC. Mainly light terrain driven winds less than 10 kts
thru about 23/19Z...then nwly 10-20 kts with higher gusts south and
east of KTUS before tapering off again after 24/03Z. 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


.PREV 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 Mexico.

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.





Previous Discussion...Francis

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