Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 181105

Area Forecast Discussion
National Weather Service Flagstaff AZ
405 AM MST SUN SEP 18 2016

.SYNOPSIS...Dry weather with pleasant days and cool nights will
continue this weekend. Clouds will increase on Monday with showers
and thunderstorms expected across northern Arizona Monday night
through Wednesday. Coverage of precipitation will peak on Tuesday.


Early morning water vapor imagery shows dry westerly flow over
northern Arizona, as we are currently located on the northwestern
edge of a broad ridge centered over the Big Bend region of Texas.
A low pressure trough off the northern coast of Baja California is
also apparent. Expect another couple days of dry and relatively
quiet weather, but subtropical moisture is forecast to advect
northward as the closed low pressure trough off the Pacific coast
opens up on Monday afternoon/evening and southerly flow over
Arizona increases. Clouds will be increasing throughout the day on
Monday, with precip chances bumping up primarily in
Yavapai/Coconino counties by Monday night.

The greatest coverage of rainfall is expected from about midnight
Tuesday morning through about midnight Wednesday morning. Ensemble
solutions from the GEFS show some variability in timing and
intensity of the rainfall/moisture plume as it moves from west to
east across Arizona. In general, heavier rainfall amounts should
be expected in western areas, such as Coconino/Yavapai counties
and points west. However, even here, current model forecasts are
not expecting very heavy rainfall outside of a couple outliers. In
general, expect average amounts in western Coconino/Yavapai in the
0.40"-0.70" range with the possibility of some locations receiving
over an inch. Lesser amounts are forecast farther east.

Forcing begins to decrease on Wednesday, but with some low-level
moisture still present expect a chance of mainly afternoon showers
and thunderstorms. On Thursday, the base of a large trough over
much of the northwestern U.S. begins to swing through the Great
Basin. It`s questionable how much moisture will be around when
this occurs, but should there be enough, there may be a chance of
severe storms especially across areas near the Utah state line.
By Friday, moisture is expected to be on the low side and cool
air associated with the Great Basin trough is expected to hold max
temperatures down to 5-10 degrees below average. Temperatures are
expected to warm back to near average by Sunday.


.AVIATION...For the 12Z package...A dry air mass will remain across
northern Arizona over the next 24 hours. VFR conditions will
continue under clear skies. Winds generally less than 10 kts.
Aviation discussion not updated for TAF amendments.






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