Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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000
FXUS65 KFGZ 010340
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
840 PM MST FRI SEP 30 2016

.SYNOPSIS...Expect quiet weather and near average temperatures on
Saturday, although a few light showers will be possible over
higher terrain. Increasing winds are forecast ahead of an
approaching low pressure system on Sunday, followed by strong
southwest winds and noticeably colder temperatures on Monday and
Tuesday.

&&

.DISCUSSION...
The scattered shower and isolated thunderstorm activity from this
afternoon and evening has ended and tonights forecast was updated to
capture this. Surface dewpoint depressions are at 5 degrees or less
at several sites this evening and will monitor as this may lead to
patchy fog development overnight.

&&

.PREVIOUS DISCUSSION 236 PM...On Saturday, northern Arizona will be
under the influence of high pressure. Most of northern Arizona is
expected to experience dry weather, near average temperatures and
partly cloudy skies. With that said, some model guidance suggests
there may be just enough low level moisture for a few showers.
Decided to go with a slight chance of showers over higher terrain,
although stable conditions may lead to the formation of an extensive
cumulus field and nothing in the way of precipitation.

On Sunday, things begin to change as a deep low pressure system
approaches the state from the northwest. While daytime
temperatures will remain near seasonal averages, breezy southwest
winds will foreshadow the passage of an unseasonably cold low on
Monday and Tueday. The newest GFS model run shows a south to north
oriented line of light showers crossing the region, likely in
response to a subtle increase in moisture and weak forcing from a
fast moving, low level thermal gradient. Decided to add slight
chance pop`s to the forecast during this time to account for this,
but confidence is very low at this point.

The bulk of the cold air arrives on Monday as the west coast low
crosses the state. Expect very strong southwest winds and a
noticeable drop in temperatures. Wind gusts in excess of 40 mph
will be possible. Daytime temperatures are expected to drop by
around 10 degrees as compared to Sunday at most places, which
would be around 10 degrees below average for this time of year.
The coldest low temperatures of the last several months are
forecast on Tuesday morning. A hard freeze will be possible above
6000 feet. Similar temperatures are forecast for Tuesday, with
winds weakening and shift to the northeast on heels of the
departing low.

On Wednesday and Thursday, a zonal flow pattern and a warming
trend are forecast in the wake of the departing weather system.

&&

.AVIATION...For the 06Z package...Dry weather is expected through
18z Sat then a slight chance of an isolated rain shower over the
high terrain of northern AZ. SW sfc winds 10-20kt btwn 17z sat - 02z
Sun otherwise light winds.  Aviation discussion not updated for TAF
amendments.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...DL RR
AVIATION...DL

For Northern Arizona weather information visit
weather.gov/flagstaff



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