Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 291643

Area Forecast Discussion
National Weather Service Flagstaff AZ
943 AM MST THU SEP 29 2016

.SYNOPSIS...Showers and thunderstorms are likely across northern
Arizona today, with lowering chances on Friday. Drier air is
expected this weekend, followed by increasing southwest winds and
cooler temperatures from a passing weather system early next week.


.DISCUSSION...This morning`s radar imagery reveals light to
moderate showers, and a few thunderstorms, primarily east of a
line from Prescott through the Four Corners. This convection is
expected to push northward throughout the day as a plume of deep
moisture continues to stream into the state from the south. The
previous discussion describes today`s forecast well, and no
forecast updates are anticipated at this time.


.PREV DISCUSSION /428 AM MST/...A deep moisture plume will stream
northward across the state today with precipitable water values
well above seasonal averages. Occasional showers are expected over
much of the region, with a few thunderstorms mainly this afternoon
and early evening. Activity could be enhanced at times due to some
weak disturbances moving across the region associated with a
trough to our west. Instability parameters don`t look impressive
today as cloud cover will reduce surface heating, but with 20-30kt
of deep layer shear a storm or two could become strong if any
cloud breaks develop and allow some better heating. Cell training
could lead to some isolated areas of heavy rainfall but this
threat does not appear widespread. Most shower activity will
diminish overnight. On Friday the upper low weakens and shifts
into northern AZ. Some low level moisture remains but most of the
mid and upper level moisture will be east of the region. There is
a chance of afternoon showers and storms with near normal

Dry southwest flow develops this weekend ahead of a deep low
pressure system moving toward the west coast. Temperatures will be
seasonable with mostly clear skies. Models are in good agreement
that the west coast low will pass north of Arizona Monday, pushing
a cold front across the state. Winds along and ahead of the front
could become strong with gusts 40+ mph a possibility. Most of the
moisture with the system appears that it will stay north of the
state at this point with only low PoPs for our forecast area.
Daytime highs early next week should be around 10 degrees below
average. Overnight lows have the potential to be the coldest we
have seen so far this season, especially if overnight winds are
able to diminish. Some areas above 6000 feet could see the first
hard freeze of the fall Tuesday or Wednesday mornings.


.AVIATION...For the 18Z package...SHRA/TSRA increasing in
coverage through the daytime hours becoming scattered to numerous
across nearly all of northern AZ. Expect scattered MVFR conditions
in showers, especially over the higher terrain. South winds 10-15
kts. Showers expected to decrease in coverage aft 06Z Fri.
Aviation discussion not updated for TAF amendments.






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