Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 261837

Area Forecast Discussion
National Weather Service Flagstaff AZ
1140 AM MST Tue Sep 26 2017

.SYNOPSIS...Another day of dry and cool weather will grace the
northland before a passing weather system delivers a chance of
showers and thunderstorms from Wednesday into Friday. The best
chance for precipitation will be on Wednesday and primarily
focused over the eastern portion of the state. Generally dry and
mild weather is expected to return for the weekend.

.Discussion...Updated forecast to increase cloud cover today.
Otherwise, forecast is on track.


.PREV DISCUSSION...A trough of low pressure was located over the
Western States during the morning hours with the trough axis
extending from the Arizona/California border northward to Idaho.
Over the next 24 hours a jet max and associated upward motion will
help deepen the trough and form a closed-low over Arizona. In
response, the air mass will cool and moisture will be drawn into
northern Arizona from New Mexico. The net result will be a good
chance for showers and thunderstorms over portions of the area.

For today...Cool and dry conditions will remain in place as the
low strengthens.

For Wednesday...The combination of cooler temperatures aloft,
increasing moisture from over New Mexico and storm forced upward
motion will result in the development of numerous showers and
thunderstorms across eastern Arizona with a good chance elsewhere.
Daytime heating will add additional energy with the most vigorous
storms and showers forming during the afternoon into the early
evening hours.

On Thursday and Friday...The low weakens and moves northeastward.
Forcing for upward motion will fade and temperatures aloft will
warm some. The result will be only a slight chance of showers and
storms for much of the area on Thursday with scattered activity
along the Arizona/New Mexico border. By Friday, only a slight
chance of showers will remain.

Over the coming weekend into early next week...Another trough
approaching from the west will bring windy and generally dry
conditions to the area. Only a slight chance of showers over the
White Mountains region where some moisture will linger. A bit
cooler over the weekend but then a decent cool down by Monday with
the passage of a cold front. It appears that fall weather is here
to stay.


.AVIATION...For the 18Z package...VFR conditions will prevail
over northern Arizona 00z though cloud cover to increase with bases
lowering to aoa 15kft msl. Aft 00Z, a slight chance of
-SHRA/-TSRA develops across Apache county, MVFR conditions possible
over the higher terrain. Aviation discussion not  updated for TAF


.FIRE WEATHER...Dry conditions, light winds, and below normal
temperatures will continue today.

An upper level disturbance developing over the desert southwest will
spread chances for precipitation from east to west from tonight
through Thursday. Wetting precip amounts are possible in
Navajo and apache counties.

Expect clearing from west to east starting Thursday night. A slight
chance of showers will linger Friday along the New Mexico border.
Otherwise expect dry, fall like weather through Saturday.






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