Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 251700

Area Forecast Discussion
National Weather Service Flagstaff AZ
1000 AM MST Mon Sep 25 2017

.SYNOPSIS...Dry and cool weather will persist through Tuesday. A
passing low will bring chances for rain showers and thunderstorms
to the area from Wednesday through the end of the week.


.UPDATE...Another cold morning was observed across the northland
with many locations dropping well below freezing. Even some of the
lower elevations of the Little ColoradoRivery Valley near Winslow
and St. Johns dropped below freezing. Temperatures will gradually
moderate each coming day.


.PREV DISCUSSION /313 AM MST/... Cool and dry conditions are
expected for the first half of the week as a large scale upper
level trough remains in place over the Rocky Mountains. This is
expected to remain in place through the week.

By midweek a shortwave disturbance will move through the trough
and deepen as it moves across the trough axis over the Four
Corners region. Current model outputs have most of the moisture
over New Mexico from Wednesday onwards with more scattered
precipitation over Northern Arizona. Multiple model runs, with
agreement between different forecast models have continued to
favor this solution.

There is an outlying chance that the trough moves back towards
the Arizona-California border with more moisture, however, this
is becoming less likely with each subsequent run showing the more
eastward precipitation shield.

By next weekend the ridge looks to finally move eastward as an
induced shortwave ridge looks to develop between troughs over the
area early next week. While confidence is low in timing and
location of this feature it could signify a pattern change to a
more zonal wind field over Northern Arizona by next week.


.AVIATION...For the 18Z package...VFR conditions will prevail over
northern Arizona through the TAF period. Aviation discussion not
updated for TAF amendments.


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

Wednesday through Friday...There will be a chance of showers and
thunderstorms Wednesday and Thursday, with the highest chances over
Apache and Navajo counties. Expect clearing conditions from west to
east starting Thursday night.






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