Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 180413

Area Forecast Discussion
National Weather Service Flagstaff AZ
913 PM MST Tue Jan 17 2017

.SYNOPSIS...Scattered light shower activity will persist this
evening across eastern Arizona. Otherwise look for mostly cloudy
skies and some patchy fog. Warmer weather is forecast for
Wednesday. A period of cold and wet weather will arrive starting
Thursday, with several disturbances delivering winter weather
through next Tuesday. Stay tuned to the forecast as there is
potential for heavy snow accumulation in the high country.


No significant changes to the forecast tonight. slightly increased
cloud cover across the western part of the cloud shield as
satellite and ground observations show a very slow clearing
overnight. Other parts of the forecast look to remain on track
with temperatures expected to drop in the early morning hours
especially where clearing occurs.


.PREV DISCUSSION /332 PM MST/... Plenty of cloud cover a a few
light showers this afternoon across areas east of Page-Flagstaff-
Prescott line while mostly clear west of this line. This cloud
cover should slowly decrease overnight as the upper level trough
generating it weakens and moves eastward.

Still expecting fair weather on Wednesday as a shortwave ridge
passes overhead.

From Thursday through next Tuesday, still expecting a period of
winter weather across northern Arizona. Model continuity is good
w/ respect to the timing of the first two systems.

The first cold front should move west to east across the northland
Thursday through Thursday night bringing rain and mountain snow.
Surface temperatures to fall through the afternoon and by Friday
morning 3 to 6 inches of new snow is forecast above 6000 feet.
Lighter amounts are possible down to 5000 feet on the tail end of
system early Friday morning.

There should be a lull in shower intensity Friday morning. A very
strong storm system will then move from west to east from Friday
afternoon through midday Saturday. Models show a strong Pacific
jet moving into the southwestern U.S. with rapidly falling heights
as much colder air pushes into the state. Snow levels look to
start at around 5000 feet at sunset Friday and fall to the
4000-4500 foot range by Saturday morning. There is a significant
moisture tap with this system. This second system will bring
accumulating snow to areas above 5000 feet Friday night. The
heaviest precipitation looks to be along the Mogollon Rim from
Williams through the White Mountains, as well as the highest
terrain of Yavapai and Gila Counties. Expect winter driving
conditions across much of northern AZ thanks to the second system.

Models do show drier weather moving in from west to east Saturday
evening through Sunday afternoon as a transitory ridge passes

From Sunday afternoon-Tuesday Progs do show another large and cold
trough moving through during this time frame. However there are
timing issues. The ECMWF has the earliest onset of precip as
early Monday morning in western AZ and spreading eastward through
the day. GFS and its ensembles about 12 hours slower.

All are encouraged to monitor upcoming forecasts for changes and
the issuance of any Winter Weather Advisories and or Warnings.


.AVIATION...For the 06Z package...VFR conditions are expected to
prevail across the area. Some mid level clouds look to slowly exit
the area mainly over the higher terrain of eastern Arizona. An
isolated shower will be possible through the early morning hours
in this region, mainly over the White Mountains. Aviation
discussion not updated for TAF amendments.






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