Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 222253 CCA

Area Forecast Discussion
National Weather Service Flagstaff AZ
352 PM MST Sun Jan 22 2017

.SYNOPSIS...A winter storm will impact northern Arizona today
through Monday night with additional moderate to heavy snow
accumulations above the 6000 foot level, with lighter amounts down
to 5000 feet. Expect hazardous driving conditions due to snow and
blowing snow. Precipitation will wind down Tuesday with very cold
temperatures continuing through at least Friday.


.DISCUSSION...The next storm system has already begun to affect
northern Arizona this afternoon, with areas of snow and rain
moving across portions of the area. Most accumulations have
remained light and above the 5500 foot elevation level, though
some heavier snow has been occurring over northwest Coconino
county. Later this evening and overnight, as the main trough and
cold front move closer to the state, winds aloft will increase
dramatically which will increase the upslope wind component and
cause precipitation rates to increase over favored areas including
the Mogollon Rim and Kaibab Plateau. Some warmer air aloft will be
pulled northward, raising snow levels above 6000 ft overnight. Sfc
winds will become gusty from the southwest (15-25 mph with higher
gusts), creating some areas of blowing/drifting snow. Winds
downstream of terrain features, will increase even more with gusts
over 50 mph possible along the highway 89 corridor from Doney Park
to Cameron, as well as the Houserock valley east of Jacob Lake.

On Monday, the trough will move into the state with much colder
air spreading from west to east. Periods of moderate to heavy snow
and rain are expected, with snow levels dropping quickly from 5500-
6500 ft in the morning to less than 5000 ft by late afternoon.
Widespread rainfall amounts in the lower elevations of Yavapai and
Gila counties of up to an inch could bring additional rises along
streams that are already running. Some low water crossings could
be flooded. Winds will continue to create areas of blowing/drifting
snow and tough travel conditions. By Monday evening, the main upper
level trough will be crossing northern Arizona with an enhanced
area of lift and heavier precipitation from around Flagstaff eastward.
By Tuesday morning, we expect precip to be decreasing, though the
very cold and somewhat unstable northwest flow will lead to some
snow showers over higher terrain. Cold air will continue to flow
into the region through at least the remainder of the work week and
temperatures below seasonal normals are expected across the region.
The deep snowcover will only amplify this with clearing skies
overnight allow for efficient radiative cooling to occur. These
cold temperatures are expected to be the major impact from Tuesday
onward as an otherwise quiet weather pattern develops over
Northern Arizona behind the impending storm system.


.AVIATION...For the 00Z package...Areas of rain and snow will
continue across northern Arizona today, with heavier precipitation
expected to sweep across the region from west to east from this
evening through Monday. LIFR/IFR conditions in low ceilings and
visibilities will be associated with the heavier bands of
precipitation, first occurring at higher elevation TAF sites. By
early Monday morning, widespread LIFR/IFR conditions are expected
across the majority of northern Arizona. An exception to this is in
the Little Colorado River Valley northeast of the Mogollon Rim,
where ceilings and visibilities may predominately be in the MVFR
flight category. In addition, strong winds will accompany this
system, with wind gusts in the 20 to 30 knot range today and
tonight. Winds may increase into the 30 to 40 knot range after 15Z
Monday. Aviation discussion not updated for TAF amendments.


Tuesday FOR AZZ016-018.

Winter Weather Advisory from noon Monday to 5 AM MST Tuesday FOR

Winter Storm Warning until 5 AM MST Tuesday FOR AZZ004-006>008-

Winter Storm Warning from noon Monday to 5 AM MST Tuesday FOR




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