Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 230436
AFDFGZ

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

.SYNOPSIS...A winter storm will impact northern Arizona 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.

&&

.UPDATE...Strong storm system is spreading showers over Arizona
this evening. Precipitation has been light so far...and will only
increase in intensity and coverage through the night and on
Monday. Current forecast and headlines handle this powerful storm
well.

&&

.PREV DISCUSSION /352 PM MST/...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...-SHRA/-SHRA will increase in intensity and coverage
from west to east through the night. 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 12Z, widespread LIFR/IFR conditions are expected across
the majority of northern Arizona. An exception to this is in the
Little Colorado River Valley, where ceilings and visibilities may
predominately be MVFR. Winds will increase tonight with gusts 20
to 30kts. Winds may increase to 30 to 40kts after 15Z. Aviation
discussion not updated for TAF amendments.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Winter Storm Warning until 5 AM
MST Tuesday FOR AZZ004-006>008- 015-016-018.

Winter Weather Advisory from noon Monday to 5 AM MST Tuesday FOR
AZZ011-039.

Winter Storm Warning from noon Monday to 5 AM MST Tuesday FOR
AZZ017.


&&

$$

PUBLIC...MAS/JJ
AVIATION...McCollum


For Northern Arizona weather information visit
weather.gov/flagstaff


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