Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 230347

Area Forecast Discussion
National Weather Service Flagstaff AZ
847 PM MST Thu Feb 22 2018

.SYNOPSIS...A cold front and upper level low will bring numerous
showers and low snow levels to northwest Arizona later tonight and
across portions of northern and central Arizona during the day
Friday. Dry and slightly warmer weather is on tap from Saturday
through Monday. A wetter storm system may arrive Tuesday.


.UPDATE...Light snow is beginning to develop near Fredonia per
latest Cedar City radar returns. Light snow will gradually pivot
into northwestern Coconino County after midnight.

The current winter weather advisory is in good shape. Only made
minor adjustments to the grids based on current obs/trends. The
updated products have been sent.


.PREV DISCUSSION /216 PM MST/... Short Term (Tonight through
Sunday afternoon)...

The upper low and cold front that will bring showers and low snow
levels was moving southward through Nevada this afternoon. While
its southern edge is in an area of no radar coverage, the southern
Utah radar is showing increasing returns.

We have issued a winter weather advisory for most of Coconino
county, starting this evening on the Kiabab Plateau and midnight
in the Flagstaff area. Precipitation will develop over the Kaibab
Plateau and western Coconino county this evening, ahead of the
cold front. The cold front does appear to hang up a bit over
western Coconino county Friday morning, (seen in the GFS QPF
forecasts for the last few runs) favoring areas near the Grand
Canyon, possibly as far south as Flagstaff. The front will move
southward to near Flagstaff during the day Friday and snow showers
will be most intense along the frontal boundary as it moves from
NW to SE. Snow ratios are looking like around 18:1, which should
allow snow to be be easily blown around in SW winds of 15-30 mph.
Snow amounts along the Mogollon Rim decrease as one heads east
from Happy Jack, as well as all of Navajo and Apache counties.
However snow levels are so low that nearly everyone that has
precipitation will see snow.

Southwest winds gusting to around 40 mph to affect all of Navajo
and Apache county Friday afternoon.

Dry and more stable air arrives Saturday. Progs still show a weak
s/wv clipping the four corners areas Saturday night through
Sunday morning, thus left the slight chance for showers north of a
Supai to Window Rock line in. Otherwise warmer conditions are
expected Sunday, with mostly clear skies.

Long Term (Sunday night through Thursday)...

Zonal flow will return to the area Sunday and Monday allowing for
cool but warming temperatures to start next week. By late Tuesday
the next weather system will look to impact the area. Current
model solutions show a slightly warmer, and wetter trajectory for
precipitation impacting Northern Arizona.

Decent agreement between operational models has increased
confidence in this event, however there is still a significant
amount of time available for the solution to change. Have
increased precipitation chances for the Tuesday-Wednesday
timeframe, with the system currently expected to exit out of the
area by next Thursday.


.AVIATION...For the 06z package...Southwest winds will continue
across the area overnight with sustained winds around 15-20 kts and
gusts to 30 kts. Lowering ceilings and snow showers will spread to
the southwest tonight and through the day on Friday. Strong mid
level winds and low level moisture will lead to orographic waves,
low ceilings over and SW of the higher terrain, and clearing on the
downwind side. By 18Z, expect MVFR conditions and local IFR/LIFR
conditions over the higher terrain northwest of a line from KPRC-
KFLG-KCEZ. Deteriorating conditions will spread over the higher
terrain of eastern AZ by 03z. Aviation discussion not updated for


.FGZ WATCHES/WARNINGS/ADVISORIES...Winter Weather Advisory from midnight tonight to 8 PM MST Friday
FOR AZZ007-015.

Winter Weather Advisory until 5 PM MST Friday FOR AZZ004-006.




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