Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 122157

Area Forecast Discussion
National Weather Service Flagstaff AZ
257 PM MST Mon Feb 12 2018

.SYNOPSIS...Rain and snow showers will continue tonight over
northern Arizona as a deep trough moves west of the area. Drier
conditions will develop late on Tuesday, with a good chance of
precipitation returning from Wednesday afternoon into Thursday.


.DISCUSSION...Scattered rain and snow showers continue to persist
along the upslope-favored areas the Mogollon Rim and Yavapai
County, as well as the Kaibab Plateau. Saturation of the airmass
is very shallow, and as such, precipitation production has
generally been light, with only a few tenths of an inch (or an
inch or two of snow) measured today in the favored areas. The
strong pressure gradient and SW flow has also produced very strong
winds over northeastern Arizona, with gusts over 50 mph reported,
and some areas of blowing dust.

The forecast through Tuesday morning is challenging - the
numerical forecast models are agressive with the strong and
saturated upslope flow producing significant rain and snow
accumulations, but the microphysics argue against copious
precipitation production. That is, the cloud top temperatures will
not be cold enough for efficient ice crystal growth, and
therefore, rain and snow accumulations will be inhibited.

Our forecast, therefore, is for light rain and snow accumulations
overnight and Tuesday morning most areas, with a continuation of
the drizzle, light snow, and occasionally heavier showers as
colder cloud elements pass over the area. Deeper moisture over
the northern portion of the state will lead to heavier
precipitation and snowfall over the higher elevations of the Kaibab
Plateau, where 4-8 inches of snow are expected by Tuesday
morning. The Winter Weather Advisory for the Kaibab will continue
overnight. We`ve also raised snow levels up a bit from the
previous forecast - now generally ranging from 6500 to 7100 feet
through Tuesday morning. Over the highest peaks, expect some
additional rime ice accumulations.

The retrogression of the trough westward will lead to a break in
the precipition from Tuesday afternoon through much of Wednesday.
There is great uncertainty later in the week as the trough (or
series of troughs) move back across the Southwest. It appears like
these systems will tap subtropical moisture, and bring a good
chance for significant precipiatation late on Wednesday through


.AVIATION...For the 00Z Package...MVFR/IFR conditions in low
ceilings and high elevation snow showers will continue over the
higher terrain through much of the next 24 hours. Gusty southwest
winds will persist over the next 24 hours at most locations, with
the strongest winds along the Eastern Mogollon Rim, White Mountains
and the Little Colorado River Valley. In these areas, expect 15-25KT
with gusts between 35-40KT until around 02Z. Aviation discussion not
updated for amendments.


.FIRE WEATHER...A trough of low pressure over the Great Basin this
afternoon will move southwest and off the San Diego Coast by late
Tuesday. This will bring strong gusty southwest winds into this
evening before decreasing some overnight. Breezy winds will continue
through Wednesday. Showers will continue...mainly over the
higher/upslope terrain through Tuesday morning before becoming more
isolated Tuesday afternoon. The trough will begin to move
northeast on Wednesday with increasing showers.

.Thursday through Saturday...The trough of low pressure will
move over southeast Arizona on Thursday as another trough drops
south along the southern California Coast. This will continue
unsettled weather through Friday. Clearing and warmer conditions are
expected Saturday.


.FGZ WATCHES/WARNINGS/ADVISORIES...Wind Advisory until 6 PM MST this evening FOR AZZ012>014-016-017.

Winter Weather Advisory until 5 AM MST Tuesday FOR AZZ004.




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