High Wind in Arizona, December 26, 2021

Area Forecast Discussion
National Weather Service Flagstaff AZ
931 PM MST Sat Dec 25 2021

.SYNOPSIS...Another period of light rain and accumulating mountain
snow arrives tonight through late Sunday morning. Even more active
weather arrives Monday night through Tuesday night, with
widespread rain and snow showers, producing more accumulating
snow at higher elevations. Breezy conditions are expected nearly
every day into next week, winds peak tonight and Sunday.

&&

.UPDATE...Light shower activity is currently to the south in the
Phoenix area and to the northwest in southern Utah. Low level
moisture is moving up from the south causing low ceilings and
possible fog along the south and west faces of rising terrain like
the I-17 corridor. Strong winds due to the approaching shortwave
trough will continue to increase overnight as rain and higher
elevation snow showers develop. Expect the heaviest shower
activity between midnight and mid morning. This afternoon's
forecast is on track with only minor adjustments. Slowed the
shower activity development based on the high resolution models
which in turn reduced the total precipitation mostly in the lower
elevations. Cold air moving down from the northwest will drop snow
levels to 6000 feet by morning, but little accumulation is
expected below 7000 feet due the to shallow moist layer limiting
dendritic growth except over the high terrain where orographic
lift affects the process.

&&

.PREV DISCUSSION /240 PM MST/...Cloud streets are evident on radar
this afternoon as upslope flow and shallow instability continues
to build ahead of an approaching s/wv. Breezy southwest winds
will turn downright windy tonight and Sunday. A wide-ranging Wind
Advisory has been issued.

Upslope flow increases tonight as a s/wv currently over central
California moves through the mean trough over the western states.
This s/wv will have a bit colder air with it (compared to
yesterday) and will generate about a 6 hour period of maximized
upslope flow. Moisture is not a problem, so we should see quickly
increasing activity along and south of higher terrain by this
evening.

Activity will peak from roughly 09Z-15Z Sunday along the Mogollon
Rim, a bit earlier on the Kaibab and a bit later over the White
Mountains. Model soundings indicate a fairly shallow saturation
layer, but at least 4 hours of -12C or colder, which should aid
the formation of dendritic snow showers.

Current forecast of 1-4 inches over favored terrain tonight and
early Sunday still look good. Favored zones, the Kaiabab Plateau
and the western Mogollon Rim, both have had Winter Weather
Advisories posted.

A deeper s/wv arrives Monday night and Tuesday, for an even more
widespread shower event, with colder temperatures. Models have
decreased QPF a bit for this event, but it still looks like a
multi-zone, advisory level event. Stay tuned.

Even farther out, longer range solutions still having trouble in
the Friday/Saturday time frame. A splitting trough may eject
inland and phase with sub-tropical moisture, or it may stay split
with minimal impacts. Time will tell on this one.

&&

.AVIATION...For the 06Z package...Expect rain and high elevation
snow showers  to the south and west of a line KPGA-KINW-KJTC. MVFR
to IFR conditions with low ceiling along the south and west face of
rising terrain, across the higher elevations and in the vicinity of
shower activity. Southwest winds 10-20 kts with gusts to 30 kts in
the higher terrain. Areas of LLWS with gains and losses of 40-50 kts
are likely along and northeast of higher terrain decrease after 12Z.
Showers and winds will diminish after 18Z. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Breezy to windy southwest winds through Monday
night. Showers increase from west to east overnight into Sunday
morning. Wetting rains are possible over the high terrain with some
accumulating snowfall above 6500 feet. Showers will decrease Sunday
evening...and then increase again late Monday.

Tuesday through Thursday...Cool and breezy with a chance of
precipitation producing a widespread wetting rain and snow.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...

Wind Advisory from midnight tonight to 5 PM MST Sunday FOR
AZZ004-006>009-011>017-039.

Winter Weather Advisory above 7000 feet from 2 AM to noon MST
Sunday FOR AZZ015.

Winter Weather Advisory above 6500 feet until 11 AM MST Sunday
FOR AZZ004.

&&

PUBLIC...DB/Peterson
AVIATION...DB
FIRE WEATHER...MAS

For Northern Arizona weather information visit
weather.gov/flagstaff