Heavy Snow in Alaska, December 20 to 21, 2022

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
516 AM AKST Tue Dec 20 2022

.SHORT TERM.../Through Tuesday night/ Cold conditions continue
across the panhandle this morning with teens, and single digit
temperatures common. The coldest temperatures are along the Haines
and Klondike Highways where teens below zero are common. Outflow
winds also continue to blow down the Klondike Highway, Lynn
Canal, and out of Cross Sound and Taku Inlet. A wind chill
advisory remains up for the White Pass area as observations there
have seen wind chills hovering around minus 50 all night.

Cold and mostly dry remains the story for most of the Panhandle E
of Cape Fairweather. The remaining outflow winds will continue to
slowly diminish and temperatures will start to moderate slightly
over the next 24 hours as the main blob of cold air in Canada
begins to pull away to the E. Overnight lows Tue night are still
expected to be cold, but will not quite be to the extremes that
were seen the last two nights (below zero readings should not be
as common).

W of Cape Fairweather, a stationary low in the northern gulf is
generating gale force winds near Cape Suckling and sending bands
of precip into the northern gulf coast. Yakutat did see some light
snow overnight, but it did not amount to much. That could change
into Tue night as a more substantial band of precipitation
develops. Latest guidance has trended eastward on where the precip
band will track. The area of max precip has shifted from Icy Bay
to in between Icy Bay and Yakutat with some guidance taking it
even further E. Snow totals for Yakutat have been increased to a
high end advisory (6 to 9 inches total over 18 hours) as a result.
If the eastward trend continues Yakutat could be under the gun
for higher snow totals if the precip maxima ends up directly
over them. However, this snow band is forecast to be rather
narrow so amounts could vary significantly over a short distance
with some areas getting high amounts while others receive only a
few inches depending on where the band ultimately sets up.

.LONG TERM.../Wednesday through Saturday/A low pressure pattern
returns to the panhandle after an extended cold and dry spell. A
gradual increasing trend in temperatures will begin to unfold as
we go into the late week and into the weekend. Highs in the teens
to low 20s are expected for Wednesday then into the low-upper 20s
for Thursday before climbing into the upper 20s to low 30s on
Friday.

As for precip, Wednesday remains dry for the most part with the
exception of the NE Gulf Coast as a low brings snow for Yakutat.
Through Thursday a frontal band associated with a surface low in
the W Gulf moves south to north over the panhandle. With a cold
Arctic airmass in place and easterly flow, there is a strong
potential that this band of precip will bring significant snowfall
across the panhandle. The southern panhandle starts the event off
late Thursday before moving into the central and northern
panhandle through Friday. Portions of the panhandle will likely
see greater than 6 inches of snow with this system. The southern
panhandle, will see a change over to rain with the first best
estimate being by Saturday morning.

By the weekend, another system looks to move towards the S Gulf
coast bringing another wave of precipitation through the panhandle
for the weekend. At this time, the southern panhandle looks to
have warmed up enough to see mostly rain through the weekend. An
Arctic boundary will likely set up somewhere around the Icy Strait
Corridor as there will still be northerly pressure gradient over
the northern Panhandle. Depending on where this boundary develops,
the central and northern panhandle will remain mostly snow through
Sunday before rain starts to mix in.

Overall, several details still need to be worked out to better
fine tune the snowfall forecast but confidence is increasing that
this event will bring the first significant snowfall for most of
the central and southern panhandle.

&&

.AVIATION...With the exception of PAYA IFR conditions with the
clear, cold, and dry VFR weather continue. Outflow winds and LLWS
will diminish later in the period as pressure gradients slowly
weaken. For PAYA snow showers will bring ceilings and
visibilities to IFR conditions however the snow shower timing is
uncertain as bands rotate around the NE Gulf low.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory from noon today to 7 AM AKST Wednesday
     for AKZ317.
     Wind Chill Advisory until 10 AM AKST Wednesday for AKZ318.
     Strong Wind through this afternoon for AKZ318.
MARINE...Gale Warning for PKZ051-052.
     Small Craft Advisory for PKZ012-013-031-043-053.

&&

SHORT TERM...EAL
LONG TERM....CC
AVIATION...PRB

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