Heavy Snow and High Wind in Alaska, October 11 to 12, 2021

Southeast Alaska Forecast Discussion National Weather Service Juneau
AK 300 PM AKDT Mon Oct 11 2021

.SHORT TERM...Very strong front moving into the coastal area so
have issued High wind warnings for coast from Sitka south to Dixon
Entrance and this includes the east side of the island and
communities near Clarence Strait. Gusts of 50 to 60 mph are expected
around Sitka, Port Alexander, Craig, Klawock, Hydaburg, Ketchikan,
Metlakatla, Kasaan and Thorne Bay. The strongest wind should be
through the area by Midnight or so and start to diminish.

The low moves to the northern part of the panhandle by Tuesday
morning and the second wraps moisture and wind will spread into the
panhandle through Tuesday. Expect gusty Southwest to westerly wind
for the coastal area. The upper trough supporting the Monday Tuesday
feature will move through southeast Alaska and attempt to create a
break in the rains Tuesday night. Light to moderate rainfall totals
with the front and second wrap will raise up some some stream and
river levels, however expect they will remain below flood levels.

A new trough will be moving across the gulf under the quick zonal
flow aloft at the 500 mb level and that troughs surface feature will
reach the coast by Wednesday morning with another low in the central
gulf. Rains from that will raise pops back to categorical for nearly
everywhere except perhaps the Yakutat area, although if it is bit
further north even they will be back in the rain.

There isn't a significant warm up or cool down through the first
part of the week so think snow levels will remain between 2500 and
4000 over the panhandle. So no snow for sea level just yet.

.LONG TERM.../Wednesday through Sunday night/...Model guidance is
in fairly good agreement that the long range forecast will be a
continuation of the very active weather pattern that had been in
place for much of the week already. The synoptic pattern looks
favorable to send several frontal systems from the Bering Sea into
the Gulf of Alaska. Timing and intensity of these systems is still
in question at this point, but at the very least we have good
confidence that this pattern will persist. WPC guidance borrowed
from the GFS and EMCWF, therefore to maintain consistence we chose
to do so as well.

At the onset of the forecast a front will be offshore of the
panhandle associated with a low in the northwestern Gulf.
Currently this low is progged to drift to the north central Gulf
before jogging a bit north. Additional waves of energy moving in
from the west will help to preserve this system. This should serve
to help keep things pretty wet in SEAK for several days. Thursday
night, this system also appears to gain a tropical connection, but
at this time, guidance shows the main impacts of that hitting to the
south of the AOR. This will be a feature of interest for future
forecast packages to see if the models want to keep it of no
consequence to us, or if they ill trend it northward.

Friday evening, another low with a more southerly track through the
Gulf moves in and becomes the dominant feature. Winds at this time
do not seem overly impressive with this low, however the pressure
gradient at this time suggest that small craft advisory criteria, at
least along the coast seem appropriate.

Yet another low begins it's trek through the Gulf Sunday evening
into Monday. While this is quite a ways out, both of the two chosen
models are indicating that this low will be the deepest of the
forecast period. Definitely quite a ways out to have anything more
than average confidence that this solution will hold up but for the
time being will be advertising winds as strong as 40 kt in the Gulf.
Deterministic models are also showing that this system looks like it
will be hauling a very robust slug of moisture as well. GEFS plumes
and NAEFS standardized anomaly IVT don't seem as impressed. Still a
ways out but this will be one to watch.

As far as that other type of precipitation, temperatures have been
getting colder, but snow does not look like it's on the horizon yet,
at least at sea level. Higher elevations such as White Pass though
may see a bit, but would not anticipate much more than an inch any
given night, if it even accumulates.

&&

.AVIATION...Ceilings and visibilities not the major aviation
hazards for Monday evening. Incoming front will lead to a period of
LLWS as the front moves through. Low level flow at 2000 to 3000 feet
are 70 to 80 kt near the front. Turbulence near terrain will likely
be an issue too. This front is not expected to be as strong as last
weeks wind storm.

&&

.MARINE...Storm force winds Monday evening for the coastal waters
north of Cape Decision to Cape Suckling with Fairly wide spread area
of Gale force winds to move through Southeast Alaska. The strongest
winds are anticipated to last 6 to 9 hours then diminish. The low in
the northern gulf will move towards coast between Yakutat and Cross
Sound headed into early Tuesday and the flow about the low and west
of there will have Gale force westerly winds to blow across the gulf
Tuesday and Tuesday night.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 7 PM AKDT this evening through late
tonight for      AKZ026.
     High Wind Warning until 1 AM AKDT Tuesday for AKZ023-027.
     Strong Wind through late tonight for AKZ025.
     Strong Wind from Tuesday morning through Tuesday afternoon for
     AKZ020-025.
     Strong Wind until 4 PM AKDT this afternoon for AKZ023.
     Strong Wind through late tonight for AKZ021.
     Strong Wind Tuesday afternoon for AKZ018-019-021.
     High Wind Warning from 7 PM this evening to 3 AM AKDT Tuesday
     for AKZ028.
     Strong Wind until 1 AM AKDT Tuesday for AKZ017.
MARINE...Storm Warning for PKZ041>043-051-052.
     Gale Warning for PKZ012-022-031>036-310.
     Small Craft Advisory for PKZ011-013-021-053.

&&

Bezenek/JDR

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