High Wind in Alaska, November 21, 2020

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
630 AM AKST Sat Nov 21 2020

.SHORT TERM...A strong front is on our doorstep early Saturday
morning. Solid gale force winds have been observed at Cape Spencer
and the outside buoys and storm force winds have been measured at
Middleton Island. The increase in winds has caused temperatures to
increase early this morning over the south and along the outer
coast. Therefore, precip that has already begun from Ketchikan to
Kake is falling as rain and snow is expected to begin for the
northern areas around dawn. The temperature in Yakutat increased
as well, to 36F, but the dewpoint is still in the teens so expect
that to wetbulb and decrease as precip begins this morning. Some
mixing with rain is likely in that area through the afternoon,
namely along the coast, but areas further inland should remain
primarily snow. Have kept all Winter Weather Advisories and
Warnings in place with no changes in timing.

As the front moves through this afternoon, some of the central and
northern inner channel winds will likely shift to the south,
causing a warm up and potential for more rain to mix in. As a
result, the snow on the ground will become heavy and wet,
compacting it, and potentially making accumulations appear lower.
This is most likely as far north as Gustavus, but portions of the
Juneau Borough could see a mix too. This portion of the forecast,
including how far north the wind shift gets, has the lowest
forecast confidence.

Westerly onshore flow, weak cold air advection (CAA), and
vorticity will keep showers in the forecast through most of
Sunday. Winds will be lower on Sunday and some places could be
variable as a weak low/wave tracks eastward over the southern
panhandle. Winds look to pick up again out of the south late
Sunday night over the offshore waters ahead of the next system.

.LONG TERM.../Mon through Sat as of 10 PM Fri/...The timing of
the onset of wintry precipitation for the early week low pressure
system for the northern Panhandle has been delayed a bit until
around 18Z on Mon, due to the progression of the low being a bit
slower. There still looks to be potential winter storm watch rates
of snow for the Juneau, Gustavus, Haines, Skagway, and Hyder
areas with potential snow accumulations of around 5 to 10 inches.
The precipitation begins to move out of the area around 12Z Tue
morning. Winds up to storm force are possible over portions of the
eastern Gulf of AK with the Mon system as it moves through.

We dry things out on Tue. Some of the latest guidance
extends the dry spell through Wed. We went a little bit more
conservative and brought in the higher PoPs toward the latter half
of Wed. We didn't want to alter things too much and go too far
with the dry spell. This is due to the possibility of the models
flip-flopping, once again.

A system moving into SE AK around Thanksgiving will bring
precipitation to the area, but the type and amount of
precipitation is still up in the air. Temperatures at 850mb, MOS
guidance, and the ensembles indicate warming to borderline
temperature values for wintry precipitation across the Panhandle
around when the precipitation arrives.

The weather pattern remains active through the end of the period
with a series of low pressure systems parading across SE AK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Warning until 9 PM AKST this evening for AKZ018-019-
     025.
     Strong Wind until noon AKST today for AKZ022.
     Winter Weather Advisory until 6 PM AKST this evening for AKZ020.
     Winter Weather Advisory until 5 AM AKST Sunday for AKZ017.
     Winter Weather Advisory from 10 AM this morning to 11 PM AKST
     this evening for AKZ029.
MARINE...Storm Warning for PKZ043-051-052.
     Gale Warning for PKZ022-033-036-041-042.
     Small Craft Advisory for PKZ021-031-032-034-035-053.

&&

Ferrin/JLC

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