Gale Warning 334, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
253 PM AKST Tue Dec 22 2020

.SHORT TERM.../Tuesday night through Thursday night/...The
Panhandle is leaving the calm before the storm, today. The mini
atmospheric river and wind event is upon us. A storm force front
is approaching the Panhandle, today, and will impact the Panhandle
from tonight through Wednesday. This will bring heavy rain to the
majority of the Panhandle for that time period. Rainfall totals
anywhere between 1 to 2.5 inches are expected. This system carries
with it a long fetch of deep moisture from the central Pacific.
IVT values of 700 to 800 kg/(ms) are pushing toward the Panhandle.

Areas in the extreme northeastern Panhandle and around Hyder in
southeast Alaska can expect wintry precipitation out of this
system. The rest of the Panhandle should remain in the mid-30s to
lower-40s to keep the majority of the precipitation as rain. The
Haines Highway west of Haines to Haines Border Customs and the
Klondike highway north of Skagway to the Canadian border can
expect appreciable snow amounts from this system. These areas are
expected to receive 6 to 13 inches of snow. Blowing snow and heavy
snow will cause slick roads and limited visibility. The Hyder
area looks like it will remain just cold enough to receive
significant snow amounts with a potential for higher totals than
the Haines and Klondike Highways as a bit more moisture will be
available to that area. A Winter Storm Warning for snow is in
effect for that area from 3AM to 9 PM AKST Wednesday.

As for winds, There are some Storm Warnings for the outside waters
for tonight, some Gales for the inner channels into tomorrow
morning, High Wind Warnings are in effect for areas along the
outer coast into tomorrow morning. Strong Winds are in effect for
the inside land areas for tonight into tomorrow the morning. This
is due to a strong pressure gradient between the front's
associated low and a strong area of high pressure in British
Columbia.

As shown on model soundings at the location and upstream, there
is a possibility of freezing rain up the Haines and Klondike
Highways toward Klukwan and Skagway Customs this evening. This is
due to a dry layer in the upper levels near the beginning of this
event giving an inadequate snow growth region. There will be
enough moisture in the lower levels and a hallow enough layer of
cold air for freezing rain to be a possibility for a few hours.
This morning, the ECMWF showed nearly borderline temperature
values at 850 mb for snow for this evening for the beginning of
the event, but the other models do not.

As this event comes to a close, winds subside, and the area
receives some decreased cloudiness, some locations in the central
and southern inner channels may receive some areas of fog for
Wednesday night into Thursday morning.

As for the models, the agreement is not as good as what it
typically is for the short-term forecast period. Toward the latter
third of the period, the models diverge somewhat in terms of
location, speed, and strength of a closed low that will be
approaching the area around the later Thursday to early Friday
timeframe. Therefore, there is a little bit of uncertainty in the
forecast for that timeframe and beyond. changes in the wind from
this could impact temperatures and precipitation type as moisture
begins to flow into the southern Panhandle toward the end of the
short-term forecast period.

.LONG TERM.../ Thursday to Tuesday as of 10 pm Monday / The
forecast for Thursday and Friday which earlier in the week was
struggling to find any sort of model agreement is doing better
after another day of model runs. Upper levels support a
trough/closed low lifting NE into the southeastern Gulf of Alaska
on Friday. The surface reflection of the upper levels move
northward through the eastern gulf from right along the coast or
to about 120 nm offshore. With the surface features initially
about 970 mb Friday morning before weakening in the operational
solutions, and if that holds the will will likely be strengthen
during the next forecast or two. Gales force winds should make
another return for Holiday morning. As the low is moving up the
higher pressure holds over northwestern Canada. Northerly outflow
and mountain wave winds for the standard locations of Lynn Canal
and Juneau begin ramping up for Friday as well.

For Saturday into start of the week however there is no strong
feature over the gulf to influence the weather so a general area
of lower pressure will likely prevail with a light onshore or
along shore pattern near the outer coast for scatter light rain
or showers. Closer to the coast mountain range a weak offshore
component may hold. The stronger anchoring  features will located
near the far western Aleutians and the western Bering Sea.

Forecast confidence for Thursday and Friday rose to a moderate
level, with the far extended forecast having a low confidence due
to the lack of any strong signals.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 6 PM AKST this evening through Wednesday
     morning for AKZ025-026.
     High Wind Warning from midnight tonight to 9 AM AKST Wednesday
     for AKZ027.
     Strong Wind from 6 PM AKST this evening through late tonight for
     AKZ027.
     Strong Wind from 9 PM AKST this evening through late tonight for
     AKZ020-021-024.
     High Wind Warning from 6 PM this evening to 6 AM AKST Wednesday
     for AKZ017-022-023.
     Strong Wind from 6 PM to 9 PM AKST this evening for AKZ022-023.
     Strong Wind late tonight for AKZ017-018-022.
     Strong Wind Wednesday morning for AKZ023.
     High Wind Warning from 3 AM to noon AKST Wednesday for AKZ028.
     Strong Wind from midnight AKST tonight through Wednesday
     afternoon for AKZ028.
     Strong Wind Wednesday afternoon for AKZ029.
     Winter Storm Watch from late tonight through late Wednesday
     night for AKZ029.
     Winter Storm Warning from 6 PM this evening to 9 AM AKST
     Wednesday for AKZ018-019.
     Strong Wind from midnight AKST tonight through Wednesday morning
     for AKZ019.
MARINE...Storm Warning for PKZ042-043-051-052.
     Gale Warning for PKZ013-021-022-031>036-041-053.
     Small Craft Advisory for PKZ012.

&&

JLC/Bezenek

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