Heavy Snow in Alaska, December 9, 2022

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
501 AM AKST Fri Dec 9 2022

.SHORT TERM...Snow and rain showers continue to move through the
panhandle this morning. A Winter Weather Advisory remains in
effect until 9 AM for Sitka, Kake, and Petersburg. For these
locations a general 3 to 6 inches is expected. Elsewhere, an
additional 1 to 2 inches is expected through Friday morning with
the remaining snow showers. Some breezy conditions are still
ongoing as showers move through. By this afternoon, southerly
winds become northerly and begin to increase while conditions dry
out across the panhandle. The northern inner channels are expected
to increase up to gale force by late this afternoon.

Sky cover will begin to diminish tonight making way for sunny
conditions for Saturday. With the northerly outflow winds
increasing through today, cold air advection will also follow.
Temperatures are expected to slightly decrease through the day.
Daytime highs in the mid to upper 30s are expected this morning
with overnight lows in falling into the upper teens to mid 20s to
upper 20s further south.

.LONG TERM.../Weekend into next week/...A familiar pattern sets up
over SE AK this weekend. A near 1030mb high will build just north
of the panhandle, giving the area strong outflow winds, no
precip, and clear skies.

Biggest forecast challenges are:
-How strong will outflow winds be?
-How cold will the area get at night?
-Will the marine areas see freezing spray again?
-When the next round of precip comes early next week, will the
 area remain cold enough to see snow or will we warm up and see
 rain?

For now, maintained 30 to 40 knot winds in Lynn Canal and 25 to 35
knots in Stephens Passage Saturday. 15 to 25 knots elsewhere. As
the high slides SE into central Canada on Sunday, the winds will
lighten, however, stronger winds are likely to come outside of
interior passes. There is still some evidence of a mountain wave
and stronger winds in downtown Juneau Friday night and Saturday.
For now, increased winds to Strong Wind criteria - so gusts to 40+
mph.

The temperatures will be cold this weekend as well. For now,
temps will be around 10 to 15 degrees colder than normal. So lows
in the single digits to teens in the north, low 20s for the south.
Highs will be generally be in the teens to 20s in the north, 20s
to near 30 for the south.

When we saw the outflow last week, freezing spray was observed on
polar satellites. So going forward, freezing spray was included
in the marine forecast for areas that freezing spray was observed
last time - so Lynn Canal, Stephens Passage, Glacier Bay, and near
the Stikine.

Ensemble data shows the next round of precip moving in Sunday
night and Monday. As of now, this looks to be a snowy system for
the north and along the NE coast. This will be looked at closer
over the coming days as high res models becoming more available.

&&

.AVIATION...Bands of showers are moving onshore across the central
and southern panhandle under SSW flow at the lower levels,
causing reduced conditions. Between the showers, CIG/VIS are VFR.
Showers are falling as primarily snow, which tend to have lower
CIG/VIS (LIFR-IFR), but some places are still mixing with rain at
times and conditions are therefore slightly higher (MVFR-VFR) at
those places. Expect the bulk of showers to shift southward
through Friday daytime while the north sees improving CIG/VIS but
increasing N-NELY flow at all levels. Mountain wave potential
increases through the next 24hrs.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from this evening through late tonight for AKZ318.
     Winter Weather Advisory until 9 AM AKST this morning for AKZ323-
     326-327.
     Strong Wind from noon AKST today through late tonight for AKZ325.
MARINE...Gale Warning for PKZ012-013-031-033-043-052.
     Small Craft Advisory for PKZ011-021-022-032-034-035-041-042-051-
     053.

&&

SHORT TERM...CC
LONG TERM....GJS
AVIATION...Ferrin

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