Wind Chill Advisory 2, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
229 PM AKST Mon Jan 13 2020

.SHORT TERM...The short term forecast into the middle of week has
no surprise changes in it, so clear and breezy and cold remains
the unchanging forecast.  Very cold outflow from Northwest Canada
through the panhandle even the southern panhandle is seeing
overnight lows in or near single digits or colder. Some stations
around southeast haven't seen temperatures this cold in a decade
or longer. Wind chills 25 to 45 below over the northern inner
channels the next couple of days can be expected, with the coldest
being Skagway to White Pass. Expected to see similar or slightly
cooler overnight lows compared to this morning for Tuesday and the
same for Wednesday.

Small craft winds for portions of the inner channels, some
enhanced more fully developed seas in the longer straighter
channels, and freezing spray is the norm for much of the inner
channels.

Forecast confidence is good into the middle of the week.

.LONG TERM.../Wednesday through Monday as of 10 pm Sunday/ Signs
of change in the works as precipitation makes a return and outflow
winds diminish toward the latter half of the long range forecast.
Upper level pattern supports this with large upper ridge over
Western Alaska and the Aleutians Islands at the start that gets
undercut by upper lows from both the west and east on Fri and
Sat. These two upper lows merge over the AK Peninsula cutting off
the upper high and eventually forming a broad trough over much of
Alaska by the late weekend. Reasonable agreement from the long
range models on this pattern, but the strength and placement of
the trough axis for the late weekend varies. Later long range
model runs could also hang onto the upper ridge longer than
currently indicated so forecast confidence past late week is moderate at
best.

At the surface, outflow winds and cold temperatures will remain
the rule through late week at least. Expect 20 to 40 kt winds out
of the usual outflow areas to continue and freezing spray will
still be a hazard for many marine areas. Single digit and even
below zero lows are still likely for many areas into early Fri.
Little change in the forecast in that time period.

Past Fri things start to change as the merging low over the AK
Peninsula starts to turn regional flow to more onshore rather than
offshore. A low that was skirting E along 50 N latitude will take
a turn to the north Fri afternoon and spread a front into the
panhandle Fri night. Possibility of significant snow for the
southern panhandle at that time as the cold air will still be
deeply entrenched. Lesser amounts possible farther north as
strong pressure gradients along the coast mountains indicate that
outflow will still be going strong at that time so low level
drying will limit any snow that does try to fall. Better precip
chances into Sun (especially for the north) as the outflow
collapses. Warmer air will also be starting to move in from the
south but right now it looks to be slow in coming so snow remains
the main precip type through the weekend.

Complicating this part of the forecast is that the long range
models can not decide where they want to take that initial
surface low. The GFS is the farthest north, and the Canadian is
the farthest east (taking the low into Haida Gwaii rather than
keeping it out to sea). Ensemble means, NBM, and WPC had a better
more consistent clustering of solutions so headed in that
direction more than anything else.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind through late tonight for AKZ025.
     Strong Wind through Tuesday afternoon for AKZ018.
     Wind Chill Advisory until 6 PM AKST Wednesday for AKZ018.
MARINE...Heavy Freezing Spray Warning for PKZ012.
     Heavy Freezing Spray Warning for PKZ031.
     Gale Warning for PKZ012.
     Small Craft Advisory for PKZ013-022-031-041>043-051-052.

&&

Bezenek/EAL

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