High Wind in Alaska, January 12, 2021

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
309 PM AKST Mon Jan 11 2021

.SHORT TERM.../Through Wed night/ Southerly flow and showers are
the main rule of the day today. some of these showers have been a
little intense as far as rainfall is concerned, but they have been
lacking in lightning. Only one strike near Sitka was detected
overnight and a few just S of Yakutat around 2 pm but that has
been it so far.

The main focus of the short range is the compact and strong low
that will be coming up along the outer coast tonight into
tomorrow. Main concern is how much wind is this thing going to
produce. 925 mb low level jet of around 55 to 62 kt, particularly
on the S side of the low in the Southwesterlies. Gusts of 40 to
50 mph are expected for many areas of the panhandle from Juneau
and Elfin Cove southward tonight into tomorrow. Whether some areas
will get high wind gusts to 60 mph is very uncertain but the
outer coastal areas of Prince of Wales and Baranof islands will be
the most likely places to get it in the SW flow behind the low.
Opted to stay below high wind criteria for now, but still have
gusts approaching 55 mph in the strong SW flow behind the low.
Gales and wide spread small craft winds will also be a common
feature for many gulf and inner channel marine areas as well. The
northern inner channels will likely get in on the act by Tue
afternoon as well as the pressure gradient suddenly flips south in
the wake of the low.

Another period of precipitation is in the works for the panhandle
with this low as well. Most areas will be warm enough for rain
except for possibly the higher elevations of the Klondike. However
with this system moving through rather quickly. Precip amounts are
expected to be rather low.

Behind this low SW onshore flow and showers resumes with a gradual
decreasing trend into Wed night. Atmospheric instability does not
appear to be as strong as it is with the current shower activity
so the showers should not be as intense as todays are.

.LONG TERM.../Wednesday through Monday night/...The long range
forecast period begins with a large upper low centered over
Bristol Bay, a much weaker upper circulation west of Haida Gwaii,
and a very broad upper trough which encompasses both of these
features. The base of the trough extends from the dateline east to
the west coast of southern British Columbia with the trough axis
extending south to 40N. A very strong 190kt upper jet associated
with this trough will begin to dig south of the Aleutians early in
the period, sharpening up the trough axis and inducing a
negatively tilted upper ridge across the southern Gulf by
Wednesday afternoon. This will produce a new upper low which will
take up a position over the western central Gulf by Friday
morning. As this happens, the upper ridge will continue to build
and then be displaced to the east as a trough axis pivots north
about the new low. The upper low will retrograde northwest and
become absorbed in the upper flow as large scale onshore flow
dominates the eastern Gulf Friday night heading into Saturday. The
extended range forecast will end with another upper low
approaching the central Gulf from the southwest Sunday through
early next week.

At the surface, a southwest flow pattern sets up over the entire
region with a surface low located around Bristol Bay. The next
impactful system moves northward into the gulf on Thursday with a
low heading towards Kodiak Island and an associated gale force
front pushing into the Panhandle. The parade of storm systems
continue through early next week with a series of lows moving
into the gulf, following almost the same track and swinging strong
fronts into the coast.

The sensible weather pattern will continue to be wet, as is
typical for this time of the year, with multiple fronts and waves
bringing plenty of precipitation. The general onshore pattern will
provide for continued warmer (relatively speaking) air such that
the precip type will be predominantly rain for lower elevations
except the far northern inner channels. There, daytime rain will
periodically give way to overnight snow. Only the highways will
remain reliably cold enough for consistent snow.

Overall model agreement is good for the long term regarding the
general weather pattern. However, there are disagreements between
models regarding the finer details of the forecast, which is to
be expected this far out. Used a blend of EC/Canadian for winds
and timing of the front on Thursday, which brings it in 6 hours
faster than the GFS. The exact timing and details of the next
systems moving in for the weekend and early next week will be
worked through in the coming days as models come into better
agreement. Trended towards WPC for the latter part of the long
term, which heavily used the EC and EC ensembles. Despite model
differences, there is high confidence that this wet and warmer
pattern will continue into next week.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 9 PM AKST this evening through Tuesday morning
     for AKZ026.
     Strong Wind through Tuesday morning for AKZ027.
     Strong Wind Tuesday morning for AKZ024.
     Strong Wind from 3 AM AKST Tuesday through Tuesday afternoon for
     AKZ025.
     Strong Wind from Tuesday morning through Tuesday afternoon for
     AKZ022.
     Strong Wind through Tuesday afternoon for AKZ023.
     Strong Wind until 3 AM AKST Tuesday for AKZ028.
     Strong Wind Tuesday afternoon for AKZ018-019.
MARINE...Storm Warning for PKZ041-042.
     Gale Warning for PKZ012-013-022-031>036-043.
     Small Craft Advisory for PKZ011-021-051>053.

&&

EAL/Fritsch

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