Gale Warning 90, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
257 PM AKST Wed Mar 4 2020

.SHORT TERM.../Through Fri night/ Rather significant change in the
first 12 hours of the forecast as a convergence band that was
expected to develop over the northern inner channels out to Cape
Spencer area actually formed much farther west out in the central
gulf and over Yakutat this afternoon. This was a result of
multiple factors, not least of which was the low in the northern
gulf wrapping the band around it and to the west, and the stronger
low to the south spreading easterly offshore flow across the
panhandle stalling the eastward march of the band. What we are
left with is scattered to numerous showers across the inner
channels with accumulations of only around an inch or two at most
observed through the day while temperatures have been hanging
around the mid 30s. With the farther west position of the band it
was decided to cancelled the winter storm warnings that were out
for the Haines and Gustavus areas.

For the rest of the short range, A significant arctic outflow
event is still in the works for late tonight into Thu night. Winds
are expected to switch from southerly to northerly this evening in
the northern panhandle and will be rapidly increasing in strength
overnight. Northerly storm force winds are expected to be blowing
down Lynn Canal and out of the passes east of Yakutat, while gale
force winds will be blowing down many of the channels in the
northern half of the panhandle Thu. In addition with the colder
temperatures, freezing spray is also expected in many of the
northern inner channels. On land, the Klondike Highway will see
significant winds, and dropping temperatures on Thu with the
potential for low wind chills (down to -30F) and blowing snow
(visibility down to a quarter mile) in the vicinity of White Pass.
A blizzard warning is now in effect until 6 pm Thu for that area.
For other areas, wind gusts up to 40 mph or more are likely in the
usual outflow areas and a possible Taku wind event will be ongoing
in the downtown Juneau and Douglas areas Thu. For the Taku wind
event, the critical level appears to be the limiting factor as
the wind shear aloft is not well defined, so gusts should be
limited to between 40 and 50 mph. Higher gusts could still be
possible if this critical level becomes more defined or becomes
self induced.

Outflow expected to weaken by Fri as the low over the SE gulf
weakens and the Yukon high also weakens. Still going to have some
small craft winds blowing down some channels like Lynn Canal and
Taku Inlet, but the significant winds and freezing spray should
have diminished by that point. Temperatures will also remain cold
across the north with highs not reaching out of the 20s on Fri.
Coldest temperatures are expected Friday morning where some areas
of the northern panhandle could dip into the teens and single
digits. Southern panhandle will still have some southeast to east
flow from the low in the gulf so temperatures expected to remain
warmer there. Little in the way of precip as the earlier outflow
will have dried out the panhandle by this point.

The largest change in the forecast was in the first 12 to 24 hours
trying to figure out where the convergence zone was going to
settle. Favored more Gfs and Nam for updates today.

.LONG TERM.../Friday through Wednesday/As of 10 pm Tuesday/Generally
progressive upper flow pattern continues through the extended
period. Initially, upper ridging will be in place early Friday
over the western Gulf with deep troughing over SE AK. This will
promote continued outflow winds which should slowly diminish as
the upper ridge gets pushed eastward towards the Panhandle and
flattens by Saturday. This will allow the resumption of westerly
onshore flow at all levels of the atmosphere for the weekend.
Arctic air will be in place and some light overrunning snow may
occur through the weekend, though strong fronts will have a hard
time pushing through the upper ridge.

After the weekend, operational models diverge in their solutions.
Ensemble means agree with continuing the progressive pattern with
the propensity for some broad ridging over the NPAC near 170W
which leads to broad troughing over the Gulf of Alaska. In terms
of sensible weather, this will likely lead to a wet pattern
resuming with low snow levels similar to what we experienced much
of the month of February.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from midnight AKST tonight through late tonight for
     AKZ017-023-026>028.
     Strong Wind from Thursday morning through Thursday afternoon for
     AKZ025.
     Strong Wind Thursday morning for AKZ018-023.
     Strong Wind Thursday afternoon for AKZ023.
     Strong Wind from late tonight through Thursday morning for
     AKZ019.
     Strong Wind from midnight AKST tonight through late tonight for
     AKZ018.
     Blizzard Warning from 6 PM this evening to 6 PM AKST Thursday
     for AKZ018.
     Winter Storm Warning until 3 PM AKST this afternoon for AKZ017.
MARINE...Heavy Freezing Spray Warning for PKZ012.
     Storm Warning for PKZ012-013-051.
     Gale Warning for PKZ021-022-031>033-036-041>043-053.
     Small Craft Advisory for PKZ011-034-035-052.

&&

EAL/DEL

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