Gale Warning 265, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
228 PM AKST Sat Nov 24 2018

.SHORT TERM...Satellite imagery this afternoon showing a storm
force low in the central gulf tracking northward toward Middleton
Island. The associated front increased eastern Gulf winds to max
gale force with storm force barrier jet over the NE Gulf coast.
The front is now crossing over the AK Panhandle with increasing
winds and precipitation. Strong winds along the western panhandle
coast will drop off this evening but will have small craft to gale
force winds over the inner channels. Precip for the panhandle
coast and points south of Icy Strait is falling as rain but cold
air mass currently in place for the north/central panhandle is
starting out precip as snow. As warm mid level air mass moves in
with the front precip will change over the rain overnight. There
may be enough cold air in the Haines area for the change over to
be delayed and with warm air aloft and cold surface temps could
see some freezing rain/drizzle before changing to all rain. Higher
elevations such as White Pass will stay all snow or at least a
snow/rain mix with only a few inches of accumulation expected.

Next storm force low/front moves in soon after the current
low/front dissipates. As of now expect the front to move over the
eastern Gulf Sunday then over the Panhandle Sunday night into
Monday. Once again strong winds will pick up along the coastal and
southern panhandle areas. Solid warm air with this system so
should have all rain for all locations with the exception of high
elevations which will only receive a few inches of snow due to
warming temps. Temps will be well above normal for this time of
year.

Timing issues with surface temps warming initial problem with
respect to precip type and timing of turn over the rain. Due to
multiple potential wave development along the front on Sunday
models have been having difficulties on either to place an open
wave trough, a closed low or nothing. 12/18z GFS showed little
wave development. 12z Canadian and NAM put in 968 mb lows in the
SW Gulf tracking north, while the 12z ECMWF placed a weaker closed
low further north. Of course the 18z NAM now has no closed low
and is closer to the GFS. Due to this uncertainty kept with
inherited grids which were closer tot he GFS/ 18z NAM. Forecast
confidence is low.

.LONG TERM.../Monday through Saturday night/...Extended range
forecast begins with a large negatively tilted upper trough over
the western Gulf of Alaska and a strong southerly jet situated
over Southeast Alaska. The jet will shift east within the first 24
hours, but numerous shortwave pulses rotating around the base of
the upper trough will maintain that feature over the Gulf until
late Friday night. At that time, a weak ridge and strong upper
level zonal flow will displace the trough off to the east. The
upper ridge will not last long, as an upper trough will depress
both it and the strong upper jet energy to the south. This
situation will remain dynamic, as a highly amplified upper ridge
will be moving east from Bristol Bay and the Bering Sea late in
the weekend.

A weak low level warm pool of air over the Gulf and Southeast
Alaska at the start of this long range forecast period will shift
east through the week. Based on the prevailing deep layer flow and
forecast temperatures at 850 mb, snow at the lower elevations is
not likely. Nonetheless, temperatures for late next week going
into the weekend were lowered by a few degrees.

At the surface, a high end gale force front at the tail end of
the short term forecast period will be pressed up against the
outer coast and weakening steadily through Monday night. After
that, southeasterly winds of 15 to 25 kts over the eastern gulf
will prevail for much of the coming week. Small craft winds on the
inside with gales over Clarence Strait Monday morning will also
relax to 15 kts of less, except 20 kt or less over Lynn Canal, by
Tuesday.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from Sunday morning through Sunday afternoon for
     AKZ023-027.
     Strong Wind until 9 PM AKST this evening for AKZ022-023.
     Strong Wind through Sunday morning for AKZ017.
     Strong Wind Sunday afternoon for AKZ028.
MARINE...Storm Warning for PKZ051-052.
     Gale Warning for PKZ022-036-041>043-053.
     Small Craft Advisory for PKZ011-021-031>035.

&&

PRB/Fritsch

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