Gale Warning 254, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
259 PM AKST Fri Dec 27 2019

.SHORT TERM...The short reprieve Southeast Alaska has been
experiencing is coming to an end. A well defined trof visible on
water vapor imagery is pushing across the Gulf of Alaska.
Infrared satellite imagery shows a formidable front associated
with the trof steadily pushing across the gulf. The front's impacts
are just beginning to be felt as of the time of writing across SE
Alaska. Winds have already begun to pick up off the coast, with
gale force, and even storm force winds, likely in some coastal
waters during the evening hours. As the front pushes into the
area, elevated winds and precipitation will spread across the
panhandle. Many locations throughout the panhandle will see gusty
conditions, and strong wind headlines are in place across much of
the panhandle. In most areas, the precipitation should be
primarily rain in nature, with warm air advection along the front
helping to keep temperatures above freezing for most of the time
period. The exceptions will be the usual suspects - the Klondike
and Haines Highways, as well as Hyder. In these areas, pre-
existing cooler air is expected to remain more firmly entrenched,
which should allow substantial snowfall totals to emerge from this
system. Overrunning warmer air, as evidenced by the models at 850
mb, will fuel steady accumulations in these areas. One area of
uncertainty will be the city of Skagway, if the winds in Skagway
stay mainly from the S, then only minimal snowfall totals are
likely to occur in the city proper. However, if cooler outflow
winds coming down from the Klondike Highway prove sufficient to
flip the wind direction and consequently send temperatures
downward, then the city could receive some measurable snow totals.
Ultimately chose to compromise between the two in the forecast,
but uncertainty still exists on what the exact outcome will be for
this location.

The upcoming system's impacts will be felt primarily during the
overnight hours, and the system itself does not appear likely to
linger for long, departing the area through Saturday morning.
Behind the system, showers will linger throughout much of the
panhandle, and winds in the inner channels will drop down below
small craft advisory levels as the pressure gradient weakens over
Southeast Alaska. However, storm season is far from finished, and
another system is already anticipated to take aim at the panhandle
late Sunday night. Some guidance is suggesting that this system
could have some very impressive QPF values, driven by a
substantial plume of moisture which, should it materialize, could
bring some respectable rain totals. Significant uncertainty
remains with this system however, and will need to keep monitoring
the data as the event draws closer in order to gain a better
picture of what its full impacts will be. Overall forecast
confidence is average.

.LONG TERM.../ Sunday to Friday as of 9 pm Thursday / Long wave
trough in the southwest upper level flow pattern is will move
through the area Sunday with a large portion of the energy
breaking off and headed to the Pacific Northwest. Further to the
west a cut off low in the north pacific reorganize and then move
to the Bristol Bay area Tuesday which will shorten the flow
pattern about the trough over the Bering Sea.

Sunday through late Tuesday the persistent southwest flow into
the panhandle continues. A strong weather front with a large QPF
forecast will move through the panhandle Sunday then trailing
front will slide southeast with the atmospheric river moving
southeastward with upper level support into British Columbia by
Tuesday.

A more significant front band will be moving across the gulf and
then into the panhandle Wednesday  the up upper low relocating to
the Bristol Bay area on Tuesday. The model solution for the end
of the week are showing varying intensities from the moving out of
the Pacific to the southeast gulf and southern panhandle.

One of the consistent parts in the model solutions is when the
upper level low moving into Bristol Bay it allows a blast of
very cold arctic air to move south through the Bering Sea and
then to the north Pacific, where then curve east-northeast to the
panhandle. The Wednesday system will usher in some of the coldest
air to move into the panhandle this winter right at the end of the
forecast period.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from 6 PM AKST this evening through late tonight for
     AKZ024-026-027.
     Strong Wind from 9 PM AKST this evening through late tonight for
     AKZ022-025-028.
     Strong Wind until midnight AKST tonight for AKZ023.
     Strong Wind through late tonight for AKZ021.
     Winter Storm Warning from 6 PM this evening to noon AKST
     Saturday for AKZ029.
     Winter Storm Warning from 6 PM this evening to 6 AM AKST
     Saturday for AKZ018-019.
     Strong Wind from midnight AKST tonight through late tonight for
     AKZ017.
MARINE...Storm Warning for PKZ043-051-052.
     Gale Warning for PKZ013-031>036-041-042.
     Small Craft Advisory for PKZ011-012-021-022-053.

&&

GFS/Bezenek

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