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FXAK67 PAJK 181438

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
538 AM AKST Wed Jan 18 2017

.SHORT TERM...A gale force low west of the Dixon Entrance early
this morning is forecast to track north and cross the outer coast
south of Sitka this evening. Satellite imagery and surface
analysis charts indicating that the low may be tracking farther to
the east. This would likely prevent strong wind gusts over the
southern inner channels and gales over Clarence Strait. Have
adjusted the forecast according to this line of thinking.
Regardless of the actual track, low level warm air advection will
raise snow levels from south to north through the short term
forecast period. Only locations forecast to remain cold enough for
snow through the short range forecast period are the far northern
inner channels and the outer coast north of Cape Fairweather.
However, the farther north, the less PoP and QPF, so snow totals
not expected to amount to much more than 2 inches at best.
Elsewhere, rain, or a rain/snow mix changing to rain later today
and then back to a mix tonight.

As the low tracks north and then inland, stiff northerly winds
with shift to the south, but this transition may not be complete
by the start of the extended range forecast period Thursday
morning for the far northern inner channels.

Apart from small craft winds over some of the inner channels,
marginal gale force winds near the center of the low will affect
the southern coastal marine zones and the extreme southeast
portion of zone 310. It is difficult to characterize the wind
direction, as the band of gale force winds will be close to the
center of the low and, as such will rapidly change direction as
the low moves over the area. Similar situation with regard to wind
direction as the low transits over the panhandle, but wind speeds
will be lower by then as the low weakens over land.

Changes tonight limited to PoP/QPF and some minor adjustments to
temperatures. Overall forecast confidence is average.

.LONG TERM...Dry and cool late week into the weekend period as the
Pacific storm track gets pushed south by a cold arctic air mass.
An upper level trough moving through Thu night will only
reinforce that trend as it brings a piece of the cold air in the
Alaskan interior east to the southern Yukon on Fri. The result is
the increased likelihood of another period of strong outflow
winds Fri into Sat. Model pressure gradient forecasts are
reaching around 4 to 7 mb between stations in the northern
panhandle with rather good agreement now between the various
models on bringing the cold air east. Decided to increase winds
in many of the northern inner channels Fri into the weekend to
account for this (also added some freezing spray for the northern
inner channels and blowing snow for higher elevations). Lynn
Canal will again have the strongest winds with gales likely during
this period. There is also a good chance of another mod strength
Taku wind event for downtown Juneau Fri into Sat as cross barrier
flow reaches 40 to 50 kt and a decent critical level and inversion
sets up.

As for precip and cloud cover, the stronger outflow reinforces the
the possibility of a dry forecast with strong offshore flow. Cloud
cover will also be low with many places expected to see partly
cloudy skies. With the partly cloudy skies and the outflow, temps
were lowered a few degrees for fri into the weekend.

Overall pattern turns back to a warm scenario next week as the
Pacific storm track turns back to the north. Next major front
shows up Mon night with gale force winds for the gulf. Some issues
on how far to the east individual models take the front resulting
in low confidence on exactly how wet and windy the panhandle will
get next week. Overall left chance pops in the extended as a
result with some higher winds in the gulf.


.AVIATION...LLWS and turbulence will be an issue over the next 24
hours as a low level jet to 50 kts situated over the northeast
quadrant of the low passes overhead and shifts to the southern
quadrant of the low. MVMC will be interrupted by periods of IMC
due to CIGS and VSBY.


.AJK Watches/Warnings/Advisories...
MARINE...Gale Warning for PKZ041.
     Small Craft Advisory for PKZ012-031-034>036-042-043-051-052.



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