Small Craft Advisory 10, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
303 PM AKST Wed Jan 3 2018

.SHORT TERM.../ Wednesday night through Friday / Overall pattern
continues on previous track. High pressure ridge over British
Columbia, while a stalled frontal band is over the eastern gulf
and northern panhandle. The next wave along it is passing north
of the 50N latitude this afternoon. Further west another front is
moving towards the western gulf, though it seems that it will
shear apart Thursday and will be replaced with another Friday to
reach the western gulf Friday night.

Closer to home, the stalled front over the central panhandle will
be lifting northward tonight and Thursday and spreading more rain
northward over the panhandle. Overnight the pressure gradient
will switch back around to a more of low level northerly gradient
so temperatures in the far northern lynn canal are expected to
cool overnight. Expect precipitation for Haines/Skagway northward
to be more snow than rain for a good portion of the morning.
Closer to the border on the Haines Road and above 1000 feet for
the Klondike Highway. Am preparing a Winter Weather Advisory
primarily for those regions of both zones. Think that snow will
lessen some Thursday night so amounts will lessen.

Model agreement not superb with low in the southeast gulf late
Thursday to Friday but suspect that the low will weaken drift
east to the southern panhandle for Friday night. Generally, an
onshore southerly flow for much of the southern panhandle so rain
expected to continue for the end of the week.

.LONG TERM.../Friday through Tuesday night/ Some small trends in
the upper level pattern are producing some notable changes in the
long range forecast today. The first trend shows up Fri into Sat
with a slightly slower eastward progression of an upper level
trough over the area. While not much of a change aloft, at the
surface, a weak surface low is now sticking around in the SE gulf
into early Sat. The results of this leads to a wetter forecast
for the early weekend as a frontal band now spreads precip into
much of the panhandle into Sat (pops raised to chance or likely).
Coupled with this is more southerly flow through the panhandle.
Temperatures have been raised a few degrees for Fri and Sat as a
result and features more areas in the central inner channels
staying mostly rain during this event.

Second trend is a possible developing split flow pattern aloft for
early next week as a trough develops to our SW and a ridge
develops over eastern Alaska. This has several effects. First is
a drying trend as storms are directed well south of the area.
Second is a possible cool air mass settling into the Yukon toward
Mon and Tue. Air mass is rather weak though so only a slight cool
down is expected across the panhandle and weak outflow possible at
the same time. Differences in timing of this feature as well as
structure between the models make this scenario likely to change
with subsequent model runs so confidence is low. Favored a more
ensemble approach for updates this far out with WPC and ensemble
means.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory from 6 AM to 6 PM AKST Thursday for
     AKZ018-019.
MARINE...Small Craft Advisory for PKZ012-041>043.
     Small Craft Advisory due to Seas for PKZ022-051>053.

&&

Bezenek/EAL

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