High Wind Watch 4, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
236 PM AKST Tue Feb 6 2018

.SHORT TERM...Weather through the short term period will be
dominated by the interaction between mid/upper troughing in the
northern stream over Canada and ridging in the southern stream
currently positioned over the Panhandle. Weak surface low remains
over the northern Gulf early this afternoon with an occluded front
extending SE along the Gulf coast of the Panhandle. This front
will weaken as it continues to encounter a cold, stable low level
airmass in place over especially the interior panhandle tonight.

Currently many sites across the Panhandle are reporting light
snow, with rain over Prince of Wales Island and the southern
channels near Ketchikan. Based on WV imagery early this
afternoon, some dry air aloft has limited snow growth in the
dendritic zone which has allowed freezing drizzle to occur north
of Frederick Sound. Weak onshore flow and shallow moisture will
continue this evening so expect a mixed bag of snow with areas of
freezing drizzle tonight especially in and around Juneau. Light
icing and snow accumulations are likely and with the very cold
ground temps, transportation impacts are likely. Issued a Winter
Weather Advisory for freezing drizzle for the Juneau area where
the commute will likely be impacted by light icing. A bit
concerned for the Petersburg area later this evening as moisture
becomes shallow here but for now am holding off on winter
headlines.

By early Wednesday, a strong shortwave will dive south out of
Canada and begin to interact with a southern stream shortwave
moving NE out of the central NPAC. Partial phasing of these two
systems will carve out a mid/upper level trough over SE AK
Wednesday.

At the surface, a weak low sill slide south of Dixon Entrance on
Wednesday keeping some chances of precip going over the extreme
southern Panhandle during the day. Temperatures will have warmed
so only expecting rain with this system. To the north, strong and
cold surface high pressure will be building yet again over the
Yukon. Cold advection commences in earnest over the north by
Wednesday afternoon and will peak Wednesday night and early
Thursday. Low level gradients are once again impressive with the
PAGY/PAJN MSLP gradient peaking at 10 to 12 mb Wednesday night.
Storm force northerly winds will develop for Lynn Canal with
gales out of Cross Sound and upper Stephens Passage near Taku
Inlet. As the cold high slides to the the E on Thursday, tight
thermal and pressure gradient along the Klondike will likely lead
to the potential for NE'ly gusts to 60-65 mph at Skagway so have
issued a high wind watch for this potential. Strong winds are also
possible near downtown Juneau/Douglas but mountain wave guidance
is less impressive than with the last system at this time so
limited gusts below high wind criteria. As the northern stream
wave passes across the Salibury Ridge late Wednesday night it may
excite some mountain wave activity but still time for later shifts
to evaluate this potential.

.LONG TERM.../Thursday through Tuesday as of 10 pm Monday/ Long
range starts with upper ridge building over the gulf and interior
AK. Upper shortwave trof will be moving SE out of the area on
Thu. Main adjustment to Thu-Fri was to increase outflow winds
over the northern channels with stronger sfc high over the Yukon.
Models begin to differ on upstream shortwaves moving NE toward the
gulf for the weekend and early next week. They appear strong
enough to at least flatten the upper ridge over the area during
this time. Models were suggesting a slower movement of a front
over the weekend so ended up slowing precip threat into the area
some. Further out, the model differences increase. Ended up using
an 18z/05 GFS and 12z/05 EC blend to handle system departing the
area Thu, then went with mainly WPC after 12z Fri, except for the
adjustment to POPs mentioned above.

Lowered some temps for Thu night and Fri as some colder air moves
in from the N, then basically kept temps as is from the weekend
onward. Does look like some moderation in temps will occur over
the weekend and early next week, but lack of a deep layer S flow
will limit them to only a few degrees above average at most.

&&

.AVIATION...

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ022-042-043-051-052.
     Small Craft Advisory due to Seas for PKZ041.

&&

DEL/RWT

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