Small Craft Advisory 656, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
246 PM AKST Sun Dec 24 2017

.SHORT TERM...A small low west of Dixon Entrance has developed
more than models were suggesting the last couple days. Most
models, although not all, now have the low center shifting north
toward Cape Decision this evening then turning back to the east
and crossing over POW Island through Monday morning. So far precip
assoc with this low can be seen as far north as S. Baranof Is. on
radar and rain was observed on the Hydaburg webcam. Think that
the chance of rain/snow inches northward this evening to about
Angoon, but general offshore flow will be limiting what actually
makes it to the ground. Locations along the southern/outer coast
have the potential of seeing a half to 1 inch of snow tonight,
namely along E-SE facing slopes.

Clouds extend to the NW from the low center to Anchorage as seen on
satellite. These are assoc with a stationary boundary that is been
held over the gulf by high pressure to the east. Tonight an upper
level trough will help to push it eastward and over the panhandle
through Monday. The surface trough and precip will be weakening as
it moves onshore. Therefore have up to likely POP for Yakutat on
Christmas Day and slight chance as it reaches the inner channels
near Juneau Monday afternoon. So a flurry or light accumulation
is not out of the question for most of the panhandle for the
holiday.

Winds were a primary area of change today. Stronger winds were
shifted around the more northerly track of the low introduced into
the forecast. Additionally, models have trended toward a stronger
pressure gradient over the Panhandle, especially the northern
Panhandle, Tuesday. Wind from Fredrick Sound northward were
increased to account for the stronger northerly outflow.

The latest ECMWF came into better agreement with the GFS/NAM on the
low position this morning, giving us better confidence in shifting
it northward. Generally these 3 models were used for most updates.

.LONG TERM.../ Tuesday to Sunday / By Tuesday the old blocking
ridge will have closed off, with the high center over the eastern
Beaufort Sea. This leaves the parent ridge over the Gulf of
Alaska that will get suppressed southward as a low in the western
gulf/North Pacific moves towards Haida Gwaii by Friday.

Tuesday will have 20-30 percent chance of light snow/rain for the
panhandle, with a short dry spell on Wednesday. From Thursday out
through the weekend increasing chances of precipitation advancing
from the south and along the outer coastal areas. Did lower temps
somewhat as it looks like colder air will move in from the N,
although how strong the cold punch will be differs in the
models. This will likely mean more snow than rain for the more N
and E areas, with more rain along the outer coast and far S.

Did a hard nudge to using WPC for pressure and wind, coordinating
well with our forecast neighbors to the west. National Blend of
Models contributed to the update to the temperatures and related
elements, as it represented a good middle ground compromise. With
colder temperatures continuing late into next week and some
increasing winds in Lynn Canal there is a risk for freezing spray
in the forecast there.

&&

.MARINE...A small band of Gale force winds will be impacting the
coastal waters between Prince of Wales Island and Baranof Island.
These winds will diminish through early Monday as the low center
drifts to the southeast. Higher seas will persist into Tuesday
over the gulf waters. Tuesday a strong pressure gradient over the
northern Panhandle will support stronger winds over the inner
channels and out of interior passes. Strongest winds look to be
over northern Lynn canal where gales are expected.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Gale Warning for PKZ041-042.
     Small Craft Advisory for PKZ022.
     Small Craft Advisory due to Seas for PKZ043-051>053.

&&

FERRIN/BYRD/KV

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