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Southeast Alaska forecast discussion 
National Weather Service Juneau Alaska
337 PM akdt Monday Oct 20 2014

Short term...widespread showers have fallen over the
Panhandle as a trough has pushed through the northern/central
Panhandle today. Lightning and thunderstorms have remained south
of US in hecate Strait...but a risk late this afternoon continues
across the outside waters and the southern Panhandle. Building
offshore flow with some stabilizing conditions aloft should limit
this risk to late Monday afternoon. As this trough has moved
in...pressure rose across the Panhandle and thus allowed Lynn
Canal to rise to 25 knots this afternoon. However, as the isobars
re-tilt northwestward in response to the developing system over the
central outer Gulf, winds will largely flip north and begin
strengthening into Tuesday.

Tuesday this gale force low in the outer Gulf will curve to the
northeast to lie squarely in the southeast Gulf by Tuesday. Gales
will spread as far north as 43 and will penetrate the inside in
both Clarence Strait beginning Tuesday morning and southern
Chatham beginning Tuesday afternoon. Prince of Wales Island will
begin experiencing strong wind gusts to 40 miles per hour early Tuesday
morning and remaining strong through the rest of the day.
Ketchikan and Metlakatla will see winds rise a few hours later

The lobe of vorticity supporting the low will usher a wave of
sorts through the Panhandle tomorrow and should help induce some
mountain wave gustiness over downtown Juneau beginning late
Tuesday morning. High resolution models indicate sustained wind
speeds of close to 30 miles per hour...also raised the Juneau downtown high
temperature to capture downsloping compressional temperature
rises. Certain rain should hold south of Angoon/Sitka Tuesday
afternoon...but still decorate the north with at least a chance.
Yakutat should remain dry after showers diminish tonight. Added
some snow mixing in to Yakutat late, but more likely temperatures
will not cool enough for snow until after showers have ended.

Some thought given to precipitation character. Convection
parameters over the Gulf unstable enough to include slight chance
of thunderstorms even though textbook paradigms urge stratiform
ahead of the system. In actuality the atmosphere will have a
complex hybrid stability. Where thunderstorms forecast...went
convective...where not went stratiform...generally over the land.

Some patchy fog may form tonight as showers diminish and clouds
begin showing breaks, but felt winds may be too strong over the
inside waters itself so confined it to land areas over the
northern areas.

Used guidance from NAM early...but as it began to become the odd
model out with the low in the Gulf...was inclined to follow a
Gem/European model (ecmwf) consensus. Forecast confidence good.

Long term...the main low for the incoming system loops around the
Gulf of Alaska through middle week and diving south-southeast to out
of the Gulf of Alaska. Models hint at small wave moving upto
towards the Prince of Wales Island area Thursday helping to pull the
old low southward. Expect an inverted trough of low pressure
across the eastern Gulf along the Panhandle Friday to Saturday
that will deflect an ridge ahead of the next weather system south
of the Gulf of Alaska. This next system will be developing in the
North Pacific and will head east toward Vancouver Island for next
weekend. It is last low that looks to have absorbed the remains of
Ana currently passing by Hawaii.

Believe that the gale force winds and isolate thunder from Tuesday
will continue into Tuesday night before subsiding and tapering
off. Think most of the precipitation will be acting similar to
showers thus was my reasons for making the precipitation that type.
The low when it does finally start to pull of the of the Gulf will
be pulling some cooler air from the interior out over the Gulf
maintaining a good shower pattern through much of the week.
Confidence is generally good to Thursday or Friday and lower next the models have some consistency issues handling the Ana


Ajk watches/warnings/advisories...
public...strong wind from late tonight through Tuesday evening for akz027.
Strong wind from Tuesday morning through Tuesday evening for
Strong wind from Tuesday afternoon through Tuesday evening for
Strong wind from Tuesday morning through Tuesday evening for
Marine...Gale Warning for pkz022-033-036-041>043.
Small Craft Advisory for pkz011>013-021-031-032-034-035-051.
Small Craft Advisory due to seas for pkz052.




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