Area Forecast Discussion
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FXAK67 PAJK 222238

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
238 PM AKDT Sun Oct 22 2017

.SHORT TERM...through Tuesday night...A weakening gale force low
pressure system will move across the central panhandle this
afternoon and evening. Another gale force low will develop over
the eastern Pacific and move northeast through the central
panhandle Monday afternoon and evening. These systems will
maintain cloudy skies and periods of rain and showers across the
panhandle the next few days. The cloudy skies and periods of rain
will maintain cool temperatures across the panhandle. The winds
will increase as the low pressure systems and associated frontal
boundaries advance across the gulf and inland across the
panhandle. Primarily used the NAM and ECMWF models for the short
term forecast which were in fairly good agreement.

.LONG TERM...Tuesday through Sunday...As the surface low that is
expected to impact our area Monday exits east into Canada, an
additional two surface lows are expected to develop, one over the
northern gulf and a second out of the south-central gulf. The low
to the north should quickly weaken and lift northeast into the
Yukon Territories of Canada. The second low with a more southern
origin is expected to push east-northeast through the southern
portion of the panhandle and continue into British Columbia,
Canada. This system will also bring a more subtropical push of
moisture on Tuesday; precipitable water analysis shows some
anomalously high values with this system, so we`re expecting a wet
event centered near the southern panhandle, as of right now. As
both of these features weaken, a ridge of high pressure will begin
to build over the eastern gulf Wednesday, with the ridge axis
stretching north to south just offshore of the panhandle. The
offshore flow with this ridge should provide a brief respite from
the precipitation that has been constant these last few days.
Winds are also expected to diminish across the panhandle briefly
with this ridge.

All models continue to point to a very wet event Thursday into
Friday of next week. The remnants of Typhoon Lan are expected to
wrap into a trough coming across the Bering Sea early this week,
with the moisture becoming embedded with the circulation.
Precipitable water analysis also indicates some anomalously high
amounts with this system. However, models still cannot agree as to
where the more significant precipitation amounts will fall in our

Generally, there has not been a lot of model agreement as of late,
especially regarding the set up of surface level features. We
decided to lean more towards the ECMWF for the earlier long term,
mainly Tuesday through Thursday, as it has had more run to run
consistency and has performed better than other models with
current systems.


.AVIATION...Variable conditions for the southern panhandle as
remaining bands of showers move eastward. As next low moves up
into the SE gulf the southern panhandle will experience strong
wind shear as 925 mb llj of 40-60kt moves in. Surface winds not
expected to be as strong due to wwa and low level inversion
limiting any mixing. Heavy rainfall will reduce visibilities to
near IFR conditions.


.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind Monday afternoon for AKZ027.
MARINE...Gale Warning for PKZ041>043.
     Small Craft Advisory for PKZ012-013-022-031>036-052.
     Small Craft Advisory due to Seas for PKZ051.




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