Gale Warning 188, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
253 PM AKDT Fri Sep 15 2017

.SYNOPSIS...A ridge of high pressure over the eastern gulf will
continue to weaken Friday night, as a weather front moves into
the central gulf. This front will move eastward this through the
weekend.

&&

.SHORT TERM.../Friday Night through Sunday/ A weather front
located over the central gulf will move eastward through the night
Friday. Chances of rain associated with the front continue to
build through the overnight hours. Rain is forecasted to begin
along the outer coast Saturday and spread inland through the day
Saturday. The extent that the front's precipitation is able to
penetrate into the panhandle remains an area of uncertainty in the
forecast as easterly upper level winds act to counteract the
fronts approach from the west. Most of the significant winds are
confined to the gulf where gales are forecasted; however, gustier
winds near Cross Sound and Cape Decision are likely as the front
approaches. Largest rainfall totals are expected to remain along
the outer coast. Sunday is expected to follow a diminishing shower
and decreasing wind trend.

Significant changes were not made in the short term. Winds were
increased slightly within the inner channels Saturday and Sunday
associated with the front. In addition QPF values were raised
slightly after coordinating with the RFC. Primary guidance was a
blend of the NAM and GFS with RFC's QPF fields used.

.LONG TERM.../Sunday through Friday/Extended forecast starts out
with what is left of the weekend front diminishing along the
southern outer coast on Sun with most of the rain moving out Sun
night. Mon still looks mostly dry but some models are suggesting
that some easterly waves may bring some light precip especially to
the southern half of the panhandle. Decided to keep some chance
pops for that area as a result with mostly cloudy to cloudy skies
as a result.

Past this point the forecast becomes more uncertain as some short
wave energy comes across the gulf for Tue. Most models don't do
much with it getting a 1008 mb low at most. The GFS on the other
hand decides that it is going to turn it into a 990 mb gale force
low that heads towards Haida Gwaii. Since there is no other
support for this (even from the ensemble means) decided to regard
the GFS suggestion as an outlier and mainly focus on the ECMWF and
Ensembles for guidance. The result is some chance to likely pops
for Tue with more chances of rain after that as agreement between
the models becomes poor with the next series of front approaching
for late week.

The wind forecast has average confidence with no significant
winds (25 kt or higher) expected through at least mid next week.
General direction is some variation of westerly as various weak
troughs and ridges move through.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Gale Warning for PKZ043-051-052.
     Small Craft Advisory for PKZ022-041-042.
     Small Craft Advisory due to Seas for PKZ053.

&&

Byrd/EAL

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