Gale Warning 58, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
304 PM AKST Thu Feb 1 2018

.SHORT TERM.../Through Saturday night/ A weak low pressure area
will move ENE across the far SE gulf tonight, then inland across
the southern panhandle Fri into Fri evening. A strong high will
persist over NW Canada into the weekend. Another weak low and
front will approach the area from the SE over the weekend, but
model differences remain on how far N this system will get before
turning E. Blended in the 12z GFS to handle Sat-Sat night to show
better definition to the pressure gradient over the area.
Otherwise made mostly manual adjustments to the forecast, mainly
to speed up system moving across the area tonight and Fri.

With faster system, ended up ending the current WSWs over the S
area several hours sooner than previous forecast had it. Still
looking like 6-10 inches of snow for zones 23 and 26, with 12-18
inches for 29. There is some concern that precip could remain
snow a bit longer over N end of zones 27 and 28 this evening, but
not putting out any winter hazards for those zones. Precip should
taper off from the W Fri afternoon and evening, mostly exiting
the Hyder area by midnight.

Flow regime aloft favors potential for Taku Winds in the Juneau
area Fri night and Sat. Strong cross barrier flow (40+ kt) is
expected with inversion base near 850 mb and critical level around
500 mb. Not showing a flow reversal scenario though, so may not
get maximum wave reflection off the critical level. Going for
gust potential to 65 mph in downtown Juneau and Douglas Fri night
into Sat, with diminishing trend by late Sat afternoon as some
weakening of cross barrier flow occurs. Will issue high wind watch
for the Taku wind area for Fri night and Sat.

Otherwise, will extend the wind chill advisory headline for zone
18 until 18z Sat based on updated temp/wind forecast for White
Pass area. Keeping strong wind headlines going for zones 18 and 25
as well through Fri afternoon. Kept in gale to storm force N winds
for much of the N inner channels and out of interior passes into
the NE gulf. Much of the N will have freezing spray with heaviest
expected over Lynn Canal and N end of Stephens Passage. Still have
10-16 ft seas for Lynn Canal, N end of Chatham Strait, and far N
end of Stephens Passage W of the Auke Bay area.

.LONG TERM.../Sunday through Wednesday/ As of 10pm Wednesday
Higher pressure over the Alaska Interior and Northwest Canada will
be keeping most of the precipitation over the southern gulf and
southern half of the Panhandle. Precipitation will be mainly south
of Frederick Sound through Sunday before again advancing north.
This second push of precipitation will reach up to the far reaches
of Skagway- Haines areas by late Sunday night/early Monday
morning. Heaviest precipitation remains in the southern half of
the Panhandle.

Temperatures will continue to be warm enough for rain in the
southern parts of the Panhandle this weekend. By Monday areas as
far north as Tenakee Springs/Pelican could see daytime highs go
above freezing. The gentle warm push will continue northward by
mid week reaching all but the far north in the Haines/Skagway
area. As temperatures are looking to be warming into the upper 30s
by the end of the weekend for the south, a swing of precipitation
type could occur. Daytime precipitation will likely change to all
rain while nighttime precipitation will change back to snow, with
a mix during the transition hours.

With a surface low in the gulf, and the high pressure in the
Yukon, outflow winds will continue across the northern Panhandle.
Strong gales force wind will continue Sunday for Lynn Canal.
Skagway/Haines area will be windy, as well. Winds will be on the
diminishing trend early next week as the gradient weakens over the
northern Panhandle, a much awaited reprieve for Lynn Canal.

An ensemble approach with a lean to the GFS was the main solution
for the minor adjustments to the forecast. The ECMWF and the NAMnest
lent some value, while moving through the updates. The main
message is for increasing temperatures and decreasing winds into
mid week. Both changes will be slow, but persistent in its
advancement from south to north.

Forecast confidence is average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Storm Warning from 6 PM this evening to noon AKST Friday
     for AKZ023-026.
     High Wind Watch from Friday evening through Saturday afternoon
     for AKZ025.
     Strong Wind through Friday afternoon for AKZ018-019-025.
     Winter Storm Warning from 6 PM this evening to midnight AKST
     Friday night for AKZ029.
     Wind Chill Advisory until 9 AM AKST Saturday for AKZ018.
MARINE...Heavy Freezing Spray Warning for PKZ012.
     Storm Warning for PKZ012-013.
     Gale Warning for PKZ021-022-031-034-035-043-051.
     Small Craft Advisory for PKZ011-032-033-041-042-052-053.

&&

RWT/KV

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