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FXAK67 PAJK 192309
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
309 PM AKDT Thu Apr 19 2018

.SYNOPSIS...A gale force low S of Cape Suckling will move ashore
in Prince William Sound as a ridge of high pressure builds over
the Panhandle Thursday night. Another low will move N to Haida
Gwaii Friday as high pressure settles across the Panhandle.

&&

.SHORT TERM...Rain and wind has been the story of the day, and a
little snow at higher elevations. First a strong April front is
trekking north and east across the Panhandle. Very strong winds
with potential gusts to 60 mph affected Downtown Ketchikan off and
on today, but there have been no known reports of damage.
Elsewhere, communities from Juneau to Sitka have experienced gusts
to 45 mph. But as the front pushes through, we expect winds for
all but the far northern Inner Channels notably Skagway to ease
quickly this evening. Winds in Lynn Canal and Skagway have not
been as strong as some of the higher res models have indicated,
and perhaps is an example of how some of these models tend to
overmix the boundary layer. The near parallel flow and the very
lax gradients between Skagway and Juneau also have not supported
it. But gradients have begun to rise this afternoon and we are
still confident on gales developing this evening and wind gusts to
45 mph in Skagway.

Another low will approach Haida Gwaii on Friday and push high
pressure over the Panhandle. This will help ease winds over much
of Southeast Friday. But as the low moves into northern BC, we
expect southerlies once again to rise to moderate levels into
Saturday, but at this point, we do not expect any impactful winds.

Rainfall amounts have been markedly higher today and last night
as stronger short-waves have moved ashore. Much of the coast from
Sitka southeast to Ketchikan have seen rainfall amounts close to
an inch or more and this should help the drought situation.
Farther north rainfall amounts have been lighter, but still by
April standards substantial. Higher up at White Pass, we received
word of 6 inches of accumulation of snowfall, which seems to be
verifying the winter weather advisory that is still in effect
until 6 PM.

Finally, the parent upper low will move into Yakutat this evening,
and with it we are carrying a slight risk of a thunderstorm. No
lightning yet, but the risk is there. With the rising lapse rates
moving into the northern Panhandle overnight, there could be some
mix to snow in heavier showers late, but snowfall amounts will be
negligible.

The forecast was largely on track, so only strategic updates were
implemented.

.LONG TERM.../ Saturday through Wednesday / The overly simplified
forecast for this time frame is continued wet. Aloft there is a
broad complex pattern of lows from Kamchatka Peninsula to Bristol
Bay. Occasionally a trough, some stronger than others, will break
free of the eastern cluster and move across the gulf to the SE
Panhandle and British Columbia coast. Am expecting one system late
saturday and early Sunday, a weaker one Monday and likely another
stronger feature around Tuesday. Thus continue moisture flowing
onshore to the panhandle from the weekend to mid week will keep
the area fairly wet.

Winds got a small nudge up Sunday, however have kept the winds
with that weather front right now just shy of Gale force, though
will need to keep an eye on the situation, if it continues to
strengthen on future runs. The Tuesday system could also have
windy conditions associated with it.

Not expecting much in way of a change to the temperatures across
the region for the next week. May see some snow Monday-Tuesday
with the next system that could put minor accumulations on the top
of the pass.

Good confidence for model solutions again into the Sunday
timeframe, Used a GFS/NAM blend then WPC solution changed very
little so few if any modifications were needed. Confidence is good
to average through the extended portions.

&&

.MARINE...With the exception of the northern Inner Channels and
the northern gulf, the rest of the winds should be on the
diminishing trend. Seas however, will remain high in post-frontal
swell.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until 4 PM AKDT this afternoon for AKZ025-028.
     Winter Weather Advisory until 6 PM AKDT this evening for AKZ018.
     Strong Wind from 6 PM AKDT this evening through late tonight for
     AKZ018.
MARINE...Gale Warning for PKZ012-013-036-051.
     Small Craft Advisory for PKZ022-031>034-041>043-052-053.

&&

$$

JWA/Bezenek

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