Gale Warning 288, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
248 PM AKST Tue Dec 1 2020

.SHORT TERM.../Tuesday evening through Thursday/

***SIGNIFICANT DECEMBER STORM IMPACTING SOUTHEAST ALASKA***

An atmospheric river and associated storm force front continue to
batter Southeast Alaska with high winds, very heavy rain, and
snow. On the wet side of the story, copious amounts of moisture
have been streaming northward all the way from Hawaii due to a
strong baroclinic zone over the region and a very strong LLJ
around 75 kt. With IVT reaching max values for this time of year
(1000 kg/m/s) and high PW across much of the region, heavy rain is
expected to continue through tomorrow. The North central
Panhandle was upgraded to a Flood Advisory including the cities of
Juneau, Sitka, Gustavus, and Hoonah. As of 2 PM, 2 to 4 inches of
rain has fallen across much of the region with an additional 3 to
5 inches expected over the next 24 hours. Creeks and streams have
been spiking and are expected to reach bankful, especially where
the Flood Advisory is in effect. The main axis of heavy rain that
spread across the entire Panhandle today will become more
north/south oriented, shifting the axis of heaviest rain toward
the north and central Panhandle tomorrow. The south, including
Ketchikan and Misty Fjords may receive a 12 hour break in the rain
tomorrow afternoon. At the same time, a wave will ride up along
the stalled front that has been draped over the region. This wave
will move northward tomorrow and Thursday, then push the front
through the Panhandle...bringing an end to this extreme
atmospheric river event. (More rain is on the way with the next
system Thursday night into Friday).

On the windy side of the event... An intense 75 kt low level jet
has remained in place today pummeling the central Panhandle. High
Wind Warnings have been verifying through the day along the Outer
Coast from Sitka to Hydaburg and even to Ketchikan. As the
aforementioned wave moves northward tomorrow, the axis of
strongest winds (75 kt at 925 mb) will retrograde and push up the
outer coast, increasing surface winds once again with gusts over
60 mph. High Wind Warnings have been extended until midday
Wednesday for the outer coast of Prince of Wales and Baranof
Island including Hydaburg and Sitka. Put gusts to 55 mph in the
forecast for Yakutat and Juneau as confidence was not high enough
to include these areas in the High Wind Warning. Feel that the
main energy with this system will linger along the outer coast and
may not reach as far north as Yakutat or Juneau. Still would not
rule out a gust to 60 mph in those areas; however no warning will
be issued at this time. Regardless of the actual numbers, strong
winds will continue to batter much of the Panhandle through
tomorrow causing additional impacts.

On the winter side of the event... Winter Storm Warning was
allowed to expire as snowfall rates have diminished along the
Haines Highway. About a foot of snow fell near Haines Border
Customs today, a little less than forecasted due to the extremely
low snow ratios. The foot of snow melted down to about 2" of
liquid indicating snow to liquid ratios were near 6 to 1! Snow
will continue to fall along the highways; however snow levels are
expected to rise to over 3500 feet by tomorrow afternoon switching
most places over to rain. Low confidence in the snowfall and wind
forecast for Skagway to White Pass. Parallel gradient today
allowed winds along the Klondike Hwy and Skagway to become light
and switch north, allowing temperatures to drop to freezing and
changing rain over to snow. Guidance has been performing very
poorly in this area as they were indicating strong southerlies the
entire day. Have gone against guidance tonight, keeping winds
light and colder air entrenched for Skagway and White Pass. As the
gradient slightly kinks and becomes more N/S oriented tomorrow,
have southerly winds slowly developing and increasing through the
afternoon hours. This will warm temperatures and change most areas
over to rain. This is a low confidence forecast for Upper Lynn
Canal as guidance has been consistently poor.

Confidence in the overall forecast drops off Thursday into
Thursday night as the current system departs and another one moves
in from the south. Deterministic models disagree on the track and
strength of a low moving north from the Pacific and into the
region. Ensembles and the American models agree on a general track
of the low moving north out of the pacific, through the eastern
gulf and near the northeast gulf coast by Friday morning. This
track would spread rain northward once again through the region
Thursday night into Friday. Rainfall totals of a half to one inch
appear reasonable for this system with IVT values around 300
kg/m/s or less and PW values around average for this time of year.
Winds through the Southern Inner Channels may increase to small
craft levels as the low passes by late Thursday. More detail will
be put into this next system in the coming forecast packages as
the most focus today was put on the current atmospheric river.

.LONG TERM.../Thursday through Tuesday night/ The remains of the
atmospheric river are moving east over the coast mountains into
western Canada on Thursday. Trailing being the frontal band
moving out of the eastern Pacific and northward over the eastern
gulf, there is some minor positions differences
between the operational solution early Thursday, although they
seem to think landfall just southeast of Yakutat Thursday night.

Mid range models Trying to suggest yet another weak low Friday
over Haida Gwaii, and a larger ones somewhere of the central gulf
Later Friday. A larger and deeper low south of the Aleutians with
a chaotic placement of the lows near it. Overall the pattern for
SEAK is to stay on the 'wet side', with most of any precipitation
to fall as rain, but in much lighter amounts that is occurring for
the first part of the current week.

Forecast confidence is average for Thursday and below average for
Friday to Tuesday. Model agreement is the biggest reason for lack
of confidence.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Watch through late Wednesday night for AKZ018-019-022-024-
     026>028.
     Strong Wind until midnight AKST tonight for AKZ026-028.
     High Wind Warning until noon AKST Wednesday for AKZ027.
     Strong Wind until 3 PM AKST this afternoon for AKZ027.
     Strong Wind from midnight AKST tonight through late tonight for
     AKZ024.
     High Wind Warning until 3 PM AKST this afternoon for AKZ025.
     Areal Flood Advisory until 8 AM AKST Wednesday for AKZ020-021-
     023-025.
     Strong Wind from midnight AKST tonight through Wednesday
     afternoon for AKZ025.
     Strong Wind Wednesday morning for AKZ022.
     High Wind Warning until noon AKST Wednesday for AKZ023.
     Strong Wind Wednesday afternoon for AKZ023.
     High Wind Warning until 9 PM AKST this evening for AKZ028.
     Winter Storm Warning until 5 PM AKST this afternoon for AKZ018.
     Strong Wind from Wednesday morning through Wednesday afternoon
     for AKZ017.
MARINE...Storm Warning for PKZ042-043.
     Gale Warning for PKZ022-033-036-041-051.
     Small Craft Advisory for PKZ011>013-021-031-032-034-035-052-053.

&&

CM/Bezenek

Visit us at http://www.weather.gov/Juneau

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>