Gale Warning 100, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
330 PM AKST Sat Mar 4 2017

.SHORT TERM...Windy but sunny day across the northern panhandle
today while the extreme southern panhandle is still dealing with
some lingering snow showers. Starting with the snow showers,
Ketchikan and Annette have been dealing with the brunt of it as a
band of showers remained nearly stationary due to a convergence
zone extended from northern Haida Gwaii into Misty Fjords.
Snowfall from last night ranged up to 5 inches in some areas. That
band is slowly shifting south and weakening as the low that is
sustaining the convergence zone drifts southward. Snow showers
will continue to linger into tomorrow but they will be weakening
and becoming few and far between. As such continue to mention
scattered showers tonight for zones 28 and 29 but then gradually
reduce it to isolated by tomorrow with low accumulation expected.

Moving on to the wind. A 1020 mb cold high in the Yukon is
producing outflow winds for many areas of the northern panhandle
today. Gusts to 40 mph were observed at Skagway and in downtown
Juneau and Douglas overnight. Gale force winds were also observed
in Lynn Canal, Cross Sound, and Taku Inlet. Since then winds have
lightened up a little as pressure gradients slackened today
(enough to bring gusts at Skagway and downtown Juneau down below
40 mph and Cross Sound below gale force). Winds will remain
relatively low tonight before they once again increase tomorrow as
a new stronger push of cold air begins to work into the Yukon.
Gusts at Skagway, the passes near Yakutat, and in the downtown
Juneau and Douglas area, will again increase to 40 mph or more.
Strong wind headlines issued as a result. Gale warnings and small
craft advisories remain up for many of the inner channels and near
coastal areas of the gulf through Tomorrow as well. Heavy freezing
spray warnings are also still up for many northern inner channel
areas as the combo of high winds and cold temperatures are kicking
up lots of freezing spray.

Speaking of Temperatures, they will be a mixed bag as areas with
wind (well mixed atmosphere) or with cloud cover (less radiational
cooling) will see overnight lows only drop into the 20s or teens.
Meanwhile, wind sheltered areas with clear skies will plummet
into the single digits (or lower in the northern panhandle)
tonight. Temperatures will recover tomorrow as the increasing sun
angle of late winter provides enough heating to warm most places
back into the 20s or low 30s where mostly clear skies prevail.

Short range models remain in rather good agreement today.
Preferred the more hires models to get details on the outflow
winds and on trying to get the right position of the band of snow
showers across the southern panhandle.

.LONG TERM...An upper level trough drops down from the Yukon and
AK interior into the AK panhandle and gulf and remains there
through most of the week. Blocking high pressure ridge over the
western gulf remains in place until late in the week when it is
expect to shift eastward and eventually move over the panhandle.
A weak surface low develops over the eastern gulf Monday into
Tuesday under the trough. The low should drop southeast toward
Haida Gwaii then shifts to the east over Dixon entrance. This
system will dissipate by mid week as it continues to move east.
Potential for another system to develop over the southern
panhandle towards the end of the week but most model consensus
keeps it to the south.

As systems this week are expected to remain centered to the south
of the panhandle and precip will mainly be limited to points south
of Frederick Sound with the northern areas getting mostly some
increased cloud cover. Far southern points, such as Ketchikan, may
get a few inches of snow out of this event, will monitor through
the week.

With cold surface high pressure remaining over the Yukon and low
pressure system to the south, strong northerly and outflow winds
last through the week. Temperatures still in the teens to low 20s
and into the single digits or lower overnight for wind sheltered
areas. Not until the end of the week will temps potentially rise
into the upper 20 to low 30s and potential near 40 for the
southern areas. Keeping mention freezing spray due to the strong
winds and cold arctic airmass.

Used a blend of 12z GFS/NAM to day 4 then kept with WPC. ECMWF was
more of an outlier early on and Canadian was a definite outlier
later in the period moving the late week low into the central
panhandle. Overall changes were minor, did lower temps Wednesday
and Thursday a bit with cold air aloft still in place. Forecast
confidence is above average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from Sunday morning through Sunday afternoon for
     AKZ025.
     Strong Wind from late tonight through Sunday afternoon for
     AKZ018.
     Wind Chill Advisory until 3 PM AKST Tuesday for AKZ018.
     Strong Wind Sunday afternoon for AKZ017.
MARINE...Heavy Freezing Spray Warning for PKZ031.
     Heavy Freezing Spray Warning for PKZ012.
     Heavy Freezing Spray Warning for PKZ013.
     Heavy Freezing Spray Warning for PKZ013.
     Heavy Freezing Spray Warning for PKZ013.
     Gale Warning for PKZ012-013-022-031-051.
     Small Craft Advisory for PKZ011-021-032>035-041-043-052-053.
     Small Craft Advisory due to Seas for PKZ042.
&&

EAL/PRB

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