Gale Warning 262, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
211 PM AKST Fri Nov 23 2018

.SHORT TERM...The main forecast issues through the weekend deal
with two storm force lows, one right after the other, moving
through the western Gulf Saturday and Sunday. Associated fronts
will bring gales and storm force winds across the Gulf along with
wet weather draped over the Panhandle and Gulf coast.

Much of the panhandle is experiencing a pleasant late November
day with this brief break in the weather. Friday afternoon
satellite imagery indicates skies are clearing from NW to SE, but
the cloud shield from the next system can also be seen lifting
across the western Gulf, approaching the NE gulf coast. Ridge
aloft over the Gulf is quickly shifting eastward and has pushed
the weakening trough into BC. Behind the ridge another trough with
upper low over the Aleutians will drive the strong weekend fronts
with multiple waves embedded within. First wave lifts into the
Gulf Saturday morning. Gales are forecast to commence Saturday
afternoon across the central and eastern outside waters with storm
force winds located more along the northern Gulf. Strong wind will
also likely occur along the central and northern outer coast,
including from Sitka to Yakutat. Rain moves in, nearly parallel
to the coast, from SW to NE beginning Saturday morning, and
extending to the NE Canadian border by late afternoon. The second
wave moving through Sunday is a bit more complex and model
guidance has been somewhat inconsistent with details. Surface low
wobbling near SW Gulf will eject another strong front across the
Gulf. Some models try to develop a secondary wave across central-
eastern Gulf Sunday afternoon. Wet and windy pattern expected to
continue through the weekend.

Snow concerns are minimal at this time, confined to the Haines/Chilkat
Valley and White Pass/Klondike Highway areas. Not a lot of cold
continental air in place so don't expect much in the way of
accumulation. Will likely start as snow Saturday afternoon along
the Haines Highway, but with warming temperatures and low QPF values
only expect 1-2 inches Saturday night. Precipitation should remain
as rain Sunday, except near White Pass. Forecast confidence through
Saturday is above average.

.LONG TERM.../Sunday through Friday/ A mostly warm and wet
scenario is still in the works for the long range as an upper
level trough remains firmly entrenched in the Bering Sea bringing
onshore flow for most of the week. There is a chance of some
cooler weather showing up for late next week as a ridge builds in
the gulf, however that feature has low predictability and appears
to be very transient if it does develop, so any cooling it might
provide will be short lived.

Surface forecast remains mostly unchanged from yesterday save for
the Sun into Mon period. One change was an increase in pops to
categorical Sun into Monday as timing for the incoming front
becomes more certain. The other more minor changes was a delay of
about 3 hours in the decrease of gale force winds out in the gulf
Sun night as guidance for the front has slowed up a little more
then yesterday, and a slight increase in temperatures overall
given the persistent onshore flow through the week. Otherwise,
forecast becomes much quieter after Sun night as mostly minor
waves in the onshore flow come ashore with lighter winds and on
and off rain.

No snow in sight for sea level locations given the warm onshore
flow for most of the period. Only places that may see it are the
Haines and Klondike Highways, and higher elevations, thought even
those locations may be questionable Sun night into Mon as warm
air advection drives snow levels up to 3000 feet in the north and
near 5000 feet in the south. Snow levels expected to remain
relatively high (around 2500 to 3500 feet) through at least mid
week.

WPC and NBM were the main guidance used for any changes.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from Saturday afternoon through Saturday evening for
     AKZ017-022-023.
MARINE...Storm Warning for PKZ051-052.
     Gale Warning for PKZ022-041>043-053.
     Small Craft Advisory for PKZ011-013-021-031>036.

&&

DDH/EAL

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