Heavy Snow and High Wind in Alaska, January 5, 2021

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
621 AM AKST Tue Jan 5 2021

.SHORT TERM...A deep low churning in the Gulf is pushing strong
southerly winds into the region today. Many areas, mainly along
the coastal waters and into the interior of the southern
panhandle are already seeing strong winds out of this system and
are on track to receive even higher wind gusts on the order of
about 60 mph over the course of the day. Expected strong wind
should continue to push north with the low today, eventually
making it as far north as Haines and Yakutat by this evening. This
wind will also prove a challenge for mariners as storm force
winds can be expected up the southern coastline. Gales in the open
Gulf, further north up the coastline and into ocean entrances.
Otherwise, small craft advisories aplenty for the rest of the
inner channels.

Precip regarding this system has been the forecast challenge of
the day as the elusive rain/snow line has likely set up slightly
further north than previously forecast. Greatest precip is still
anticipated for the southern panhandle today with rainfall totals
exceeding an inch appearing the norm. Total precip decreases as
you go north as the flow gets disrupted by the terrain. Most
locations see mainly rain today with some snow mixing in for some
inland locations such as the Mendenhall Valley. Later this
evening, most areas of the Icy Strait corridor and further north
should see a transition over to snow as the temperature drops.
At higher elevations along the Haines and Klondike Highways, temps
remain cold enough that snow will be the precip type through the
duration of the event. Snow totals overnight in Juneau of 1-3
inches look fair with slightly higher amounts north and obviously
the greatest amounts occurring at higher elevations.

Continued southerly flow into the region should keep up some
decent precip chances going into Wednesday. Another low spinning
up in the Gulf will maintain a strong pressure gradient which
should keep things breezy through the duration of the forecast
period.

.LONG TERM...A consensus trough of low pressure over the Gulf
of Alaska such as in the pattern we have endured favors wet and
breezy weather for Southeast, with precipitation falling as rain
near sea level and snow up Upper Lynn Canal--at least along the
highways and Hyder. While rain is a near certainty at times, snow
is not out of the question as between systems, some colder air
could offer the chance for accumulating snow to fall at times
overnight in Juneau and much of the rest of the northern
Panhandle. But by no means do not expect a winter wonderland.
Aside from Upper Lynn Canal, snowfall will generally be a
temporary feature across Southeast landscapes.

Ensembles and operational models first indicate a low pulling NW
from the North Pacific into the western gulf on Thursday. A gale
force front extended into the eastern gulf should produce
widespread precipitation across the region Thursday. Snow could
present issues along the highways.

Confidence begins to fall on Friday as a new system begins to
emerge from the south. The ECMWF brings the system sufficiently
farther to the west faster and maybe suggests a bit of a break in
the precipitation for Friday. While the GFS is much slower with
the phasing, and keeps things wet.

This weekend another storm--possible storm force--pulls north into
the gulf with wind and rain for the southern Panhandle and the
coast, and snow and wind for portions of the north as well as
Hyder. Currently impacts from this storm look most likely late
Saturday into Sunday.

All in all, the uncertainty in this pattern exists in timing and
track of these systems, rather than whether these strong systems
exist or whether they will affect Southeast.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind through late tonight for AKZ026.
     High Wind Warning until 4 PM AKST this afternoon for AKZ023-027-
     028.
     Strong Wind until 8 AM AKST this morning for AKZ023-027-028.
     Strong Wind from 4 PM AKST this afternoon through this evening
     for AKZ027-028.
     Strong Wind from noon AKST today through this afternoon for
     AKZ024.
     Strong Wind through this evening for AKZ025.
     Strong Wind from noon AKST today through this evening for AKZ022.
     Strong Wind from 4 PM AKST this afternoon through this evening
     for AKZ023.
     Strong Wind from 3 PM AKST this afternoon through this evening
     for AKZ020.
     Strong Wind from 3 PM AKST this afternoon through this evening
     for AKZ021.
     Winter Weather Advisory until 6 AM AKST Wednesday for AKZ019.
     Strong Wind this evening for AKZ019.
     Strong Wind from this evening through late tonight for AKZ017.
MARINE...Storm Warning for PKZ041>043.
     Gale Warning for PKZ022-031>036-051-052.
     Small Craft Advisory for PKZ011>013-021-053.

&&

JDR/JWA

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