An atmospheric river brought strong winds and significant amounts of precipitation to Southeast Alaska late November and Early December. This episode details the initial wind report that occurred in November as winds developed along the northern Gulf Coast.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS AJK wrote it up.
An atmospheric river brought strong winds and significant amounts of precipitation to Southeast Alaska late November and Early December. This episode details the initial wind report that occurred in November as winds developed along the northern Gulf Coast.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Juneau, AK wrote its last area forecast discussion before the first event at Nov 30, 2:50 PM AKST, 6 hours 10 minutes earlier.
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
250 PM AKST Mon Nov 30 2020
.SHORT TERM.../Monday evening through Wednesday/
...IMPACTFUL STORM WITH MULTIPLE HAZARDS IN SOUTHEAST ALASKA...
A significant storm system is forecast to bring flooding, near
record rainfall, high winds, and heavy snow to Southeast Alaska.
Low pressure over the western gulf and high pressure over western
Canada put the entire region in a strong baroclinic zone. A stacked
jet stream through the column with winds as high as 75 kt at 925
mb will transport copious amounts of subtropical moisture
northward into the Panhandle over the next several days. At the
surface, a frontal band will stall around the central Panhandle
with waves riding up along it, increasing rainfall rates in the
central and northern areas. Ensembles indicate IVT values of 1000
kg/m/s will be associated with this atmospheric river. Expecting
record 24 and 48 hour rainfall amounts across much of the north
central Panhandle as the EC is showing 75 to 100 year 24 hour
rainfall totals. Current forecast is for 7 to 10 inches of rain to
fall through Wednesday afternoon including the cities of Sitka,
Angoon, Juneau, and Gustavus. A Flood Watch remains in affect for
this time frame.
The winter aspect of this system mainly affects the Haines and
Klondike Highways where Winter Storm Warnings are already
in affect. Small changes made to the forecast in this area. Due to
strong southerly flow, expect temperatures to continue to rise
through the night and into Tuesday, even at upper elevations. Snow
levels will rise to 3000 to 4000 feet, changing heavy snow over to
heavy rain along the highways by the afternoon and evening hours.
Snow accumulations of 18 to 30 inches are still expected tonight
through Tuesday morning before the changeover to rain occurs.
Areas near sea level should remain all rain. Refined the times for
the Winter Storm Warnings across this area. WSW for Haines
Highway will be from 6 PM Monday through Noon Tuesday as the
heaviest snow will fall during this time frame before changing to
rain tomorrow afternoon. The Warning for the Klondike Highway
begins at 9 PM tonight and goes through 5 PM on Tuesday.
Confidence is lower on the changeover to rain at White Pass
tomorrow afternoon.
Winds will be another impactful story with this system. Storm
Warnings are posted for the outside waters overnight tonight as
the front passes by. Storm force conditions expected to remain
through the day on Tuesday across the southeast gulf as the front
stalls. Gales will develop and move into the Inner Channels
early Tuesday morning. With such strong winds aloft, 75 kt at 925
mb, expect high winds to reach the surface along the outer coast
including Yakutat, Sitka, and Port Alexander. A High Wind Warning
is in effect for those areas from 9 PM this evening through 6 AM
Tuesday. A stable atmosphere with a warm nose moving in aloft
should keep the strongest winds from mixing down to the surface
across the rest of the Panhandle. Expect gusts to 50 mph elsewhere
late tonight through Tuesday night.
These conditions are expected to last through Wednesday evening.
before the atmospheric river is pushed out of the area. There
will be a very small break in between systems before the next
precip maker works its way in from the south on Thursday. No major
changes made to the forecast today, just minor adjustments and
detail added.
.LONG TERM.../Wednesday through Monday night/ The atmospheric
river is still in place across the northern panhandle and the
weather front running southward towards Hawaii. A developing wave
on the front will move along it into the northern panhandle
Wednesday enhancing the heavy precipitation for another 18 hours
or so into early Thursday morning. The front then moves into
Western Canada by Thursday midday. Totals from the event are
looking very impressive based on the climate stats, and are in
ranges that flooding and other related heavy rain issues become
much more likely. A hydro product has been issued in coordination
with the River forecast center, and further updates may change the
specific product issued.
Warm air being driven north ahead of the front will have warmed
most highs in the 40s to near 50. Behind the front expect some
minor cooling, however most freezing levels will still be between
2000 and 2800 feet for the northern panhandle.
Depending on the intensity of the warming, and the snow level, the
higher elevations of the Klondike Highway could see a significant
event near the summit with accumulations around 2 feet, thats
only if the warming doesn't completely rise above the 3000 foot
level there. A winter weather product has been issued in regards
to the potential threat.
Model agreement Thursday still not the best, however timing and
strength are different, at least the low seems to following a
similar track north-northeast over the central panhandle through
Thursday. Rain and potentially wind looks to be in store for
Thursday.
The complex pattern continues through the upcoming weekend. As a
myriad of the lows between the various solutions are vying to
spread rain into the panhandle. The strongest features are
southwest of Kodiak and south of the Aleutians headed into
weekend. The general idea is that SE AK will remain on the wet
side with no significant drying feature anticipated to visit SEAK
through the first week of December. However confidence is low in
any one solution offered by the models.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Watch from late tonight through late Wednesday night for
AKZ018>026.
Strong Wind from 9 PM AKST this evening through Tuesday
afternoon for AKZ026-027.
Strong Wind from 9 PM AKST this evening through Tuesday morning
for AKZ025.
Strong Wind from 9 PM AKST this evening through late tonight for
AKZ022.
High Wind Warning from midnight tonight to 3 PM AKST Tuesday for
AKZ023.
Strong Wind from midnight AKST tonight through late tonight for
AKZ020-021.
Strong Wind from midnight AKST tonight through Tuesday afternoon
for AKZ028.
Winter Storm Warning from 6 PM this evening to noon AKST Tuesday
for AKZ019.
Strong Wind from midnight AKST tonight through late tonight for
AKZ019.
Winter Storm Warning from 9 PM this evening to 5 PM AKST Tuesday
for AKZ018.
High Wind Warning from 9 PM this evening to 6 AM AKST Tuesday
for AKZ017.
Strong Wind Tuesday morning for AKZ017.
MARINE...Storm Warning for PKZ041>043-051-052.
Gale Warning for PKZ013-021-022-031>036-053.
Small Craft Advisory for PKZ011-012.
&&
CM/Bezenek
Visit us at http://www.weather.gov/Juneau1 high wind. Local standard time, as filed.
Yakatat ASOS reported a peak measured wind gusts up to 63 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alaska in 2020Every state in 2020This day in weather historyWarnings in Alaska, November 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 929355.