An extremely strong northerly pressure gradient occurred due to a low approaching from the south and all Taku Mountain wave ingredients present.
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 extremely strong northerly pressure gradient occurred due to a low approaching from the south and all Taku Mountain wave ingredients present.
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 17, 4:26 AM AKST, 6 hours 47 minutes earlier.
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
426 AM AKST Tue Nov 17 2020
.SHORT TERM.../Through Wed night/ Arctic outflow is starting to
ramp up across the panhandle this morning. Gale force winds are
already being observed in Lynn Canal, out of Taku Inlet, and down
Stephens Passage. Gusts to 40 mph have also been observed at times
at Skagway and in downtown Juneau and Douglas. These winds are
only expected to increase through the day as cold air outflow
continues and pressure gradients increase due to an approaching
low from the south. Gale and even storm force winds are expected
for many northern marine areas, and gusts to 40 or 50 mph are
likely for areas like Skagway, and Haines. These winds will
lighten up on Wed and Wed night as pressure gradients relax due
to the low to the south weakening.
Winds at downtown Juneau and Douglas in particular will be
increasing noticeably today as the Taku winds develop. All three
ingredients are present for a strong mountain wave event to
develop this afternoon. Cross barrier flow will be reaching 60 to
70 kt by this afternoon and will continue into tonight, critical
level with directional shear at around 500 mb, and an inversion
above the ridge line are all present. Gusts will likely reach 60
to 80 mph by this afternoon. As such the high wind warning remains
up for the downtown Juneau and Douglas area through 9 am Wed.
Farther south, the focus is more on the low that will be
approaching from the south today. Not much has changed on the
forecast track with it eventually stalling just W of Prince of
Wales Island and weakening there. The main concern with it is how
much snow various areas will receive especially with how dry the
atmosphere is due to the outflow from farther north (12z sounding
from Annette already shows a rather dry atmosphere up to 750 mb
this morning). Elected to not change anything at the moment so we
are still expecting around 1 to 3 inches of snow for areas south
of Sumner Strait Tue night into Wed morning. Some rain may mix in
near Annette Island late Tue night and early Wed as some southerly
flow brings some warmer air into that area.
Overall forecast changes were minimal with most changes focusing
on local effects for winds and temperatures.
.LONG TERM.../Thursday through Tuesday as of 10 pm Monday/ Pattern
transition through the week as the cold dry offshore/outflow
pattern reverts to a typical late fall/early winter pattern with a
series of low pressure systems moving into the AK Gulf from the
west. Main issues will be precipitation type and how far the
arctic boundary moves north for the more impactful weekend
system.
Synoptic pattern for the end of the week still has a surface low
in the SE Gulf which weakens and dissipates through the day.
Shower activity, depending on model choice may make it as far
north as Skagway but since the main low will be on its last legs
little in the way of forcing mechanisms and thus not much QPF or
snow associated with this system. Outflow winds diminish early in
the day. As this low weakens another open wave trough and weak
front cross the AK Gulf through Friday ahead of the main weekend
system. Except for an increase in Gulf winds there will be few
impacts with Friday's weather expected to be rather quiet.
To the west multiple low centers over the Bering Sea and Aleutian
chain develop. Still fair spread in operational models on exact
potion of the eventual low forming over the AK Gulf Friday into
Saturday but ensembles have been more consistent with the pattern
trend, but also vary on details. What is expected: At least gale
force winds along a frontal boundary to move across the AK Gulf
and impact the Eastern Gulf and Panhandle late Friday into
Saturday. Precipitation along the front to reach SE AK by Saturday
with 12 hour QPF amounts in the 0.25 to 0.50 range as of now. The
issue as usual is where the rain snow line will be. Both NAEFS
and ENS anomalies have a warming trend with the ENS more
aggressive. Final position of the low center will be determining
factor but initially rain snow low drops across the Icy Strait
corridor. Getting snow amounts in the 2 to 5 inch range, a decent
amount but as indicated by EFI and NAEFS/ENS not expecting a high
impact event. yet. For the rest of the weekend and into next week
a gulf low will remain in place, keeping a wet pattern along with
the uncertain snow levels.
Used operational GFS/ECMWF blend for Thursday keeping the SE Gulf
low intact a bit longer. Low confidence on northward extent of
precip around this low. A nudge to WPC for the rest of the long
range. Might have some higher winds along the Friday-Saturday
front if the operational GFS is correct. As discussed above
forecast issue is where the low center winds up for the weekend
and thus where the rain/snow line winds up. Forecast confidence is
below average.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning until 9 AM AKST Wednesday for AKZ025.
Strong Wind through late tonight for AKZ019.
Strong Wind through late tonight for AKZ018.
MARINE...Storm Warning for PKZ012-013.
Gale Warning for PKZ022-031>034-041>043-051.
Small Craft Advisory for PKZ011-021-035-036.
&&
EAL/PRB
Visit us at http://www.weather.gov/Juneau1 high wind. Local standard time, as filed.
Numerous gusts in excess of 60 mph were measured around the downtown Juneau docks during the day and early evening of November 17. A peak gust of 68 mph was measured at the Juneau Library at 224 pm.
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: 926308.