Deep low pressure tracked northward along the outer coast causing impacts across Southeast Alaska beginning Halloween night through November 2nd. High Winds were felt over the outer coast and heavy rain caused rivers to rise out of their banks across the southern half of Southeast Alaska with minor impacts.
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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.
Deep low pressure tracked northward along the outer coast causing impacts across Southeast Alaska beginning Halloween night through November 2nd. High Winds were felt over the outer coast and heavy rain caused rivers to rise out of their banks across the southern half of Southeast Alaska with minor impacts. The ground was already saturated by moderate to heavy rain leading up to November 1 and 2 with amounts ranging from 5 to 9 inches. Multiple mudslides occurred near steep terrain after rain amount of 3.5 inches over 36 hrs along with wet antecedent soil conditions. Tight pressure gradient along the Coast Mountains resulted in strong northerly outflow winds and cold air to push southward through the northern inner channels resulting in heavy snow.
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 1, 7:18 AM AKST, 4 hours 38 minutes earlier.
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
718 AM AKST Sun Nov 1 2020
.SHORT TERM...Very complex weather system affecting the region
today with nearly every wx element expected to cause impactful
conditions. A developing low center is approaching the SE gulf.
Meanwhile building high pressure over interior Alaska, along with
a digging upper level trough, has pushed an arctic front into the
northern inner channels. The tightening pressure and thermal
packing between the two will cause very strong winds. The north
winds have already begun to increase and northern Lynn Canal has a
Storm Warning in place for tonight. Haines saw a wind shift to
the north Saturday afternoon and Skagway shifted in the evening,
both subsequently had temperatures steadily fall below freezing.
This cooling trend will likely continue across the north for the
next couple days.
The interaction between the developing low racing up from the
southern Gulf, and the outflow event in the northern panhandle
continue to pose a challenge for the wind forecast. Starting with
the impacts of the low, the impressive 925 mb winds associated with
the system in the southern gulf continue to point to the potential
for high winds across the Southern Coastal areas. A high wind
warning remains in effect for these places with locales like Craig,
Hydaburg, and Metlakatla especially favored during this event. It
continues to look likely that the strongest winds for these areas
will be through the evening and overnight hours on Sunday. Not to
be left out, the formidable pressure gradient associated with the
system will also contribute to strong wind headlines across much
of the southern and central panhandle across a similar time frame.
As the low moves north, it will ultimately run up against the
outflow winds descending out of the northand move in a more
easterly direction, coming ashore Baranoff island early Monday
morning, then racing east and moving into BC through the day on
Monday. In the maritime waters, widespread galeforce and
smallcraft winds will be predominant by Sunday afternoon and last
through Monday night. Storm Force winds will be present near the
Dixon Entrance and Clarence Strait during the evening hours on
Sunday.
The approaching low has a ton of moisture assoc with it and is
causing moderate to heavy rain across the south this morning. The
rain will spread back northward through mid-day with additional
rainfall amounts of 2-4 inches, from Juneau south, thru Monday
morning. The rainfall rates may lead to flooding and the addition
of wind could cause slides in prone areas through early Monday
morning. As the precipitation reaches the northern inner channels
in the afternoon, heavy snow is expected. This along with the
north winds will result in blizzard conditions for Haines/Skagway
and the highways. The timing of the blizzard warning was shortened
some due to models delaying when the precip gets to the north.
Also, as the low moves inland Monday morning, the snow will become
more showery and decrease in intensity along with decreasing
winds a bit earlier in the day. Snowfall totals were adjusted
somewhat for this reason as well.
As usual, as the cold air pushes south, the rain/snow line seems
to set up in the vicinity of Icy Strait. The GFS was used to
adjust snow levels as it matched best with the cold air already in
place over the north. As the low moves up, cold air filters down
to Juneau/Gustavus in the late afternoon/early evening. Have
included a mix of snow in the forecast for this reason, but then
the low brings the temperatures back up as it moves overhead,
changing things back to heavy rain, and thus little in the way of
snow accumulation. Then, once the low moves inland on Monday, the
cold air pushes south and causes a transition to showers - that
change over to mainly snow thru time.
.LONG TERM.../ Tuesday to Sunday as of 10 pm Saturday/ Long wave
trough is forming over the Gulf of Alaska Tuesday to Thursday
with combination of a low moving south from Alaska to near Prince
William Sound with a short wave driving southward from northwest
of the Arctic Slope over the western part of the state into the
western gulf. By late Thursday this short wave is offshore the
Pacific Northeast and the WA/OR coastlines. A broad ridge flat
aloft covers the western gulf into the western part of the state
although it slowly gains in amplitude over the central gulf
Sunday.
A low low over the northern gulf will persist Monday into midweek
while another low moves NE across Haida Gwaii and perhaps the
Misty Fjords region Tuesday. The northern low will tend to keep
onshore flow with scattered shower activity going, while the
southern low Tuesday may spread some heavier rains and locally
gustier winds to the southern Panhandle.
High pressure will be building into the 1040s over Northwest
Canada through the first half of the week and this will increase
the northerly gradient and outflow winds of cooler temperatures.
Winds through Lynn Canal were increased more Wednesday and
Thursday, however will need to watch to see if more increases are
needed. Confidence is average for Tuesday to Thursday, with a
little better confidence into the weekend as the broad ridge will
settle the situation down and lead to what looks like a drier
weekend.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Watch through Monday morning for AKZ020>028.
Strong Wind from this evening through late tonight for AKZ026.
High Wind Warning from 6 PM this evening to 5 AM AKST Monday for
AKZ027-028.
Strong Wind from this evening through late tonight for AKZ025.
Strong Wind this evening for AKZ023.
Blizzard Warning from 3 PM this afternoon to 1 PM AKST Monday
for AKZ018-019.
Strong Wind until noon AKST today for AKZ018.
MARINE...Storm Warning for PKZ012-036-041.
Gale Warning for PKZ013-022-031-032-034-035-042-043-051-053.
Small Craft Advisory for PKZ011-021-033-052.
&&
Ferrin/Bezenek
Visit us at http://www.weather.gov/JuneauThe national radar mosaic for the moment the first event began.
3 heavy snow, 2 blizzard, 2 debris flow, 1 high wind. Local standard time, as filed.
Snow began around noon on the 1st and accumulated 8.9 inches by 5 AM on the 2nd as measured by a Co-Op in Gustavus. The greatest snowfall measurement was 12 inches at 9 AM by trained spotter.
Snow fell across the Hoonah area with a Co-Op observer measuring 11 inches at 845 AM on the 2nd.
Rain changed to snow around noon on the 1st and quickly accumulated 7 inches by 5 PM as measured by an NWS Employee on Douglas Island. Snow continued through the night and occasionally mixed with ice pellets and freezing rain the morning of the 2nd. The greatest snowfall measurement was 11.5 inches at midnight by a CO-OP observer at Lena Point. Multiple power outages were reported between the early evening of the 1st through the morning of the 2nd.
The Skagway ASOS reported heavy snow and visibility quickly falling to 1/4 mile at the beginning of the event. Meanwhile the DOT RWIS sensor at White Pass was already measuring wind gusts out of the north of around 35 mph. These conditions continued into the morning of the 2nd. By 630 AM DOT reported the road closed and of 12 to 15 inches of snow near sea level. Later in the morning Skagway Customs reported 2 to 3 foot drifts.
The Haines ASOS reported heavy snow and visibility quickly falling to 1/4 mile at the beginning of the event. Meanwhile the wind was already reporting gusts of around 30 mph and marine points further south were reporting much higher winds. These conditions continued into the next morning with the ASOS exceeding wind gusts of 35 mph after 1 AM. Haines DOT reported blizzard conditions, blowing and drifting snow on the highway. Haines Customs reported 14 inches of snow in 24 hours and the Co-Op and spotters around town and Mud Bay measured 16 to 22 inches with mention of blowing and drifting snow.
It had been very wet in the area with 3 to 5 inches of rain over the 3 previous days. Heavy rain from an atmospheric river moved into the Sitka area on November 1 and persisted into the morning of November 2 with an additional 3 to 5 inches of rainfall. Rain rates were greater than 0.5 inches per hour. The heavy rain along with the already saturated soils increased the risk of debris flow near steep terrain. In the early evening of November 1 a debris flow blocked Sand Dollar Road. One lane was cleared for travel in the evening but another debris flow came down during the overnight hours going into November 2 and the road was blocked again. One home at the top of Sand Dollar Road was not damaged but was now on a earth cliff that needed an engineering assessment for safety reasons. Overall there were around 18 debris flows from October 26-November 2. There was also extensive flooding around the Indian River and caused damage to the dam and fresh water diversion for the Sitka Sounds Science Center's hatchery. There was damage to the dam and the road to the water intake was washed. At the hatchery the motors for the drum screen that filters the fresh water were overrun, burned out and destroyed the motor and pumps.
It had been very wet in the area with 3 to 5 inches of rain over the 3 previous days. Heavy rain from an atmospheric river moved over western Prince of Wales Island on November 1 and persisted into the morning of November 2 with an additional 3 to 5 inches of rainfall. Rain rates ranged from 0.30 to 0.40 inches per hour. The heavy rain along with the already saturated soils increased the risk of debris flow near steep terrain. A debris flow was initiated above Port St. Nicholas road and blocked the single lane road to a subdivision with mud, trees and other debris. This blocked the road going to Craig, the main town in the area.
Peak wind gust of 63 mph measured at the Sitka Airport during the evening of November 1st.
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: 926261, 926262, 926248, 926265, 926270, 927766, 927836, 926245.