Alaska, 2024Debris Flows in Alaska, August 25, 2024
August 25, 2024 · NWS AJK · 2 events in 1 county or zone
A low-pressure system moved out of the North Pacific Ocean into the Gulf of Alaska and quickly intensified into a 995 MB gale-force storm on the Sunday morning of August 25th, 2024. By the late afternoon, this system had nearly stalled along the northwest Gulf Coast, stretching an occluded front across the central and southern Panhandle.
Every event with a place to put it. Tap one for its entry below.
- Tornadoes
- Tropical storms and surge
- Floods
- Wind
- Hail
- Winter weather
- Heat and drought
- Cold
- Fire, smoke and dust
- Marine and coastal
- Other
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- Deaths
- 1
- Injuries
- 3
- Property damage
- $4.0 million
- Crop damage
- None recorded
- Events
- 2
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.
A low-pressure system moved out of the North Pacific Ocean into the Gulf of Alaska and quickly intensified into a 995 MB gale-force storm on the Sunday morning of August 25th, 2024. By the late afternoon, this system had nearly stalled along the northwest Gulf Coast, stretching an occluded front across the central and southern Panhandle. This setup was accompanied by a moderate atmospheric river (AR) which transported subtropical moisture over Southeast Alaska. The AR produced hourly rainfall rates at elevation that exceeded a half inch per hour at times with storm total amounts ranging from 2.55 inches at the airport to over 10 inches at higher elevation sites. There were other stations at sea level that did report over 5 inches for this event. This AR was also associated with strong surface sustained winds of 15 to 25 MPH with gusts ranging from 30 to 50 MPH.
The most intense rainfall came in a 12 hour period ending at 20:00AKST on August 25th with a precipitation station reporting a 10 year annual reoccurrence interval and others reporting a 6 hour period of a 5 year reoccurrence interval for rain intensity. This did produce large river rises on small streams across the area like Ketchikan Creek but no flooding was reported from rivers. Two landslides were reported that destroyed homes, caused damage to roads, businesses, and infrastructure, and resulted in one fatality.
What forecasters said that day
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 Aug 25, 3:56 AM AKST, 7 hours 4 minutes earlier.
Area forecast discussion, Aug 25, 3:56 AM AKST, 7 hours 4 minutes before
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
456 AM AKDT Sun Aug 25 2024
.SHORT TERM.../Through Sunday night/ A fall like storm is moving
through the panhandle today bringing rain and wind as it comes.
Winds generally started increasing in most areas after midnight
overnight, and the highest gust so far was 39 kt observed at
Hydaburg this morning. Rain has also been widespread and been
moderate at times overnight especially in the north. Amounts over
the last 24 hours have ranged from nearly nothing in the far
southern panhandle to nearly nine tenths of an inch in the higher
elevations of the northern panhandle.
The main frontal band will be moving through the panhandle today
from SW to NE spreading rain and wind as it comes. The highest
winds are expected to mainly be today with diminishing winds this
afternoon and evening. The main change in the forecast was the
inclusion of higher southerly winds in the Lynn Canal (up to 30
kt) and Skagway (up to 20 kt) areas later today when the southerly
winds post front finally reach that area.
Many areas expected to be wet today as rainfall continues.
Rainfall intensity will start diminishing in the north late this
afternoon and possibly become more showery in nature as the front
begins to move through. The southern panhandle will still be
under the gun until late tonight though as the front hangs up for
a bit in that region. Total rainfall amounts expected to range
from 1 to 3 inches with the higher amounts through the next 24
hours mainly focused on the southern panhandle.
.LONG TERM.../ Monday through Thursday night / The long wave
trough that is beginning to weaken over the Gulf of Alaska
travels east into Western Canada Monday. A closed low and mid
level trough starts to spread into the western Gulf Tuesday and to
deepen and slide into the western gulf, then to the panhandle
Wednesday and Wednesday night. Early hints suggest minor IVT plume
in the weak atmosphere river range, what hold me back from
labeling that at the present is fact is also quick moving through
the region. Potential rainfall totals of 2 to 4 inches, this time
over the Northeast Gulf Coast area. Anticipate near similar
amounts to move to the central and southern panhandle, however, if
the track shifts or a wave develops these rain totals will be
adjusted. Will need to watch this area if anything more
significant develops Wednesday to Thursday. For now, no flooding
concerns, but the rain for low reservoirs in the south/central
will be a good to see.
In the longer timeframe (to the weekend) another low will be
moving Southeast into the central Bering Sea and drift south to
anchor near the Aleutians there into the weekend. The response is
ridging over the panhandle area. This results into persistent
moisture flow into the south central Gulf Coast and to the
northeast gulf coast.
&&
.AVIATION...Expect -RA to RA across the region, with the main
band of heavier rainfall shifting to the south through the day. In
the north expect MVFR to VFR to continue, the exception being
northern Lynn Canal where we could hang on to IFR from CIGS. For
the south… expect IFR from +RA, especially areas east of Clarence
Strait. There is a low probability of seeing an isolated
thunderstorm or two lurking in the central and northern region.
Southeasterly winds and associated shear will be at their
strongest this morning before the system begins to cross into
Canada in the afternoon, leaving behind southwesterly winds with
speeds and shear diminishing further overnight Sunday.
&&
.MARINE...Widespread small craft advisory winds are the norm this
morning for both the near coastal waters of the gulf and in the
inner channels. The highest winds are actually on the back side of
Douglas Island where E winds to 35 kt have been observed at Scull
Island this morning. These winds will persist through the morning
and will start to diminish across the central inner channels and
outside waters this afternoon after frontal passage while the
southern inner channels will start to diminish in the late
afternoon. Lynn Canal will have the opposite trend today with
increasing southerly winds expected to reach 30 kt by afternoon
before starting to diminish in the evening. Lighter winds expected
across the area tonight in the post frontal environment as
lighter SW onshore flow prevails.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind until 7 AM AKDT this morning for AKZ323-327-328.
Strong Wind until 1 PM AKDT this afternoon for AKZ330-332.
MARINE...Small Craft Advisory for PKZ012-013-021-022-031>036-641>644-651-
661>664-671.
&&
SHORT TERM/MARINE...EAL
LONG TERM....Bezenek
AVIATION...AP
Visit us at http://www.weather.gov/JuneauDebris Flow, Ketchikan Gateway Borough
- When
- August 25, 11:00 AM AKST to 6:00 PM AKST
- Where
- Ketchikan Gateway Borough County, 1.08 mi ESE of Ketchikan to 1.11 mi SE of Ketchikan
- Cause
- Heavy Rain
- Deaths
- 1 direct, 0 indirect
- Injuries
- 3 direct, 0 indirect
- Property damage
- $4.0 million
- Reported by
- Utility Company
- Coordinates
- 55.353, -131.666
Shortly after 1500AKST on August 25th the larger of two landslides crossed the 3rd Avenue Bypass, a state road which is one of two routes for local traffic to get across town. There were 2 city employees that were working to clear culverts in their vehicle as the landslide occurred and killed the driver and significantly injuring the other passenger. As the landslide progressed down the slope, it destroyed 5 houses, caused 2 additional injuries, and damage to other surrounding properties. The entire area around the slide was evacuated until the hillside was evaluated. The 3rd AVE Bypass was closed and produced major congestion due to summer tourism as there was only one main road to move through town and this made it difficult for emergency services to get around in a timely fashion.
Debris Flow, Ketchikan Gateway Borough
- When
- August 25, 11:00 AM AKST to 6:00 PM AKST
- Where
- Ketchikan Gateway Borough County, 1.23 mi ESE of Ketchikan to 1.36 mi ESE of Ketchikan
- Cause
- Heavy Rain
- Property damage
- $10,000
- Reported by
- Utility Company
- Coordinates
- 55.354, -131.660
The second landslide, on the opposite slope of the first, went down Copper Ridge and affected a private construction yard. Construction materials stored at the yard were destroyed in the slide, which was significant loss, along with the damage/destruction of the upper part of the access road.
- Debris Flow
- A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.
After NWS Directive 10-1605, the rules offices file Storm Data by.
- Flash Flooding in New Mexico, August 25, 2024$600,000 · 2 events
- Damaging Winds in Texas, August 25, 2024$128,000 · 70 kt wind · 6 events
- Excessive Heat and Hail in Nebraska, August 25 to 29, 20243.25 in hail · 31 events
- Excessive Heat and Heat in South Dakota, August 25 to 26, 202424 events
- Excessive Heat in South Dakota, August 25, 202416 events
- Flash Flood and Hail in South Dakota, August 25, 20242.75 in hail · 16 events
- Excessive Heat in Iowa, August 25 to 26, 202411 events
- Excessive Heat and Heat in Minnesota, August 25 to 26, 202411 events
- Excessive Heat and Damaging Wind in Iowa, August 25 to 29, 202452 kt wind · 9 events
- Damaging Winds in Wyoming, August 25, 202457 kt wind · 4 events
- Damaging Winds in South Dakota, August 25 to 26, 202461 kt wind · 4 events
- Debris Flows in Colorado, August 25, 2024$10,000 · 3 events
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: 1199210, 1199212.