An unusually high amount of snowfall, combined with an anamolously cold April set the precedent conditions for an impactful break up season. Ice was thicker across the rivers than it had been for several years.
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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 AFC wrote it up.
An unusually high amount of snowfall, combined with an anamolously cold April set the precedent conditions for an impactful break up season. Ice was thicker across the rivers than it had been for several years. A rapid warm up across Interior Alaska caused upstream snow melting, leading to ice jams and widespread flooding along the lower Kuskokwim River.
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 Anchorage, AK wrote its last area forecast discussion before the first event at Apr 27, 3:45 PM AKST, 15 minutes earlier.
Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 445 PM AKDT Mon Apr 27 2020 .ANALYSIS AND UPPER LEVELS... The upper level high pressure remains over the mainland part of the state today. The 250 mb jet stream is south of the region with zonal flow south of the Aleutians that digs into an upper level trough with a weak upper level low south of Cold Bay. This pattern is keeping the surface lows away from mainland Alaska with one in the far eastern Gulf of Alaska and a set of weak lows in the Central and Eastern Aleutians. Some stratus is in the central and eastern Bering Sea and even made it inland in Bristol Bay early this morning before burning off. && .MODEL DISCUSSION... While the models remain in good synoptic agreement with each other through the majority of the week, there are a few issues that are impacting today's forecast. One detail is in regards to the 500 mb low moving across Southcentral and Southwest mainland Alaska out of the Yukon Wednesday night through Friday. This low does look to be a little faster in arriving across the area. && .AVIATION... PANC...VFR conditions and light winds will persist. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... Sunny and dry conditions persist across Southcentral through Wednesday. Increasing clouds are expected Wednesday night with chances for rain on Thursday as a weak front over the Gulf is pulled northward along upper level flow transitioning from northwest to southwest. Over the Gulf, a front across the southeast waters tracks northwest bringing its front toward the Northeast coast on Tuesday. This system diminishes quickly as it runs into the dry air mass across Southcentral. A change in the pattern begins Wednesday night as low pressure develops over the Gulf in response to the upper trough digging farther south. This trough will bring increasing clouds into Thursday and chances for rain. There is still a bit of uncertainty on rain development, so only made minor changes with rain most likely along the Gulf Coast and chances inland. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3/Monday afternoon through Thursday)... A ridge of high pressure in place over the Mainland will keep the clear conditions in place through the middle of the week. Light northerly flow is expected with temperatures falling below freezing overnight, especially across inland locations. Low level stratus and fog will likely form overnight and remain in place across the Bristol Bay area through tomorrow morning. By Wednesday morning, an upper level trough with an axis oriented from the NE to the SW will drop southward over the Mainland from the Yukon. This trough will ultimately force the ridge northward, and will bring increasing cloud cover across southwest Alaska for Thursday. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3/Monday afternoon through Thursday)... A weakening frontal boundary over the central Aleutians dissipates as it moves eastward this evening. Plenty of low level stratus and fog continue to blanket the Bering this afternoon, with that trend likely to continue through midweek. Farther west, a gale- force front associated with a Kamchatka low moves in over the western Aleutians, spreading in rain and southerly flow. As the front moves eastward along the Chain, it will weaken as it nears the Pribilofs, and eventually stalls over the eastern Bering by Thursday. On the backside of the low, colder air will wrap in, allowing for showers and gale-force westerlies over the western Aleutians Wednesday. The low will gradually weaken as it slowly drifts southward Thursday afternoon. && .MARINE (Days 3 through 5/Thursday through Saturday)... Quiet conditions are expected over the Gulf of Alaska Thursday as weak low pressure remains in place. By Friday night, there is increasing confidence that a North Pacific low moves northward into the Gulf, however there is still a lot of uncertainty in the track. Expect generally easterly flow at small craft levels with the potential for winds to increase through the weekend. Meanwhile, for the Bering, a large low will bring gale force winds to the western Aleutians through Friday afternoon. The low weakens as it moves south of the Chain Saturday morning. Expect weak flow across the Bering until Saturday night when another front reaches the western Aleutians. && .LONG TERM FORECAST (Days 4 through 8/Friday through Tuesday)... Model solutions continue to lock on to two key features next weekend; an upper level ridge over the Mainland and an upper level trough over the Bering. A third feature includes a North Pacific low lifting into the Gulf of Alaska late Friday. Overall, there is little confidence in how these systems interact with each other by early next week. At this time, thinking several upper level waves moving over Southcentral will bring increasing chances for precipitation on Friday, however the ridge in place over the Interior looks to have enough influence over Southcentral on Saturday, which may allow for some clearing. Farther west, an active pattern will be in place across the Bering as a low centered over the Aleutians on Friday eventually moves south of the Chain late Saturday. A second, faster moving low arrives Saturday night over the western Aleutians and reaches the North Pacific by Sunday night. Unsettled conditions will continue over the western Bering through early Tuesday as another, stronger front reaches the central Aleutians midweek. Additionally, the low in place over the Gulf of Alaska looks to drift to the northwest, bringing the potential for several upper level disturbances to rotate inland over Southcentral early next week. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...Gales 177 178. FIRE WEATHER...NONE. && SYNOPSIS AND MODEL DISCUSSION...EZ SOUTHCENTRAL ALASKA...KH SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO MARINE/LONG TERM...KO
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
Minor ice jams cause minor flooding at the villages of Sleetmute and Crooked Creek.
The catastrophic ice jam which began on 4/30 held through 5/4 at the Kolmakof River. As a result, 16 cabins and several other buildings were destroyed or submerged, and the airport was under with feet of water. Most damage occurred in the vicinity of the Native Village of Napaimute.
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, April 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: 889058, 890564.