A low pressure system with an associated warm front moved northward over Prince William Sound and the Copper River Basin. Overrunning brought extremely heavy snow to Thompson Pass, and a rain snow mix caused difficult travel through the Copper River Basin.
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.
A low pressure system with an associated warm front moved northward over Prince William Sound and the Copper River Basin. Overrunning brought extremely heavy snow to Thompson Pass, and a rain snow mix caused difficult travel through the Copper River Basin.
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 Dec 5, 5:24 AM AKST, 36 minutes earlier.
Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 524 AM AKST Tue Dec 5 2017 .ANALYSIS AND UPPER LEVELS... A deep highly amplified trough over the Bering and eastern Aleutians is causing plentiful active weather across Southern Alaska this morning. Around it lies a strong jet, representing the dividing line between warm and cold air. For southern mainland Alaska, this means the jet is aligned nearly due south to north, causing an amplified ridge to develop across western North America and eastern Alaska. As Southcentral lies underneath the core of the strongest part of the jet, it is acting as a conveyor belt for storm after storm to track northward out of the Pacific and slam into the north Gulf Coast. Waves in the jet are causing those storms to target different portions of the coastline for each one, but, in short, a very wet pattern continues for Southcentral. Over Southwest Alaska and especially the Bering, the atmosphere is far more unstable, and thus, more convective with cold air aloft. So the precipitation is much more spotty. The southerly flow into Southcentral is keeping temperatures very mild. Anchorage got to 44 degrees yesterday, remaining just shy of the record. Thus, precipitation-type concerns remain, and can at times be entirely dependent on the intensity of the falling precip. Meanwhile over Southwest Alaska, more cold air in place is keeping most of the precipitation in the form of snow. && .MODEL DISCUSSION... Continuing the pattern of the past several nights, the models are in decent agreement through the first 24 hours or so, getting a better handling of the next few waves of moisture tracking north towards the Gulf Coast. Beyond that, they continue to differ immensely, making the forecast difficult once again beyond that time frame. In addition, the small differences between the models, on things such as storm track, end up making a world of difference regarding impacts to the forecast. For Anchorage for example, the track of the low impacting Southcentral on Wednesday could mean the difference between downsloping and warm temperatures again, or the return of cold air and a snowfall. The difference between those two very different solutions is just a matter of 50 miles or so east or west. The further west, the less chance for snow and greater for warm temperatures, and vice versa. The models are still honing in on their chosen solution. Thus, needless to say, much of the forecast to that level of detail remains low confidence. Much more confidence exists in the forecast for Southcentral to remain well above normal for temperatures, and continue to deal with round after round of moisture from the subtropical Pacific. Meanwhile Southwest Alaska and the Bering will remain relatively tranquil, much more seasonable temperature-wise, and more showery. && .AVIATION... PANC...The latest round of precipitation has largely left the Anchorage area to the west, though a lingering shower or two is possible through the early morning. Winds may briefly turn out of the southeast late this afternoon and evening as a weak wave brings the threat for additional rain and/or snow showers. The next more major storm system moves in Wednesday morning, with snow expected. Most indications are for the heaviest snow to begin after 18Z, and thus the worst conditions are not yet included in the TAF. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... An atmospheric river is aiming at the Prince William Sound area for the next few days. The series of lows riding up this river will kick off heavier times of precipitation. Thompson Pass will see some of the heaviest snowfall with the greatest rates falling between midnight tonight and late afternoon Wednesday. Snow will mix with or turn to rain just outside Valdez which will limit snow amounts in town there. Heavy snow is also likely to fall from Glennallen southward in the Copper River Basin as well. Gusty southerly winds will occur along the Copper River and will complicate things a bit. These winds will cause limited visibilities in blowing snow as well as bring in the possibility of freezing rain toward Glennallen. Typically the gusty southerly winds downslope the precipitation but the depth of the moisture in the atmospheric river will be enough to override the full effect of the downsloping. Anchorage and the Matanuska Valley will be on the western periphery of this system. What this means is that temperatures will be cold enough for precipitation tonight and Wednesday to be all snow. There will be a sharp edge to where the snow diminishes and Anchorage will be near that line. Snow will likely be heavier in the Palmer and Wasilla areas just because they are farther east. There is a good chance that advisory level snow will fall in both the Anchorage and Matanuska Valley from late tonight through most of the day Wednesday. However, there is still a great amount of uncertainty as to where the line of quickly diminishing snow will be with models ranging by a factor of three on the amount of snow. Therefore, will wait at least another model run to hopefully get a better handle on where the heaviest snow will be as it is possible the Anchorage and Matanuska Valley will see just a few inches over the whole event. It will be that sharp of a dividing line. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)... As the gradually filling low just offshore of the Y-K Delta coast drifts to the north-northwest today, snow showers along the Kuskokwim Delta coast will gradually taper off. An area of deformation will bring a fairly narrow band of moderate to briefly heavy snow to the greater Bristol Bay area north and east of King Salmon north to around Sleetmute. A cold, troughy pattern will persist across Southwest Alaska tonight through Wednesday with small shortwaves bringing additional scattered snow showers through at times. Strong southerly flow into the Gulf of Alaska will begin pushing a warmer air mass up along the east side of the Aleutian Range Wednesday night and Thursday. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)... A broad trough with abundant cold air aloft will keep the Bering and Aleutians well supplied with scattered snow showers and an occasionally isolated thunderstorm through midweek. A north Pacific frontal system will slide south of the western Aleutians tonight and then continue east to be just south of the central Aleutians on Wednesday. This low will then turn to more to the southeast Wednesday night, tracking clear of the area Thursday. && .LONG TERM FORECAST (Days 3 through 7)... The mid/long term forecast beginning Wednesday night has ridging over southeast Alaska with a longwave trough extending through the Bering. In the base of the trough a low south of the Central Aleutians will track east before dissipating. Meanwhile, multiple waves will move up the western side of the ridging toward Southcentral Alaska through the weekend. There is decent agreement with the models on the overall pattern but there is inconsistency with the timing and exact location of the various waves moving through. Friday night into Saturday there has been good consistency amongst the models with a North Pacific low moving toward the Western Aleutians. The deterministic runs all have the low rapidly deepening to around 950 mb. However, on Sunday, models diverge heavily with what happens to the low leading to low confidence moving into next week. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...Winter Storm Warning: 131. MARINE...Gale Warning: 119 125 351 352. && SYNOPSIS AND MODEL DISCUSSION...JPW SOUTHCENTRAL ALASKA...EZ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR LONG TERM...DK
SPECIAL WEATHER STATEMENT National Weather Service ANCHORAGE AK 538 AM AKST Tue Dec 5 2017 AKZ101-111-121-145-052100- Anchorage-Matanuska Valley-Western Kenai Peninsula-Susitna Valley- Including the cities of Anchorage, Eagle River, Indian, Eklutna, Palmer, Wasilla, Sutton, Chickaloon, Kenai, Soldotna, Homer, Cooper Landing, Talkeetna, Willow, and Cantwell 538 AM AKST Tue Dec 5 2017 ...Potential for moderate to heavy snow Wednesday morning... There is potential for moderate to heavy snow to develop sometime Tuesday night or Wednesday morning from the Western Kenai Peninsula to Anchorage and the Mat-Su. This would produce hazardous travel conditions along area roadways. At this point in time forecast confidence in both timing of snowfall and amount of snow accumulation is low. Stay tuned for more information on this developing storm. As always, the latest forecast for your area can be found at www.weather.gov/afc.
2 heavy snow. Local standard time, as filed.
Thompson Pass received 40 inches of snow in a 24 hour period. 15 inches of snowfall were measured in a 90 minute period, close to a record snowfall rate. The road through the pass was closed due to avalanche danger.
Eureka Lodge reported 14 inches of snowfall in 24 hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alaska in 2017Every state in 2017This day in weather historyWarnings in Alaska, December 2017
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: 726976, 726977.