A high impact, heavy snowfall event unfolded across large portions of Southcentral Alaska between 11/8 and 11/9, with the most intense and prolonged snowfall recorded across the mountain passes near Prince William Sound and out towards much of the Kenai Peninsula, Matanuska Valley and greater Anchorage area. The setup for this event was very complex, unique and incredibly challenging from a…
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 high impact, heavy snowfall event unfolded across large portions of Southcentral Alaska between 11/8 and 11/9, with the most intense and prolonged snowfall recorded across the mountain passes near Prince William Sound and out towards much of the Kenai Peninsula, Matanuska Valley and greater Anchorage area.
The setup for this event was very complex, unique and incredibly challenging from a forecast perspective. A deep, negatively tilted upper trough stalled out between Southwest Alaska and the Alaska Gulf as a front and atmospheric river surged out ahead of this feature into the Gulf Coast, allowing very high moisture to stream north and west along it into Prince William Sound. A small but very intense low spun up along this frontal zone, moving northwest into Prince William Sound late on 11/8 and continued north into the Susitna Valley as it dissipated by the afternoon of 11/9. An axis of deep lift and moisture near the nose of the atmospheric river and to the east of the low as it tracked north and west remained focused between the Prince William Sound and Mat-Su Valleys for several hours, resulting in several feet of heavy, intense snowfall across the Chugach Mountains and between 12 and 36 inches of new snowfall from portions of the Kenai Peninsula out to Anchorage and across the Matanuska Valley.
Some numerical model guidance leading up to this event performed very poorly, projecting a much more west track for the low as it crossed the mountains towards Susitna Valley. This scenario would have allowed much warmer air to flood into the Anchorage and Matanuska Valley, and would have also resulted in a transition over to rain during the highest intensity of precipitation. This never materialized, and the bulk of precipitation during the event fell as snow for most locations.
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 Nov 6, 4:37 PM AKST, 12 hours 58 minutes earlier.
Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 437 PM AKST Mon Nov 6 2023 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... Key messages: * Areas of light snow tonight through Tuesday morning. * A major winter storm will bring widespread impacts from wind and precipitation to Southcentral and the Gulf Tuesday night through Wednesday night. The upper level low which brought accumulating snow to Anchorage and vicinity yesterday is now tracking into the eastern Gulf. A trough axis extends from the low northwestward across the Kenai Peninsula and Cook Inlet. A weak surface low has formed over the northern Gulf to the north of the upper center. A vorticity- maximum rounding the upper low is tracking northwestward toward Prince William Sound, with precipitation spreading out ahead of it from eastern Prince William Sound (Cordova/Valdez areas) across the southern Copper River Basin and Prince William Sound toward the northern Kenai Peninsula, Anchorage, and the Mat-Su. Today's light snow will gradually taper off from south to north tonight. Meanwhile, the vorticity maxima will help pull the upper low and trough northward, ultimately lifting into the Copper River Basin tonight then exiting northward on Tuesday. This will bring widespread accumulating snow to the Copper Basin through Tuesday morning. All attention will then shift to what will be a major winter storm for Southcentral and the Gulf Tuesday through Wednesday night. A shortwave trough digging across the Aleutians into the north Pacific will lead to cyclogenesis south of the Alaska Peninsula and Kodiak Island on Tuesday. In response to this, a high amplitude ridge will form downstream, forming a strong southerly jet streak and atmospheric river pointed at Southcentral Alaska. Gale to storm force winds will accompany the leading front northward across the Gulf on Tuesday with strong winds and heavy precipitation spreading onshore along the north Gulf coast and Prince William Sound Tuesday night. Cold air in place will lead to snow or a rain/snow mix as precipitation first arrives, but temperatures will quickly warm with snow levels rising to 2000 feet or higher for the coastal zone by Wednesday afternoon. The orientation of the leading front along with the low position south of Kodiak means that downsloping across the Kenai and western Chugach Mountains will be fairly weak. This will allow precipitation to make it over the mountains to the western Kenai Peninsula, Anchorage, and portions of the Mat-Su Tuesday night and Wednesday. Similar to the coast, precipitation will start as snow, but warmer air will advect in aloft leading to a transition to mixed precipitation or rain. Strong pressure and thermal gradients ahead of the front approaching from the Gulf will lead to gusty northeast winds in the Matanuska Valley, with northerly winds continuing down Knik Arm to north to west Anchorage and down Cook Inlet. These winds will maintain drier air, which could limit the ability of precipitation to reach the ground, especially in the Matanuska Valley. Still, with strong dynamical forcing and the presence of an atmospheric river, ultimately expect some precipitation to fall in all areas. The primary area of uncertainty with this storm system is on Wednesday with the track and strength of upper level short-waves and surface frontal waves from the Gulf up to Southcentral. A stronger surface frontal wave crossing the northern Gulf would strengthen what will already be a strong barrier jet along the north Gulf coast and into Prince William Sound. The GFS is the strongest solution, brining hurricane force winds from Cape Suckling to Prince William Sound. Meanwhile, the upper level waves will intensify precipitation, especially along the coastal mountains. The constant barrage of short-waves moving up from the Gulf will help drive the front onshore Wednesday night. With southerly low level flow behind the front, surface temperatures will likely rise well above freezing for much of the region. The weather impacts will be many with this system, leading to widespread hazardous travel on water and on land. As we get closer Advisories and Warnings will likely need to be hoisted for much of the area. Here are some of the potential impacts: 1. Storm total rainfall (or rain and melted snow) of 2 to 4" with localized amounts up to 6" possible for the eastern Kenai Peninsula/Prince William Sound areas (highest over the eastern Kenai Peninsula). 2. Multiple feet of snow in the coastal mountains, with hurricane force wind gusts possible for the east Turnagain Arm mountains. 3. Blizzard conditions possible through Thompson Pass. 4. Snow to rain transition for most of Southcentral. 5. Snow and blowing snow possible for the Mat Valley, Anchorage, and western Kenai Peninsula Tuesday night through Wednesday morning. SB/ER && .SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3)... A 984 mb parent upper low sits over the northern Bering this evening. Rotating around the southern periphery of the low is a secondary low/trough, currently passing through the Central Aleutians. This secondary low is forecast to deepen and become the dominant low as it passes across the Eastern Aleutians into the Pacific side of the Alaska Peninsula by tomorrow morning. Satellite imagery shows the pair of lows, almost mirror images of each other at the moment. Widespread cloud cover is blanketing the Bering with the areas of clearing filled with scattered convective showers. What this means for Southwest Alaska is diminishing precipitation and lighter winds through Tuesday evening and beyond. What the weather pattern means for the Bering and Aleutians is that unsettled conditions are unlikely to change anytime in the near future. ASCAT passes over the Bering show westerly gales associated with the Aleutian low moving into Amchitka currently. These winds and storm force gusts will spread eastward with the low tonight, briefly clipping Adak and Atka over the next 6 hours or less. For tomorrow, northerly small craft to gale force winds will spread across the central Bering on the backside of the broader Aleutian low. At the same time, westerly gales are forecast to overspread the Eastern Aleutians and Alaska Peninsula as a front lifts toward the Western Alaska range over the latter half of the day. Westerly winds are to transition to a northerly direction over the Eastern Aleutians and Alaska Peninsula by early Wednesday with gales spilling out of the gaps and passes. The next upper low and front sweeps across the Aleutians late Wednesday into Thursday with renewed westerly gales and potential storm force winds, especially on the Pacific side of the island chain. An extended period of showers may accompany the front through Thursday as it becomes somewhat stationary over the southern Bering. BL && .LONG TERM FORECAST (Days 4 through 7: Friday through Monday)... A series of well developed low centers stretching from Siberia across the Bering into the Gulf of Alaska gets interrupted by a short wave ridge that moves over the Aleutians and Alaska Peninsula through the weekend. This ridge also introduces uncertainty in the forecast models with the changes through the weekend. The longwave upper level trough reorients from the Western Chukchi Sea along the Asian Coast, while the Gulf low gains support from a developing Beaufort Sea low. This shortwave trough continues Southward along the Canadian Coast. The shortwave ridge flattens out over Southwest Alaska by Sunday. Widespread precipitation and windy conditions continue across the Bering, while stronger winds build along the Aleutians as the ridge moves East. Northwesterly gales will dominate with isolated areas approaching storm force Friday. Gulf of Alaska weather will remain unsettled as the low center loops nearly stationary around the Gulf. Heaviest and most continuous rainfall will occur along the Southcentral Coast. Further inland, conditions will be a mix of rain and snow, with snow at the higher elevations. Gale force winds extend into the North Pacific from the Alaska Peninsula and around Kodiak Island. Return flow sets up a gale force barrier jet along the North Gulf Coast, diminishing late Saturday. KZ && .AVIATION... PANC...MVFR and occasional IFR conditions will continue through the evening and into the overnight hours. Light snow will gradually taper off this evening, with increasing visibility as a result. The ceiling forecast is a bit more uncertainty with plenty of moisture through the low-levels. CIGs are likely to prevail in the MVFR height range through the night, though some instances of IFR CIGs are certainly possible. Conditions will improve late tomorrow morning as drier air mixes into the layer, raising clouds well into VFR range. Brown &&
SPECIAL WEATHER STATEMENT...UPDATED National Weather Service ANCHORAGE AK 337 AM AKST Tue Nov 7 2023 AKZ102-103-112-121-071345- Anchorage-East Turnagain Arm-Matanuska Valley- Western Kenai Peninsula- Including the cities of Anchorage, Eagle River, Indian, Eklutna, Girdwood, Portage, Palmer, Wasilla, Sutton, Chickaloon, Kenai, Soldotna, Homer, and Cooper Landing 337 AM AKST Tue Nov 7 2023 ...SNOW, BLOWING SNOW AND RAIN LIKELY LATE THIS EVENING THROUGH WEDNESDAY EVENING... An area of low pressure will bring strong winds and widespread precipitation to much of Southcentral Alaska from late today through late Wednesday. Strong winds are expected from the Matanuska Valley southward through the Cook Inlet. Winds gusting to 30 mph will result in reduced visibility to one half mile at times. Stronger wind gusts out of the Matanuska Valley may reduce visibility even further in locations such as Palmer and Wasilla. Snow is expected to begin across the Kenai Peninsula and Anchorage late today and then the Mat-Su Valley early Wednesday morning. A couple inches of snowfall are expected for much of the area before transitioning to rain on Wednesday as temperatures warm above freezing. Rain on snow may reduce blowing snow potential.
4 blizzard, 3 heavy snow, 1 winter weather. Local standard time, as filed.
Gusty north winds knocked down trees and caused power outages with winds gusting to 40 mph along with falling/blowing snow between 11 PM 11/7 through 3AM 11/8. Power outages would continue to affect residents of the area through 11/9/2023.
The Richardson Highway was closed around 2 PM from Thompson Pass north due to 'hazardous' road conditions and very heavy snowfall of up to 72 inches of new snowfall near the top of the pass.
The Richardson Highway was closed around 2 PM from Thompson Pass north due to 'hazardous' road conditions and very heavy snowfall with the D.O.T reporting 72 inches of storm total snowfall.
Heavy snow closed Seward Highway between Moose Pass and Turnagain Pass which was featured in an article on KSRM Radio Broadcast (https://radiokenai.com/road-closures-along-the-seward-highway-in-moose-pass-and-turnagain-pass/).
DOT reported up to 2 feet of new snowfall accumulation along the northern end of the Sterling Highway.
Trained spotter initially reported 22 inches of snow along the Anchorage Hillside. Overall storm total snowfall ranged from 16-20 inches in Anchorage to 25-30 inches on the Hillside. Reports of fallen trees and power outages affecting over 4000 customers by the end of the snow event on November 9, 2023 (Chugach Electric).
A spotter reported a storm total snowfall of 15.5 inches in Butte between the afternoon of 11/8 and the afternoon of 11/9. The remainder of the Matanuska Valley saw around 10 to 15 inches of snow during the event. Precipitation briefly turned over to rain during the early morning of 11/9, but the majority of heavier precipitation fell as snow. Over 6000 customers were without power across the Matanuska Valley by the time snow ended on the afternoon of 11/9.
SN to +SN reported with 1/4 to 1/2 SM visibility at PATO for much of the duration of the event. Snow was heavy as long as precipitation type was snow, beginning the afternoon of Nov 8 until around midnight, and again for most of the morning of Nov 9. Webcam images showed near whiteout conditions during this same timeframe.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alaska in 2023Every state in 2023This day in weather historyWarnings in Alaska, November 2023
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: 1140745, 1140823, 1140746, 1140824, 1140825, 1140826, 1141827, 1141006.