Winter Weather — Bristol Bay, Alaska

2022-12-12 to 2022-12-13 · Bristol Bay, Alaska

Event narrative

The Cape Newenham observation showed visibilities of 1/2 mile or less from 2336z-0316z; the Platinum observation showed visibilities of 1/2 mile or less several times between 0045z-0242z.

Wider weather episode

Three back-to-back snowstorms impacted Southcentral and, to a lesser degree, Southwest Alaska over the course of an 11-day window in early December. These snowfall events resulted in particularly significant impacts to the Matanuska-Susitna Borough and Anchorage Borough areas. These conditions occurred as a highly amplified and transitory pattern affected Southern Alaska, bringing 3 to 5 feet of snow to the Matanuska-Susitna and Anchorage Boroughs within the December 5 to 15, 2022 window.

There were a number of commonalities between the three snow events as follows:

1. All snowstorms occurred as a result of frontogenetically induced lift and associated banded snow.

2. All snowstorms occurred in conjunction with a mature trough, indicating increased instability associated with the pattern.

3. All snowstorms were reinforced by some version of an atmospheric river feeding the system.

4. All snowstorms were associated with a 'weak' surface low. More frequently during the winter months, strong lows and associated wind fields produce upslope/downslope effects which tend to limit widespread heavy precipitation to the Gulf coast areas. In this case, winds crossing the mountains were generally weak, which allowed for a particularly long period of snow west of the Kenai and Chugach Mountains.

It is uncommon to see three storms in a row with such similar characteristics.

In all cases, these ingredients came together to produce abundant snowfall, with the heaviest snowfall generally falling across the higher elevations. The three events occurred December 6-7, 2022, December 11-12, 2022, and December 14-15, 2022, resulting in 3 to 5 feet of snow total over the course 11-day period. Periods of light snowfall in between these dates were noted, but did not have a meaningful impact on snow totals.

These snowfall events hit a few records. For instance, in the city of Anchorage, they hit the 14th highest snowfall amount for a 2-day period December 11-12, 2022 with 16.2 inches of snow. More notably, the only other 11-day period to see higher amounts on record was in 1996 with 44.6 inches, while this 11-day period measured 41.1 inches of snow. To put this event in perspective, these systems pushed Anchorage to the third snowiest snow-year to date and within six tenths of an inch of the snowiest December on record as of December 16, 2022.

Source: NOAA Storm Events Database, event_id 1098717. Narrative written by the NWS forecast office that issued the report.