About this time of year, most Alaskans are thinking about Spring with every other brain cycle. Old timers will often say “If you put that snow shovel away now you’re just asking for a big dump of snow.” Are these late season dumps a likely reality, or do the few that have happen just stick in the memory so well?
Here’s a graph that shows the climatological occurrences of a calendar day snowfall of 6 inches (15 cm) or more for a selections of Alaskan stations. (click on image for larger version).
The reality is that for most of Alaska, winter is over, at least for significant snowfalls. The “chances” in April are under 10% for the vast majority of Alaska. Part of the reason is the warming of spring, but another reason, probably a larger reason for the colder parts of the state, is that storms and precipitation slack off quite a bit from late March through June in most areas of the state. Click here to see a table with this data plus five more stations.
Lets take a closer look at the exceptions on the graph: Denali Park and Valdez.
Denali Park is up in the mountains, elevation a little over 2,000 ft (610 m). Its elevation plus its almost 64 degree north latitude mean snow is possible any month, and significant amounts have occurred in all months except July and August. This data is for McKinley Park coop station near the Denali NP entrance. Higher elevations in the park are obviously going to have more snow and longer winter (the mountain glistens with snow all year).
Valdez is not only at sea level but on the sea, so its snow record is nothing short of amazing. The difference with Valdez is that although it is a port city, the salt water is but a narrow arm of the Pacific, connected to the interior by the valleys which lead through Thompson Pass. The town is well situated to allow the right mix of moist, relatively warm marine air necessary for heavy precipitation, and the cold air of the interior which keep the precipitation as snow. There are a few other weather stations with this situation (see Haines Customs on the spreadsheet), and many more such valleys without habitation or measurement.
Barrow is also worth a mention. North of 71 degrees, Barrow’s arctic climate means precipitation of any type is scarce and follows the temperature curve through the year: The warmest months are the wettest, the coldest the driest. Snow is not rare in any month, and the heavier snows are actually less likely in the coldest months. Note on the graph how the months with a 6+ inch snowfall on record seem almost random. July has one but not December or February. April-June have none, primarily for the reason stated above. Keep in mind, however, that in any season snowfall more than 6 inches is very rare, so even with almost a century of records, patterns are a bit speculative.
So, go ahead, put that snow shovel away…I dare you.