From the Weather Center: April 2022

by John Simon
April 2022


The spring thaw typically occurs in early spring when the temperatures are beginning to rise, and the snow and ice begin to melt.
The resulting snow melt in particular can sometimes lead to problems.
One of the most common results of a spring thaw is what is known as a freshet. Wikipedia defines a freshet as a flood resulting from heavy rains or runoff. The severity of a freshet usually depends upon local climate and the topography of the land.
Late spring melts allow for faster flooding; this is because the relatively longer days and higher solar angle allow for average melting temperatures to be reached quickly, causing snow to melt rapidly. Snowpacks at higher altitudes and in mountainous areas remain cold and tend to melt over a longer period of time and thus do not contribute to major flooding.
Here in the eastern part of North America, annual freshets occur from the Canadian Taiga ranging along both sides of the Great Lakes, then down through the heavily forested Appalachian mountain chain and St. Lawrence valley from Northern Maine and New Brunswick into barrier ranges in North Carolina and Tennessee.
The Fraser River in British Columbia experiences yearly freshets fed by snowmelt in the spring and early summer. The largest freshet ever experienced in the Fraser River occurred in 1894.
A freshet can also result from tropical storms or cyclones, and the term can also refer to a small stream of fresh water.