Homer, Kenai, Palmer, and Soldotna all saw their coldest temperatures since winter 2013-2014 Sunday night.
How did it get so cold?
1) Cold air mass already in place: The cold air already had become entrenched across all of Southern Alaska, thus there was no wind to mix the air around and prevent cooling.
2) Snow Pack: Existing snow acts to cool the air in contact with it much faster than bare ground. With no wind to replace the air in contact with the snow, that air was allowed several hours to cool uninterrupted.
3) Clear Skies: The earth is always emitting heat. Snow cover speeds up this process. With no clouds in the sky, there was no "atmospheric blanket" in the form of clouds that would trap the escaping heat.
Tonight, more clouds and a somewhat warmer air mass moving in will prevent a repeat of last night's cold temperatures.