Thursday, January 1, 2015
A very cold low pressure system that brought our frigid temperatures is now cut off from the main jet stream and is spinning in the southern Great Basin. This storm’s weather will likely stay to our south as it moves eastward over the next day, keeping the current temperature inversion and cold valley temperatures around through tomorrow.
This eastward movement of the Great Basin cutoff low is due to a separate Pacific storm currently in the gulf of Alaska that entrains some cold Canadian air and moves towards our area from the northwest tomorrow. The amount of cold air that mixes with this storm system is currently not well forecasted and leads to uncertainty in the snow amounts from this system on Saturday.
There is also uncertainty as to whether a piece of energy from the southern cutoff storm breaks off from the main circulation and begins light snow over our area as soon as Friday night. Nonetheless, snowfall should be either starting or continuing early Saturday in advance of the cold front that should move through the area around Saturday afternoon. Moderate to sometimes heavy snowfall will accompany this storm, though its quick movement will limit accumulations. Ironically, the cold front and its associated winds will physically mix the stagnant valley air, breaking the inversion and warming low-elevation temperatures. I currently expect between 5-10” of low density powder to be on the Sunday morning report, with most of that falling during the day Saturday as snowfall should end by midnight Saturday.
Another weak storm in northwest flow looks to graze our area on Sunday, starting snow in the morning and peaking in the afternoon before ending around midnight. This storm looks to be weaker and warmer than the Saturday storm, producing 2-5” by Monday morning.
Models are currently forecasting a ridge of high pressure to build over our area around midweek, bringing dry weather and warmer temperatures that should persist through the workweek. More Pacific energy is forecast to cross the west coast around then and may bring some storminess into our area for next weekend.