Thursday, December 12, 2013
Mountain slopes have warmed nicely while the valleys remain cold while trapped in strong temperature inversions. In fact, warming temperatures aloft counter-intuitively strengthen lower-level inversions as vertical mixing in the lower levels is suppressed in the stabilizing airmass. The cold air in the valley bottoms then stays cold as the surface warming is minimized by the shallow sun angle and reflective snow surface.
There are some weak disturbances influencing our area starting tomorrow, though there is very little chance of significant accumulations. A wave to our south crosses too far south Friday morning for any snow, while another wave from the northwest is forecast to split as it moves over us later Friday, perhaps producing some light snow showers. Yet a third wave is forecast for early Sunday morning and that may produce a bit of snow as well.
Waves graze our area in warm and dry northwest flow Tuesday and Wednesday, but only a slight moderation of temperatures are expected. The developing story is the likely return near the end of the work week of Big Blue, the meteorological euphemism for an arctic outbreak similar to what we observed last week.
Lots of details are still to be resolved by the numerical models, but agreement between the models is trending stronger with this major cold and likely snowy pattern change near the end of next week.