Following a rather stormy and deadly Christmas week, and a protracted period of warmth across the eastern U.S., the weather pattern is shifting into a more tranquil mode. In fact, the 7-day quantitative precipitation forecast (QPF), issued by NOAA’s Weather Prediction Center, is calling for mostly dry conditions nationwide for the first week of January 2016 (Fig. 1). Only the southern tier (from California to the Gulf Coast) is expected to see any significant rainfall. The California rainfall (and mountain snowfall) will be very welcomed. The opposite can be said for the Texas and Louisiana precipitation.
This rainfall pattern is linked to a “split flow” upper level wind pattern (Fig. 2). Here, westerly winds at high altitude split as they approach the West Coast, with one wind flow current heading north into the Arctic before plunging southward over the eastern U.S. The other current continues unabated (mostly west-to-east) across the southern states. This keeps moisture locked into the southern states, while allowing colder air masses to cover much of the Nation.
The only anomaly to this overall pattern will the occurrence of “lake effect” snows across favored snow bands, especially to the east and southeast of Lakes Erie and Ontario. Given the warmth of the lakes, and the expected persistency of the northwest wind flow, look for some significant snowfalls during the next week.
© 2015 H. Michael Mogil
Originally published 12/30/15