All Hope Isn’t Lost for Wintry Precipitation Occurring in the Southeast and Southern Plains This Winter
I’m currently keeping a close watch on the small but noteworthy possibility of a winter event occurring across parts of the South after January 15th.
If you strictly look analyze model data at the mid and upper levels of the atmosphere, you’d be tempted to believe that the pattern is complete garbage for wintry weather probabilities farther south. However, the GFS model has a ridge building into the Gulf of Alaska and Alaska and a trough downstream of that ridge just off the West Coast. Then, it has a broad ridge over the central U.S with another trough over New England. Overall, the mean-layer flow is pretty zonal across the central U.S. and Southeast. Ridging usually means warmer weather, but how is this different?
You must consider the placement of these features aloft, and what will occur at the surface in response. I drew some arrows to show the overall flow with a pattern like this. Essentially, winds aloft go up and over the ridge, and winds also go around and under the base of the western trough. As a result, confluence occurs over western Canada. In response, surface high pressure develops over western Canada, and if the high moves into the U.S., it funnels cold, Arctic air into the U.S. due to the clockwise flow associated with high pressure in the Northern Hemisphere.
If a southern stream shortwave were to become embedded within the zonal flow and precipitation were to occur as a result, then it’s not entirely impossible to get some wintry precipitation (ice or snow) across parts of the Southern Plains and Southeast with this type of pattern.
Keep in mind that this pattern needs to keep showing up in the models. Any minor changes in the placement of these mid to upper level features can greatly change the outcome of a forecast. I do believe there’s value in using pattern recognition to consider the different possibilities using model data. Even if nothing occurs, it’s still good to learn about what would happen under a given pattern.