UPDATE: Fri 21 Jan 2011 / 5:15p.m.
The extended forecast remains the same. I'm taking any mention of snow out of the forecast for now since temperatures look too warm.
Even if a few flakes fall during one of these light precipitation events, it'd be flurries as opposed to anything sticking.
We will be in a rather cold pattern during the next week, with temperatures averaging 5-10 degrees below normal on any given day (the “normal” temperatures for late January are a high in the low 50s and lows near freezing).
What makes this a forecaster’s nightmare is the steering flow aloft. A deep low will re-develop over the eastern U.S. in the coming days. A fairly stout ridge will re-form over the western U.S., putting the middle of the nation in a NW steering flow. This pattern has more or less persisted since November.
A series of short waves will ride down the ridge and across the southern Plains (discussion continues below map).
Accurate timing of each wave will be very tricky. Troughs (dashed white lines on map above) of shorter wavelength move more quickly so even a small error in their estimated speed or direction gives a bigger “bust” potential. There’s also the problem of moisture. The lower levels will remain rather dry as high pressure cells drop into the northern Gulf during the next week and keep higher dewpoints well to our south.
However, the strength of a trough can sometimes overcome this shortage of moisture and generate some precipitation. So I'm keeping low chances for rain and/or snow with these waves as they pass.
The models are all over the road on the timing of each short wave, but they all agree on a fairly cold period for Texoma. The ECMWF continues to perform the best and has done so for most of the winter, so I’m using it for my 7-day timing.