UPDATE: Tue 10 Jan 2017 / 5:15 p.m.
The supply of cold air looks even more feeble than it did yesterday; so while we're not giving an "all clear" to Friday's ice threat, an updated map shows the risk decreasing and only in our northwestern sector.
More updates will be posted as needed - Steve LaNore
On January 6, we had our first significant snowfall of the season; there’s been talk that nature might repeat the “favor” on January 13, this Friday, and there’s certainly a threat, although the chance for winter precipitation appears lower than it did last week. Several reasons for this:
1. The Jet Stream is blowing west to east, (see first map below) driving the next batch of arctic air mainly to the east. The density of the cold air is allowing it to move southward also, but at a much slower speed than its eastward push. So in essence the air behind this next front is very cold, but it is being partially deflected by the jet stream. We’re just going to get the fringe of it, where we took the full force of cold last week.
2. Frontal speed: The steering winds are expected to become even less favorable for southward frontal movement by Friday. In other words, the winds aloft will blow from southwest to northeast and hinder the progress of the next cold front (see second map). This should keep the deep cold air well to our north. We will just get a glancing blow. It will be cold for sure, but nothing like last weekend.
3. Rain is expected to develop as an upper low (shown in red, lower left region of map) takes shape to our west; the rain will transport warmer air from a few thousand above the cold front downward, also promoting a slight warming rather than a cooling.
Of course, we’re several days out and if the cold air pushes farther south than expected, then we will have greater potential for ice. Right now, I’d say there’s a low to moderate chance (30-40%) of ice in our northern/western counties but only a very low chance over the south and east (see third map). Since this air mass is not as cold or as deep as the previous batch, we would unfortunately be facing ice rather than snow for our winter precip type. This would probably be freezing rain.
One problem in pegging the temperatures will be the front’s position. It will probably stall somewhere over Texoma or perhaps just to our south on Thursday night. So let’s say it stalls along an Atoka-Gainesville line, putting Ada and Ardmore in the cold air and Sherman, Durant and Paris in the warm. In this example, Ada/Ardmore might only reach 40 degrees Saturday while Sherman and Durant would be in the 60s. It’s going to be one of those kinds of deals, or so it seems right now.
The 7-Day Forecast must choose an average temperature for each day so in cases like this, it doesn’t tell the whole story and that’s why it helps to watch the weather broadcast or read our text discussion for a more complete picture.
Putting it all together, we face some potential for wintry precipitation this weekend but the set-up is marginal for a major ice event, primarily due to limited cold air. The north and west have the greater risk.
As is frequently the case, we’ll probably have to tweak the forecast to some degree as we get closer to the weekend. Stay tuned.
News 12 / KXII-TV