Clouds will increase Thursday night and that's where the disagreement beings with the forecast model guidance. Some forecast guidance suggests the shallow cold air that is brought in by tonight's cold front will stay locked in place Friday morning while others suggest a brief period of sleet and freezing rain early Friday morning before changing all over to rain as the warm air from the south takes over. The key is the dry air at the surface. This is represented well by the Dew Point. Basically it's the measure of the amount of moisture in the air. Rain that falls through dry air cools the air by a process known as evaporative cooling.
Here are three models I'm looking at to put together the forecast. By far the RPM model is the driest which is the reason it keeps everything as freezing rain and sleet. This model has been very consistant the past 36 hours and I'm watching to see if the other models begin to trend in that direction. We probably won't have a better idea until the Thursday morning model run. That doesn't leave a lot of time for a Friday forecast.
Here is a graphic that explains the warmer air and moisture moving over the top of the shallow cold air at the surface.
Think of the atmosphere as a building. The bottom floor on Friday will start out below freezing in some areas. The temperatures on the third floor of the building (atmosphere) will be above freezing. The rain drops fall into the dry and cold air making freezing rain and sleet possible.
At this point in time it looks like we will see a period of freezing rain and sleet early Friday morning before changing all over to rain. Until the forecast guidance comes closer to agreement there will remain a lot of uncertainty regarding any possible travel problems.
This is the time frame for sleet and freezing rain that I am expecting as of right now.
WAFF 48 Storm Team
We Track Storms