High Impact Weather Briefing #2
What: Potential High Impact Winter Storm
When: Thursday December 28th - Saturday December 30th 2017
High pressure will build south into the Ohio Valley on Thursday Morning. A wave of low pressure will develop over the ARKLATX and move East throwing moisture North. This moisture will ride up and over subfreezing temps to produce some type of winter precipitation over the area. There are great discrepancies in the models on the timing, the amount of moisture, and where a transition zone from snow to freezing rain sets up. This mornings briefing will rely on experience and the middle road of the model suite. The European has been more constant in its scenario than the GFS, although both have had their issues with this system over the last 8 runs or so.
The GFS had lost the system as per its normal operation 5-7 days out from the onset of an event. With this morning's 06z run the model came back into somewhat of a line with the European model. The European brings moisture in during the nighttime hours of Thursday into Friday and the GFS has also trended that way. So right now our timing of this winter storm looks to be Thursday Evening between 3pm and 10pm. Both models hinting that this will be a quicker shot and the storm moves out Friday in the early afternoon. However I think models may correct this more in the coming runs and this could be a longer duration winter storm than models currently depict. We will monitor the trends.
Moisture will stream North from the Gulf of Mexico Thursday Night. Dry and cold Arctic high pressure will build south into the Ohio Valley Thursday Morning, sending Arctic air down the Eastern slope of the Blue Ridge. This cold air will dam up against the Eastern slopes. As moisture overruns this precipitation will start to fall and become heavy Thursday Night. This could impact travel Friday Morning. Low pressure then develops along the Coast and lifts North up the coastline. The exact track of this low pressure and where it develops will be key as to how much precipitation falls across the area. As the low lifts North a reinforcing shot of Arctic air sweeps in to dry things out. Temps Thursday Night will also be key. Right now we expect those to be around 30F. A sharp boundary will set up between the snow and freezing rain. Right now we think this will be all snow in the mountains and adjacent foothills, along and North of I-40. It looks like freezing rain may have a high impact to areas along and just North of Hwy 74. South Carolina could be dealing with a big ice storm too. This is one that we have to watch close and you should be prepared on. The last snow we received was really good. It didn't stick to the roads through the night and when precipitation let up the roads cleared. This one likely will not be the same because air and ground temps will be colder than they were with that first winter event. This storm could impact travel, power, and heat sources. It is important to monitor the latest forecast and its developments over the next two days. Right now plan for the possibility.