Once again, we're dealing with a storm system that will move through the Valley in the coming week. But this one has been a horror to deal with - the models are flip flopping constantly on whether or not the Valley will be cold air dammed to around freezing, warmer than freezing, or well below freezing. Here's a discussion of the current models, but remember - we're still 4 days out! Lots can change.
The GFS model has the storm approaching during the wee hours of Monday morning from the west. At this time, temperatures would be marginal, at best. A weak high pressure system is located to the north of Lake Superior, with a more localized high pressure system in central PA. By 7am Monday, the localized high pressure in PA has dissipated. The GFS shows damming along the Appalachians from the high pressure in Canada, but not very strong damming. The northern half of the Valley would likely see ice or snow while the southern Valley would see rain. Damming is eroded by 1pm Monday, leaving most of the area under rainfall.
The Canadian model, or the CMC, has the system moving much slower through the Ohio Valley. Precipitation would start around the evening rush hour on Monday. High pressure is centered north of Lake Huron. At 7pm Monday, the majority of the Valley is dammed and we would see ice or snow. As colder air wraps around the low pressure Tuesday morning, all precipitation would turn to snow. Once low pressure reaches the Delmarva, it gains some energy, delivering some potent wrap around snow to the northern Valley and DC/Baltimore Metro areas through late Tuesday night.
Our regional model, the WRF, only goes out to 84 hours. Looking at the last frame of the model run, it is colder in the low and mid levels of the atmosphere than the GFS, and on par/slightly colder than the Canadian. We'll be able to see more from the WRF model Friday and especially Saturday.
The ECMWF (European model) keeps us relatively warm like the GFS, with a similar time frame as well. However, by Tuesday morning, the Euro has us cooling down and some wrap around precipitation forming.
I have to write the disclaimer again - we're still 4 days out! You can see the amount of disagreement that lies within these models. Keep it tuned right here to TV3 for the latest updates. I'll have another discussion of the models Friday morning and once again Sunday afternoon.