Slow thaw will lead to warm weekend

There is much still to be said and analyzed about the actual impacts of the polar vortex’s pass through our area early this week, but for now – the main story will become its exit and the ensuing warm up. High temperatures on Wednesday have already rebounded several degrees, and less aggressive wind gusts have allowed wind chills to warm up as well. Don’t get us wrong — the airmass remains downright frigid — but the record breaking cold is moving out of the picture. The polar vortex is already retreating well to our north and will continue to do so through Thursday and Friday.

Temperatures in the mid levels of the atmosphere will respond, and warm, as the week comes to a close. Forecast models are in good agreement that surface temperatures will, as well. Highs should slowly warm into the 30’s by the end of the week. The pattern, then, will begin to change. The first sign will be a weak storm system which will slingshot towards our area from the Mississippi Valley on Friday, and may provide a period of light snow. Minimal accumulations are expected. But by this weekend, a stronger storm system will be organizing over the Central United States and the southerly flow ahead of it will begin pumping warmer air into our area.

GIF image animation showing rising temperatures at the 850mb level on Wednesday.

As a storm system approaches the area on Saturday and strengthens, with a low pressure system moving to our north and west, temperatures will warm even further — possibly into the 50’s. Concerns also build for potential heavy rain and strong winds as a frontal system nears the area this weekend.

Much of the concern stems from a few developments which are fairly new on forecast guidance. First, the mid level disturbance will shift farther to our north and west and strengthen, with a subsequent surface low pressure system tracking across the Great Lakes. This means a cold front will be draped to its south, and will eventually swing through the Northeast US. Second, and more notably, a developed and moderately strong low level jet will enhance along the front as the system nears our area.

NAM model shows strong winds just above the surface, at the 925mb layer, on Saturday.

This provides the potential for heavy rain, and the concern for strong winds near and along the cold front. Forecast guidance indicates the potential for 925mb winds of 60+ knots in some areas, and when combined with the potential for heavy rain to mix those winds down to the surface, leads to some increasing confidence in strong winds throughout the area during the day on Saturday when the front passes. We’ll have to carefully monitor guidance over the next few days as the system approaches to try and get a better handle on the rain and wind event.