The coldest air of the season (temps about 5000 feet above the ground -22 to -30 degrees Fahrenheit!!) is building right now across southern and central Canada and is poised to enter the United States later this week. Behind a potentially major snowstorm for portions of the Mid Atlantic states (DC, Baltimore, even Philly could see several inches of snow on Saturday), the arctic air will enter the Great Lakes and Northeast with frigid temps and gusty wind. But this time, the cold blast is not slated to push full force into the southeast. What's different this time compared to the early part of January?
Once again, there are a few ingredients for extra cold air to move into the US: low pressure south of Alaska, low pressure (polar vortex) moving south over central and southern Canada, and high pressure in the north Atlantic Ocean south of Greenland. All of these will be present this time and, in fact, the polar vortex will be even stronger this time. However, low pressure near the Aleutian Islands and high pressure near Greenland will be much, much weaker. The stronger these features are, the farther south the jet stream can dip -- thus allowing the cold air to flow south. With these features much weaker this time, though, the bitter cold air will only make it as far south as the Ohio Valley and the Mid Atlantic. Sure, we'll be a little cooler behind our front on Saturday (highs Sunday only in the upper 60's), but highs in the 40's and 50's? Not this time!
Brian
