Friday, 11:55 a.m.
Today's post will be brief, but it will be solely on the upcoming change for next week. The hype is out there now about the 'polar vortex' that's coming for next week. While it is going to mean an impressive cool down for the middle of summer, just about coinciding with the typical peak of summer heat, let's really see how this measures up before we buy into all of the hype!
What is it really? An upper-level low pressure area, plain and simple. The 12z July 11 NAM 500mb forecast shows it very nicely approaching the Upper Midwest and Dakotas:
It's really two separate features, with the whole thing really being one elongated upper-level low stretching from North Dakota and northwestern Minnesota Monday morning to east of James Bay. The 0z July 11 GFS forecast for Tuesday morning has it becoming more consolidated over the Great Lakes:
For any month of the year, that feature would be impressive! It represents a pocket of chilly air aloft, and it will translate into an uncommonly cool and dry air mass getting pushed unusually far south for this time of the year. The actual cold front will get deep into the South and off the East coast in time, and the indications are quite strong that record lows are apt to be set in many places next week. Is it a 'polar vortex'? No, because this isn't arctic air! Now, if this were occurring in January, that it probably would be! But it's July, so instead of it being hot and humid like it typically is at this time of the year, it will be much below normal with no heat and no humidity. For many, that will be a welcome sight, as it will decidedly save on energy costs! So don't buy into the hype! An upper-level low, yes! Polar vortex? Not really!
A building upper-level ridge of high pressure in the West will promote hot, dry weather in the Northwest, while a downstream trough brings cooling through the Midwest into the Great Lakes and Ohio Valley.
A pattern more typical of late July and early August is shaping up around the country, one with heat and humidity, but with fewer incidents of severe thunderstorms and flooding.
There will be plenty of heat and humidity from the southern Plains to the East Coast this week while much cooler air prevails for a time over the Northwest to the northern Plains.
Severe thunderstorms raked across the Midwest and Ohio Valley in the past 24 hours, with more on the way this afternoon. The pattern will repeat itself over the next week.