The Polar…I Mean…The Odd Weather PatternJuly 14th, 2014 at 8:46 am by Jeremy Wheeler under Weather
It’s Monday. So I apologize in advance… but coming out of the gate I’ll say that the media is back to using the term Polar Vortex again, and I am not a fan of the name. This is a very overused and misused term by many. The Polar Vortex is actually a year-round phenomenon of cyclonic upper level winds around the north and south poles. Once in a while a piece of it drops south and that typically coincides with colder air at the surface. Sometimes it’s a huge drop in temps. The problem is that many people tend to think that the cold air at the surface IS the polar vortex itself. And that is not right. Here is the definition and explanation of the Polar Vortex: Polar Vortex. I guess some of the National Weather Service offices initially used the term, but were instructed to not use it anymore with this event. This is according to a recent blog from the Capital Weather Gang here: NWS changes tune about Polar Vortex.
Still… there’s no doubt that there will be a very unusual weather pattern developing this week. Here is what a typical July weather pattern looks like:
The jet stream typically runs along or near the U.S.-Canadian border. Heat and humidity sit across most of the country. High pressure usually dominates a large part of the U.S., and many areas see pop-up showers and thunderstorms. However, tomorrow into Wednesday the jet stream will take an unusually large dip. A significantly cooler air mass will surge into the Midwest.
Low temperatures may be in the 40s around the Great Lakes and parts of the Midwest. I’m from Illinois, and I know that that is a rare thing in July. They will have highs in the 60s and 70s over that same region. Meanwhile we’ll see some cooler weather here, but it won’t be that dramatic. The jet stream is in the upper levels, but a cold front will move through at the surface. This will enhance our chance for storms late tomorrow into tomorrow night, but it will also cool us down on Wednesday.
So let’s put all this together into our forecast. We are well out ahead of this cold front today. High pressure is in the region.
High temperatures will rise into the low/mid 90s with the heat index rising to near 100. Winds will be southwest at 10-15mph. So at least there will be a breeze again. We may see a few isolated afternoon showers and thunderstorms, but the chance for rain is only 20%. Tomorrow as the front moves into western/northern Virginia the rain chances will increase. Showers and storms will expand and strengthen through the late afternoon. By the late afternoon into the evening we’ll see strong to possibly severe thunderstorms move in from the west. I will highlight the particular threats in tomorrow morning’s weather blog, but it looks like straight-lined winds will be the main threat at this time. Heavy rain will be possible tomorrow night into Wednesday morning. The rain chances should decrease by Wednesday afternoon-evening. We could pick up another 1-2″ of rain. My weather watcher Don in Toano said he still needs rain, but we have been doing really good on the Southside after Arthur and last week’s storms. Highs will be in the low 80s Wednesday. By Thursday morning lows will be in the 60s. Highs will be in the low 80s with mostly sunny skies. Ahhhhh. It sounds lovely. Unfortunately, the models show scattered showers and storms next weekend. Maybe they’ll change their tune before we get there.
Meteorologist: Jeremy Wheeler