Our hottest day of the year is on the way!

- The month of May has started off nice and pleasant, but it’s about to get warm quick!  After a quick cold front pushes through the state late Tuesday, the warm up is on… and it’s all because of a Greek letter.  The weather pattern expected across the United States late this week is nothing unusual, but it can lead to some unusual weather.  Take a look at the upper levels of the atmosphere Thursday afternoon…

The upper levels is where the jet stream resides, that river of air that pushes storm systems across the planet, and on the map it is the orange arrowed line.  The US is located in the Midlatitudes of our planet, therefore we are in the westerlies, or in the location on the planet where winds, storm systems and otherwise, typically travel from west to east.  But as you see in the picture above, that’s not exactly happening late this week.  That jet stream dives southward into the Desert Southwest, then veers north way up and over Minnesota, and then back south again along the East Coast.  This pattern happens every so often, but is very well known in the meteorology world as an Omega block.  It is called this because the jet stream closely resembles the Greek symbol Omega.  This pattern is also very well-known because if it sets in, it can put a kink in the overall flow of the atmosphere and you can be stuck with the same weather for days or even weeks.  This is typically when Minnesota gets its hot dry spells in the summer.  In this case though, it appears that it won’t last long with a 1 day “heat wave” setting up for the state.  Underneath that Omega, southerly and southwesterly flow can bring very warm air that originated in Mexico northward to the Canadian border in just a few hours’ time and set the stage for one very hot day…

In our case, the omega block builds on Thursday and sets up on Friday before a cold front can push in on Saturday.  So the 60s of Wednesday turn into the 70s of Thursday, and the 80s & possibly even 90s of Friday, before more seasonable weather returns for the weekend.

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