Following a top five coldest April on record for much of the central US, the remainder of May will be hot and humid thanks to a dominant, upper-level ridge. A big northward surge in the jet stream will practically sit over the central US into the beginning of June. The jet stream often separates different air mass. South of the jet stream, or the strong winds at 30,000 feet, is where the hot air will be; north of it are the cooler temperatures. This upper-level ridge allows for warmer temperatures than normal.
This Thursday, temperatures will be above normal coast-to-coast, but the warmest of air will be found in the Northern Plains and Upper Midwest. It’s these areas where highs may exceed levels of 20 degrees above average while the remainder of the Plains and Midwest are anywhere from near average in Texas to mainly 5 to 15 degrees above normal for the rest of the region. In terms of actual high temperatures, widespread maximums in the upper 80s to 90s are forecast. Temperatures in the 90s may even reach the Canadian border, affecting cities like Fargo and Minneapolis. Believe it or not, temperatures will not be enough to be record-breaking.
The heat will continue to dominate to end the week on Friday. The northern and central Plains and much of the Midwest will feel highs 10 to 20-plus degrees above normal. Texas will heat up further with highs generally about 5 degrees above average. This time, however, a few locations in the Dakotas, Minnesota, and just east of the Rocky Mountains may break their daily record high. The Plains will experience highs in the 90s and possibly in the low 100s in West Texas while the Midwest mainly deals with temperatures maxing out into the 80s.
A brief upper-level disturbance will pass through the upper Midwest on Saturday, so temperatures will be about 5 degrees cooler, allowing for a brief reprieve from the heat. For all other areas, it will remain hot and humid. Dew points across most areas will be between 60 and 75 degrees, which means that the humidity in the air will feel sticky to even uncomfortable and oppressive. High temperatures in the Northern Plains will be 15 to 25 degrees above normal while remaining areas are 5 to 15 degrees above their typical high for this time of the year. Highs in the 90s will be commonplace, but it will even get into the 100s across much of the Southern Plains. There may actually be a few locations that near or even touch 100 degrees in the Dakotas. In fact, it will be hotter in the Plains than in Florida. Many locations in the Sunshine State, which will be dealing with rain for the Memorial Day Weekend, are expected to achieve record cold high temperatures, or record low maximums, due to highs in the low 80s.
Sunday will be quite similar as an omega block-like pattern sets up. This omega block pattern looks like the omega symbol on the 500 millibar geopotential heights weather charts, like the one below, highlighting an upper-level low over the West and the Gulf Coast while a strong ridge dominates in between over the Plains.
Widespread highs of 10 to 20 degrees above average are forecast in the Plains and Upper Midwest. The remainder of the central US will be 5 to 10 degrees above normal. This will allow for another day of highs in the upper 80s or 90s. It will remain in the 100s across much of the Northern Plains. Nearly a dozen locations across the middle third of the US are expected to either tie or break their record high temperature.
As we look ahead to next week, the heat will actually intensify, especially over the southern Plains. A tool that we use to gain hints at the heat potential are the 500 millibar geopotential heights, like in the model image above. This week, heights are expected to reach 585 decameters while next week is may reach 592 decameters, which is basically off the charts. When heights reach these levels, it allows for a thicker amount of hot air in the atmosphere, is thus warmer temperatures. By next weekend, those heights may even rise further. Therefore, highs in the 100s will persist into all of next week. Some locations may even exceed 110 degrees based on the evolving upper-level pattern. Meanwhile, in the northern Plains and Midwest, high temperatures in the 80s should be more common as cold fronts allow for rounds of warmer and cooler air.