Well, we all wished for warmer weather back in April but May has certainly proved more than just warm. For the country it's expected to be the warmest on record. In much of my area May will finish up anywhere from 1st to 3rd warmest...just the opposite of April! Here's the May temperature departures with 2 days to go.
While the MJO (Madden Julian Oscillation) is not as good of a temperature indicator in the warmer months of summer, it still has merit when looking at trends. After spending several weeks in phases 1-3, it's set to spend most of the next 2 weeks in phases 4 and 5 (follow the dotted green lines). As you can see below, both phases 4 and 5 correlate to above normal temperatures in the Midwest.
If you buy the MJO, you would expect above normal temperatures would continue right into mid-June. The operational EURO is in agreement showing these temperature departures days 1-8.
However, the cycle is broken in the 8-15 day period as it digs a deep trough into the northeast third of the nation. Personally, I think the model is a bit strong on the strength of the trough so I doubt it will cool as much as it shows across the Midwest. That said, I do expect the extreme heat we've been experiencing will break and temperatures will be inch closer to seasonal levels, at least for a few days.
Precipitation will be more of a factor in the 8-15 day period as a weak version of the "ring of fire" sets up across the central Midwest and Ohio Valley. It will be interesting to see how it all plays out.
Speaking of wet weather, after the scattered storms of Tuesday night, there will be some more of that in the region Wednesday. The remnants of Alberto will bring moisture and energy and a dry line advancing across Iowa should spark scattered storms. There's a threat for a few strong storms during the peak heating of the late afternoon or evening. The simulated radar of the 3k NAM shows this line of broken storms at 7:00pm.
After Wednesday, dry weather should hold the rest of the week with well above normal temperatures. June comes in the way May goes out. Roll weather...TS