As we grow closer to the big Indy 500 and Memorial Day weekend, forecast guidance continues to back away from what at one point looked like a rather unsettled weekend. Instead, it appears as if heat and humidity will grab the headlines. While we can’t rule out an isolated to widely scattered thunderstorm (best chances of that coming Sunday and Monday), most will remain rain and storm free this weekend. Even if you’re one of the “lucky ones” to get under a storm, it’ll pass quickly and sunshine will return.
While “tropical mischief” approaches the central Gulf Coast this weekend, an upper level ridge will dominate our weather. This supports the drier trend the models are now going to and also will help boost temperatures. We forecast highs at or around the 90° mark Saturday through Memorial Day- well above the average high of 78°.
The other big story, especially for those planning to attend the race, will be increasing humidity over the weekend. Forecast dew points will approach and exceed the 70° mark Sunday afternoon, providing a very tropical feel to the air.
Back here on the home front, a quiet start to our Monday will turn stormy at times this evening as the front nears. We think best coverage of showers and thunderstorms will come between 5p and 10p. There will be some winners and losers when it comes to rainfall amounts by midnight. Some can expect over an inch in the stronger storms while others may only see a tenth of an inch, or so. Something that must be taken into forecasts moving forward is the tendency of most model data (high resolution and global data alike) to “over forecast” rainfall amounts as of late. Also of note is for the potential of a couple of strong to severe storms to develop this evening. We always have to be wary of fronts draped across central Indiana as they’ve been known to help tornadic activity spin up. We’ve lost count of how many slight risk days with warm fronts nearby that turn busy… If you’re planning to be outdoors this evening, please have a means of receiving the latest watches and potential warnings that may be issued.
High pressure will build in for the midweek period and supply plentiful sunshine along with continued warmer than average conditions. Overnight lows will fall into the upper 50s (couple of degrees above average) with the drier air mass in place, but afternoon highs will continue to climb into the lower and middle 80s (around 10 degrees above average).
Longer term, thoughts are shifting towards the open to meteorological summer (where is this year going?!). The GFS ensemble suggests the overall warm pattern remains intact as we open a new season with widespread warmth expected through the first few days of the June.
By the time all is said and done late Monday night and early Tuesday, expect widespread rainfall totals between 0.50″ and 1″ with locally heavier amounts where the stronger storms track.
High pressure will build into the region through the midweek stretch and result in increasingly sunny and pleasant conditions. With a drier air mass in place, overnight lows will fall into the 50s through the midweek period.
Our attention will then shift to the potential of strong thunderstorms late Sunday. Higher resolution guidance suggests storms will begin to rumble into western Indiana late Sunday evening (around 9p to 10p) before tracking east into the overnight hours.
With a stalled front nearby, shower and thunderstorm chances will remain in our forecast into the middle of the week. While it won’t rain the entire time, unsettled conditions will remain into Wednesday before high pressure provides drier conditions Thursday and most of Friday.
Otherwise, look for considerable cloudiness and highs topping out in the lower 70s today.
As we look ahead to the end of May, there really aren’t any significant changes to the overall warmer than normal theme we’ve enjoyed so far this month. Longer range guidance off of the European ensemble continues to support broad scale upper ridging across the Mid West and Ohio Valley and a corresponding warmer than average regime. From a precipitation perspective, the next couple of weeks do look more active compared to the dry start to the month. Case in point, the balance of the upcoming week will be dominated by a stalled frontal boundary. While we’ll have to fine tune exactly where the front stalls, daily chances of showers and thunderstorms (scattered fashion) can be expected.
