HOT, THREATS OF STORMS

terryswails1
5 hours ago
4 min read

Tuesday was another summery day spent in the 80s. Most locations ended up in the range of 81-85, well above the norms that are currently close to 70. In Cedar Rapids, 5 of the past 7 days have been 80 or higher, a nice change from April where only 1 day hit 80, the 28th. We did get off to a fast start, though, with the first 80 of the year arriving March 14th.

In the graphic below on the right, you can see the earliest 80 degree high in Cedar Rapids occurred March 3rd, 2024. That makes this year's 81 on the 14th, the second earliest 80 degree high. Number 1 and 2 back to back, we are on a roll! The average date of the first 80 is April 21st, and the latest Cedar Rapids has gone to reach the 80 degree threshold is June 3rd, 1953

Going forward, there is high confidence the region will get at least 3 more days in the 80s before a break to cooler weather occurs. There's also a good chance the central and south see their first 90 degree day of the year Thursday. That's well ahead of normal, too, with most spots not hitting 90 until June 9 in the south and June 19th in the north.

Before we get to Thursday, with its heat and storm potential, Wednesday looks to be a repeat of Tuesday, only 2-3 degrees warmer. That should get most areas into the range of 84-88. There's also enough instability for a few stray showers and storms later in the day. These look to be hit-and-miss and low in coverage. Most areas will stay dry. However, as happened yesterday, some isolated spots could get a good downpour. The Doppler rain estimate from Tuesday shows coverage was less than 20 percent across my area, with amounts light. But don't tell that to the folks in Hillsdale northeast of the Quad Cities, where up to 8/10ths of an inch fell in a highly localized cell.

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INTO THE COOKER THURSDAY...

That leads us into a complicated set of circumstances for storm potential late Wednesday night and then again Thursday afternoon. The Wednesday night set-up has two components to it. First, a complex of storms is set to develop to the west in Kansas and Nebraska Wednesday evening. As it matures, if it can hold together, it may ride a CAPE boundary (instability associated with a warm front) into my western counties late at night or early Thursday. Kind of a long shot.

Additionally, the warm front advancing into Iowa brings its own forcing and a low level jet capable of producing a wing of elevated storms to its north through warm advection. This would be after midnight and most likely to the north of I-80. This has a better chance but is still far from certain.

Both of these scenarios are currently not strongly supported and thus low confidence. It could be most areas avoid any storms all together. The timing is not optimal, that's for sure.

Thursday the table is set for some sizzling temperatures, especially if the EURO is correct and that's the way I'm leaning. With the warm front north of the area, very warm air aloft with 850 temps +24 and 925 temps of +31 surge in the south. This creates a sizable CAP that thwarts thunderstorms and allows robust heating through the afternoon. For days now, the EURO has been advertising highs of 90 north to 98 south. It still is.

Records for May 15th look like this. I will be surprised if at least Burlington and Moline do not break records.

Cedar Rapids.....94, 1941

Burlington..........93, 1944

Moline (QCA).....91, 1941

Dubuque............90, 1944

Thursday starts out quite humid with dew points reaching 65 to 70. However, a dry line punches through in the afternoon, dropping dew points into the upper 40s to lower 50s in the afternoon. The HRRR clearly shows the dry line as it blasts into central Illinois at 4:00PM. Once the dry line is through, that's it for any storms, as the convergence it creates departs and moisture is depleted.

So basically, you have a huge CAP to overcome and a front arriving at a time that makes it extremely difficult to break. Far NW Illinois may be in play for a short time? I still think the majority of my area avoids the severe threat which could materialize in parts of Wisconsin and Illinois. It's a good thing too as shear and instability is quite significant further east where tornadoes are possible. With all this potential for storms Wednesday night and Thursday, my area looks to be in the right place at the right time to avoid them. Heat looks to be our biggest issue locally.

The one bad thing about missing the storms is we could really use some rain. While we may see a few stray showers in the north Friday, nothing beneficial is likely until next Monday night or Tuesday. That system has some potential as a rainmaker. Until then, we turn noticeably cooler, especially beyond Friday, with highs in the north struggling to get out of the low to mid 60s Saturday and Sunday. South of I-80, 70 to 75 still looks attainable, but it appears blustery.

Here's what guidance is indicating for rain through Thursday evening. That's got the look of a nothingburger!

The EURO