THROTTLING DOWN...

Summer officially arrived Friday, and it took no time to introduce itself. Now after three consecutive days of wickedly hot conditions, (heat index values up to 105!), a kinder, gentler brand of heat is anticipated that will also have the additional capacity of producing thunderstorms. The ring of fire is setting up shop.

Before I get into it, I did want to mention that there was something unique about the heat we experienced over the weekend. Specifically, that was the rare combination of heat, humidity, and strong winds. Typically, those three ingredients don't happen simultaneously as strong winds tend to promote lower atmosphere mixing, which decreases afternoon humidity levels as drier air aloft is forced down to the surface. Additionally, the strong pressure gradient that powers winds are less frequent during the summer months.

According to data from the Iowa Mesonet, the combination of high temperatures, high dew points, and strong winds Saturday had never occurred (simultaneously) at all of the reporting stations below. To clarify, there have been observations with higher temperatures, dew points, and wind speeds, but none that occurred at the same time that were as extreme. For example, take Dubuque, below. Since the advent of modern records in 1951, never was there a temperature as warm as 91, that had a dew point as high as 76, and a wind that was as strong as 24 kts. (27.6 mph). Seriously, that wind was a blow torch!

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IF IT AIN'T ONE THING, It's ANOTHER...

So much for the past. The focus now becomes thunderstorms, with the eastern ridge weakening and sagging slightly southeast. You can see the heat dome lose some of its intensity and definition in the 500mb jet stream depiction through Saturday. It's not a dramatic change, but just enough to allow the heat and its storm thwarting CAP to at least be breached NW of the Quad Cities.

The process is already underway, as you can see in the satellite. The western fringe of the heat dome Monday evening cuts from Cedar Rapids to about Dubuque. Look at the clouds and storms in the ring of fire that arcs western Oklahoma and eastern Iowa to Wisconsin

The tough challenge going forward is where does the thermal boundary set up the remainder of the week. Near and northwest of it, it remains sticky, but thunderstorms will likely produce heavy rains and rain cooled air. To the southeast, the CAP could still be in play, limiting thunderstorm coverage and allowing very warm and humid conditions to continue. It's nearly impossible to draw the line where that transition will occur, but the EURO shows it right on the Quad Cities. Here's what it depicts for highs the next 3 days. Quite a difference from the NW to the southeast.

Tuesday (82 in Dubuque to 94 in Burlington).

Wednesday: (84 in Dubuque to 98 in Burlington).

Thursday (88 in Dubuque to 98 Quad Cities and 99 Burlington).

Needless to say, the pattern is not going to budge much the remainder of the week with near daily chances of rain, especially from the Quad Cities northwest. The air mass will be loaded with moisture, which means when and where it rains, heavy downpours are likely. Both Nick and I have seen the heat and ensuing rains coming for more than a week, so this should come as no surprise. This is a classic ring of fire pattern that is climatologically favored in late June.

Heavy rains upstream recently, along with what's fallen Monday (I've seen Doppler estimates Monday night of 4–5 inches near and south of Dyersville), combined with what's to come the next few days, will no doubt have impacts on area rivers in eastern Iowa. The Wapsi, Cedar, and Iowa will likely see significant increases with at least minor flooding anticipated by the NWS. The Mississippi will also see a spike that could be evident come the 4th of July.

The National blend of models through Saturday morning shows this for rain totals

The EURO ensembles have this for the same period.

And here's the GFS

Through July 8th, the EURO ensembles indicate amounts like this

The GFS operational goes wild with a huge bullseye of 6-10 inch rains from NE Iowa into SE Minnesota and much of Wisconsin. There is at least moderate confidence that the next 2 weeks could be quite wet in parts of the mid and upper Mississippi River Valley.

The most likely area for rain in my area Tuesday is in the afternoon and especially in my Iowa counties near and west of the Mississippi. As I mentioned earlier, temperature the next few days should range from the low to mid 80s NW of the Quad Cities to the low (to perhaps mid 90s) from there southeast.

If it isn't the heat, it will be the storms and rain. As the saying goes, if it's not one thing, it's another. Roll weather...TS.