IF AT FIRST YOU DON'T SUCCEED, TRY TRY AGAIN...
If it weren't for bad luck, we'd have no luck at all. There are places in my area that have to be thinking that after missing out on several opportunities to pick up beneficial rains over the past few days. Not to say some places didn't get some gully washers, but again the majority of areas that needed rain the most didn't fare well. Below you can see where rain fell Sunday night and early Monday. The HWY 20 corridor from near Waterloo to Dubuque and points east did very well.
Over the past 7 days, much of the area from HWY 20 north into Minnesota and Wisconsin picked up 1-4 inches with some areas getting far more than that. Notice the black hole effect encompassing my area. Nice rains in every direction but here. That's just awful luck.
Well, as the saying goes, if at first you don't succeed try, try again. So while there are no guarantees it will happen in any location, we do have additional opportunities for rain in the next 2-3 days before cooler and drier air invades the region. The next chance comes Tuesday. Much of the day should be dry with a stout CAP in place. That allows temperatures to reach the low 90s in many areas (perhaps mid 90s in spots) with dew points in the mid 70s. That produces heat index values of 100-105+ and advisories are out for the resulting steam throughout the region.
The heat and humidity will also produce extreme instability which is measured in CAPE (convective available potential energy). The EURO and the convective allowing models are showing levels near 5,000 j/kg+. That's a powder keg and high octane fuel for any storm that can go up in that environment.
Most models do show storms forming at some point late Tuesday or Tuesday evening as a mid-level disturbance punches the instability. How long the cap holds ( assuming it breaks) is the big question that remains on the table. This will have big implications on where storms develop and the degree of intensity. The 3k NAM shows two storm clusters Tuesday evening, one over the north and the other over the far south. I'm not that focused on where storms form as models generally struggle at this distance to resolve all the mesoscale details. However, the trend for storms somewhere in my area is strong but contingent on breaking the cap. We'll know much more as the day unfolds but at least for now chances look best across the north.
The Storm Prediction Center already has an enhanced risk in place for for parts of the region. The greatest concern is for damaging winds on the southern flank of the mid level speed max. Other modes of severe weather are also in play but strong winds are the biggest concern.
Wednesday, whatever is left of Tuesday nights storms is gone early in the day. At that point a front is expected to lay out across the area into Thursday night. It will provide the focus for additional storms which again have the potential to be strong with localized downpours. Determining the timing, placement, and intensity is low confidence as mesoscale details from previous bouts of convection are impossible to predict. Day by day adjustments will be necessary.
One thing you can count on is very warm and humid conditions continuing through Thursday. Heat advisories are likely in many parts of the area through that period with heat index values of 100 to 105 degrees. By the coming weekend cooler and drier air is established ending this round of heat and humidity.
By the way, today is the anniversary of last years super Derecho, the costliest thunderstorm in U.S. history. The NWS has produced a nice account of the event which you can read by clicking on this link. The August 10th, 2020 Derecho
With that I will call it a post. Here's hoping that those of you who need rain will get your fair share in the next 48 hours. Roll weather...TS
