:: Soggy Weekend
75 didn't happen yesterday...oh well. What gets me is that we missed it by ONE DEGREE. Yesterday was nice, all things considered. Today...as predicted...not so nice. The rain was desparately needed, but it isn't going to leave anytime soon.
As I discussed last night, the trough did get to that line from Devils Lake to Huron, but not until about 7AM. So, I was a little too eager...the bad news is that my prediction of the stall out did occur. The trough is parked about Watertown, SD now, with the lowest central pressure somewhere between Huron and Watertown. This is also where the jet noses in per earlier models, and convection is greatest here as a result. Sure enough, at the time there are some severe thunderstorm echos on the ABR WSR-88D radar:
I drew in the center of the low and the associated trough (brown dashed line), and an arrow pointing at the area of storms. These cells may be carrying small hail, and have some strong winds associated with them. But as you can see, the rest of the precip is really tame on the convective side. But the atmosphere is plumb with moisture. The system will continue to tap moisture from two sources: Pacific moisture carried from a southern low that moved from the desert SW into the Texas panhandle. This system will start to tap Gulf moisture, and ride up a strong southerly flow in the mid-level winds. The Texan low will basically "merge" with the Dakotan low and park over Iowa for the weekend.
The parking of the system is typical of a "cutoff low" - and this was a feature predicted to visit earlier in the week, but it never transpired. Cutoff lows or "closed" lows do not get carried along with the upper winds, and here again, the models have predicted the jet stream to "split" around our rainmaker, leaving it parked over the IA cornfields. The main "polar jet" is going to hang out in nothern Manitoba, and a southern branch or "sub tropic" jet will continue to stream along the southern US. (This is the same jet that has been the "conveyor belt" for southern storms this spring - and it should continue through early next week.)
Longer range models show the low will spin out of IA by late Tuesday (ugh)...this means we are expecting rain showers, and maybe a few rumbles of thunder here and there through Monday for sure. Weekend rain totals could push two inches, with some forecasters thinking Sunday will see the most rain. I have not studied the precip "amount" potentials, but I can confidently say that we have a 100% chance of rain thru the weekend.