CheeselandSkies

Multiple 0Z CAMs came in pretty hot for tomorrow across IA into S. WI. HRW-FV3 did as well, but it won't let me attach more. Still on the fence whether to try my luck with attempting to get a in Iowa again (after Keota last year, I've struck out three times there this year including April 26 and May 21), stay close to home and hope those discrete cells in WI on the 3KM verify, or stay *at* home and just watch the derecho roll in.

Edge of the polygon missed me by about a mile to the east.

Looks like watch in MN busted hard, strongest deep-layer shear remained behind the cold front with no sustained discrete development out ahead of it.

More recent runs of the GFS since my earlier post show a more robust low-level response; so could certainly get interesting on Thursday afternoon/evening.

SPC has Day 4/5 outlooks out for portions of the central-northern Plains to Midwest for Wednesday/Thursday. Global models show moisture returning north under a brisk northwest flow aloft; but not much in the way of a discernible surface response (deep SLP center, 850mb LLJ) for a focused threat. Will have to keep an eye on finer-scale mesoscale details for that, if it materializes.

Tonight is the 40th anniversary of the Barneveld, WI F5 of 1984. Still by far the most significant tornado since 1950 for the south-central part of the state. Although we get our share of severe weather in southern Wisconsin, we average a Plains/Dixie Alley caliber cyclic, intense-violent tornadic supercell about once every 10-15 years. To have one occur in the middle of the night was even more extraordinary. With every regional severe weather event in my memory; storms that form as supercells in Iowa have invariably either grown upscale or weakened by the time they reach here late at night. https://www.wmtv15news.com/2024/06/07/barnaveld-torando-40-years-later/

Hadn't seen a single one in Wisconsin...then went to the Brookfield Zoo with my cousin, his wife & 2 kids today.

Amazing how the haves and have-nots really lock in for a particular season across a relatively small region. I remember some recent springs where Madison was among the "have-nots" while nearby parts of northern IL, eastern IA or central WI got repeated rounds of precipitation and it sure was annoying.

Looks like another 2% MCV threat popped up for the WI/IL stateline region on the Day 2 outlook (marginal was way down in S MO on yesterday's Day 3 outlook). SPC is on top of this one so it probably won't do anything.

True; but that's one of the variables that can come into play with a long-tracker.

Latest HRRR and the abundance of sunshine in Illinois (despite overcast and steady rain here all morning and early afternoon) has me thinking "Not so fast" to my above, despite SPC's lack of even a 2% tornado contour in NE-NC IL/SE WI on the current outlook.

Well, my chase today is hosed. Had expected/hoped the OFB would end up closer to/merge with the synoptic warm front extending east from a low near Quincy through the Springfield, IL area and possibly east into west-central IN as per the forecast thinking from about 3 days ago. If I wanted to chase in the jungle, I'd stay in Wisconsin.

Yup...seems it's always in the close-in quick RI'ers that make the 130kt+ landfalls...Michael, Ida, Ian, etc. The 10-day basin crossing ACE machines like Ivan and Irma are less likely to be as intense at U.S. landfall (if they make one), even if multiple model runs and NHC advisories call for them to be. Hugo was actually something of an anomaly in that regard, remaining a 115-120kt (sources seem to vary) Cat. 4 at time of SC landfall.

That's the supercell composite; STP is 15.7 (cin)/11.8 (fix). Still very impressive numbers.

Oh, my goodness.

Reality must have set in for the HRRR as the 18-19Z runs have considerably backed off on the intensity/updraft helicity with the simulated cells that redevelop in the 22-00Z timeframe compared to the 15Z-17Z runs. Although, we are just now finally seeing some peeks of sunshine here.

Surprisingly, HRRR is rather insistent over multiple runs that we will get enough destabilization for a renewed severe threat this evening here in southern WI.

Looks like HRRR was right yesterday per SPC's 13Z update, ongoing complex and its cold pool will bollox afternoon supercell chances north of IL/WI line. NWS, and the mets at my work were way off predicting a sunny morning with storms holding off till mid/late afternoon.

Meanwhile, 18Z 3K NAM wants a Tuesday redux for Wisconsin, with UH tracks extending way north of where SPC has the slight.

I'll spark the kindling again. Tomorrow snuck up with a 5% contour right over southern Wisconsin, as well as far eastern Iowa and northern IL on the SWODY2 update. CAM solutions vary though; if the HRRR were to verify it looks like the 5% would end up being too far north, with WI mostly getting mid-morning MCS activity (which goes against the forecast from the NWS, which calls for morning sun followed by PM storms). Saturday the focus looks to be mainly west of the sub over in the Plains (Central/Western); but Sunday as mentioned in the general severe thread looks quite interesting and potentially significant; further east and south of the parts of the sub that were impacted on Tuesday although the NAM solution suggests northern IL and even southern WI could be in play again.

Did it do any clear-cut instances of textbook EF5 damage, though? It was unquestionably a violent tornado; but did it completely sweep away at least one anchor-bolted frame house? The problem I have is when tornadoes actually do this and are still rated EF4, such as Vilonia, AR April 2014.

The biggest excitement from my chase yesterday (didn't go far enough southwest to catch the tornadoes; thought storms would continue to produce further east at least most of the way across Iowa, SPC apparently did too; ended up on the storm which was tornado-warned near Corydon but it didn't look too impressive and the warning was dropped shortly after it got away from me over Eddyville) was when I was almost home. Multiple roads blocked/obstructed by downed power lines, trees (including a broken tree a block from my apartment building), and road construction signs/cones/barricades blown over and scattered in the travel lanes. Some neighborhoods were pitch-black with streetlights and even traffic lights out.

Thinking about targeting the Waterloo-Webster City area. Multiple HRRR runs and the 06Z 3K NAM suggest slightly better backing of the surface winds in north-central to northeast Iowa, with a relative maximum of 3CAPE/EHI and some discrete-ish cells making their way through there in the afternoon. Besides, along and north of the US-20 corridor is the best chase terrain in Iowa. Almost as flat and open as western Kansas. I got lucky that Keota was in a fairly open spot along Highway 92 but encountered issues with hills and trees while trying to chase it toward Wellman/Kalona.

CAM solutions have varied wildly from model to model and run to run since this event came into range. Still clear as mud how tomorrow might evolve.

***Edit: Added tomorrow (Monday) to the thread title as there is broad agreement among the CAMS in an MCV-driven setup along the IL/WI border region tomorrow (SPC added a small slight risk to the updated SWODY2 to account for this). These events are subtle with generally modest parameters depicted beyond Day 1, but if everything comes together just right they are capable of producing some prolific localized outbreaks in this area, such as 8/9/21 and 7/12/23.*** Guidance has been in good agreement for several days now that a compact, negatively tilted shortwave will impinge upon the IA/MN/WI/NW IL region on Tuesday with strong southwesterly flow at 500mb. At the surface, a low will deepen throughout the day with warm sector dewpoints well into the 60s, if not upper 60s by 00Z Wednesday. Basic pattern recognition suggests a very high ceiling and I'm frankly baffled why SPC's day 3 outlook does not at least include an all-hazards hatched area for wind potential if nothing else. That said, strictly in terms ofchase potential, there are several potential flies in the ointment as it seems there always are. One of them is, exactly how many rounds of storms initiate, where and when? For example, models have EXTREME levels of SRH along the warm front in southern Wisconsin, but suggest late-morning/early afternoon convection preventing that area from destabilizing. Other models suggest supercells might initiate in western Iowa, but might not be colocated with the best tornado parameters until they have begun to congeal into a QLCS (of course, this was also a concern with 3/31/23). Regardless, I think this day will end up a noteworthy regional severe weather event and worthy of its own thread.