7/18/10 FCST: MI, IN, IL, WI, MO, IA

[Zachary Lassiter]

note - this is my first forecast on here, so be gentle when raping it

Well The 00Z GFS shows a very unstable CAPE and a lot of lift around Southern Michigan northern IN tomorrow afternoon. I'm think target area of Northern Indiana or Northern IL

 

[John Vandehei]

I'm certainly encouraged with what I see for lower Michigan. The southern half of Lower Michigan escaped the convection that's ongoing across the northern half. Although mostly cloudy right now, it's higher thin clouds that I expect to clear out later this morning. That should give the area plenty of time to destabilize before the front comes through.

 

[Ben Holcomb]

NAM is showing 3800 CAPE near Grand Rapids today at 21Z. Pretty much unidirectional windfields south of M-55, but still excited about the prospect of a 'tree eating' squall line today. Just not liking how socked in clouds we are this morning. Hopefully some of them can burn off in the next few hours.

 

[L.B. LaForce]

Once again, Here is another classic MI setup! lovely veered winds :-/ I think the better tornado potential will be farther north where helicity is greater, and you'll want to hug that surface low too.

Clouds need to clear out this morning too-which always seems to be the case with MI weather LOL

 

[John Vandehei]

It figures; after my initial post, it appears that some of the leftover showers from yesterday's activity currently occurring over Lower Michigan are starting to increase in coverage and are also spreading southward. Not sure of the reason for this, although I noted on the models that the strongest upper level winds are progged to occur over the region during mid-day, with best instability to arrive late in the afternoon. I still believe most of this should clear out by noon, at least south of I-96.

 

[Robert Dewey]

There's some good clearing in southern WI working its way east pretty quickly, and the cloud cover is being eroded from the south as well. HRRR doesn't have a good handle on the activity across lower MI at the moment, either.

If we had seen full sun this morning, I'd be inclined to say that the complex between Milwaukee, WI and Green Bay, WI would be the best show of the day (at least for MI). There's 50-60knts of effective shear and 200-600m2/s2 of effective SRH trailing along it. However, instability downstream is weak; <500j/kg with significant CIN.

Seeing the latest VIS (1445z), it does appear that some clearing is possible. The question is whether this will be enough to boost temperatures / associated instability before the complex pushes in.

 

[Bob Hartig]

Frankly, this looks better than I expected. Latest HRRR shows southerly sfc winds at 18Z. Clearing and cloud burnoff are moving in across the lake and from the south, as Rob has mentioned. While I haven't looked, I'm assuming that northwesterly flow is still a go at 500 mb. And it doesn't hurt my feelings that KGRR has mentioned the possibility of tornadoes as the triple point moves through. Courage, droogs, this could work. I'm going to have my Sunday visit with me mum earlier than usual today so I can respond to changing conditions this afternoon. It'll be interesting to see how this all plays out.

 

[John Vandehei]

If we had seen full sun this morning, I'd be inclined to say that the complex between Milwaukee, WI and Green Bay, WI would be the best show of the day (at least for MI). There's 50-60knts of effective shear and 200-600m2/s2 of effective SRH trailing along it. However, instability downstream is weak; <500j/kg with significant CIN.

Considering that cluster of storms over Lake Michigan is following right behind the overcast and showers over Lower Michigan, I'm surprised at how robust is is. I agree with Robert that those storms may not be the best show. However, if you draw a line back from the tail of that cluster into SE WI, it appears that some new activity may be developing (as noted on VIS Sat.). Skies are clearing nicely along and south of I-94 in Michigan. Anything that develops in SE WI will take a couple of hours to get into Michigan, giving more time for things to destabilize around here. Already, a ridge of LI's near -4 is poking into far SW Lower Michigan as per SPC mesoanlysis. Also, this late in the season, water temperatures over Lake Michigan should be high enough not to be too much of a hinderance for any storms crossing the lake. If a few discrete storms can form and/or move into Lower Michigan, I think somewhere near I-94 or even up near the Lansing area could be good for tornadoes.

 

[Robert Dewey]

13z HRRR initiates convection near GRR around 21z. It also shows 2000-2500j/kg overspreading the area. Best low-level helicity is generally found from Muskegon, MI to Port Huron, MI and northward. I'd would say areas along that line have the best shot at tornado potential.

 

[nickgrillo]

Yeah, I agree. Even though I'm not thinking there's much tornadic potential today -- given the marginal deep-layer shear profiles across much of the warm sector -- boundary layer SRH / vorticity will be maximized invof the warm front. Therefore, the northern halves of the DTX and GRR CWA's will have the greatest potential for an isolated tornado. Now, surface-based instability is stronger further south where some diabatic heating has increased sb/ml parcel CAPE. Deep-layer unidirectional shear and generally weak flow aloft will be more supportive of linear convective bands closer to I-94, as opposed to further north where kinematic profiles are slightly more supportive of discrete / supercellular convection.

The line pushing into westcentral MI looks pretty nice... http://www.benholcomb.com/live .

13z HRRR initiates convection near GRR around 21z. It also shows 2000-2500j/kg overspreading the area. Best low-level helicity is generally found from Muskegon, MI to Port Huron, MI and northward. I'd would say areas along that line have the best shot at tornado potential.

 

[Robert Dewey]

Regardless of the cloud cover, we've managed to get up to around 85F here in Rochester... which isn't bad. Hopefully we can advect in more low level moisture and bump MLCAPEs up a bit. I think the line over Lake MI will get better organized once it reaches land. Water temps aren't too cold thankfully, but better instability exists over land where temps are 10-12F warmer.

 

[Robert Dewey]

I have to say, I'm not impressed at the moment. Storms are really struggling as they push east. The intense bow echo that produced 80MPH winds across extreme SW MI is nothing more than scattered showers and a few rumbles of thunder at the moment... and the cell just SE of Grand Rapids has really started to bite the dust. I'm guessing they're either outrunning the best instability, or there's a bit of a cap.

SPC mesoanalysis shows decent shear, but I'm not impressed with directional shear at the moment. DTX VAD is pretty much unidirectional, limiting any tornado threat.

 

[James Gustina]

It's been the same further south in the SLGT as well. It was clear this morning but a lot of clutter started around noon then turned into a thin cirrus sheet. Some showers are about to move in from down the river. At this point, i'm gonna guess a nighttime cluster of showers with some weak thunderstorms w/gusty winds. Looks like anyone who dared go into Northern Michigan might get lucky