05/06/04 FCST: GREAT LAKES

[Robert Dewey]

Latest 18Z ETA (4/4 run) looks interesting for the Great Lakes on Thursday afternoon. Good instability combined with good low level helicities, may create a good severe weather threat. ETA indicates convective initiation around 18-21Z THU across this area, so it should be during prime heating...Overall, looks like a decent threat for severe weather, with the potential for some supercells...Unlike the last couple "events" across the Great Lakes, maybe this one will actually happen...

Robert

 

[Dan Cook]

LOT's HWO mentions large hail and damaging winds possible for Thursday. DVN's mentions the same thing but tornadoes are possible.

http://kamala.cod.edu/il/latest.flus43.KDVN.html

 

[Robert Dewey]

Yeah, looking at the latest 00Z ETA...Im thinking there is a decent threat for severe weather from eastern IA ENE into lower MI. Instability looks pretty good with CAPE in threat region of >2000J/KG, also of interest are the 0-3km helicities in excess of 300m2/s2 over a rather large area overlapping instability...So if the ETA turns out to be right, I wouldn't doubt supercells and tornadoes in the least bit...With bow echos possible (bow echo and HP supercell environments overlap quite a bit). Event is still a good 42-48hrs away, so still some time for change...

Robert

 

[Dan Cook]

I really hope this pans out as thrusday might be my first chase opportunity.

 

[Tim Stoecklein]

Yep, this might be our best chance yet. It looks like there is a minor discrepancy on where the front will be tomorrow afternoon, but the rest seems like it might be in place. It was trying last evening, got some lightning pictures, but it has wet my appetite for the next two days. Now........where to go, hmmmm.

Tim

 

[Todd Sprinkmann]

Andrew,

Call me a bit cynical, but I wonder how much the recent, unexpected tornadoes (Utica, IL) have to do with the heightened awareness on ILX's part. The forecast discussions I've been reading seem to point more toward Friday as the better severe threat. I imagine someone will be opening up a thread for Friday (5/7) very soon.

Here's hoping that whatever happens, it stays the heck away from towns.

 

[rdale]

Feeling pretty good about an active severe weather day tomorrow... Looks like the cold front will be a little closer than earlier anticipated (bad news for Friday's forecast) which will enhance the instability / moisture pooling across the southern half of Mich.

The atmosphere will be capped early in the day which should allow plenty of heating through afternoon. The Eta has temps near 80 with dew points in the mid-upper 60's. That gives us CAPEs > 3000 and LI to -10. Ouch. Even tweaking those numbers down a bit still leaves CAPEs of 2000+.

The jet axis is over northern MI but we still have pretty healthy winds aloft. Hail parameters are very good. The only negative I see is that low-level winds (up to 850mb) are fairly weak, but I don't see that being enough of an issue to prevent winds & hail from being in the area tomorrow -- just keeping tor's out of the mix.

After that the front moves well to our south - knocking Friday's temps into the upper-50's or lower 60's instead of approaching 80 once again!

 

[David Draun]

NIU's Gilbert Sebenste only mentions dewpoints rising to mid or upper 50's tomorrow. Couldn't that make storms high-based? Also, that cold front is expected to be already south of Chicago by early afternoon Thurs. I would expect that to end storms quickly in my area unless there is overrunning moisture from the south.

 

[rdale]

"NIU's Gilbert Sebenste only mentions dewpoints rising to mid or upper 50's tomorrow. Couldn't that make storms high-based?"

You determine the 'high-vs-surfaced' based question from soundings, not surface dew points.

- Rob

 

[David Draun]

I meant high-based, not elevated. To my understanding, a thunderstorm updraft can be rooted at the surface, but have a high base. Am I correct?

It looks like maximum convergence right through my area by 4:00 pm. That front will be just to the north. It could get interesting tomorrow afternoon. I'll be waiting. I haven't seen a good storm since 03/01/04 when that low-topped CG producing hailer came through.

 

[rdale]

"To my understanding, a thunderstorm updraft can be rooted at the surface, but have a high base. Am I correct? "

Yes, but you still need to look at the sounding parameters to determine the cloud base.

 

[Tim Stoecklein]

I already told them I might be sick tomorrow and Friday...I...feel...a cough...coming on. Is it looking to be farther along tomorrow afternoon than originally thought?

 

[Robert Dewey]

Well, looking at the latest 12Z ETA, things are looking pretty good...But as Rob Dale mentioned, tornado threat is not to high, but that could change (wishcasting). I am stuck at school until 3PM tomorrow, but I believe I won't have too far to travel, since I am already in southern lower MI...Still looking forward to an active day though!

Robert

 

[Robert Dewey]

Just reviewed the latest 18Z ETA, and I am staying right here in MI. CAPE looks like it will be in the 2500-3000j/kg range, with excellent wind fields and shear to go along with it. ETA initiates convection across lower MI between 18-21Z (closer to 21Z), and then slides it southeastward. I am thinking large hail and damaging winds will be the main threats, but I could see a few tornadoes come out of this situation as well...

Overall, the threat for severe weather looks pretty high...and as the NWS GRR stated, it has the potential to be the best severe weather event this season (which isn't saying much though)...

Robert

 

[Craig Maire II]

Iowa

My area (eastern Iowa) looks pretty decent tomorrow with SPC increasing potential shear from 30 to 40knots to 50 to 60knots now! Will be plenty of moisture/instability will just have to hope the cap breaks. Cap could hold and I will see nothing or more likely cap will break and tomorrow at this time I could be under tornado warnings!! Atleast the weather pattern has shifted to a "stormier) pattern