6/27/10 FCST: IL/WI/MI/IN

[Robert Dewey]

NAM is trending stronger with the shortwave on Sunday... Becoming more similar to the previous runs of the GFS. Hodographs are pretty straight between 18-21z SUN across MI. Decent instability (CAPE 2500-3000j/kg), good wind fields, and shortwave energy sweeping across the area should lead to the development of severe thunderstorms, most likely in the form of clusters... or even a squall line as has been the case with the past few systems. Actually, this shortwave appears to be stronger than the one which produced the derecho / intense squall line on 6/23 as the sfc low deepens to 992-994MB over the Upper Peninsula of MI / Canada at 0z MON.

 

[John Vandehei]

I'm not feeling very confident about Michigan right now. As I type this, storms are rolling across much of Lower Michigan, except for parts south of I-94. I suspect these clouds will hang around long enough to prevent a good deal of destabilization from the sun. South of I-94, there is a better chance for the sun to get in and destabilize things. However, the next batch of storms, which currently extends from SW Wisconsin into Missouri will likely get here early in the afternoon. I'm not sure that will give enough time for things to destabilize much, at least in southern Michigan. I think things are looking better for Indiana. They are getting more sun and they will have more time to heat up before that southern batch of storms gets in there.

 

[John Vandehei]

We're getting some sunshine in far southern Michigan. Line of storms is just starting to move over Lake Michigan. SPC mesoanalysis shows meager CAPEs under 1000J/Kg in the SW corner of the state, with LI's between 3 to 6. Normally, I wouldn't get especially excited about that. However, most recent visible satellite shows what appears to be an outflow boundary leftover from this morning's batch of storms. This boundary is roughly aligned along I-94. I'm kind of curious to see what's going to happen when the line of storms to the west interacts with this boundary.

 

[Robert Dewey]

I honestly think this setup is better than 6/23 (for MI)... which was a laughable MDT risk for areas north of Ann Arbor. Temps right behind the warm front are already in the mid 80's, with Tds in the low 70's... providing sfc-based CAPE of 3500j/kg. This is combined with effective shear on the order of 55-60knts, which should continue the development of thunderstorms across northern IN and southern MI.

12z HRRR shows upscale development over SW MI between 18-19z, continuing eastward, as good sfc-based instability advects northeastward. HRRR nailed the 6/23 event, so we'll see how it verifies.