This is going to be one of those days when it may be better to be indoors rather than out. Temps have only dropped to 71° this morning. Yesterday we reached 83° after a low of 62°. There is a fairly good chance of widespread rain today with some storms. The main concern will be the wind and torrential rainfall which could cause localized flooding. Tornado chances are 2% within 25 miles of any one location and hail chances are 5%. Heat and humidity will also be a concern, especially in the southern tiers of the state.
A shortwave trough over the upper MS Valley this morning will shift east across the Great Lakes vicinity through early evening before shifting into southern Ontario and Quebec. At the surface, a cold front will extend south/southwest from a low near James Bay into southeast MN and then western KS. Ahead of the front, mid 60s to low 70s F dewpoints will reside beneath modest midlevel lapse rates. This will contribute to the development of moderate to strong instability (2500-4500 J/kg MLCAPE). While stronger large-scale ascent will be focused across the Great Lakes, the southeastward-advancing cold front will provide focus for thunderstorm develop from WI/MI into IL/MO. Vertical shear will remain fairly modest across the entire region, though somewhat better over MI. Modest shear and steep low-level lapse rates will generally favor outflow dominant storms, and organized clusters will pose a threat for damaging gusts, with some sporadic marginally severe hail also possible.
We have a heat advisory going into effect at 1 pm lasting until 6 pm this evening for Allegan-Barry-Eaton-Ingham-Van Buren-Kalamazoo-Calhoun-Jackson Counties. With temps in the low 90s and dewpoints in the low to mid-70s, we will have feels like temps around 105°.
Thunderstorms will be on the increase today and some of them could be severe. Torrential downpours and frequent lightning will accompany the strongest storms. Local urban and poor drainage flooding could occur. Monitor conditions closely if you have outdoor plans today. It will be hot and increasingly muggy, especially south of a Holland to Lansing line.
Clusters of convection stretch from northern Michigan to southern Minnesota early this morning, where a low-level jet is transporting moisture underneath steep mid-level lapse rates. Outflow at the surface sinking south from near TVC and GRB will be one feature to watch this morning as it may serve to focus sporadic convective development in our area, and depending on how late in the day this denser pool of air can be maintained, could be a source of low-level vorticity for afternoon storms. Of note from the 00Z HREF is that most of the members (except the HRRR) failed to initiate the ongoing convection in Wisconsin and most do not capture the southward extent of the storms west of TVC. Some development north of I-96 cannot be ruled out this morning as impulses and waves ripple through an atmosphere that is increasingly unstable in the midlevels. However there is better agreement among models for broken lines or clusters of storms developing this afternoon across much of our area. If the surface temperature forecast pans out, moderate to strong MLCAPE 2000 to 3000 J/kg will be present. Modest to moderate west-southwesterly 0-3 and 0-6 km shear would support some locally severe wind gusts especially in any north-south oriented line segments. An incidental tornado or cell with large hail cannot be ruled out. Heavy rainfall rates may also lead to flooding if storms repeat over the same area. The heat advisory today south of a Holland to Lansing line remains unchanged as it still is the more likely zone for the heat index to reach 100, despite the uncertainty of how far south storm outflow and clouds will inhibit deep boundary layer mixing. Temperatures will be less hot behind the cold front Thursday into Friday. Another plume of warmer air advecting from the western US heat dome will wash over the area over the weekend. Ensembles of the ECMWF point to a chance of storms on Sunday with the next upper level trough.