Yesterday was as near to perfection as we get in Michigan with low dewpoints and comfortable temps. Our high in Otsego was 77° after a morning low of 60°. Most places will remain dry today with plenty of sunshine, but a few showers and perhaps a thunderstorm cannot be ruled out this afternoon.
Our Hazardous Weather Outlook
Isolated thunderstorms are expected over parts of Lower Michigan this afternoon and evening, mainly along and east of US-131. Any storms that develop will move toward the southwest at 10-15 mph. Severe thunderstorms are not expected.
-- Mainly dry through Fri -- A broad mid/upper-level cutoff low will remain situated east of the region through Wed, reinforced by modest height falls accompanying New England coastal cyclogenesis. This cutoff low is associated with moderately cold temps aloft (e.g., -14 to -12C at 500 mb) over much of Lower Michigan. RAP forecast soundings at LAN suggest that boundary-layer heating should yield modest instability (MLCAPE of 400-800 J/kg) over the eastern CWA by late afternoon. Expect cumulus development inland today as convective temps (in the mid 70s F) are reached, with a few vigorous cumulus congestus yielding widely scattered showers or perhaps isolated TS. This expectation is supported by latest CAM guidance, indicating that showers should initiate over the interior of Lower Michigan today. This activity will likely drift SW--approximately with the 0-6 km mean flow--and should make inroads into the CWA before dissipating this evening. However, most locations will remain dry today. Diurnal showers should similarly develop on Wed afternoon as the NE CONUS cutoff low remains in place and boundary-layer moisture persists over the forecast area. -- Chances of rain this weekend -- A vigorous shortwave impulse / vort max evident in water-vapor imagery over BC this morning will crest the western ridge today and tonight. This feature will then dig southeastward on Wed/Thu, facilitating the gradual ejection of the NE CONUS cutoff low. Meanwhile, the mean longwave trough will undergo discontinuous retrogression, becoming reestablished west of its original longitude via the height falls accompanying the digging shortwave trough. This shortwave may subsequently evolve into a closed low on Fri. EPS and GEFS means differ on the details/timing of this process, and each has exhibited recent run-to-run adjustments. Nevertheless, some agreement exists suggesting that a modest surface low will consolidate over the Upper Mississippi Valley on Thu night, then slowly meander southeastward through Sun. PW will increase with the approach of this system, nearing 1.4 inches (~80th percentile of climo distribution) by Sat night. Some showers may arrive as early as Fri afternoon/evening across the northern counties, but greatest coverage of precip is currently expected for the Sat-Sun timeframe as the deep-layer low traverses the region. Still, precip timing/placement/amounts are fairly uncertain at this time, owing to the aforementioned ensemble uncertainty in the evolution of the digging shortwave trough/low.