What has changed

No major changes to the forecast package are indicated.

Messages

Scattered to numerous showers and a few thunderstorms through this evening, mainly north of US-422, with very low severe weather potential.

Mostly dry through Wednesday. Precipitation chances increase Thursday, with some low-end potential for severe weather depending on future model trends.

Discussion

KEY MESSAGE 1. Upper level low pressure continues to spin over far southern Ontario, with associated troughing in place over the eastern Great Lakes and the Upper Ohio Valley. Two main vorticity maxima rotate through the flow into tonight - one closer to the Lake Erie shoreline this afternoon and a more vigorous one dropping across our forecast area this evening. These will be responsible for continuing the chances for scattered to numerous, but brief, showers and localized thunderstorms through 06Z or so tonight. Coverage appears best with the second wave, with most activity north of US-422. Still, thunderstorms will become a bit less likely with that wave with daily stabilization.

Chances of strong to severe thunderstorms this afternoon/evening remain quite low overall. While surface-based storm energy may peak in the 1000-1200 J/kg range this afternoon, particularly north of I-80, drier air above 700mb should limit updraft depth, and 0-6km shear of less than 30 knots will be a detriment to storm organization. Along with downdraft storm energy values of 500 J/kg or less, this suggests that the damaging wind threat is very low. Hail may be observed with a few of the more vigorous cells, but the above parameters point to diameters remaining below severe limits.

Precipitation coverage drops off after 06Z with the departure of the second shortwave, but a few isolated showers may continue north of I-80 with continued northwest flow off of Lake Erie.

KEY MESSAGE 2. Lingering cool advection within northwest flow results in high temperatures around 10 degrees below the daily average Monday while high pressure supports dry weather (save for low probability showers north of I-80).

The upper low lifts toward Quebec by Tuesday, while surface high pressure overspreads the region. This continues dry weather through Wednesday, while the rising 500mb heights point to temperatures rising back to close to seasonable levels.

The next trough is still pegged by ensembles to arrive Thursday. Timing issues that far out mean that the hazard potential is difficult to ascertain currently. Long- range machine-learning guidance does show a slight uptick in severe weather potential, but this risk will need more time and model cycles to be properly evaluated.