Slow moving showers and thunderstorms for Montreal

With nearly 25mm of rain in the last 24 hours, a heavy rainfall warning has been issued for most of southern Quebec. A very moist airmass is in place, with slow moving showers and thunderstorms forecast to develop along a frontal boundary this evening and into the overnight period. Some flooding is possible. The front should drift to our east on Thursday, with precipitation diminishing.

Heavy Rainfall Warning posted for southern Quebec. Severe thunderstorm watch for eastern Ontario and west Quebec.

A stationary front over southern Quebec will become the focus for slow moving showers and thunderstorms this evening and into the overnight period. Showers and thunderstorms early Wednesday morning have moved well southeast of Montreal after close to 25mm of rain fell over the last 24 hours. Montreal is now in the warm sector, with temperatures in the middle 20s and dew points climbing into the upper teens.

The moist airmass will set the stage for very wet, slow moving showers and thunderstorms across the St. Lawrence Valley. Amounts in the 30 to 50mm range will be possible this evening and overnight, and may even reach 70mm locally in the slowest moving storms. The storms will moving be moving from north to south across southern Quebec.

The ground is quite saturated at this point, so there is a risk of some isolated flooding and ponding of water in places. Precipitation for the month of June is now above normal in Montreal, with 91.6 mm falling at Trudeau Airport to date, with even more in other parts of the city. 

Temperatures will be mild, with overnight lows in the upper teens and daytime highs Thursday in the lower 20s. The warm and humid airmass present across the US Midwest and Ontario will become fully established in Montreal on Friday into the upcoming weekend, with daytime highs in the upper 20s and lower 30s.