Thunderstorms

Flooding in Plaquemine Parrish, Louisiana from Lee. (NOLA.com)

7:00 am Update: Severe Thunderstorm Watch in effect for Montreal until 8pm this evening. A rare day long watch is in effect for thunderstorms. The potential exists for dangerous flood producing storms today. Warnings may be required at any time. So far the radar is clear in southern Quebec.

We have lots of weather to talk about this morning as moisture from Tropical Storm Lee and a cold front will interact to produce some heavy weather today. First it is another very humid and warm morning at 20C in Montreal. Temperatures yesterday were close to 30C, but with the thick and oppressive humidity it felt more like 40C. All that saturated air will help produce some big wet and windy thunderstorms today with the potential for flash flooding as up to 50mm could fall quickly. Once the front clears Montreal to our south tonight it will become nearly stationary and be the focus for more heavy rain from Lee. Moisture will feed into the Ohio Valley and upstate New York and eventually southern Quebec. Another 50mm through Tuesday is not out of the question. The heavy rain will result in flash flooding, especially in regions affected last week by Irene. For that reason a flash flood watch remains posted for New York and Vermont. A heavy rainfall warning is now in effect for areas southeast of Montreal including the Eastern Townships for up to 60mm of rain. It will be warm again today, near 30C, before the cold front drops temperatures into the low 20's for Monday. It will not dry out until mid-week.

Tropical Storm Lee this morning is moving very slowly onto the coast of Louisiana about 80 miles west of Morgan City. Lee has produced torrential rain and tornadoes in the last 48 hours with nearly 10 inches at both Pascagoula, Mississippi and metro New Orleans. Lee will continue to be a big rainmaker today across the south with moisture streaming into Tennessee, Ohio and the northeast US.

Severe weather occurred yesterday in southern Ontario. Strong thunderstorms produced wind gusts to 90km/h near Toronto along with damage. Heavy rain and hail were also reported.