Heavy rainfall warning issued for southern Quebec

Mount Royal and the Montreal skyline during a spectacular October sunrise on Wednesday morning. The sun is gone for a few days, with heavy rain and gusty winds arriving just in time for Halloween. (Valley Weather Photo)

Widespread heavy rainfall warnings have been issued for southern Quebec and eastern Ontario, with 40-70mm forecast. Deepening low pressure will move from the Ohio Valley into southern New England today, while a secondary low develops along the middle Atlantic coast. That low will draw in some moisture form hurricane Melissa as it travels between Bermuda and the offshore waters of Atlantic Canada. The heavy rain may cause some minor flooding issues, especially where falling leaves are blocking sewers and gutters.

Rainfall from the first low has already arrived in Montreal Thursday morning, and should fall throughout most of the day. Overnight into Friday morning, additional moisture will arrive from the southeast, with localized heavy rain possible. Winds will increase from the northeast Thursday 20-40km/h, backing to the northwest Friday afternoon, and increasing to 30-50km/h. The cool, damp and breezy weather will make for a rather challenging Halloween in Montreal. I still think that the weather may break for Trick or Treating, with more showery conditions opposed to heavy rain.

Regardless of the precipitation falling, the weather will dark, windy and downright spooky. Temperatures will be chilly, in the 5C to 9C (41F to 49F) range throughout the forecast period and into the weekend. There may even be a few snowflakes on Halloween night as much cooler air moves in behind the departing low. They will most likely be confined to the higher elevations, but I would not be surprised to see a flake or two around Montreal into Saturday morning.

Skies will finally clear by Sunday as high pressure settles into the region.