Unsettled cold wet start to May in Montreal

A late season winter storm dumped 6 to 12 inches of snow on portions of Colorado including metro Denver. (Photo A. Comeau)

The wet weather of April will sadly continue into the start of May across southern Quebec. Flood concerns are easing for the time being, but are highly dependent on the upcoming rainy weather. To date 150.8mm of precipitation has fallen in Montreal for the month of April. With just a few hours left in the month, and rain to our west, we may nudge into second place or perhaps even first, 158.8mm set in 2005. Unfortunately we are looking at very cool temperatures this Sunday morning, only 4C (39F) currently. With increasing northeast winds and cloud cover, expect a very cool day in Montreal, perhaps 6C (43F) for a high. Clouds and rain along with cool weather will prevail for most of this upcoming week.

A powerful wedge tornado shown on the ground near Canton, Texas Saturday evening. (Weather Nation Photo)

Fire and Ice
A strengthening storm system located over the central US, is forecast to move into the Great Lakes on Monday. A warm front ahead of the storm, will produce rain in southern Ontario and Quebec over the next 24 to 36 hours. Amounts may exceed 50mm (2 inches), especially where thunderstorms occur. There may even be some wet snow in the upper elevations of southern Quebec, New York and Vermont and the backside of the storm late Monday.

This storm had been powerful and deadly. Strong thunderstorms and long lasting tornadoes occurred in Texas and Oklahoma on Saturday evening. In Canton, Texas, five fatalities and multiple injuries were reported from a large and violent wedge tornado. Widespread damage was reported across central and northeast Texas. Lightning from the severe storms also sparked several house fires. Elsewhere, torrential rain has produced major flooding in Missouri and Arkansas, northward into Illinois. On the backside of the storm, unseasonably cold air is producing a narrow band of heavy wet snow and near blizzard conditions. The snow stretched from Colorado, including metro Denver where nearly 8 inches fell, northeast across western Kansas. Snow is forecast into the Dakotas, Minnesota, southern Manitoba and northwest Ontario today into Monday. The late season heavy snow has toppled trees and power lines.

Water levels slowly receding in southern Quebec

Above and Below: The swollen Ottawa River slowly receding at Parc de la Maison Valois in Vaudreuil-Dorion. (ValleyWeather Photo) 

The rain has ended for the short-term, and water levels are slowly receding across the Ottawa River basin, into southern Quebec. Over 400 homes were under evacuation orders in Rigaud, west of Montreal, and a state of emergency remains in effect. Some of those residents chose to leave while others remained in their homes. Numerous roads in the region were impassable due to the rising waters. Closer to Montreal, minor flooding occurred in several shoreline communities on the West Island and in Laval. Municipalities such as Hudson and Vaudreuil-Dorion made sandbags available to those residents who required them. Water levels along St Charles Avenue in Vaudreuil were quite high late last week, with flooding reported at Parc de la Maison Valois, as well as near Chateau Vaudreuil. Over the weekend, the water was nearly level with Highway 40 near the approach to the Ile aux Tourtes Bridge. Water also crept up onto the boardwalk in Sainte-Anne-de-Bellevue.

Sunshine finally returned to the region on Sunday, along with warmer temperatures. We will have a short break to start the week, with sunshine forecast, however more rain is on the way. Low pressure is expected to develop over coastal North Carolina early this week and move towards New England. Clouds and showers will return late Tuesday and persist into next weekend. There is even the risk of isolated thunderstorms on Friday. The rain will be scattered and not continuous. Temperatures should warm again this week, reaching 20C (68F) by Thursday. Montreal has recorded one of the wettest starts to any year, dating back to 1872. Additionally, April 2017 is now one of the top 5 wettest. To date 138.6mm of precipitation has fallen, the record is 158.8mm, established in 2005.

More rain equals more flooding for southern Quebec

Flooding along the Ottawa River at Pointe Fortune, Quebec. (Traversier le Passeur Photo) 

Flooding concerns continue to mount tonight across southern Quebec and eastern Ontario, with more rain in the forecast. A state of emergency has been declared in Rigaud, northwest of Montreal, as a result of flooding from the Ottawa and Rigaud Rivers. Melting snow upstream, combined with heavy rain during the month of April, have pushed the Ottawa River and its tributaries to near record levels. In Rigaud, evacuations have been ordered, with numerous roads impassable. All that water continues to flow towards Montreal and Laval. Water levels along the rivers surrounding Montreal, as well as on Lake of Two Mountains and Lac Saint Louis, are producing flooding. Greatest concern at this time are low-lying areas in Laval, as well as Sainte-Anne-de-Bellevue, Pierrefonds, Senneville and Ile Bizard. Minor flooding is also occurring along the shoreline of L'Ile Perrot. The Town of Hudson is also watching Lake of Two Mountains which is expected to rise by several centimetres into this weekend. Sandbags are being made available by that municipality.

Laval communities are on high alert as flooding continues along the Milles Iles and Riviere des Prairies. (Radio Canada Photo)

Southeast of Montreal, Lake Champlain reached flood stage of 100 feet on Tuesday, but has since lowered slightly. Minor flooding is occurring along shore front communities in upstate New York and Vermont, northward into the Richelieu Valley of Quebec. More rain and isolated thunderstorms are in the forecast as low pressure moves from the Great Lakes into eastern Ontario on Friday. Rain will develop early Friday and taper of Saturday. Another 15-20mm is possible for the entire region.

Flood watch posted across southern Quebec

Lac St-Louis lapping at the shoreline of L'Ile Perrot early Monday morning. Minor flooding is occurring around the lake, as water levels continue to slowly rise. (ValleyWeather Photo)

Above-normal precipitation, along with seasonal snow melt, has prompted authorities to issue a flood watch for southern Quebec, including metro Montreal. According to Quebec water watchdog Hydro Meteo, several rivers have or will exceed flood stage this week. They include, but are not limited to, the Ottawa, St. Lawrence, Mille Iles and Riviere des Prairies around Montreal and Laval. The Richelieu River, southeast of Montreal, is also on the rise, as is Lake Champlain, which is expected to approach 100 feet this week. The normal level for the lake is either side of 95 feet. North of Montreal, flooding has already occurred in Rawdon, along the Ouareau River. In Mirabel, 22 homes have been evacuated.

Moderate flooding is occurring north of Montreal in Rawdon, Val Morin, Val David and Mirabel, shown above. (CBC Photo)

Minor flooding is anticipated along river roads in and around the entire region. Rivers and lakes are swollen, and in some cases, with rapid and erratic water levels and flows. Caution is advised near any body of water. Precipitation amounts in southern Quebec over the last two months have been well above normal values. In March, Montreal measured 114.6mm of precipitation at Trudeau Airport. The 30-year average is 69.1mm. To date in April, over 114mm of precipitation has fallen, with only half the month gone. April usually records 82.2mm for the entire month. A break in the rain is expected on Tuesday, before another series of storms arrives for Wednesday through Friday. Low pressure is forecast to approach New England Wednesday, spreading rain into southern Quebec. Another 25mm is expected. Additional flooding is likely.

A month's worth of rain in four days in Montreal

Just one of the hundreds of Quebec homes impacted by heavy rain and flooding over the weekend. Hardest hit were Sainte-Thérèse and Mirabel, but numerous other communities were impacted as well. (CTV News)

The weather across southern Quebec has gone from winter to summer in less than a week. That is fantastic, as long as you are not one of the hundreds of residents affected by flooding. The combination of very heavy rain, melting snow and ice jams has created moderate to major flooding in several regions of the province.

Trudeau Airport recorded 84.4mm of rain between April 4 and 7. The long-term normal rainfall for the entire month of April is 67.7mm. The heavy rainfall, combined with the snow melt from March storms, produced both sewer backup and river flooding. Hundreds of Quebec homes have had basements inundated with water and mud. Hardest hit to date have been the lower Laurentians, including Mirabel and Sainte-Thérèse. Numerous homes have also received flooding in Two Mountains and parts of Laval, along Lake of Two Mountains. There has even been flooding reported on the Island of Montreal. Currently, Lac St-Louis is running at record levels, 22.13 metres as of April 4th. Over the weekend, the Ottawa River was almost level with Avenue St-Charles in Vaudreuil.

Flooding north of Montreal (Global News)

Most of Quebec is currently under a flood watch as more rain is forecast. As I am writing this blog, temperatures have soared to near record highs in southern Quebec. L'Ile Perrot reached 27C (81F) at 1pm Monday, while the airport is slightly cooler at 25C (77F). The record high for the date is 26.1C (79F) set in 1945. While most of the snow is gone in metro Montreal, there is still plenty upstream, along the Ottawa River Valley and into the Laurentians. Rapid snow melt will continue to be a problem, adding to the high water levels. Vigilance is recommended near any rivers or lakes, through at least the end of the month. Cooler air is on the way for the balance of the week. Seasonable daytime highs near 10C (50F) are expected. However, rain is forecast as well. A cold front will produce scattered showers and thunderstorms tonight and Tuesday. Another 10 to 15mm of rain is expected.

Another round of heavy rain for southern Quebec and Ontario

A strong storm system will produce more heavy rain across southern Quebec over the next 24 to 36 hours. (AccuWeather)

Strengthening low pressure will slowly move from the Ohio Valley into New York State today. This storm will be responsible for a wide variety of severe weather, from the southern US northward into the Great Lakes, as well as Ontario and Quebec. Environment Canada has posted a heavy rainfall warning for southern Quebec, as well as most of southern and eastern Ontario. Flood watches are in effect across New York and New England. Southern Quebec and eastern Ontario can expect heavy rain once again, starting by the noon hour today and continuing into the overnight hours. As colder air wraps around the back end of the storm, the rain will change to snow west of Ottawa and across central Ontario tonight. In Montreal, we are expecting 25 to 40mm of rain. This amount is in addition to the 35mm the city received on Tuesday. Minor flooding was reported already, with the new rain adding to the sharp rises on rivers and streams. Temperatures will remain chilly, in the 3 to 5C (38 to 41F) range through Saturday. Winds will become rather strong and gusty in the St. Lawrence Valley, up to 60km/h.

The expected track of this low pressure would have produced a major snowstorm last month, but enough warm air is in place to guarantee rain for Montreal. Further north, heavy wet snow is expected. The same storm system produced widespread severe weather across Indiana and Georgia, stretching into the Carolina's Wednesday and today. Multiple tornadoes produced damage and injuries. More strong thunderstorms are expected today.

Behind the storm, a surge of warm air will arrive by Monday in Quebec and Ontario. Temperatures are expected to rise into the upper teens in Montreal.

More springlike with heavy rain forecast for Montreal

Spring flooding, such as that shown above in Huntigdon in 2014, is possible this week across southern Quebec. (CBC Photo)

Environment Canada has issued heavy rainfall warnings for portions of the St. Lawrence Valley. The first of two potent low pressure areas will begin to impact southern Quebec on Tuesday. Steady rain should move into Montreal early Tuesday and continue into Wednesday. Expect between 25 and 37mm (1 to 1.50 inches) of rain. The rain will cause sharp rises in area rivers and streams and could lead to some flooding. At this time no flood watches or warnings are in effect. North of Montreal, a period of freezing rain is possible early Tuesday. Closer to Quebec City and points north and east, snow is likely before a changeover to mixed precipitation and eventually rain. Icy travel is expected in those regions. Temperatures in Montreal will remain above freezing Tuesday, with lows near 2C (36F) and daytime highs of 5C (41F).

After a brief respite Wednesday afternoon, a stronger storm will move from the lower Mississippi Valley towards New York State. This system will deliver another 25 to 50mm (1 to 2 inches) of rain to southern Quebec through Friday. The rain will begin early Thursday morning and become heavy at times. The combination of heavy rain, melting snow and ice breaking up on rivers and streams, will elevate the flood risk once again as we head towards the end of the week. Monitor river levels closely, especially if you live in flood prone areas of southern Quebec.