March will be going out like a lion this year as a strong Colorado Low is expected to move across Southern Ontario bringing 20 to 50mm of rain, 10 to 20mm of freezing rain and 15 to 30cm of snow.
Snowfall
Blue or '1':
Areas in the blue or marked with a '1' can expect less than 5cm of snow. This includes areas just north of the St. Lawrence River including Hawkesbury, Cornwall, Smiths Falls, Brockville, Kingston, and Prince Edward County. This region also includes portions of Northeastern Ontario including Manitoulin Island, Sudbury, Espanola, and Thessalon. Local totals towards 4 to 8cm may be possible along the border of this region near Westport and Smiths Falls as well as Killarney and Central/Eastern Manitoulin Island. This is dependent on the exact track of the low and the timing of the rain to snow switch over.
Green or '2':
Areas in the green or marked with a '2' can expect between 5 and 15cm of snow. This includes all of the Extreme South, Golden Horseshoe, GTA and much of Southwestern Ontario, including everything south of Saugeen Shores, Hanover and Shelburne. In Central and Eastern Ontario, this includes a thin swath between and including Ottawa, Perth, Belleville, and Peterborough. Towards the north, this also includes Britt and North Bay. The highest amounts towards 15cm are likely towards Shelburne and Orangeville near the Dundalk Highlands, alongside the border to the next (yellow or '3') region.
Yellow or '3':
Areas in the yellow or marked with a '3' can expect between 10 and 20cm of snow. This includes much of Central and Eastern Ontario including portions of Southwestern Ontario. This includes Tobermory, Wiarton, Saugeen Shores, Markdale, and Barrie. This area can mainly expect 15 to 20cm of snow, although locally fewer amounts may be possible towards Tobermory and Saugeen Shores, near the Lake Huron waters. Locally higher amounts between 20 and 30cm are possible between Owen Sound and Collingwood, including Meaford. This is due to possible lake enhancement off of Georgian Bay. In Central Ontario, a widespread 10 to 15cm swath of snow is possible including Woodview, Parry Sound, Huntsville, Plevna, Mattawa, and Arnprior. Amounts towards 15 to 20cm, locally higher, are more likely near Haliburton, Dorset, and Denbigh.
Orange or '4':
Areas in the orange or marked with a '4' can expect between 15 and 30cm of snow. This includes Algonquin Park, Bancroft, Pembroke, Cobden and Deep River. Locally fewer amounts are possible between Stonecliffe and Mattawa where 10 to 15cm may be possible. Locally more amounts are possible in isolated pockets across Algonquin Park, possibly extending as far south as Barry's Bay.
During the switchover from rain to snow across much of Southern Ontario, the snow could possibly be falling at rapid rates of 2-4cm/hour for at least an hour during the switch, reduced visibility is possible and quickly accumulating snow may be possible.
Disclaimer: due to the expected rain before the snow, multiple centimeters of snow may melt-on-contact which will appear to lower the snowfall totals from the map.
Freezing Rain
Blue or '1':
Areas in the blue or marked with a '1' can expect less than 2mm of ice accretion. This includes areas between Lion's Head and Saugeen Shores extending inland towards Owen Sound, Hanover, and Meaford. This area also includes Collingwood and Barrie, as well as, Kitchener, Cambridge, and Brampton. Towards Central and Eastern Ontario, this includes Orillia, Newmarket, Peterborough, Belleville, Brockville, Morrisburg, and Petawawa. These areas can expect light freezing rain or drizzle during the change over period, or, for areas such as Kitchener, a few hours of freezing rain may be possible.
Green or '2':
Areas in the green or marked with a '2' can expect between 2 to 5mm of ice accretion. This includes portions of the higher elevation terrain in Southern Ontario such as Mount Forest, Arthur, and Guelph. In Central and Eastern Ontario, this includes Pembroke, Dorset, Minden, Madoc, Westport, and Cornwall. A few hours of freezing rain are possible in these areas. Locally higher amounts are possible towards Pembroke and Cornwall depending on the time the rain/snow switches to freezing rain.
Yellow or '3':
Areas in the yellow or marked with a '3' can expect between 5 to 10mm of ice accretion. This includes portions of the Blue Mountains such as Markdale, Shelburne, and Orangeville. Amounts may slightly overachieve depending on the switchover from freezing rain to snow although this is less likely. In Central and Eastern Ontario, this area includes much of Far Eastern Ontario such as Ottawa, Kemptville, and Hawkesbury as well as Kaladar, Apsley, Haliburton, Madawaska, and Cobden. Areas such as Perth, Smiths Falls, Sharbot Lake, Kaladar and Kemptville may see locally higher amounts towards 15mm of ice accretion.
Orange or '4':
Areas in the orange or marked with a '4' can expect between 10 and 15mm of ice accretion. This includes a pocket of Eastern Ontario including Bancroft, Arnprior, Renfrew, Barry's Bay and possible Perth/Sharbot Lake/Kaladar depending on the track of the freezing rain line and transition time.
Red or '5':
Areas in the red or marked with a '5' can expect between 15 and 25mm of ice accretion. Models are hinting at significant freezing rain totals from 6 to 12 hours of freezing rain over portions of the Ottawa Valley, near Calabogie, Denbigh, Bon Echo Park, and Plevna.
Major impacts on roads are expected, especially untreated and rural roads. Hydro outages are possible due to the weight on the hydro wires. Remember to report all downed power lines to your local provided and to NOT approach them.
Rainfall and Flooding
Blue or '1':
Areas in the blue or marked with a '1' can expect less than 10mm of rain. This includes portions of the Blue Mountains such as Owen Sound, Meaford, Collingwood, and Markdale where snow and freezing rain will be more dominant. In Central and Eastern Ontario, this region includes Pembroke, Bancroft, Haliburton, Midland, and Huntsville, again, due to other 'main' precipitation types in this event. Locally higher amounts may be possible depending on the change between rain, snow and freezing rain.
Green or '2':
Areas in the green or marked with a '2' can expect between 10 and 25mm of rain. This includes a large swath from Kincardine to Ottawa, including Saugeen Shores, Amberley, Wingham, Arthur, Orangeville, Shelburne, Barrie, Beaverton, Woodview, Bon Echo Park, Perth, Ottawa, Cornwall, Hawkesbury and Smiths Falls. This is due to the main threat including snow and/or freezing rain for these regions, or, they are not in the main path of the precipitation. Besides this, fewer amounts are possible between Shelburne and Orangeville due to freezing rain, although, we felt to include it in this legend region as there is enough model confidence to support this.
Yellow or '3':
Areas in the yellow or marked with a '3' can expect between 25 and 50mm of rain. This includes all the Extreme South and Golden Horseshoe regions including everything south of a line from Goderich through Listowel, Newmarket, Peterborough, Madoc, Kaladar, and Prescott. Locally fewer amounts may be possible near Kaladar and Westport with locally higher amounts near Hamilton, Niagara Falls, and Port Dover. Local pockets between 15 and 25mm may be possible although this is unexpected in this region.
The Ministry of Natural Resources and Forestry have issued a flood watch for all of Southern Ontario with many local areas issuing watershed condition statements. They can be found here: https://www.ontario.ca/law-and-safety/flood-forecasting-and-warning-program