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Significant Ice and Snow Expected Across Southern Ontario; Power Outages Possible; Whiteouts

We are closely watching a large and complex weather system as it crosses the Central United States before impacting Southern Ontario throughout the day on Sunday (December 1st).

Discussion:

A complex weather system with a history of producing hurricane-force winds, blizzard conditions and tornadoes is currently moving towards Ontario. As this system approaches, the temperature will begin to rise with temperatures on Sunday ranging from 5-10 C in Essex County and the shores of Lake Erie to -4 to 0 C across Southwestern Ontario including Toronto. In the Dundalk Highlands between Orangeville and Collingwood extending into Central and Eastern Ontario, including portions of the Eastern GTA and the Bruce Peninsula, temperatures will range between -4 and -10 C. These temperatures will come with a wide span of wind chills throughout the day as well.


Alongside the wide range of temperatures, a wide range of precipitation types will also occur. Rain showers are expected along the shores of Lake Erie with the risk of an isolated non-severe thunderstorm across Essex County into Chatham and Extreme Southern Lambton County. Further north between Goderich-Kitchener-Brantford-Niagara-London regions, freezing rain is likely. Further north toward Kincardine-Hanover-Arthur-Guelph-Western GTA-Hamilton, ice pellets are likely. Finally, Owen Sound-Midland-Peterborough-Eastern GTA-Central Ontario-Eastern Ontario can expect snow. At times, the snow will be very heavy with rates approaching 3-5cm/h alongside winds of 50-70km/h which should produce brief, but intense whiteout conditions.

Timing:

System Timing Forecast, for Southern Ontario. Issued December 1st, 2019.

Start Time: 4-8am

Rain is likely to begin from west to east across this Extreme South between Wallaceburg through to Newbury and St. Thomas. Areas to the north of this region including Sarnia, Strathroy, and Grand Bend could see a beginning rain shower before freezing rain takes over.


Start Time: 7-11am

Rain will continue to spread across the region along the shores of Lake Erie including Port Dover, Long Point, and Fort Erie from west to east. Freezing rain will spread east into the region to affects areas such as Lodon, Goderich, Stratford, Woodstock, Brantford, Kitchener, and Niagara Falls. Freezing rain mixed with ice pellets is likely from Hamilton through to Listowel and Kincardine. Ice pellets are likely from Burlington through to Hanover, Owen Sound and Brampton. Snow mixed with ice pellets are likely in the City of Toronto.


Start Time: 10am-3pm

Snow will spread into Central Ontario over the Bruce Peninsula as well as areas between Barrie, Orillia, Midland, Uxbridge, Peterborough, and Belleville. Snow may mix with ice pellets at times along the Lake Ontario shores towards the GTA. As the snow pushes into Belleville-Peterborough-Orillia-Midland regions, it could be heavy with large snowfall rates between 2-4cm/h alongside the strong wind gusts discussed below in the article.


Start Time: 2pm-6pm

Light to moderate snow will spread across Central and Eastern Ontario towards Kingston, Borckville, Perth, Bancroft, Haliburton, and Huntsville. The snow may come alongside some isolated blowing snow. The snow could be heavy at times.


Start Time: 5pm-10pm

Light snow will spread across Eastern Ontario towards Cornwall, Ottawa, and Algonquin where less than 5cm is expected.


An isolated band or two of precipitation could come before the main core of the precipitation for this system. These pre-system bands will be weak and not included in the forecast map.

Snowfall:

Snowfall Forecast, for Southern Ontario. Issued December 1st, 2019.

Areas in the orange and marked with a '4' can expect snowfall totals between 15 and 25cm. Across the Bruce Peninsula, snowfall totals between 15 and 20cm can be expected from this system. Some models have shown enhanced snowfall which brings the snowfall totals between 20 and 25cm. This is possible due to the possibility of heavy snow and high snowfall rates of 2-4cm/h. A little further south towards Meaford, snowfall totals around 15cm are likely with local amounts towards 20cm. Due to the strong wind gusts between 75 and 85km/h, blowing snow and whiteout conditions are likely. Road closures on the Bruce Peninsula are possible.


Areas in the yellow and marked with a '3' can expect snowfall totals between 10 and 20cm. Across most of Central and Eastern Ontario, snowfall totals near 10cm are likely. This region includes Southeastern Manitoulin Island, Parry Sound, Huntsville, Bancroft, Kingston, Belleville, Peterborough, Barrie, Midland, Newmarket, and Owen Sound. Areas towards Georgian Bay such as Parry Sound and Midland could see between 10 and 15cm while areas between Owen Sound and Collingwood in the 12-17cm range. Across much of this region, snowfall totals will remain near 10cm although there will be patches of 10-15cm and even local patches of 15-20cm of snow. This is why much of the region is included in the large scale of 10-20cm. Along the shores of Lake Ontario between Kingston and Belleville, snowfall totals between 10-15cm are likely. Leading into the GTA along Highway 401 between Cobourg and Oshawa, snowfall amounts between 10-15cm. If the precipitation across the region, mainly in the 'area of interest' falls primarily as snow instead of a mix of snow and ice pellets, snowfall totals could reach as high as 20cm.


Areas in the green and marked with a '2' can expect snowfall totals between 5 and 15cm of snow. Across the southwest between Kincardine, Hanover, Markdale, Arthur, Guelph, Hamilton, St. Catharines, and Burlington, ice pellets are likely. Ice pellet totals alongside snowfall totals will combine to have totals between 6 and 12cm (including the wrap-around snow as the system pulls away from the region). Across the GTA including Mississauga, Toronto, Vaughan extending towards the higher terrains of Orangeville and Shelburne, snowfall and ice pellet totals around 10cm are likely. If the precipitation is mainly snow instead of ice pellets, snowfall totals between 10-15cm are likely across the GTA with isolated pockets of 20cm possible due to lake-enhancement. This is highlighted for the 'area of interest.' Across Eastern Ontario, snowfall totals between 5 and 10cm are likely extending from Brockville and Gananoque through to Perth, Barry's Bay, Sundridge, and Britt, as well as much of Central and Western Manitoulin Island.


Areas in the blue and marked with a '1' can expect snowfall totals under 5cm. This includes the remaining portions of Southwestern Ontario which could see ice pellets or light flurries in the system as well as light snow on the wrap-around as the system pulls away into New York State. The remaining areas in Eastern and Northeastern Ontario are also highlighted to see under 5cm with most places seeing no snow at all.

Freezing Rain:

Freezing Rain Forecast, for Southern Ontario. Issued December 1st, 2019. - Updated at 10am

Changes with the last update (10:00am December 1st, 2019)

Orange Region (4):

- Lowest freezing rain totals across Western London from 12-16mm to around 10-14mm, elsewhere, freezing rain between 12-16mm is likely with patches towards 18 and even 20mm.


Yellow Region (3):

- Extended the yellow region further between Cambridge and Kitchener extending towards Mitchell and Exeter. Freezing rain totals between 8-10mm are likely.

- Extended the yellow region further south between Dunnville, as well as areas between Delhi, St. Thomas, and Port Dover such as Glen Meyer and Straffordville. Freezing rain between 8-12mm is expected.


Green Region (2):

- Extended the green region further north to include Listowel, Wingham, Kincardine, and Tiverton. Grimsby and more of Hamilton are now included in this region where 3-5mm of ice is likely.

- Extended the green region further south to include portions of Fort Erie, Dunnville, and Port Dover (besides the direct lake shore). Freezing rain between 2-4mm is expected.


Blue Region (1):

- Extended the blue region further north to include Mississauga, Orangeville, Shelburne, Owen Sound, Hanover, and Arthur. Freezing rain between 1-2mm is expected.

- Extended the blue region further south to reach the Lake Erie shores. This includes Port Rowan, Port Burwell, and the shores in Fort Erie. Freezing rain between 1-2mm is expected.


Area of Interest:

- Extended the area of interest further north along County Road 86 to include Listowel and Wingham.

- Extended the area of interest further between Strathroy and Grand Bend.

- In both of these regions, freezing rain totals are expected in the 2-6mm range, although, freezing rain totals could reach as high as 10mm across this region.

Original Freezing Rain Forecast (some aspects are still valid):

Areas in the orange and marked with a '4' can expect ice accretion totals between 12 and 20mm. Along Highway 401 in the Woodstock-London region extending through to Brantford, freezing rain will fall for 4-8 hours. The freezing rain will be heavy at times. Due to gusty winds between 60-75km/h, power outages are likely, possibly widespread across this region.


Areas in the yellow and marked with a '3' can expect ice accretion totals between 6 and 12mm. This extends from the Niagara region through to Delhi, Lucan, Stratford and Cambridge. Freezing rain totals will average out around 8-10mm with the highest near Delhi and the lowest near Niagara Falls and Lucan. Due to the strong winds near Lake Huron, areas between Stratford and Lucan could see widespread power outages compared to areas on the Niagara Peninsula which could only see isolated outages, as the wind is not as strong in that region. If the precipitation mainly falls as ice pellets, freezing rain totals will be limited. This is most likely from Niagara Falls through to Dunnville and Cambridge.


Areas in the green and marked with a '2' can expect ice accretion totals between 2 and 6mm. Across most of the region, 6mm is likely with fewer amounts towards the north near Amberley and south near Fort Erie and St. Thomas. Freezing rain totals in these regions will be between 2 and 4mm. Elsewhere, regions such as Sarnia, Grand Bend, Goderich, and Exeter could see totals near or even slightly above 6mm towards 8 and even 10mm. The best risk for this to happen is across Huron and Perth Counties as well as portions of Lambton and Middlesex Counties. This is highlighted in the 'area of interest' as to where locally higher amounts are possible.


Areas in the blue and marked with a '1' can expect ice accretion under 2mm. This extends along the Lake Erie shores to include Fort Erie, Port Dover, Newbury and areas just south of Sarnia. This also includes Hamilton through to Listowel and Kincardine. Freezing rain totals near Listowel and Wingham could be locally higher towards 2-4mm. Some models are displaying freezing rain extending into Bruce and Grey Counties towards Tiverton, Hanover, Walkerton and Markdale, although, we have left this off of our map due to low confidence. This is however still possible. If this were to happen, freezing rain totals between 1-3mm would be likely with isolated pockets between 2-5mm.


Due to the strong wind gusts, not all the freezing rain shown in the forecast will accumulate...

Wind:

Wind Forecast, for Southern Ontario. Issued December 1st, 2019.

Areas in the orange and marked with a '4' can expect peak wind gusts between 70 and 85km/h. This includes a large portion of the region. Across the Extreme South near Rondeau Park, Rodney, and Long Point, peak wind gusts will bear near 70km/h, although peak gusts towards 75km/h are possible. Towards Southwestern Ontario, peak wind gusts around 70km/h are possible with isolated gusts towards 75km/h. This is likely extending from Lake Ontario between Hamilton and Cobourg through to Barrie, Midland, Orillia, Cambridge, Kitchener, Orangeville, and Woodstock. Towards the west, there is an 'area of interest.' In the 'area of interest,' peak wind gusts will be between 70-80km/h. This includes London through to Grand Bend, Goderich, Kincardine, Owen Sound, Mount Forest, and Stratford. Finally, areas around the Bruce Peninsula can expect peak wind gusts between 75 and 85km/h. Isolated gusts between 80 and 90km/h are possible across the 'area of interest' with the best chance on the Bruce Peninsula, but sustained peak gusts of 90km/h are not expected. Blowing snow and blowing ice pellets will be of major concern for areas in the east and north while power outages due to significant ice will be of concern in the south and west.


Areas in the yellow and marked with a '3' can expect peak wind gusts between 60 and 75km/h. This includes the Extreme South between Sarnia, Chatham, St. Thomas, and Windsor. Peak wind gusts in the 60-70km/h are expected with wind gusts peaking between 70-75km/h in the Chatham region. This region also includes Port Dover, Grimsby and Brantford where wind gusts around 70km/h are likely. Across Central Ontario, peak wind gusts between 60 and 65km/h are likely over Parry Sound and Rosseau towards Huntsville, Sundridge, Britt, Washago, and Peterborough. Wind gusts between 65 and 75km/h are likely over portions of Prince Edward County and Manitoulin Island along the North Channel.


Areas in the green and marked with a '2' can expect peak wind gusts between 40 and 60km/h. This is expected across the Niagara Peninsula where wind gusts between 50-60km/h will be the peak. Across Eastern and Northeastern Ontario, wind gusts will peak between 45 and 55km/h.

Rainfall:

Rainfall Forecast, for Southern Ontario. Issued December 1st, 2019.

Areas in the green and marked with a '2' can expect rainfall totals between 15 and 25mm of rain. This includes Essex County along the shores of Lake Erie including Fort Erie, Port Dover, Long Point, Rodney and Chatham. A majority of the region will only see near 15mm although heavy bursts of precipitation and thunderstorms could bring totals up to 25mm for some regions, mainly across Essex County.


Areas in the blue and marked with a '1' can expect rainfall totals from a drizzle to 10mm. Across near Fort Erie and Rodney could see up to 10mm, including areas south of Sarnia while areas in Sarnia, Delhi, Grimsby and Hamilton only seeing near a drizzle during the morning or afternoon on Sunday while the temperature rises to the peak of the day, near 0.

We will be closely watching the development of this system and will update if needed.

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