Ottawa, Montreal and surrounding areas have yet to see snow this season; however, it is becoming apparent that there are two chances of snow in the upcoming week.
November 4-5 – Confidence: moderate
A system will move through N ON on Sunday. Some precipitation may enter the cold air present over E ON and S QC early in the day, resulting in a period of snow before WAA kicks in and changes it to rain. The 18Z NAM also introduces a dry layer near 900 mb, resulting in virga in most areas. In any event, no more than a few centimetres is anticipated.
November 7-11 – Confidence: moderate
There is some model agreement forming with regards to a potential system within that period, including with the global models’ ensemble suites. The 12Z GEFS strongly supports a snowfall event in Montreal:
48% of the members have snow falling at YUL between 1 and 7 am November 8 with some models delaying the snow to the next day where 43% of all members have it occurring during the same timeframe 24 hours later.
The 12Z OP ECMWF and EPS seem to favour a weak, suppressed low on November 8/9 with seemingly no impacts here; then on the 11th on the OP, a storm develops in S ON and crosses through Montreal.
The 12Z GGEM has a storm similar to the ECMWF but farther north and stronger as it hits the coast; accumulating snow north and west of Montreal.
As usual, its ensembles are not bullish with the snow but more than a third still predict it.
Snowfall amounts could be in excess of 10 cm with this system, barring any sudden changes.
As the Euro weeklies state, warmer anomalies should gradually subside by late November, starting our conversion to winter and hopefully, improving our opportunities for snowfall.