Tuesday, 26 November 2013

Snowstorm Forecast Nov 26-27

Winter Storm Discussion

After a long summer, winter is back and so is snowstorm tracking across eastern canada. A low pressure area formed across the central gulf coast yesterday night and has since began its trek eastwards, now stationed across western NC according to noaa mesoscale analysis. Snow will begin to break out across the niagara region over the next few hours with snowfall moving into eastern ontario and southern quebec in the 7pm-10pm timeframe. The snowfall is expected to come in two waves, with a secondary low forming and riding along the east coast tomorrow bringing a reinforcing shot of precip to Eastern ON/QUE by tomorrow afternoon and evening. The heaviest snow is expected to fall southeast of ottawa and west of montreal in an area from east of kingston up towards saint jerome, the laurentian's and the eastern suburbs of ottawa. Over this area, a general 25-35cm's of snow is expected to fall, with isolated amounts in the 40cm range.

For the city of montreal itself, precipitation type will be a huge issue and likely a headache for EC and many forecasters across the area. Precip should start off as snow in the city with 7-15cm of snow likely before a change over to rain and maybe a brief period of ice pellets between 7am and 1pm. The east end will be seeing a longer period of mixing while the west island gets less. Higher elevations NW of the city should be the jackpot zone with all snow, nice isentropic ascent and a plethora of moisture available. After the change over to rain, another 5-12cm is likely in the afternoon/evening hours with a change over back to mostly snow occurring around the 12-2pm time frame. RGEM/GFS have this changeover a little bit earlier with only a brief period of RN/PL in the early morning hours. I am going with the RAP/NAM WRF/NAM/SREF consensus for now, based on surface analysis at the current time. For the GTA, looks like the heaviest precip will fall overnight, mostly in the form of 10:1 ratio snowfall. Expecting 2-9cm amounts over the city, with highest amounts over the east end(oshawa area). In terms of the ottawa valley, I am expecting a solid 15-25cm of snow with some isolated 30-35cm amounts over the east end. Perhaps ratios are a little bit better then 10:1, but not by too much.

With that being said here are my forecasted snowfall totals across eastern canada. Questions, comments ETC are encouraged.

Kingston: 20-30cm
Ottawa: 15-25cm
Montreal West Island: 12-25cm
East Montreal: 8-20cm
Belleville: 10-20cm
GTA: 2-9cm
Hamilton/Burlington: Trace-4cm
Niagara: 5-12cm
Quebec City: 8-18cm, locally 20cm
Trois Rivieres: 7-15cm, locally 15-20cm

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