Sharp Cold Front to Advance into Southern Ontario

A strong cold front will push its way east across Northern Ontario before arriving into Southern Ontario by Saturday. A much cooler and drier airmass will be ushered into Southern and Eastern  Ontario by Sunday.

                                                                            Courtesy of TwisterData.com

Widespread showers and thunderstorms will be possible ahead and along the cold front. The severity of some of these thunderstorms will depend on the timing of the cold front passage on Saturday.

If things play out by the GFS model, as shown above, then the front will be making its way into Southern Ontario and Eastern Quebec in the afternoon with more daytime heating to allow for an unstable environment and storms to be locally severe.

However given that some models have the cold front advancing faster on Saturday morning would diminish the threat of severe thunderstorms in Eastern Ontario and Quebec.

Behind the cold front, daytime highs will be between 17°C and 20°C on Sunday and Monday with lows in the single digits.

                                                             -------- Update ----------

I have posted two soundings for Ottawa (CYOW) to contrast the difference before and after the cold front passage. The top sounding is for 5 pm Eastern on Saturday just before frontal passage. The temperature will be in the high 20s and the dew point temperature in the high teens. If the timing of the front works out like it does on the GFS model, a thunderstorm will certainly not be out of the question.

The bottom sounding is for Sunday at 8 am Eastern well after the cold front passage, where a much cooler and drier airmass sets in. With a northerly wind and the low temperature in the single digits, Sunday will feel like an Autumn day!