Wednesday through Saturday
Threat level: MODERATE
Impacts: MODERATE to HIGH (based time of year, travel impacts, public awareness, etc)
Confidence: MODERATE (based on model agreements)
Expected hazards: WINTER STORM (possible) // STRONG WINDS // BLOWING SNOW
Expected snowfall: 10-15cm
Locations impacted: extreme southeastern Manitoba // North Dakota
Expected watch: special weather statements (already issued), snowfall warnings and/or winter storm watches (localized)
Most likely areas impacted: Trans-Canada Highway from Steinbach, MB to Kenora, ON and possibly highway 75 from Morris to US border.
Discussion: evening analysis places a surface low pressure in extreme northern Saskatchewan with a large cold front stretching to BC. Mid level water vapour puts shortwave trough entering western Canada this evening and set to translate east next few days. Models becoming more in agreement with previous thinking, therefore only minimal adjustments to previous forecast. Increased confidence level to MODERATE and generalized snowfall totals for Manitoba for 10-15cm. Adjusted forecast to exclude Winnipeg into risk map since temperatures likely too warm in city and warm ground will limit accumulation in urban areas. Also, added an impact level from MODERATE to HIGH to account for early-season winter storm, travel impacts, awareness of population (most caught by surprise by this and vehicles/homes no "winter ready") and vegetation (some of which still have leafs, etc).
NWS, WPC and ECCC forecast offices now in agreement with impactful winter weather event mid-week for Northern Plains, including Manitoba/Northern Ontario. Used RDPS/NAM 12km/GFS blend to produce forecast maps. Generally agree with below GDPS run for today.
Here are some discussions by Environment Canada and the National Weather Service Grand Forks, ND:
3:30 PM CDT Monday 07 October 2019 Special weather statement in effect for areas in grey
An unseasonably warm spell for Monday and Tuesday through southern Manitoba will give way to colder temperatures with rain and snow for the latter half of the week and into the holiday weekend. A cold front from Alberta will bring some rain or snow into Westman Tuesday night which will then slowly push through southern Manitoba on Wednesday. More significantly, there is also a potential for the development of a Colorado Low which could bring heavy rain or heavy snow to parts of southern Manitoba beginning sometime Thursday and continuing into the weekend. It is too early to predict exactly where and how much of this precipitation will fall. More specific details will be forthcoming as these weather systems develop.
...EARLY SEASON WINTER STORM POSSIBLE AT THE END OF THIS WEEK... "A strong storm system and Arctic cold front will converge at the end of this week, bringing a period of winter weather Wednesday evening through Saturday. Widespread snow accumulation is likely, and heavy snow is possible. However, confidence in the timing and placement of the heaviest snow remains uncertain. Travel impacts are likely, especially on Friday and Saturday. Significant travel impacts and tree damage are possible where the heaviest snow occurs. Check the forecast frequently as confidence increases in snowfall timing, placement and amounts." - NWS Grand Forks, ND