Heat, humidity, and thunderstorm chances return. Severe weather also makes a return.

 Southern Manitoba, will experience a very hot and humid airmass over the next few days we will be sitting over a very strong southwest flow as a ridge of high pressure sits off to the east in Ontario. Given the favourable upper pattern much of the region here will see a threat for severe thunderstorms as an amplified trough sits on the west coast and low pressure systems sit over our area. There will be concerns as this pattern develops, there is the potential for heat and humidity with severe weather and tornado threats. 

Monday early evening (Above): Today: mA complex weather situation will be working out today, a low pressure system sitting over southwestern Manitoba will increase the risk for severe weather as a cold front sits over the western half of Manitoba. Temperatures will rise into the high 20's and low 30's, dewpoint temperatures will also be a lot higher than the average lately with high values reaching the high teens and low 20's. There is a concern that because shear will be in the 50-60knots range that a tornado or 2 could happen. Instability will also be in the 1,000 to 2,000J/Kg CAPE range which increases the prospects that thunderstorms will develop. Overall there is a risk later in the to mid evening today for isolated to scattered supercell thunderstorms to develop with the risk for winds over 100km/h, golf ball to soft ball size hail, and heavy rain over 50mm likely. The best threat areas right now appear to be from the Saskatchewan Border east to Shilo or just west of MacGregor along a north south line from the North Dakota border to the northern parklands by Winnipegosis. After storms form there will be upscale growth into clusters or a MCS which will move north and may provide a risk for tornadoes after sunset into the early overnight hours. 

Monday Night (Above simulated radar images): Storms are once again forecast for the overnight period as another upper wave moves in from North Dakota, which will allow a mesoscale convective system to develop in western North Dakota. This same complex will move through southern Manitoba and it has an opportunity of bringing heavy rainfall in excess of 50-75mm, hail up to golf ball size wind gusts over 100km/h max could be as high as 120km/h this would be a result of bowing segments along the main line. There would also be a risk for a tornado or 2 especially earlier in the night in southwestern Manitoba. Main points are that this system will move from the southwest to northeast and move from the corner of the Melita and Coulter areas northeast into lake Manitoba and portage La prairie areas into the inter lakes and the red River valley. I have seen a few model runs bring it through the red River valley as far south as Morris. If it doesn’t hit the red River valley it has a higher chance of moving into the interlakes as it follows the LLJ or low level jet. Temperatures tonight will drop into the high teens and in the southeast ahead of the front most likely low 20’s are a strong possibility. 

Tuesday (Above): Is going to be one of those days you will definitely have to watch for; for severe weather (Threat map from EC above). This threat is going to be considered conditional as it’s all dependent on the convection from last night. If convection can clear in time and allow for sufficient heating then storms will also be a higher probability of being significant, also there could be outflow boundaries leftover from the storms during the night on Monday night and instability may be lower than expected. Regardless if these factors don’t play in then we can expect things to get wild tomorrow afternoon. I’m looking over model data for this event and dew point temperatures will more than likely rise into the low 20’s, and high teens across the south part of Manitoba. I am seeing temperatures rise into the high twenties and low to mid 30’s hotter in the southeast ahead of the front. Of concern will be a cold front sitting over the southern part of Manitoba which will provide a focus area for severe thunderstorm development. Based on what I’m seeing CAPE values will be over 3,000J/Kg and the EHI values are well within an area I would have concerns for supercell and tornado development. Overall during the latter half of the day there will be thunderstorms developing along a line from Pilot Mound to the Winnipeg region, moving into the interlakes and down into central North Dakota. These storms will move east southeast with initial threats of tornadoes, large hail up to Golf ball or larger  , damaging winds in excess of 100km/h. These storms will move into the southeast part of Manitoba during the evening hours.  We will know more as new model data comes in. Regardless rain and severe thunderstorms remain possible tomorrow. You can read up about the threat areas, from EC right here: https://umanitoba.ca/environment/envirogeog/weather/conv_otlk/ 

You can learn more about the convection values I used here: https://www.theweatherprediction.com/severe/indices/

Tuesday Night: Remaining convection from the storms earlier remain possible, and they will leave the province or weaken by 10pm-12am. Overnight low temperatures are likely to drop once again into the low 20’s in southeast Manitoba as far east as Portage La Prairie with lows westwards in the high teens. 

Wednesday: Another unsettled day is in store across southern Manitoba this time for south central and southeast Manitoba, a chance for early afternoon showers and thunderstorms are possible with a threat for some of them to become severe. The threat will then shift into eastern Manitoba into the afternoon as the front cuts through however this front again remains stationary so the threat for thunderstorms may continue in the red River valley towards the evening hours. Scattered thunderstorms are more than likely than organized severe weather. Temperatures on the day Wednesday will rise into the high 20’s in the south central and south east before dropping into the mid 20’s during the day. 

Wednesday Night: Another chance at convection moving into the red River valley and southeast part of Manitoba remains likely, possibly in the form of a MCS or thunderstorm complex which would bring a risk for damaging winds, hail and flooding rains. Details on this are still being worked out but we will know more as the data comes in through the next 12-24 hour period. Temperatures on Wednesday night will drop into the mid to high teens. 

Second half of the week: Calmer weather is in store as high pressure moves in which allows a stable airmass to return. Temperatures for the period will more than likely return to more normal values giving us a break from the heat with temperatures in the mid to high 20's and low to mid teens for overnight lows.