Heat and Humidity Return; increasing severe weather threat

 Southern Manitoba is poised to experience another round of heat and humidity, surprisingly we are already into late August and by this time we would already be seeing cooler temperatures more similar to fall. Weird weather eh!??? 🤦‍♂️🤣🤣🤣🤣 However you can thank all of this heat and humidity to a ridge of high pressure that brought temperatures into the low to mid 30’s over BC and Alberta, this pattern won’t stay as the ridge moves through our area it will be flattening in the process as a low pressure system rides over the northern end of it. This could potentially lead to some hot humid and stormy weather, find out when and where in this weekend’s blog. Details for Friday night are included. 😊. 

(Above: Dewpoint temperatures forecast for Saturday evening, this humidity will stick around for Sunday as well. This humidity will provide a perfect environment for severe thunderstorms on Saturday afternoon and evening).

Friday Night: This is when the humidity will increase and most of the noticeable mild weather arrives, high pressure will move off to our east allowing for a southerly flow to continue to spill northwards. Mild overnight lows in the mid to high teens are likely in central and eastern Manitoba, low to mid teens are likely in the western part of Manitoba. There’s a chance for increasing clouds in the southeast with a very small chance for showers in the southeast portion of Manitoba. 

Saturday: Will start off cloudy in the southeast but overall it should clear out by the noon hour, Temperatures will rise into the mid to high 20’s, dew point temperatures will rise into the high teens to low 20’s. It will end up feeling like the mid to high 30’s with the humidex. Of concern later in the day will be a warm front coming through which will increase the risk of storms along a large area of 1,000 to 2,500 J/Kg of CAPE with 1-4 on the supercell composite scale which could bring in possible supercells in the late afternoon  which will be centered over south central and southwest Manitoba. Isolated to scattered storms are possible and some of them may end up being severe. Scattered storms are possible during the late afternoon. A better chance comes in on Saturday night.

Saturday Night: This is where things get interesting, a low pressure system with a attached warm front will move through southwestern Manitoba during the early evening likely encountering an already hot and humid airmass. There are signals that a cluster of strong thunderstorms may form along the boundary before dinner time south of lake Manitoba with them moving into the red river valley by the evening hours. If you are planning for camping best advice is to prepare for deteriorating weather conditions and pay attention to weather alerts that get posted. Once storms move through, temperatures will drop into the mid to high teens staying well above our normal overnight lows. Some areas near lake Manitoba and lake Winnipeg may end up being cooler with lows around 10 to 15C. 

Sunday: Will be another hot and humid day with a stream of moisture coming up from the Gulf of Mexico, the latest NAM 18Z has an area of showers moving in during the morning with clearing during the afternoon which seems to be an outlier at this point in time. As current thinking I’m sitting with is that with the heat and humidity increasing there will be another day of possible unstable weather. Temperatures will soar into the mid to high 20’s ahead of a cold front, dewpoint temperatures will also rise throughout the day but will drop off as the front moves east which will make most humidity stick around in the red river valley and eastern Manitoba. If you combine the fact dew points will be in the high teens and low 20’s, sufficient CAPE will exist which will allow large instability upwards of 3,000J/Kg. Thunderstorms look possible in areas of southwestern Manitoba during the afternoon into the late afternoon. The threat shifts east into the supper hours into evening for the red river valley and southeastern Manitoba. If the front slows down there will exist a severe threat further west than Winnipeg, which could give the valley a chance of convection. Based on data the best areas for convection on Sunday evening are portage la prairie all points east to the Ontario border, so all of south central southeast Manitoba into Eastern North Dakota and NW Minnesota. It will not be an all day rain event but some localities could see thunderstorms more than others, so nothing widespread but more scattered. 

 

Sunday Night (Above): The threat for convection and or severe storms will persist into the overnight period for south central and southeastern Manitoba as the front takes a while to pull through the ridge dominating the USA. There’s a chance for strong to severe storms with possible straight line winds as a threat with hail possibly as well. Temperatures will likely drop into the mid to high teens overnight. 

The week ahead: Much calmer weather  but more seasonal temperatures look to be in store with highs in the low to mid 20’s and lows in the low to mid teens once again with the possibility of lows in the high single digits.