Shower and Thunderstorm Chances return to Southern Manitoba, Fall Severe Thunderstorms to start October. Unusually Mild.

 Good afternoon and good evening southern Manitoba folks, looks like a very interesting weather setup is in store for this weekend with the potential for some active weather on the day Sunday, unusually warm air mass is expected to filter into southern Manitoba this weekend with a possibility of high temperatures rising into the high 20s with humidity values in the low 30's. A low pressure system coming up from Montana will influence the weather this weekend which will provide this summerlike weather. 

Saturday: Warm weather will increase overall as a warm front approaches from the south, temperatures will rise into the mid 20’s for the southern half of Manitoba and high teens in the Interlake regions. Calm and sunny weather is likely on Saturday. 

Saturday Night (Thunderstorms likely as shown on the RDPS above.. and NAM Below..

Saturday Night: (Above: Photo of SkewT Graph of Winnipeg area during sunday night). A warm front will lift north into the overnight period , as a result temperatures will remain mild with lows in the mid teens around 12-15C. THUNDERSTORM POTENTIAL: What is most of concern is that as the warm front moves into a cooler airmass that air will begin to rise, during the late evening into the overnight period CAPE values will begin filling into the very Unstable range over southwestern portions of Manitoba into eastern sections. Likely providing an opportunity for the development of thunderstorms some of which may end up becoming severe especially in the morning hours. Data at the moment is showing development happening in western Manitoba by 3am moving east into the red River valley by sunrise. If the warm front gets slowed down moving north then the threat for storms will occur during the latter half of the morning into the early afternoon. Regardless a threat for hail the size of 1-4cm in diameter is a possibility meaning pea size to golf ball size, damaging wind gusts and heavy rainfall in excess of 40mm in localized areas. Storms will fire wherever the front can interact with the cool airmass to the north and anywhere from the USA border to the interlakes is a possibility, all of West MB to the whiteshell. 

Sunday: I am expecting on the day Sunday that showers and thunderstorms will clear the area as the front continues to move northwards with the hot and humid air mass enveloping much of southern Manitoba on the day in the afternoon. Temperatures on Sunday may reach the high 20s with humidex in the low 30s, there is some inconsistency with some model runs. The NAM is saying the majority of the heat will be centred over northern North Dakota whereas the RDPS and GDPS both show it impacting majority of the southern Manitoba so it depends on how far north the warm front can position itself in the afternoon. There may be a threat for severe thunderstorms in the afternoon however more than likely in eastern and central Manitoba and the interlakes. If any storms form in the capped and unstable airmass from lake breeze interactions storms may be stronger than in the morning with the potential for supercells as a possibility, large hail, damaging winds and heavy flooding rains.

Sunday Night (Left): Photo of the NAM showing thunderstorm chances in the central and eastern parts of Manitoba): A possibility exists for some isolated to scattered thunderstorms on Sunday evening as a   occluded front moves through a hot humid air mass, The Zero Zulu NAM model is the only one showing this at the moment so we'll need to bear watching as we get into the afternoon on Sunday to see if there will be a chance at thunderstorms some severe on Sunday evening. It is doubtful though as main forcing remains to the north. Overnight low temperature on Sunday will slowly decrease from the mid 20s to the high teens centred over eastern Manitoba as a cold front remains further off to the east which means by morning temperatures will still be in the teens in South Central Manitoba. A mild night is expected on Sunday night. 

The week ahead (Above: Thunderstorms are possible on Monday Night): 

Showers and thunderstorms are likely for the day on Monday and Tuesday with a cold front moving through a  unstable air mass. Temperatures on Monday will likely reach the low 20s to mid 20s with some areas of Western Manitoba and interlakes seeing high temperatures in the high teens. More than likely overnight lows in the mid to high teens and high temperatures in the low 20's are likely, before  a switch to temperatures in the mid to high teens for highs. Cooler weather arrives behind the cold front on Tuesday evening. 

Regardless enjoy the unusually warm start to October thanks to El Nino and Climate Change. 

-Mike McGregor