Clash of seasons brings severe weather threat to Prairies
Saturday, September 15, 2018, 4:05 PM - It's a tale of two seasons across the Prairies this weekend, as we face the potential for September-record snow, and severe weather -- including the risk for an isolated tornado. A clash of air masses from the north and south is to blame for both features; two rounds of significant snow in the west, and the threat of strong to severe thunderstorms in the east. We take a look at the timing, as well as the most likely risks, below.
(COMING SOON: 2018 FALL FORECAST AND A SNEAK PEEK AT WINTER. DON'T MISS THIS ALL DAY EVENT ON MONDAY, SEPTEMBER 17)
- Risk of mainly non-severe storms on Saturday
- Stronger storms likely Sunday, especially for southeastern Manitoba/northwestern Ontario
- Cooler, drier weather on the way next week
WATCH BELOW: TRACKING STORM ENERGY THIS WEEKEND
SATURDAY - SOUTHERN TIER THUNDERSTORMS
Thunderstorms are expected to be more widespread, but less severe, on Saturday, as a boundary develops across the southern foothills. This boundary provides the focus for storms across southwestern Alberta and into southern Saskatchewan for the late morning and early afternoon, spreading eastward through the afternoon and evening as a low pressure system starts to push up from the central U.S.
This encroaching low pressure system brings a surge of warmer, more unstable air into southern Manitoba through the later afternoon, raising the risk for isolated severe storms. This same system is also what brings us a greater risk for strong storms on Sunday.
SUNDAY - STRONGER STORMS EXPECTED
It's the latter half of the weekend that we'll be watching for more widespread severe weather, as a region of heat and humidity bulge into Manitoba and northern Ontario, drawn north by the low pressure system. This surge of late-summer heat will be short-lived, however, as the system's cold front comes crashing through later Sunday afternoon and into the evening hours; it's this period we'll be watching for the risk of severe weather.
While the primary threats from these late-in-the-season storms will be heavy rain and strong winds, we can't entirely rule out the possibility of an isolated tornado in southeastern Manitoba and northwestern Ontario. Winds look favourable to support some strong, long-lived thunderstorms, mainly over extreme southeastern Manitoba through the afternoon hours. If you have outdoor plans during this time, you'll want to keep a close eye on any developing weather.
Some storms are likely to persist into northern Ontario into the overnight hours, but storm energy will start to wane after sunset, diminishing the risk for severe storms.
A quieter, but cooler, pattern takes hold for much of next week as we head toward the first day of Fall next weekend.