Another day, another severe weather risk for Southern Saskatchewan. Below we breakdown the risk ahead.
Thursday June 10, 2021
Threat level: HIGH
Confidence: MODERATE (based on model agreements)
Expected hazards: VERY LARGE HAIL // DAMAGING DOWNBURST WINDS // TORNADOES
Locations impacted: Southern Saskatchewan: Assiniboia, Weyburn, Gravelbourg and vicinity
Timing: 7pm CDT to 12am CDT
Expected watch(s): tornado watches across Southern Saskatchewan & severe thunderstorm watches for Southwestern Manitoba
Discussion: a surface trough across SE AB will provide lift, aided by a surface low pressure currently across Montana and a warm front moving north throughout the day. Morning convection across Southern SK left a stable atmosphere with low clouds across the forecast area. Atmospheric recovery will need to occur and only an hour or so of sunshine is needed to destabilize the environment across Southern SK. When/if this occurs would lead to an environment characterized with elongated hodographs, steep lapse-rates and MLCAPE values in the 3000 J/kg. HRRR is hinting at mixing around 1-2pm CDT, which may be overly optimistic. However, ensemble runs show supercells initiating in that time frame, while NAM 3km waits until the 7pm CDT time frame. Time will tell, but a volatile environment conducive to tornadic supercells is apparent across Saskatchewan this afternoon/evening. The SPC NREF ensemble has a 5% tornado probability extending across Southern SK for today.
Discussion by the Prairie and Arctic Storm Prediction Centre in Canada:
DISCUSSION... EASTERN PRAIRIES...FOLLOWING THE ROUND OF SEVERE CONVECTION LAST NIGHT IN SOUTHWESTERN SK, THE FOCUS FOR SEVERE WX WILL SHIFT A TAD FURTHER EAST IN THE PROVINCE THIS AFTERNOON. THE SAME AREA OF LOW PRESSURE RESPONSIBLE FOR LAST NIGHT'S ACTIVITY WILL REMAIN STATE-SIDE, AND LIE OVER EASTERN MONTANA THIS AFTERNOON. A WARM FRONT WILL EXTEND OVER NORTH DAKOTA WITH AN INVERTED TROUGH SLIDING BACK UP INTO WESTERN SK. AMPLE ISENTROPIC LIFT OVER THE WARM FRONT ALONG WITH AN ABUNDANCE OF MOISTURE ADVECTION ALONG WITH STEEP MID-LEVEL LAPSE RATES WILL HELP WITH THE INTIATION PROCESS THIS AFTERNOON. ALL THIS, COUPLED WITH MLCAPE VALUES NEARING 2500 J/KG AND BULK SHEAR VALUES OF 40-50 KTS WILL HELP TO PROMOTE SUPERCELL DEVELOPMENT. ALL SEVERE WX THREATS, THAT IS, TORRENTIAL DOWNPOURS, LARGE HAIL AND DAMAGING WIND GUSTS ARE LIKELY WITH THESE STORMS. IN ADDITION, 0-1 KM SRH'S GREATER THAN 200 J/KG AND SIG TOR VALUES IN EXCESS OF 2 OVER SOUTH-CENTRAL REGIONS SUGGEST A DISTINCT TORNADO THREAT DURING THE AFTERNOON AND FOR REGIONS FURTHER EAST INTO THE EVENING. A 40-50 KT H85 SOUTHERLY JET AHEAD OF THE LOW WILL MAINTAIN THE SEVERE WX THREAT WELL INTO THE EVENING, PUSHING INTO SOUTHERN MB DURING THE OVERNIGHT HOURS AND INTO FRIDAY MORNING. THE ONLY FLY IN THE OINTMENT WILL BE THE ROLE LAST NIGHT'S CONVECTION WILL PLAY WITH THE POTENTIAL FOR FURTHER STORMS LATER TODAY. RESIDUAL CLOUD COVER AND THE EXPANSIVE COLD POOLS FORMED BY THESE STORMS WILL INEVITABLY ALTER THE PRE-STORM ENVIRONMENT FOR THIS AFTERNOON'S CONVECTIVE INITIATION. JUST HOW MUCH REMAINS THE MILLION DOLLAR QUESTION. COMPLICATING MATTERS FURTHER, MODELS OVERNIGHT HAD TROUBLE RESOVLING THE LINGERING CONVECTION, ALLOWING LITTLE TO NO IMPEDING FACTORS FOR STORM DEVELOPMENT THIS AFTERNOON.