Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Thu Jun 27 2019
...Montana through western ND... Easterly near-surface winds will persist over the northern Plains north of the stationary front resulting in westward advection of boundary layer moisture with dewpoints in the 50s F expected across central MT and near 60 F in the eastern part of the state. With steep lapse rates already in place, MLCAPE should climb to around 1500 J/kg as the surface layer warms during the day. Another in a series of vorticity maxima will rotate through the upper low circulation and into the northern Rockies during the time of peak destabilization, and storms should redevelop over the higher terrain and spread northeast into central and northeast MT. A mid-upper jet along the southeastern periphery of the upper low will contribute to 40-50 kt effective bulk shear supportive of supercell storms as the initial mode. Very large hail and damaging wind will be the main threats. Veering low-level wind profiles with height will contribute to sufficient 0-2 km storm relative helicity for low-level mesocyclones, and a few tornadoes will be possible especially toward early evening north of the front across central and northern MT where LCLs should be lower. Storms may eventually congeal into an MCS and spread east, reaching western ND overnight with a continued threat for damaging wind.
Those are some pretty fancy words, but it just means strong storms will lift from Montana later today into southeastern Alberta. Wind profiles and instability will be favorable for supercell storms initially, but may become more "multicellular" once they reach Alberta/Saskatchewan, which would pose more of a wind/hail threat on the Canadian side.
Below is the Storm Prediction Center's tornado risk. They have a 5% probability of seeing a tornado today in that brown circle, which extends into Alberta/Saskatchewan. For updated tornado probability, simply click on the image.
For a more technical discussion, head over to our previous discussion here: https://www.nzpchasers.com/post/severe-weather-outbreak-possible-thursday-in-ab-sk
Below is the PASPC's (Canadian version of Storm Prediction Center) risk for today. While we think there is a tornado threat, the graphic below is outdated from yesterday. Click the image and it will take you to the updated version:
Area(s): Central and Southern Alberta
Timing: Thursday afternoon and evening
Threats: 2-4 cm hail, wind gusts 90-100 km/h
Scattered thunderstorms are likely over central and southern Alberta Thursday, with severe thunderstorms likely over southeastern Alberta Thursday afternoon and evening. Thunderstorms that develop east of Calgary will have the potential to produce 2-4 cm hail and 90-100 km/h wind gusts as well as locally heavy downpours.