Severe Weather Returns

A hot and humid airmass will be in place the next few days along with a trough of low pressure that will move through the region, so that will be the main weather maker the next few days as it moves east into Ontario. As a result severe weather will be commonplace as it passes through.

My own severe weather risk map for the night ahead, a high risk is present for the extreme southwest.

Severe weather risk map for Tonight as put out by the RDPS model

For the night ahead an area of low pressure will be moving into Southern Manitoba encountering a hot and humid airmass, thunderstorms have already developed in Western North Dakota and they are expected to move into southwestern Manitoba over the coming hours. Let's have a lookk and see what ingredients are present here:

Moisture: Dewpoints will be in the upper teens low 20's for most tonight mixed in with humidex readings in the mid 30 range should give sufficent amounts of moisture for storms to drop, Excess of 50mm+ in less than a hours time possible.

Instability: CAPES on the order of 2,000 J/kg in the central parts of the province to 3,000 J/Kg in southern parts of the province overnight. A few places along the border could see CAPES of 4,000 to 5,000 J/Kg. Along with Lifted indicies of -5 to -11. Supercells although weak will be possible in the southern half of the province given Bulk Richardson Numbers in the high 30's to near 45. Anything less than 45 means supercell potential.

Shear: Not that impressive but it should be enough to sustain severe storms with 30 to 40 knots of bulk shear expected. That should supply the chance for some funnel clouds in places and maybe a few weak tornadoes, the chance is only 5% though.

Trigger: Frontal system will be moving Northeast overnight bringing in a severe weather threat, as it encounters the hot and humid airmass.

So what do we expect overall???
As thunderstorms continue to develop in North Dakota, they will push northwards overnight and if not either way given the high or extreme levels of instability I expect the storms to either grow upscale into a MCS or elevated thunderstorms that will develop in the form of a MCS with the likelihood of north and east expansion in a squall line/bow echo/derecho. As a result severe weather will be possible through the late evening and overnight timeframe, given high MUCAPES baseball sized hail will be possible for most, severe winds in excess of 90km/h, Flash Flooding rains with very intense frequent lightning. Most of the severe weather will be affecting the high risk area from 7 to 11pm in southwest Manitoba, moderate risk area from 11pm to 5am in the rest of the western half of Manitoba into Winnipeg and the Red River Valley. Areas from the red river valley east the slight risk area after sunrise. Stay tuned to watches and warnings at http://weather.gc.ca/warnings/index_e.html?prov=mb Overnight lows will be mild and it will be muggy with lows of 21C in Winnipeg and 19C in Brandon with high teens and low 20's for most and humidex values of 25 to 30C. Thunderstorms should clear by morning leaving behind another sunny and muggy airmass.

Monday another round of severe weather 

 

High dewpoints stay in place on Monday in Southern Manitoba, fueling storms.

Severe weather risk map for Monday as put out by the RDPS model

Severe Weather including Tornado risks are possible in the red river valley including Winnipeg tomorrow.

Monday looks like another busy day weatherwise as a potent cold front drives through the province, there will be a setup for decent severe weather this time in the Red River Valley, hot and humid conditions will be present in the afternoon with humidex values near to above 40C. Let's look at the details about tomorrow's atmospheric conditions...

Moisture: Dewpoints in the low 20's and humidex values in the 40's, PWATS in excess of 30 to 50mm will provide significant amounts of moisture for storms to drop.

Instability: Will be off the charts tomorrow afternoon, 3,000 to 4,000 MUCAPE, lifted indicies in excess of minus 7 to minus 12. Enough for baseball sized hail again given MUCAPE fuels the updrafts in thunderstorms which creates hail.

Shear: Very impressive!!! 50 to 60 knots of bulk shear expected giving storm organization into potential supercells and continued storm growth.

Trigger: A powerful cold front moving in from the southwest in North Dakota.

It will be a very busy day weatherwise as we approach the day Monday, as mentioned a powerful cold front will go through a hot humid airmass, as a result I expect storms to fire in the western red river valley and northern north dakota in the late afternoon hours. They will likely grow upscale into a thunderstorm squall line by mid afternoon into the evening.  There will be a potential for baseball sized hail, frequent lightning, and heavy rainfall in excess of 100mm an hour. Winds will also be a concern as hefty amounts of shear are available for thunderstorms tomorrow. The risk for tornadoes is there in the red river valley and eastern manitoba tomorrow afternoon and evening with supercell potential.Storms should weaken as they move north into Northern Manitoba by late evening. Watches will likely be issued tomorrow so stay tuned to weather.gc.ca for details. High temperatures will be in the mid to high 20s with humidex values going above 40C for much of the south. Clearing should come in by mid evening with temperatures dropping into the mid teens for overnight lows and much drier air will be in place.

Showers are expected on Tuesday with the odd shower or thunderstorm around that will be with the presence of a powerful low pressure system that will be centered over the interlakes, severe weather will not be anticipated on Tuesday with highs just getting above 20C. Warmer weather will arrive by mid week into late week.

I will update in the morning or early afternoon tomorrow regarding the severe threat, in case it changes.