Get the air conditioners ready: hot and humid weather is on the way for Winnipeg.
Winnipeg will see the first true blast of summer heat as a muggy Gulf of Mexico air mass builds into the region tonight. While daytime highs will be similar to those seen over the past few days, dew points climbing into the upper teens will bring warm overnight lows and muggy conditions on Thursday afternoon with humidex values in the mid-30s.
However, with this hot and humid weather will come the first significant thunderstorm threat of the year. Winnipeg will see increasing cloudiness Wednesday evening and a slight chance of showers or thunderstorms overnight. There should then be a reprieve with mixed skies until Thursday afternoon when an upper-level disturbance begins working into the region. Most of the thunderstorm activity should hold off until later in the day, but it’s likely that showers and thunderstorms develop in the evening.
Dew points will climb to nearly 20°C on Thursday afternoon in Winnipeg, making for a very humid afternoon.
Looking at the MIST principles:
Moisture: Deep moisture with dew points in the upper teens will provide plenty of energy for the storms to work with.
Instability: Moderate with MLCAPE values near 3000 J/kg transitioning to around 2500 J/kg of MUCAPE as the evening progresses.
Shear: Will be low to moderate with roughly 20 to 25 kts of bulk shear.
Trigger: An incoming shortwave will provide mid-level destabilization to help initiate convection.
All this combines for a threat of severe thunderstorms with primary threats of large hail and wind gusts in excess of 90 km/h. The high dew points will also support heavy rain with localized amounts of 30 to 50 mm possible as the shortwave moves in on Thursday night.
Thursday afternoon will also bring some breezy conditions with winds out of the south near 30 km/h.
Friday will bring potentially unsettled conditions as an upper low moves through the region. With relatively humid conditions still in place, mixed skies are likely with scattered showers or thunderstorms moving through the region.
Long Range Outlook
A bit of relief from the heat will arrive for the weekend with daytime highs cooling slightly on Saturday and humidity levels dropping. The heat quickly builds back in on Sunday with highs near 30°C again.
Next week looks to kick off with an unsettled and warm trend. Daytime highs in the upper 20’s look likely, along with mixed skies and several chances for showers or thunderstorms.
Winnipeg’s seasonal daytime high is currently 21°C while the seasonal overnight low is 7°C.
The heat will return early this week as temperatures climb up to the thirty degree mark. This warm and humid air mass will also bring another risk of thunderstorms to southern Manitoba on Tuesday.
Hot weather is in store for southern Manitoba early this week
This Week
Today will be a hot one in southern Manitoba. Temperatures are expected to climb into the low thirties in most areas. The humidity will begin to climb as well, with dewpoints reaching the upper teens in most areas by late Monday – although locally higher dewpoints will be possible. Despite these hot and humid conditions it doesn’t appear that we’ll see any storms today. The atmosphere is expected to be capped, preventing thunderstorms from developing. There is a slight risk of storms overnight, but conditions don’t look particularly good for widespread development.
Tuesday will be the more interesting day storm-wise, as humidity increases further. A low pressure system is expected to sit over southern Manitoba by midday Tuesday, maintaining a south to southeast surface flow over the Red River Valley and southeastern Manitoba. Instability will be high with the hot and humid conditions, while wind shear is also strong because of the approach of a strong upper-level trough. These conditions should be favourable for the development of severe thunderstorms. High temperatures should end up near 30C with the humidex in the upper thirties. Skies will be mainly sunny before storms begin to develop.
A strong cold front is expected to slice through southern Manitoba on Wednesday morning. This front will drop temperatures down to near the 20C mark. The front will also take advantage of the lingering humidity in the atmosphere to produce shower activity over most of southern Manitoba. Following the frontal passage, it will become quite gusty as well, with northerly winds of 40 km/h gusting to 60 km/h.
Long Range
It appears that temperatures will begin to rebound later this week following the passage of that cold front on Wednesday. Temperatures approaching the 30C mark may be possible again by the weekend – although models are still unclear as to how long and intense this next burst of heat will be.
A low pressure system tracking eastwards through Saskatchewan will bring a potent severe thunderstorm threat to Southern Manitoba today. The development of severe thunderstorms capable of producing damaging hail and winds, torrential downpours, and tornadoes is expected this afternoon over portions of southwestern Manitoba. These thunderstorms will then track eastwards across the Red River Valley & the southeastern corner of the province through the evening hours.
Hot and humid weather will return to Winnipeg today as temperatures soar to the 30°C mark while dewpoint temperatures climb towards the 20°C mark in the Red River Valley courtesy a gusty southeasterly wind of 30-40 km/h that will develop midday. This hot and humid weather will serve as the pressure cooker for severe thunderstorm development as a low pressure system tracks into the province this afternoon.
Through the morning hours, a few isolated thunderstorms are possible across the southwestern and south-central portions of the province, but they aren’t expected to be particularly notable. By early to mid-afternoon, the “main event” will start with thunderstorms developing along a north-south line west of the Red River Valley. Through the late afternoon into the evening, these thunderstorms will move eastwards across the Red River Valley and southeastern Manitoba.
These thunderstorms will be capable of producing large and damaging hail, dangerous straight-line winds exceeding 100 km/h, and torrential downpours capable of flash flooding. In the early hours of the system, over portions of southwestern Manitoba and possibly extending into the western Red River Valley, these thunderstorms will also be capable of producing a tornado.
Moisture: Dewpoints climbing into the 20-23°C range will combine with moderate vertical extent as an organized moisture feed advects into the province from the Dakotas.
Instability: Significant moisture coupled with moderate mid-level lapse rates to produce MLCAPE values 2000-3000 J/kg. MUCAPE values of 1500-2000 J/kg will continue overnight into northwestern Ontario.
Shear: Significant speed and directional shear will be in place over the province with textbook-quality looping hodographs present under 50-60 kt of 0-6km bulk shear will practically guarantee supercell development upon storm initiation and will be completely supportive of upscale growth into the overnight period.
Trigger: A frontal wave passing by the province and associated low pressure system and trough will provide ample lift and convergence to trigger thunderstorm development.
As storms develop, they will very quickly begin rotating and mature into supercell thunderstorms. These storms will very quickly develop hail and severe wind threats. Low lifting condensation levels coupled with the strongly veering hodographs and notable low-level CAPE also suggests a tornado threat for the first few hours of the storm life-cycle. This will most likely be constrained in an area from Brandon to Winnipeg along the Trans-Canada Highway and then south to the American border.
The severe thunderstorm threat will continue eastwards with the line through the evening into Ontario.
AWM Day 1 Convective Outlook for August 3, 2016
The thunderstorms will track eastwards through the evening hours, with Winnipeg most likely seeing the activity between 8PM and 1AM.
Winds will diminish tonight behind the thunderstorm activity as temperature dip to around 17°C.
Update: EC Event Summary
Environment Canada has issued a summary of the severe weather that occurred across #MBstorm yesterday. The highlights are two confirmed tornadoes, loonie to quarter sized hail, wind gusts up to 111 km/h, and 4″ of rain!
Weather summary for Manitoba
issued by Environment Canada
at 5:04 a.m. CDT Thursday 4 August 2016.
Discussion.
An intense low pressure system tracking across the Prairies brought
widespread severe weather to much of southern Manitoba on Wednesday.
Two tornadoes have been confirmed, and numerous reports of heavy
rain, damaging winds, and large hail were also received.
The following reports have been received by ECCC meteorologists
(event times are approximate):
A funnel cloud was reported 8 km north of Hartney at 5:00 pm CDT.
A brief tornado was reported near Margaret at 5:10 pm CDT. No damage
was reported with this tornado.
A larger, longer lived tornado was reported 10 km west of Baldur at
5:20 pm CDT. It tracked northwards towards Stockton where a large
shed was destroyed shortly after 5:30 pm CDT.
ECCC meteorologists continue to investigate these and other
unconfirmed tornadoes.
Hail reports:
Loonie sized hail at Brandon at 6:05 pm CDT.
Quarter sized hail at Shoal Lake at 9:20 pm CDT.
Loonie sized hail at Wasagaming at 10:10 pm CDT.
Peak wind gust reports:
111 km/h at Morden at 7:26 pm CDT.
93 km/h at Portage la Prairie at 7:10 pm CDT.
92 km/h at St. Adolphe at 9:05 pm CDT.
85 km/h at Gretna at 7:46 pm CDT.
74 km/h at Winnipeg Airport at 9:45 pm CDT.
Rainfall totals in millimetres:
Erickson 104
Neepawa 75
Glenboro 66
St. Adolphe 64
Holland 56
Ethelbert 53
Fisherton 53
Morden 53
Killarney 50
Souris 49
Cypress River 45
Elm Creek 43
Snowflake 43
Winnipeg The Forks 2.7
Winnipeg Airport 1.4
Environment and Climate Change Canada meteorologists are actively
seeking pictures or videos from Wednesday's severe weather events
and further damage they may have caused. Should you have any
information regarding these events or to report severe weather at
any time, please call 1-800-239-0484, email storm@ec.gc.ca, or tweet
#MBStorm.
Please note that this summary may contain preliminary or unofficial
information and does not constitute a complete or final report.
End/PASPC
The Rest of the Week
Thursday will be a cooler day with a high near just 21°C with gusty northwesterly winds at 30-40 km/h. There will be a slight chance of some showers as the wrap-around from this low moves across the province. The humidity will be flushed out of the province making for more comfortable conditions. Temperatures will dip to 13°C Thursday night with clearing skies and diminishing winds.
Friday will be a pleasant day with winds out of the northwest at 20-30 km/h, highs in the mid-20’s and mainly sunny skies.
Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.
Heat and humidity will build back into Southern Manitoba this weekend, bringing both mid-summer warmth and the returning threat for severe thunderstorms.
Today will be a beautiful day for Winnipeg & the Red River Valley as a ridge of high pressure exiting the region continues to bring mainly sunny skies. Winds will remain light out of the south as temperatures climb to a high near 27°C. Tonight, under a few clouds, temperatures will dip down to near 14°C.
The weather pattern will begin to change on Saturday as a low pressure system developing over the Prairies begins drawing warmer, more humid air northwards into Manitoba. Daytime highs will be similar to Friday, around 27°C, however the humidity will begin to become a little more noticeable by the end of the day as the dewpoint climbs to the 16 or 17°C mark. Alongside the increasing humidity will come a slight chance of some late afternoon or early evening thunderstorms. The severe potential looks fairly limited at this time, as does the overall ability for any storms to organize, so while an isolated strong-to-severe storm may be possible, no widespread or organized severe threat is expected.
Temperatures will then dip down to around 17°C on Saturday night with a few clouds.
Dewpoint temperatures climbing to near the 20°C mark will make for a muggy Sunday.
Sunday will see the warmest air move into the Red River Valley alongside an increment in humidity. Daytime highs will climb to near the 30°C mark along with dewpoints rising to near the 20°C mark, making it feel quite muggy. Humidex values, a "feels like" temperature that combines temperature & humidity values, will be in the upper 30's, making for quite a hot day. Skies will be mixed, and a breezy southerly wind will be in place through the Red River Valley at 20-30 km/h.
Sunday night will be a warm one with temperatures dropping only to around 20°C. A threat for thunderstorms return with a likely severe threat. Over 2500 J/kg of MLCAPE will be in place over parts of the province, alongside 35 kt of bulk shear and strongly veering wind profiles. This suggests an all-threats severe hazard, including a tornado threat in the early hours of storm initiation over Southwestern Manitoba. As the thunderstorms progress eastwards, the threat will likely shift to strong wind and large hail.
Long Range
Next week is looking like a return to more unsettled weather. Uncertainty exists with the thunderstorm system at the end of the weekend, with some models suggesting a slower progressing system that would result in more of a rain/storm threat on Monday instead. After a brief reprieve from that system, another one looks to be on the doorstep for mid-week that will bring another chance for rain and thunderstorms. Following that, the week will end off slightly cooler than seasonal.
Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.
