Southern Manitoba will be under the influence of a major low pressure system for one more day, bringing gusty winds and more rain shower activity, before drier conditions begin moving in through the remainder of the week.
Winnipeg & the Red River Valley will continue to be under the influence of a major low pressure system currently located over eastern Manitoba for one more day. Today will see cloudy skies and on and off showers through the day across the region, although they will likely be more numerous through the morning hours. Winds will be quite breezy out of the west to northwest at 30-40 km/h with gusts up to around the 60 km/h mark, and it may even feel more like late-summer thanks to a below-seasonal high temperature of just 18°C.
The rain shower activity will taper off through the late afternoon into the evening hours, leaving mainly cloudy skies in Winnipeg as temperatures head to an overnight low near 13°C. The winds will continue breezy at around 30 km/h.
Around 5mm of rain can be expected from showers across much of Southern Manitoba today.
Thursday will bring mainly cloudy skies, although a bit of sun may be possible late in the day. Winds will be lighter than Wednesday at around 30 km/h out of the northwest. Daytime highs will be a bit warmer throughout the Red River Valley at around 20 or 21°C. A lingering trough may result in a few afternoon showers near the U.S. border and extending back into southwestern Manitoba.
Skies will continue to clear Thursday night as temperatures dip to around 12°C.
Friday will be a pleasant day with light winds, plenty of sun and a high near 23°C.
Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.
Anyone looking for a good long stretch of hot, dry weather really should consider broadening their horizons because generally unsettled weather continues throughout Southern Manitoba right through the coming weekend.
Today will be the most pleasant and "summer-like" day of the coming few as the sun makes a prominent showing with temperatures climbing into the mid-20's for a daytime high. While some showers or thunderstorms are possible over southwestern Manitoba today, Winnipeg & the Red River Valley should see just a few clouds with no precipitation expected.
Tonight will continue to be fairly pleasant with a low near 13°C.
Thursday will bring unsettled weather back to Winnipeg as an upper low moves into southern Manitoba. Increasing cloudiness and showers will spread from the southwestern Red River Valley to the northeast through the morning, and then the unsettled conditions will persist through the afternoon. At this point no thunderstorm activity is expected. Temperatures will reach a high near 23°C and then head to a low near 14°C on Thursday night with a continuing chance of showers.
Several models are showing an area of rain or showers moving through the Red River Valley on Thursday afternoon.
Friday will continue with fairly cloudy skies and a slight chance of more light shower activity. Some sunny breaks are possible in the afternoon as the temperature climbs to a high near 23 or 24°C. Temperatures will drop to around 14°C with clearing skies.
Hot, Unsettled & Increasingly Humid This Weekend
The weekend weather will be dominated by a developing trough of low pressure through the western and central Prairies that will draw humid air northwards from the Central Plains of the United States and bring with it the potential for multiple days of thunderstorm potential. Early indications are that severe thunderstorms will certainly be possible on both Saturday and Sunday. Highs will be in the upper 20's with Sunday in particular beginning to feel very muggy.
The GFS is forecsting potent SBCAPE values in excess of 4,000 J/kg by Sunday evening.
With the Winnipeg Folk Festival starting off this weekend, we'll be sure to keep a close eye on this system as it develops. Early indications are that the days will be fairly pleasant with more of a chance for thunderstorms through the overnight periods both Saturday night and Sunday night. By Sunday, there may be a significant severe threat with any thunderstorms due to the sheer amount of instability that is forecast to be in place over the region. We'll have a closer look at the weekend forecast on Friday morning.
Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.
Sunday, June 19th marks both Father’s Day as well as the Manitoba Marathon, and unfortunately it appears that the unsettled weather we talked about in Friday’s post has the potential to bring a significant threat of severe thunderstorms to the region.
AWM Convective Outlook for June 18/19, 2016
The Short Version
Severe thunderstorms are possible early Sunday morning, however that threat will be conditional on the expected development of thunderstorms in Saskatchewan on Saturday night.
The current expectation is that an area of thunderstorms will develop over Saskatchewan Saturday night, expanding in coverage and accelerating eastwards through the overnight period. This area of convection will then move through the Red River Valley with a primary threat of severe and damaging winds as well as large hail and torrential rain capable of producing flash flooding.
Thunderstorm Threat Outlook for Sunday June 19, 2016
Threat Type
Threat Level
Details
Rain
Moderate
Torrential rainfall possible with flash flooding.
Hail
Moderate
2-4cm hail possible.
Wind
Moderate
Strong wind gusts in excess of 100 km/h likely
Tornado
Low
No tornado activity expected.
The thunderstorm activity is expected to occur between 4:00AM and 9:00AM, with the primary threat period between 5:00AM and 7:00AM. The timing may adjust depending on the exact speed of the system, but overall this is expected to be a morning event.
Forecast for the morning of June 19, 2016
6AM
8AM
10AM
12PM
17°C
19°C
21°C
23°C
Thunderstorms likely
Thunderstorm activity diminishes
Slight chance of showers
Partly cloudy
Alongside the thunderstorms, conditions will get notably more humid as the morning progresses.[1] By the time any thunderstorm or rain showers taper off, things will feel fairly sticky. Temperatures will start around the 16-17°C mark in the morning, climbing to around 23°C by noon, and then on to a high near 27°C in the afternoon. Winds will be fairly light until mid-afternoon when they pick up from the west to around 20-30 km/h, ushering in drier air and providing some relief from humidity.
The Details
The potent thunderstorm potential for Saturday night and Sunday morning across the southern Prairies will be the result of a potent shortwave that ejects northeastwards out of Montana on Saturday and then rides eastwards along the international border. This will spawn a surface low with cold front draped southwards as cooler air builds in behind the shortwave and warm front extending eastwards across the northern portions of the Northern Great Plains. The surface low will then slide eastwards, gradually lifting the warm front northwards as it goes.
This shortwave will [likely] initiate an area of convection over southwestern Saskatchewan that will track eastwards along with the shortwave. The orientation of the warm front will provide plenty of support for the convection with shear profiles that indicate the likely development of a MCS[2] containing bow echoes.
Going over the MIST ingredients:
Moisture: Dewpoint values near 18°C will be ingested into the convection on Saturday night. This will provide substantial energy for the thunderstorms to work with. Additionally, the high moisture content of the air being ingested will increase PWAT[3] values to over 50 mm, making very intense rainfall likely with any thunderstorms that develop.
Instability: Steep mid-level lapse rates will combine with the warm and humid air of the nocturnal inflow to produce MUCAPE values in excess of 2000 J/kg.
Shear: 55-65 kt of bulk shear coupled with veering profiles within the convection will support the development of strong, organized thunderstorms.
Trigger: Shortwave-induced mid-level destabilization coupled with the development of a strong LLJ.
For these parameters, the primary concerns will be hail and rain, however should the storms be able to break through the inversion, wind will rapidly become a significant threat as gusts in excess of 100 km/h will be possible.
The steep mid-level lapse rates combined with high MUCAPE values will produce a moderate hail threat with hail between 2-4 cm in diameter possible. The heightened PWAT values make torrential rain likely with these storms, which can result in rapid accumulations and flash flooding. The strong winds & shear profiles of the storm environment make damaging wind gusts possible. Justification for the strong winds despite the nocturnal part of the convection will be the intense storm-relative winds that will be associated with this quickly-moving system. The SR-inflow will likely be strong enough lift the low-level air mass wholesale into the storm, resulting in a surface-based or near-surface-based thunderstorm.
Summary
Father’s Day of 2016, and the Manitoba Marathon, face the potential of being remembered for severe thunderstorms if current guidance continues painting the picture it does. Thunderstorm potential is conditional on nocturnal convection developing on Saturday night in Saskatchewan, but if it does, there is a significant threat of severe thunderstorms over Southern Manitoba on Sunday morning.
The timing for the primary severe thunderstorm threat will be in the early morning, buffering the starting time for the marathon, with much of the thunderstorm activity expected to be out of the region by 10-11AM. In the wake of this system will be a warm day that will feel fairly humid until westerly winds kick in mid-afternoon, pushing out the humidity and drawing in drier, slightly cooler air for the start of next week.
Dewpoint temperatures are expected to rise from 12-13°C early in the morning to around 19°C by mid-morning. ↩
This week will get off to a great start, with warm temperatures and sunny skies. However, more rain is on the way Tuesday night as the next low pressure system moves into the region.
Warm weather is expected in southern Manitoba today
The Week
Today will be a great day in southern Manitoba. High temperatures in the mid to upper twenties are expected with sunny skies. Winds will be light from the west. Today may end up being one of the nicer days this week, so enjoy it!
Tuesday will see temperatures in the mid twenties, but with increasing cloudiness through the day as a low pressure system begins moving into the region. Winds will be breezy out of the south-east at 20 km/h gusting to 40 km/h ahead of this system. Rain is expected to move into southern Manitoba on Tuesday night with this next system.
Wednesday will see rain ending from the aforementioned low pressure system. At this potential rainfall accumulations remain uncertain, so check back tomorrow for more details. Once the rain ends skies will remain mainly cloudy with temperatures in the upper teens. Winds will be from the north at 20-30 km/h.
Long Range
The long range forecast shows warmer weather returning late this week. Models are also hinting at our next risk of thunderstorms developing on Thursday and/or Friday with the approach of an upper trough moving in from western North America. We’ll have more details about this risk later in the week. Besides the thunderstorm risk, long range models generally show above seasonal temperatures for the remainder of June, although some cooler stretches are likely to be interspersed with the warmer ones.
