Tag: Rain

Cool, Wet Weekend Ahead

Brad Leave a comment

A distinct chill will be in the air over the next few days as unseasonably cool temperatures move into Winnipeg and the Red River Valley alongside the first substantial rainfall in months.

As mentioned on Wednesday, a low pressure system will begin working its way into Manitoba today, bringing what will likely be the largest rainfall event of 2017 [thus far] to the city. The biggest change between our forecast on Wednesday and what is expected to happen today is the timing: the system’s arrival will be slightly delayed, beginning in the afternoon rather than the morning.

So, today will start off fairly cloudy skies, although a few sunny breaks are possible between now and this afternoon. As the low pressure system lifts northwards out of Nebraska into the Dakotas, cloud will thicken up over the Red River Valley with rain beginning this afternoon. The rain will become more intense into the evening with even a small chance for a crack of thunder or two. The heaviest rain should move out around midnight, with some showers or drizzle left behind.

Temperatures will be cool; expect a high near 14°C, but quickly drop to around 10 or 11°C when the rain begins. Expect a low near 8°C tonight. The winds will also be rather unpleasant, picking up out of the north-northeast to around 40-50 km/h this afternoon. The winds will persist into the evening, then diminish to 30 gusting 50 km/h overnight.

By the time the bulk of the rain pulls out of the region, Winnipeg and the Red River Valley will likely see between 20 and 40 mm, with the potential for a bit more or a bit less locally depending where exactly any heavier or lighter bands of rain set up.

RDPS 24hr. QPF valid 18Z Saturday September 16, 2017
The RDPS is suggests as much as 50-60mm of rain may be possible from Friday afternoon to midday Saturday over the Red River Valley

Saturday will bring very cool weather to the Red River Valley with daytime highs likely not even reaching 10°C. Stuck between the Friday night’s disturbance and another one that will move through Saturday evening, skies will remain cloudy with a continued chance of showers or drizzle. Winds will continue out of the north-northeast at 30 gusting 50 km/h for the day, but then diminish to calm in the evening.

As the next disturbance rolls by on Saturday evening, it will likely produce another batch of showers or rain over the Red River Valley, but amounts will be considerably less, with under 5 mm expected for most of the Red River Valley. Temperatures will drop to a low near 7°C.

And for Sunday, some morning cloud with the potential for showers or drizzle will begin moving out midday, bringing mixed to sunny skies back to Winnipeg for the afternoon. Expect a high near 15°C with winds picking up out of the west-southwest to around 30 km/h.

Long Range

The beginning of next week will start off sunny with temperatures returning to near-seasonal values for Monday and Tuesday. By Wednesday, however, another series of disturbances roll through the region, bringing what looks like another fairly good chance for more rain through the latter half of the week.

Winnipeg’s seasonal daytime high is currently 18°C while the seasonal overnight low is 6.

Slow Slide To Cooler & Rainy Weather

Brad Leave a comment

Winnipeg will see the weather slide from September Summer™ to seasonal to cool and rainy over the next few days as a developing storm system in the Northern Plains gets set to bring a major pattern shift to southern Manitoba.

Today will continue the September Summer™ for Winnipeg and the Red River Valley as daytime highs climb well above-seasonal into the mid-20s under nothing but sunshine. Winds will be fairly light today too at just 15-20 km/h, making for a gorgeous day. Some cloud cover will move through tonight as temperatures dip to a low near 13°C.

Warmer than seasonal daytime highs will continue for another day across southern Manitoba

Thursday will see the beginning of a major pattern change as a major low pressure system gradually organizes through the northern plains of the United States. As it does so, a northeast wind to 20-30 km/h will begin tapping cooler air from the central Prairies, returning near-seasonal temperatures back to Winnipeg and the Red River Valley. Skies will be mixed with increasing cloudiness overnight.

Friday’s dominant weather feature will be a trough of low pressure developing across central North Dakota into southeastern Manitoba in response to a low pressure system tracking into Nebraska out of Wyoming. This trough line will support the development of a large area of rain that will spread northeastwards from western North Dakota along the trough, likely arcing through southwest Manitoba and across the Red River Valley into the Whiteshell.

Rain will spread northeastwards out of Montana and western North Dakota on Friday morning

This feature has all indications that it will be a prolonged rainfall event, with rain beginning Friday morning and continuing into Saturday morning. Total rain will be variable and dependant on whether or not any embedded convection develops, but general amounts of 20-30 mm look quite likely. With all the rain, temperatures will be quite cool with highs well below-seasonal in the low teens.

Long Range

Unsettled weather will continue on Saturday with improvement on Sunday, but the chance for more rain will return on Sunday night into Monday morning. Temperatures will remain below-seasonal through the weekend.

Into next week, temperatures will return to near-seasonal values, but it looks like there will be multiple chances for rain as several disturbances cross the Prairies.

Winnipeg’s seasonal daytime high is currently 18°C while the seasonal overnight low is 6.

Cloudy, Cool Mid-Week Gives Way to Another Heat Wave

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Temperatures will be well below-normal today as Winnipeg and the Red River Valley remain entrenched under a cool northeasterly flow behind yesterday’s low that moved through the region. Temperatures will rebound quickly, though, with well above-normal temperatures return for the end of the work week.

Today will see high temperatures some 10°C below typical seasonal as cool, cloudy weather hangs over the Red River Valley as northeasterly winds tap cooler air underneath a cold upper-level low crossing over the region. Skies will remain cloudy much of the day — there’s a slight chance we might see some sunny breaks late this afternoon — and there will be a chance for some light rain or drizzle, particularly in the morning hours. Temperatures will reach a high of only around 16°C1 with winds out of the northeast at 15-25 km/h.

Skies will begin to clear tonight as temperatures dip to a low near 11°C with light winds.

A cold low, shown here with closed height contours at the 700mb level, will move across southern Manitoba on Wednesday, keeping skies cloudy and temperatures cool.

Thursday will be a much nicer day as the remaining cloud cover clears out and temperatures climb to a high near 23°C under light winds. There may be some scattered clouds in the afternoon, but nothing that will spoil the sunshine. Expect clear skies on Thursday night as temperatures drop to a low near 13°C.

On Friday, the upper-level ridge that brought scorching hot weather to B.C. and the western Prairies last week begins building back into the region. Under sunny skies, temperatures in the Red River Valley will climb into the lower 30’s. Areas in the southwest corner of the province will be even hotter, with high temperatures climbing into the mid- to upper-thirties. Southerly winds at 20-30 km/h will be in place as a low pressure system slumps towards the region from the northwest. These winds will draw humid conditions northwards; by the end of Friday dew point values will climb into the low 20’s, making it feel positively muggy out there.

Very warm temperatures will build across the entirety of the Southern Prairies on Friday with highs in the 30’s.

Friday night will continue to be warm with lows dropping only to around 18°C.

Long Range

Northerly winds will move into the region on Saturday, flushing the humidity southwards and making for more comfortable conditions. Daytime highs will still remain in the upper 20’s or low 30’s throughout the weekend under mainly sunny skies. With the warm air still in place, overnight lows will still be quite warm, likely bottoming out in the upper teens.

The hot weather continues next week, but there are signs that there may be some unsettled weather to begin the week before things settle down again. No significant widespread rainfall is expected in the next week.

Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.

  1. Although if more clearing were to develop than expected, temperatures would quickly reach closer to 18 or 19°C. ↩

Week Comes To A Stormy End in Southern Manitoba

Brad Leave a comment

A complex low pressure system will bring several chances for thunderstorms to Winnipeg & the Red River Valley today and tonight into Saturday morning, some of which may be severe. All the unsettled weather will clear out on Saturday afternoon, leaving us with a seasonably mild and dry weekend.

The risk of thunderstorms returns to Winnipeg today as an approaching warm front moves into the region. As it advances eastwards, leftover cloud cover from overnight thunderstorms in Saskatchewan will spread into the Red River Valley. Before we get into the thunderstorm details, today’s high in Winnipeg will be a balmy 27°C with dew points climbing up to the 16-17°C range, making it feel a bit humid in the afternoon. Winds will be out of the south-southeast at about 20-30 km/h. Expect a low tonight near 18°C. Now, onto the thunderstorm details!

The first potential thunderstorm threat is for this afternoon, and will be focused primarily over southwestern Manitoba.

  • Moisture: Surface dewpoints will climb into the 15-17°C range ahead of the surface trough moving into the region. This moisture will be relatively deep, dropping only to around 13°C at 850mb.
  • Instability: MLCAPE values will climb to 1000-1500 J/kg of CAPE through the afternoon, although capping may be an issue depending on the timing of the 700mb thermal ridge passage.
  • Shear: Shear is fairly good with veering profiles and 45-50 kt of bulk shear. Low-level shear is relatively unidirectional with moderate speed shear.
  • Trigger: Low centre with trough line extending northwards will provide focus for low-level convergence. Additional, the triple point of a frontal wave tracking along the U.S./Canada border will also provide more focus and convergence.

The main uncertainties are tied to how quickly warmer air at 700mb1 can exit area. While it’s in place, it will likely prevent the development of thunderstorms until the evening. Should thunderstorms develop, the primary threats would be large hail and strong winds. The storms should be moving quickly enough that the threat for localized flooding due to rain is minimized, and higher cloud bases coupled with relatively small amounts of low-level wind shear will also reduce the tornado threat. If these thunderstorms develop, they will track eastwards into the Red River Valley in the early evening and make their way through.

The second thunderstorm threat will develop this evening and will impact much of southern Manitoba. Another disturbance will push into the region and initiate thunderstorms.

  • Moisture: The low-level jet will be supplying air with dew points near 16-17°C, providing ample moisture for thunderstorm development.
  • Instability: MUCAPE values will hover near 1000-1500 J/kg, enough energy to strong to severe thunderstorms.
  • Shear: Will be excellent; a very potent low-level jet will develop, strengthening to 50kt by 03Z. 500mb winds will be out of the west to southwest at 45-50 kt. This shear will be very supportive of thunderstorm development.
  • Trigger: Shortwave and associated frontal wave will be trigger for thunderstorm development.

Even now, there’s significant uncertainty with this afternoon’s convection. That said, it seems likely that thunderstorms will likely develop over portions of southwest Manitoba near 6-7PM and then undergo rapid upscale growth and develop into a line that tears eastwards across the Red River Valley; the primary threats associated with these storms will be large hail and damaging winds. Significantly elevated precipitable water values also suggest very intense downpours are likely as well.

AWM Thunderstorm Outlook valid 12PM Friday June 9 – 12PM Saturday June 10, 2017

Saturday will bring some more morning showers or thunderstorms, then breezy westerly winds of 30 gusting 50 km/h will usher in drier air in the afternoon as the clouds break up and clear out. Temperatures will climb up to a high near 23°C. Expect a low near 13°C under mainly clear skies on Saturday night.

Sunday will bring mainly sunny skies to Winnipeg with winds strengthening out of the southwest to around 30-40 km/h. Temperatures will climb to a high near 25°C. Winds will taper off Sunday evening as temperatures dip to a low near 15°C.

Long Range

Next week becomes quite uncertain as a major low pressure system develops in the Northern Plains of the United States and then slowly meanders northwards. As we move into summer, these systems will increasingly be driven by thunderstorms, which carry an inherent level of uncertainty, especially in the long range as how the various rounds of thunderstorm activity develop can impact the overall development of the low pressure system. That said, conditions will turn unsettled next week with near-seasonal to slightly above-seasonal temperatures.

Winnipeg’s seasonal daytime high is currently 23°C while the seasonal overnight low is 10°C.

An Additional Note

This will be the last forecast we issue here at A Weather Moment for the next while. We’ll be taking a bit of a vacation and won’t have our regular forecast posts on Monday June 12th or Wednesday June 14th. We suggest you check Environment Canada’s forecasts while we’re away!

  1. Approximately 3km above the ground. ↩