Tag: Thunderstorms

Warm & Unsettled Weather

Brad Leave a comment

The weather over the next couple days will be two things: warmer than normal for this time of year and somewhat unsettled. While no major rain-makers are expected, a couple rounds of showers will make for some damper spells. Fortunately, daytime highs near 20°C will be above the seasonal 17°C through the weekend!

Friday
22°C / 12°C
Mixed skies; chance of showers or thunderstorms

Saturday
20°C / 10°C
Mixed skies; chance of showers or thunderstorms

Sunday
20°C / 10°C
Mainly sunny

Today will bring mixed skies to Winnipeg as a broad trough of low pressure works its way across the province. There will be a slight chance of showers this morning if any of the overnight activity manages to linger on and/or push far enough north, however nothing significant is expected. We’ll see mixed skies heading into the afternoon with a high near 22°C with winds tapering off to light.

The RDPS is forecasting a line of thunderstorms along the advancing cold front this afternoon.
The RDPS is forecasting a line of thunderstorms along the advancing cold front this afternoon.

Later in the afternoon the threat of showers or thunderstorms returns as a weak cold front begins slumping southwards. Severe weather doesn’t look likely, although if stronger thunderstorms manage to develop some marginally severe hail could be a possibility.[1]

Skies will clear out a bit in the evening and we’ll be left with partly cloudy skies on our way to a low of around 12°C.

Saturday will start off with just a few clouds around. We’ll warm up to around 20°C for an afternoon high with winds gradually increasing out of the west-northwest to around 20–30km/h. By mid-to-late afternoon the threat for shower or thunderstorm activity will increase as a shortwave sliding down in the northwest flow aloft begins triggering activity over Parkland Manitoba and the Interlake. That activity will slide southeastwards through the afternoon into the evening with scattered showers or thunderstorms looking fairly likely.

This map of a feature called vorticity – essentially a measure of spin – shows a potent shortwave moving across Southern Manitoba on Saturday afternoon.
This map of a feature called vorticity – essentially a measure of spin – shows a potent shortwave moving across Southern Manitoba on Saturday afternoon.

Some thunderstorms may be surprisingly strong given the relatively meagre convective indices for the day. The key will be the favourable storm-relative winds in place. Suitable turning will be in place that it’s possible — not necessarily likely, but possible — for an isolated supercell or two to develop with strong winds and large hail being the primary threats.

Skies will clear out on Saturday night as we drop to around 10°C.

Sunday will be a nice day with not a whole lot to say about it! A ridge of high pressure moving into the province will bring clear skies and relatively warm temperatures with a high near 20°C. The temperature on Sunday night will drop to around 10°C.

  1. Environment Canada considers severe hail to be 20mm or larger in diameter.  ↩

Week to End with Summer-Like Weather

Brad Leave a comment

Patience will be rewarded heading towards the end of the week as above-normal temperatures[1] are poised to return to Southern Manitoba thanks to a low pressure system that will push across the Central Prairies. In addition to the warmer weather, the chance for some wet weather, possibly even thunderstorms, will make a return as well.

Warmer air is forecast to spread eastwards across the Southern Prairies over the next 48 hours.
Warmer air is forecast to spread eastwards across the Southern Prairies over the next 48 hours.
Wednesday
14°C / 3°C
Mainly cloudy & cool; clearing in the afternoon

Today will be the coolest day of the next few as we remain on the periphery of a large pool of Arctic air. Plenty of stratus cloud will persist in Winnipeg until this afternoon; afterwards we’ll see clearing skies and a high temperatures near 14°C. Another chilly night lies ahead with temperatures dropping to the 3 or 4°C mark under continued clear skies.

Thursday
20°C / 16°C
Increasing cloudiness with a breezy southerly wind

Thursday will mark our entry into warmer weather. Gusty southerly winds will develop ahead of a warm front that will gradually push eastwards through the day. Winds will peak at around 30–40km/h with the potential for gusts to around 50km/h. Much of the day looks fairly sunny which will help temperatures climb to around 20°C by late in the afternoon, but by mid-to-late afternoon clouds will noticeably begin thicken up.

The potential for thunderstorms returns Thursday night, but it’s conditional and will be mainly confined to southwestern Manitoba. Substantial mid-level instability will couple with a strong low-level jet (LLJ) in the evening to attempt to produce thunderstorms. While many severe weather parameters output by various models look fairly impressive, there are a few concerns I have with development, somewhat related to each other:

  1. Even lifting from the low-level jet, convection looks capped. If lift is strong enough to break through the cap and taps into the mid-level instability, then strong to severe storms could be possible, but…
  2. Synoptic lift looks uncertain. While the LLJ is forecast to be quite strong at 25–35kt, deeper synoptic lift looks uncertain. Some models hint at a shortwave rippling through the region on Thursday evening, which could help initiate thunderstorms if true.
The NAM is forecasting winds in excess of 40kt at 850mb over Southern Manitoba on Thursday evening.
The NAM is forecasting winds in excess of 40kt at 850mb over Southern Manitoba on Thursday evening.

If thunderstorms did manage to initiate over southwestern Manitoba, they would have a chance of becoming severe, with the main threats being large hail and strong winds. As the system pushes eastwards overnight, the chance for showers or thunderstorms will spread into the Red River Valley. The thunderstorm potential will diminish as the system moves eastwards.

With all the cloud, potential precipitation and breezy winds moving through overnight, temperatures will remain fairly mild, only dipping down to the mid-teens.

Friday
22°C / 9°C
Chance of morning showers; afternoon clearing

Friday will continue the pleasant weather. A slight chance of showers may persist into the morning from Thursday night, but skies should quickly being to clear out, leaving us with partly cloudy to mixed skies for the remainder of the day. Daytime highs will climb into the low 20’s without too much wind to worry about.

Temperatures will drop just under 10°C on Friday night under mainly clear skies.

The Weekend Ahead

The coming weekend looks great! Mostly sunny skies will dominate through the weekend with daytime highs continuing to sit in the low 20’s and overnight lows in the mid-to-high single digits. It will be a beautiful late-September weekend, so get out and enjoy it!

  1. Normal temperatures in Winnipeg for this time in September are around 18°C for high temperatures and 6°C for low temperatures.  ↩

Pleasant Weekend Before Big Cool Down

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After a dreary evening last night, conditions will gradually improve to quite a pleasant weekend for Winnipeg & the Red River Valley.

The RDPS model is forecasting a line of showers & thunderstorms through the Red River Valley by 5-7PM this evening.
The RDPS model is forecasting a line of showers & thunderstorms through the Red River Valley by 5–7PM this evening.

Today will start off with a bit of cloud through the Red River Valley thanks to the Manitoba lakes. We won’t see completely sunny skies, though, as a combination of increasing instability and some cloud moving in ahead of a trough moving across the province produce mixed skies through much of the day.

Friday
18°C / 5°C
Increasing cloud; a chance of showers or thunderstorms in the afternoon.

This afternoon into early this evening will bring a slight chance for showers or thunderstorms across the Red River Valley as that trough line works its way through the region. At this point it doesn’t look like severe weather is likely. Once the trough swings through, northerly winds at around 30km/h will move into the region and general clearing will take place.

Cooler air aloft will once again slump over Southern Manitoba tonight, bringing with it a chance for lake-effect cloud and drizzle once again. Winds, in general, don’t look particularly favourable which will likely limit or exclude their development. Winds will taper off overnight and low temperatures will be near 4 or 5°C.

Improving for the Weekend

Saturday
21°C / 8°C
Cloudy periods

Sunday
23°C / 12°C
A few clouds

Warmer weather will move in for the weekend as multiple low pressure systems draw warmer air eastwards across the Prairies as they move across Central Manitoba. Precipitation is expected to remain through Central & Northern Manitoba, leaving us dry with seasonal highs in the low 20’s. Overnight lows look to dip to around the 10°C mark, give or take a couple degrees.

Big Cool Down Next Week

Unfortunately, the pleasant weather will not be sticking around. Colder air builds into the Northern Prairies behind the systems tracking through during the weekend, which will then be driven southwards early in the week as an Alberta-clipper type system races across the Prairies.

The CPC 6-10 day temperature & precipitation anomaly outlook calls for below normal temperatures and near- to slightly above-normal precipitation.
The CPC 6–10 day temperature & precipitation anomaly outlook calls for below normal temperatures and near- to slightly above-normal precipitation.

850mb temperatures are forecast to drop into the 0°C to –5°C range by mid-week, resulting in daytime highs dropping towards the low teens and overnight lows likely dipping towards the 0°C mark. By mid-week, frost will be a definite concern across Western Manitoba and into the Red River Valley. The big question here in Winnipeg & the RRV will be exactly how much cloud the lakes produce when the cold air slides over them.

At this point it looks like a brief moderate at the end of the week before another cold blast potentially moves through.

Another Storm on the Way

Brad Leave a comment

Wednesday will be a brief reprieve from the showery weather before a fairly potent low pressure system spreads more rain & thunderstorm activity across Southern Manitoba tonight into tomorrow morning and brings dreary weather for Thursday with strong northwesterly winds.

Wednesday
23°C / 13°C
A few sunny breaks; rain overnight.

Thursday
19°C / 6°C
Rain and drizzle tapering off mid-day. Risk of a thunderstorm. Windy.

Friday
19°C / 5°C
Mainly sunny.

Today will be a fairly pleasant day with mostly cloudy skies and a high near 23°C or so. There’s a slight chance of an isolated shower or three through the Red River Valley, including Winnipeg, but for now it looks like the activity should mainly remain to our west over southern Saskatchewan and southwest Manitoba.

Tonight, an inverted trough extending NW from a low pressure system moving through the Dakotas will spread rain with the risk of thunderstorms eastwards into the Red River Valley. Rain will likely start sometime after 1AM and persist until mid-morning Thursday. The temperature will dip to around 13°C.

The Canadian RDPS is one of the models rather bullish on higher precipitation amounts Wednesday night.
The Canadian RDPS is one of the models rather bullish on higher precipitation amounts Wednesday night.

Rainfall totals for tonight are still uncertain; the general agreement is for between 10–20mm, however if substantial elevated convection develops as much as local amounts of 40–50mm may be possible. The low end of precipitation forecasts produce only around 5mm of rain.

I feel fairly comfortable with 10–20mm of rain tonight, but we’ll reassess the elevated convection potential later today and update if necessary. We’ll try and have an update fairly early this afternoon.

Unpleasant Thursday

Thursday will be quite an unpleasant day as Winnipeg moves onto the back side of the low pressure system lifting northeastwards into Ontario. The bulk of the rain should taper off mid-day, but brisk northwesterly winds building to 30–40km/h will accompany cloudy skies and a high struggling to climb into the upper teens. It’s also fairly likely drizzle will persist after the main area of rain moves out, making for a generally dreary day.

Skies will clear out for the evening, although there may be some cloudy periods through the first half of the night with some cloud moving off of Lake Manitoba, and temperatures will drop to a chilly 5 or 6°C.

Fall-Like Friday

Friday will be fairly pleasant, albeit cool, with mainly sunny skies and a high near 19 or 20°C. Winds will be fairly light through the day.

Friday night should bring clear skies and a low near 5 or 6°C.

A Look Ahead to the Weekend

The upcoming weekend is looking fairly good with unpleasant weather staying to our north. It’s looking like plenty of sun is in store with daytime highs in the ballpark of the seasonal 21°C mark and overnight lows moderating by the end of the weekend.