Tag: Humid

A Brief Reprieve From Storms

Brad Leave a comment

It’s been a wet and wild week in Southern Manitoba as muttiple rounds of thunderstorms have pummeled the region with heavy rain. On Thursday, 75mm of rain fell in southwest Winnipeg, causing substantial amounts of flooding to neighborhoods, schools and retail locations. On Friday night a area of heavy rain and thunderstorms pushed into Western Manitoba bringing as much as 175–200mm of rain to some regions in the southwestern portion of the province. The town of Reston, MB has declared a state of emergency after about 7.5” of rain fell on Friday night (~ 190mm). Approximately 2/3rds of the town’s population has been affected by the flood waters that engulfed the town as it’s drainage system simply could not keep up with the intense downpour.

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The village of Reston, MB has declared a state of emergency after heavy rain caused significant flooding. Photo credit: Jillian Coubrough/CBC

On Saturday evening, an intense line of thunderstorms developed along the western escarpment of the Red River Valley and remained stationary for almost 3 hours. The hardest-hit areas just west and northwest of Portage la Prairie where – as evidenced by RADAR-estimated rainfall accumulations and a report from the town of Westbourne, MB – as much as 225mm (9”) of rain fell. On Sunday, an area of rain and thunderstorms lifting northwards through western Manitboba brought another 50–75mm of rain. This additional rainfall in an already waterlogged region has brought more overland flooding and caused mutliple highways to be closed near Riding Mountain National Park.

But a reprieve is in store for Southern Manitoba as the upper low that has been drawing a moist, unstable air mass from the Gulf of Mexico and brought catastrophic flooding to Calgary and southwest Alberta finally moves out of the region. This will allow a slightly drier, more stable air mass to move into Southern Manitoba on Monday. Things are not meant to last, though, as the heat and moisture is set to return on Tuesday as another system pushes into the Prairies and brings the storm threat back.

The Next Few Days

Monday

26°C / 15°C
Mainly Sunny
Tuesday

29°C / 18°C
Hot and humid. Thunderstorms possible in the evening & overnight.
Wednesday

26°C / 15°C
Mostly cloudy; showers likely.

We’ll see a beautiful day today with mainly sunny skies. A westerly wind will bring in slightly dryer air which will help things feel a little more comfortable as we head to a high of around 26°C. Skies will be mainly clear tonight as we drop to around 15°C.

Heat and humidity will begin to build in on Tuesday as a southeasterly wind develops and begins drawing Gulf moisture northwards again. Dewpoints should climb back towards 19–20°C as our temperature soars into the high 20’s. While the high will top out around 28 or 29°C, when combined with the humidity it will feel much closer to 35°C out there. An approaching trough will push into SW Manitoba through the afternoon and move into the Red River Valley in the evening.

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CAPE values are expected to climb towards 2500–3000J/kg in southwestern Manitoba on Tuesday.

Thunderstorms should fire along this feature in the afternoon and pretty much every single thunderstorm parameter looks fantastic. CAPEs are expected to exceed 2500J/kg, LI values are expected to be beween –5 and –10°C, surface dewpoints should pool to around 20°C along the trough and a decent shear profile will be in place. It looks likely that any storms that develop will likely have the potential to become severe with threats of large hail, torrential rain and tornadoes. The storms will likely grow into a line of storms as they slowly progress eastwards towards the Red River Valley, with a good chance of heavy showers or thunderstorms in the late evening or overnight here in Winnipeg.

On Wednesday we’ll be stuck underneath a low pressure complex. The overnight convection should clear out through the morning hours then we’ll move into a mix of sun and cloud with scattered showers through southern Manitoba. We’ll see a high climb into the mid–20’s and clearing skies overnight with a low near 15°C.

Rest of the Week

It looks like we’ll finally move into a dryer pattern for at least a few days as a weak upper ridge pushes into the Prairies. Temperatures will be mid–20’s with significantly dryer air in place making for some pleasant, warm and comfortable summer weather. A few thunderstorms may be possible throughout the latter half of the week, but with less moisture available they shouldn’t produce the excessive rainfall totals we’ve seen over the past several days.

Winnipeg Hammered By Torrential Rain; Thunderstorm Threat Continues Through Weekend

Brad Leave a comment

Portions of Winnipeg experienced a tremendous amount of rainfall yesterday evening as a thunderstorm developed over the southern half of the city and sat in the same spot for over an hour. While many areas in the city saw less than 10mm of rainfall, reports of localized flooding were numerous as rainfall rates that climbed as high as 300mm/h dumped between 50–80mm of rain over a small area of southwestern portions of the city.

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24hr. rainfall accumulations from Thursday evening. Given that we had no significant precipitation on Wednesday in Winnipeg, this is effectively the rainfall accumulations for Thursday’s thunderstorm in Winnipeg. Amounts outside Winnipeg wiil be representative of the full 24hr. period.

The storm moved into Winnipeg around 7:15PM Thursday evening as a small thunderstorm southeast of the city near Ils Des Chene moved northwestwards toward another thunderstorm stationed over Headingly that had been warned for producing heavy rainfall in that area. By 7:40PM, the storm west of the city merged into the storm inside the city and intensified. At this point, everything stopped moving.

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Flooded Roads on Sterling Lyon Parkway; Photo courtesy @shelzolkewich.

In an area roughly bounded by McGillvery Blvd., Pembina Highway and Portage Avenue, the rain simply kept coming and coming. Numerous reports started showing up under #MBstorm on Twitter. Early on it was clear that areas near Kenaston & the Sterling Lyon Parkway were being hit very hard with photos coming in showing flooded roads with water as much as just over a foot deep.

Reports began to come in of actual rainfall amounts, too. @robsobs, a very reliable source for rainfall data in SW Winnipeg (as well as the person who runs the excellent Rob’s Blog reported a peak rainfall rate of 300mm/h under the heaviest rainfall. Near the end of the event, he reported a total of 69mm that fell over the course of 2 hours:

In addition to roads being flooded, there were numerous reports of ditches & pools overflowing. The heavy rainfall also impacted one of Winnipeg’s newest and largest stores: IKEA. The IKEA on Kenaston was evacuated yesterday evening as water began pouring into the main floor of the store:

It may not have seemed like a day where severe weather was likely since skies were mostly cloudy through the day and temperatures climbed only into the mid–20’s. There was plenty of moisture building into the region, though, and many of the conditions we look for with convection were in place.

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Another shot of the flooding on Sterling Lyon Parkway. Photo by @tracylkj.

While we didn’t have enough sunshine to get the storms started, a strengthening trough of low pressure laying across the Red River Valley managed to initiate storms which then fed off the abundant low-level moisture and produced just one significant storm that impacted Headingly and Winnipeg. The Winnipeg region was included in our Slight Risk area on Thursday morning.

Friday


26°C / 16°C
A mix of sun and cloud. Small chance of thunderstorms in the afternoon & overnight periods.

Today will be a warm, humid day with temperatures climbing once again to around 25–26°C and with dew points hovering in the 18–20°C range. Once again we’ll see a risk of thunderstorms develop in the afternoon as the atmosphere destabilizes. The key ingredient for today’s threat will be our daytime high. If dew points stay close to 19 or 20°C and we can get to 27°C, we’ll see a much greater chance of thunderstorms than if the dew point is closer to 18°C and we stay near 25 or 26°C. Should storms develop in the Red River Valley, they’ll see a potent environment to develop in with substantial instability aloft and CAPE values of nearly 2500J/kg. The big limiting factor in their development will be the near absence of shear. The wind will be extremely light below 500mb which will make it very difficult for storms to develop the structure required to make them long-lasting entities. As such, any storms that develop in the afternoon will likely be pulse-type storms whose main threats would be heavy rain and/or large hail.

By the evening another round of elevated convection looks to fire up and lift northwards. It may end up west of, over, or east of the Red River Valley. It’s simply too early to tell at this point. We’ll be sure to update our thoughts below as things become more clear. We’ll head to an overnight low of around 16°C tonight.

The Weekend

Saturday

23°C / 14°C
A mix of sun and cloud. Chance of a shower.
Sunday

23°C / 12°C
Mainly cloudy. Showers or thunderstorms likely.

We’ll see the main upper low that’s been pulling moisture northwards and setting up our instability begin to work it’s way eastwards through the Prairies this weekend. Saturday actually looks to be a fairly nice day; dew points will drop towards the mid-teens and we’ll see a slightly cooler high of around 23°C under a mixed sky. There will be a slight chance of showers as a trough swings through, but things seem stable enough that they would be fairly scattered and light. Saturday night will see some cloudy periods with a low of around 14°C.

On Sunday we’ll likely see showers and thunderstorms as the upper low moves over us. Things will destabilize under the upper low early in the day and the relatively warm, moist air mass should have little trouble supplying enough instability and moisture to get things going. No severe weather is expected. Sunday will mark the return of dryer air into the Red River Valley.

Thunderstorm Threat Ramps Up Over Southern Manitoba

Brad Leave a comment

A broad shift in the jet stream is set to bring an influx of moisture from the Gulf of Mexico northwards into Southern Manitoba while a southwesterly flow aloft sets up bringing multiple upper-level disturbances & instability over the region. The increased moisture, combined with the relatively unchanging southwesterly flow will set us up for multiple days with a significant thunderstorm risk over the southern portion of the province.

Wednesday

Wednesday

26°C / 15°C
Afternoon clouds; chance of showers/thunderstorms.

Today’s weather will be dominated by an approaching warm front from Saskatchewan. We’ll might see few showers exiting the Red River Valley this morning – left over from some weak nocturnal convection – with plenty of sun through the morning. The sun will heat things up fairly quickly and there’s a chance we’ll see some showers or thunderstorms develop early-to-mid afternoon as we warm up. Any storms that develop today will not likely become severe; a majority of the shear will be isolated in the upper levels and the complete lack of low-level shear may even be substantial enough to inhibit storm development. We’ll drop to an overnight low of around 15°C as we head into a busy end of the week.

Thursday

Thursday

25°C / 16°C
More cloud than sun; getting humid. Showers or thunderstorms likely.

Thursday presents Southern Manitoba with plenty of heat and rising humidity as the day progresses. We’ll see a high of nearly 26°C while the dew point climbs into the high teens through much of the Red River Valley by the end of the afternoon. Whether or not that humidity will make it up to Winnipeg will depend on how soon the winds turn from northeasterly to southeasterly; the sooner they do, the more humid we’ll get. The building heat and humidity will create a fairly potent setup for severe storms, however.

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Severe thunderstorm outlook issued on Wednesday, June 19 @ 6:30AM CDT

By late afternoon CAPE values are expected to climb to 2500–3000J/kg near the international border thanks – in no small part – to the climbing dew points. LI values are forecast to drop to the –8 to –10°C range, indicative of the steep lapse rates aloft and the potent storm potential. Good wind shear will be in place with southeasterly surface winds veering to a strong westerly wind at 500mb. In addition, a shortwave is forecast to eject into Central North Dakota by mid-afternoon and push northeastwards into the RRV by evening, bringing with it enhanced destabilization and lift. One big question mark remains, though. While we have plenty of moisture, instability, shear, and a trigger, the cap may be make or break storms for the day, or rather, the lack of a cap may.

Models are having a hard time determining just how warm it will be in the mid-levels of the atmosphere; some want to establish a cap that will inhibit convection until later in the day, but others keep the environment uncapped which will result in the maintenance of an MCS coming out of Saskatchewan on Thursday morning. In that case, we’d see showers and thunderstorms build into the Red River Valley in the morning and persisting through much of the day. Conditions still look somewhat favourable for the development of isolated strong to severe storms in this scenario, despite the ongoing showers and thunderstorms. If the cap does develop though, the MCS will likely die out to our west and a significant threat for severe thunderstorms would mount in the Southern Red River Valley.

It’s still too early to be too certain on the threat for Thursday as models are still working to resolve the interaction with various shortwaves and the main upper low anchored over the American mountain northwest. For now I’ve extended a slight risk through Southern Manitoba along the International border.

Friday

Friday

26°C / 13°C
Mix of sun and cloud; humid.

Friday will end up a fairly hot day with temperatures climbing into the mid-to-upper 20’s with dew points rising to nearly 20°C. The humidity will make it feel closer to the low-to-mid 30’s, so it definitely looks to be one of the first really hot days of the year. Conditions should hold out through most of the day before thunderstorms develop in North Dakota and begin pushing northwards. It’s still too early to tell their exact path which will be heavily dependant on where exactly upper-level features lie. They may end up moving into SW Manitoba, the RRV or the Whiteshell through Friday night.

We’ll have a busy few days ahead so expect plenty of updates in the comments below! Briefly looking ahead to the weekend, Saturday and Sunday both look showery over much of Southern Manitoba with a risk of thundershowers. There will be some breaks here and there, but we’ll take a closer look at that on Friday.

Staying Hot, Storms Possible

Brad Leave a comment

This week will start out right where last week left off – hot!

Monday's temperatures at 1pm

Temperatures at 1pm on Monday. The dark green colour represents temperatures between 30 and 35C.

Today will be another hot and humid day in Southern Manitoba. High temperatures are expected to be in the upper twenties, or possibly thirty degrees, with thunderstorms possible both in the morning and later in the day. There will some cloud and possible rain or thunderstorms during the morning from a decaying thunderstorm complex. The speed at which this complex clears the region will determine how hot it will get. The progress of this complex will also determine if there is a second round of storms on Monday afternoon and evening. If it stays cloudy all day with temperatures remaining low then it is unlikely that there will be a second round of storms later in the day. Based on current model guidance it does appear that the clouds will clear out in the afternoon, but there remains some uncertainty with this.

Tuesday will be hot once again, but somewhat less humid than Monday. Temperatures will be up near 30C, but thunderstorms are not expected.

Wednesday will be yet another tricky forecast. A cold front is expected to swing through Manitoba at some point on Wednesday, but it is not entirely clear when that will happen. If the cold front goes through in the morning the day will be warm, but not humid, with highs in the mid to upper twenties. However, if the front only goes through in the evening it will be hot and humid with the risk of severe thunderstorms. The details of Wednesday should become more clear over the next day or two.

You’ll probably be surprised to hear that more hot weather is expected to start July (hint, I hope you’re NOT surprised). Models point to continued hot weather for at least the next 7-10 days as we roll smoothly in the heart of summer.

A quick note…Myself and Matt will be chasing south of the border today! You can keep tabs on our progress using the twitter feed by clicking through below.

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