Tag: Severe Weather

This Week May Start with a Bang

Brad Leave a comment

There will be a risk of strong to severe thunderstorms in Southern Manitoba to start the week – hence why it may start with a bang!

Positions of Fronts on Monday Afternoon

Monday

Monday

Mix of Sun and Cloud. Risk of a Thundestorm.
25°C / 12°C

Today’s weather will be dominated by a risk of thunderstorms in Southern Manitoba. These storms may become severe, with large hail, damaging winds, and heavy rain. Tornadoes will be possible, but the risk is quite low. The reason why thunderstorms are being forecast for today is due to an unstable atmosphere being in place over Southern Manitoba along with a jet stream overhead. When combined, these ingredients can produce strong storms. If you’re in the mood for a more details, please read the technical discussion below.

Technical Discussion:

There is a slight risk of severe thunderstorms in Southern Manitoba today. An overview is offered below:

Moisture: Surface dewpoints in the mid to upper teens will be in place over Southern Manitoba by this evening. At 850mb, dewpoints will be around 10C.

Instability: MLCAPEs of 1000-2000J/kg will be in place over the western half of Southern Manitoba this evening. This instability will likely be transported eastward through the rest of Southern Manitoba during the late evening to overnight period.

Wind Shear: 0-6km bulk shear is currently 25-30kts over Southern Manitoba. An upper-level jet at 250mb is in place along the International border, with speeds of around 70kts. In the low-levels a south to south-westerly low-level jet of 20-30kts will be in place this afternoon.

Trigger: A trough will be positioned through the western-most portions of Southern Manitoba today. In addition, models suggest a weak surface low may be located near Portage la Prairie by late evening. A pseudo-warm front will likely extend from this surface low north and eastward through Southern Manitoba during the day. In addition, the left exit of a 250mb upper-level jet will be position over Southern Manitoba during the day today.

Monday’s Thunderstorm Risk Map

Conclusion: There will be a risk of severe thunderstorms today through much of Southern Manitoba. This risk is contingent on sufficient daytime heating, with convective temperatures generally being in the mid-twenties. Should sufficient heating occur, storms should develop along the trough and possibly surface low during this afternoon. Storms will drift east and persist into the evening. Models suggest there will be some useable elevated instability tonight, so storms may persist after dark. However, the timing of storm evolution will be important, since the atmosphere does not destabilize in the Red River Valley, and points east, in a significant fashion until around/after dark. Thus, if storms move eastward too quickly, they may not be in phase with the plume of instability. Therefore storms may begin to weaken by late evening if the aforementioned factors are not in sync. Storms are generally expected to be multicellular in nature, however some supercells will be possible, particularly during the evening hours in south-central Manitoba.

Tuesday

Tuesday

Mix of Sun and Cloud. Slight risk of a Thunderstorm.
24°C / 10°C

The forecast for Tuesday is a somewhat tricky one. A cold front is forecast to lie somewhere near or in Southern Manitoba during the day on Tuesday. Depending on the character of this front, Tuesday may be a mostly cloudy and increasingly cool day, or it could be a rather nice day. At this point it appears most probably that Tuesday morning into the afternoon will be fairly nice, with temperatures in the mid twenties. However, at some point in the afternoon or evening rain and/or thunderstorms may move in, cooling things down and bringing an end to the nice day. There is still a fair bit of uncertainty with the Tuesday forecast, so we’ll update you again as necessary

Wednesday

Wednesday

Mix of Sun and Cloud
23°C / 8°C

Wednesday looks to be a decent day in Southern Manitoba. High temperatures are expected to be in the low to mid twenties with a breezy north-west wind of 20-30km/h gusting to 40-50km/h. Skies will be a mix of sun and cloud due to fair weather cumulus development throughout the day.

Rainy — And Potentially Stormy — Thursday Ahead

Brad Leave a comment

Sunny skies will turn rather unsettled on Thursday as multiple disturbances move across Southern Manitoba.

Wednesday

Wednesday

28°C
Mainly sunny. Chance of showers near the U.S. border.
Wednesday Night

15°C
Increasing cloud. Showers beginning overnight with the risk of a thunderstorm.

We’ll see mainly sunny skies today as we spend a short amount of time in the stable air behind the cold front that passed through yesterday. That front will be sitting south of the border in North Dakota, however a very strong upper-level jet will be in place through Northern North Dakota near the Canadian border. There will be a slight chance of showers near the border thanks to the extra lift supplied by this feature.

We’ll see increasing cloudiness tonight as the upper-level jet starts pushing back northwards and the aforementioned cold front becomes a warm front and start pushing northwards again. Showers – with the risk of a thunderstorm – will develop over SW Manitoba overnight and advect eastwards into the Red River Valley before morning. No severe weather is expected.

Thursday

Thursday

24°C
Showers ending midday then cloudy with a few sunny breaks and a continued chance of showers.
Thursday Night

15°C
Showers with the risk of a thunderstorm overnight.

Thursday morning will start off rainy with the risk of a thunderstorm. Around 10–20mm of rain is possible however any higher amounts will likely be localized to any heavier patches of rain that develop. Things should taper off by midday leaving us with cloudy skies and perhaps a sunny break or two, but a chance of showers will continue through the afternoon.

Thursday night will start off cloudy then rain will push in by the late evening period as another cold front sweeps southwards from the central Prairies. Unfortunately, this area of rain will likely start off as thunderstorms over SW Manitoba.

NAM sounding valid on Thursday evening near Brandon, Manitoba.

NAM sounding valid on Thursday evening near Brandon, Manitoba.

Quickly looking at some of the convective elements in place:

  • MLCAPE values forecast to be in excess of 2000J/kg
  • 60kt 500mb jet will begin work it’s way into the region with the left exit of the jet poking into the Melita & Virden regions early in the evening.
  • A frontal boundary will be very close to the area providing convergence that can act as a trigger for storm initiation.
  • Falling heights through the upper atmosphere should help prime things for both initiation convection and to sustain anything that does manage to get going.

Low-level shear will not be favourable for the development of tornadoes, but the strong straight-line shear combined with ample moisture and relative low freezing levels will make large hail and torrential downpours a serious concern. Given the shear profile and the strength of the winds aloft, there may be a slight chance that these storms will develop strong straight-line winds. The main threat for severe weather will be over southwest and western Manitoba; at this point it looks like points from Virden to Minnedosa east to the lake then down along the shore-line to Portage face the biggest threat for severe weather, although not much would have to change to include Melita & Pilot Mound regions in there too. We’ll take a look at things a little later today and update this post with a severe thunderstorm outlook graphic if it seems applicable.

The thunderstorms will grow into an area of rain as they travel eastwards towards the Red River Valley. Here in Winnipeg we’ll still see the threat of a thunderstorm overnight, but it should mainly be rain – potentially heavy at times – amounting to about 5–10mm. If we see a thunderstorm than naturally the accumulations could be significantly more than that. The storms and rain should move out of the RRV into Northwestern Ontario overnight.

Friday

Friday

24°C / 15°C
Mainly sunny.

Mainly sunny skies will dominate on Friday as we move into a cooler, stable air mass in behind Thursday’s system. We’ll see the cooler weather persist for another day or so before hot weather begins working it’s way back into the area with temperatures looking to climb back towards 30°C on Sunday. The weekend looks gorgeous so get out there and enjoy it!

Severe Thunderstorms Ravage Saskatchewan and Manitoba

Brad Leave a comment

A line of severe thunderstorms tore across southeastern Saskatchewan and southwestern Manitoba yesterday producing widespread damage due to rain, hail, and what is increasingly likely a tornado.

A verification of the AWM Severe Thunderstorm Outlook issued on Saturday morning. Green dots: Severe Hail Reports. Blue dots: severe wind reports. Red dots: tornado reports.

A potent severe weather setup was in place yesterday as a trough of low pressure began to move it’s way from Alberta into the hot, humid air that was pushing into SE Saskatchewan. Ample moisture, heat, instability and wind shear was in place for the development of severe thunderstorms and – given the strongly veering wind profile – the likely development of tornadic supercells. With this in mind, we issued our morning severe weather outlook with a moderate risk for severe thunderstorms in the Estevan, Carlyle, Moosomin, Virden & Melita forecast regions, with a slight risk extending further eastwards into the Pilot Mound & Brandon regions.

Saskatchewan Pounded By Large Hail

Supercell thunderstorm developing just SW of Weyburn, SK at 1900Z.

Supercell thunderstorm developing just SW of Weyburn, SK at 1900Z.

Storms developed earlier than expected; by 1900Z there was a supercell taking shape not too far SW of Weyburn, SK. This supercell ended up being the storm of the day, lasting over 8.5 hours before finally dying near the U.S. border near Gretna, MB. A line of storms quickly developed extending from the main supercell SW into Montana. It rapidly developed into a line of 5 or 6 supercells that all began rotating quickly and producing torrential rain and extremely large hail. Environment Canada had issued a tornado watch for the region around 9:30AM local time which mentioned the threat for supercell thunderstorms capable of producing torrential rain and large hail in addition to the threat for tornadoes.

The reports began flooding in on #SKstorm as the severe storms began impacting larger communities. Environment Canada issued a timeline of reports it received that went like this:

Location Time (Local) Report
Weyburn 1:49 PM Quarter size hail
Hume 2:00 PM Loonie hail
Weyburn (8 km W) 2:21 PM Golf ball hail
Arcola 2:43 PM Funnel cloud
Kisbey 2:45 PM Quarter size hail
Weyburn (5 km W) 2:55 PM Golf ball hail
13 km SE Weyburn 3:00 PM Grapefruit size hail
16 km SE Weyburn 3:00 PM Golf ball hail
Minton (13 km S) 3:15 PM Possible brief tornado
Forget 3:20 PM Golf ball hail
Lampman 4:19 PM 50 mm rain, 80 km/h gust
Redvers 4:29 PM Toonie size hail
Oxbow (8 km N) 4:45 PM 50 mm rain in 15 minutes

Photos that began coming in on Twitter were pretty incredible. Tight lowerings on storms were showing that they were spinning quite intensely and numerous funnel clouds were spotted. But int the end, the big story in SE Saskatchewan was the rain and hail.

Large hail near Weyburn, SK

A photo of large hail near Weyburn, SK. Credit: Craig Hilts

There were numerous reports of tennis ball sized hail upwards to one report of grapefruit sized hail (a grapefruit is around 9cm wide). The hail produced by these storms produced significant damage to crops in the region as well as to personal property, with many reports of car windshields being broken by the hail and images showing up on Twitter of house windows being smashed.

Photo of flooding in Bienfait, SK

Picture of flash flooding in Bienfait, SK. Credit: SK storm chaser @NickTheBody.

Flooding was also a problem in numerous places as the storms dumped unbelievable amounts of rain. At some points, rainfall rates exceeded 200–225mm/h as torrential rain brought zero-visibility conditions. @NickTheBody caught the snap above of the flash flooding that occurred in Bienfait, SK after a thunderstorm rolled through.

Doppler RADAR showing strong couplet near Carlyle, SK

Doppler RADAR showing a very strong couplet as as supercell thunderstorm bears down on Carlyle.

As the storms pushed further east, however, they began to take on some very ominous characteristics. As the storms pushed deeper into the moist, warm air the winds at the surface began to back a little bit more; further west surface winds were mostly out of the south, but as they moved towards the Manitoba border the surface winds became more and more southeasterly. Very quickly strong rotation began to show up on RADAR, with the main supercell we’ve been tracking showing a very intense velocity couplet as it moved towards Carlyle, SK. The storms had always shown rotation since nearly the beginning of their lifespan and had the capability to produce tornadoes at any time, but it was at this point these storms began to look like they could produce a large, long-lived tornado. The storm about to hit Carlyle, in particular, was becoming the storm to watch.

Supercell Tears Across Southwest Manitoba

And watching it we were! Matt, A Weather Moment contributor and @lovestormsMB was out chasing and had been on the storm for hours at this point. While hopes of seeing anything rapidly diminished as the storm became what is known as a HP supercell[1], he was able to feed important information via his Twitter account.

Supercell thunderstorm over SE SK / SW MB

HP Supercell just SW of Carlyle, SK on Saturday evening as the storm approached the Manitoba border. Credit: @lovestormsMB

This storm – for lack of any better terminology – looked vicious as it moved into Manitoba. It was tracking along Highway 13 and moved straight towards Reston – a town that has already had to deal with multiple severe storms this year already – and Pipestone, a town somewhat famous for the Pipestone tornado.

Unfortunately, it didn’t take long for word to come that there was certainly significant damage occurring under that storm. Environment Canada also issued a timeline for reports it received on the Manitoba side:

Location Time (Local) Report
Sinclair (7 km N) 6:00 PM Ping pong size hail, severe winds with trees down
Reston 6:49 PM Nickel hail, 42 mm rain
Pipestone 7:00 PM Tornado, significant damage
Pipestone (20 km E) 7:30 PM Tornado, golf ball hail
Hartney 8:00 PM Possible tornado

Dramatic photos began coming in from the Pipestone region as well:

HP Supercell Approaching Pipestone

Photo of the HP supercell near Reston, approaching Pipestone, MB. Credit: @lovestormsMB

Downed tree in Pipestone

Photo of a large tree snapped in half in Pipestone. Credit: Tim Smith / Brandon Sun

Mobile home thrown into the rink in Pipestone

Photo of a mobile home thrown into the rink in Pipestone. Credit: @Snipe_All_Day

Destroyed cattle shed in Hartney, MB

A destroyed cattle shed in Hartney, MB. Credit: @LD_StVital

The clean-up continues today in Pipestone and Hartney while damage continues to be assessed in southeastern Saskatchewan. Unfortunately for those in Saskatchewan there will be little time to recover as another potent setup for a severe storm outbreak will be in place Monday afternoon bringing, once again, a tornado, torrential rain and large hail risk. Regions in SW Manitoba should be a little safer this time. We’ll have the full details of that in tomorrow’s blog post.

  1. The “HP” in “HP supercell stands for ”high precipitation.” HP supercells often have obvious, dramatic structure form afar, but little of the internal workings are visible due to the copious amounts of precipitation falling out from them. HP supercells are extremely dangerous storms as any tornadoes they produce are often hidden from sight behind all the rain.  ↩

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.

image-1

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.

image-2

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.

image-3

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.