A Brief Reprieve From Storms

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.

Elsewhere in Weather News: June 22nd, 2013

Disastrous Flooding in Alberta

For the past few days parts of southern Alberta have been experiencing severe flooding that has forced thousands of residents to evacuate and move to higher grounds. A deep surface low in extreme southern Alberta pulled significant moisture straight from the Gulf of Mexico into southern Alberta, causing for high PWAT (precipitable water) values in the region.

Rainfall accumulations

This past week’s rainfall totals (mm) in southern Alberta up until June 21st, note the extremely high rainfall totals just west of Calgary, east of the Rockies. (Source: AB Environment)

The Canadian army has been called in to help; 1,300 soldiers have been deployed to the flooded areas to help out with sandbagging. Search and rescue missions are still being performed as people that have not evacuated are now stuck in their own homes. In southern Alberta, an estimated 100,000 people have been ordered to evacuate, including 75,000 Calgarians, because of floodwaters infiltrating low land areas and rivers spilling their banks. Even in Calgary’s city core two feet of water could be seen flowing through the streets as the Bow River overflowed its banks. The Calgary Saddledome where the Flames play has been completely flooded out on the main floor. It has not only been Calgary that has been affected though – quite a few other communities just east of the Rockies, namely; Lethbridge, Medicine Hat, Canmore and High River have experienced extreme flooding. Unfortunately, it has been reported as of Friday night that 3 people had died in the floodwaters and a few more were still missing.

Waters from the Bow River are not expected to start subsiding until midday today, however, some other rivers have already started slowly decreasing in flow already on Friday evening. Some scatted showers are in the forecast this weekend but steadier rains are possible Monday as the next trough rolls in on the West Coast.

Winnipeg Hammered By Torrential Rain; Thunderstorm Threat Continues Through Weekend

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.

Elsewhere in Weather News: June 8th, 2013

Severe Flooding in Europe

Major flooding has swept across central parts of Europe where Slovakia, Germany and the Czech Republic have all experienced crippling flooding this past week due to extreme rainfall. Amounts of 75mm were widespread across that part of the continent, and near the Alps, significantly higher amounts of precipitation were observed (some as snowfall at higher elevations). A few reports of 150-200cm of snow were recorded in Austria and Germany at high elevations.

Flooding

Severe flooding in Passau, Germany where the Danube easily overflowed its banks. (Source: AFP)

Rivers such as the Danube and Elbe have reached levels last attained 11 years ago and are threatening or have already breached sandbag dikes in some areas. Over 300,000 sandbags and counting have been prepared and put in place to prevent both rivers from overflowing their banks. The threat of a flood has forced residents out of their homes – as many as 40,000 people have been forced to move away from the nearby dikes and up to higher ground. The flooding upstream also has residents in Hungary, especially Budapest, worried as the Danube River has not crested yet but is expected to reach its peak later this weekend. Dikes there are expected to hold if the current crest projection is correct; it is believed the crest will be about a foot below maximum capacity.

Unfortunately 17 people have already lost their lives to the rapidly rising floodwaters and damage estimates top the 15 billion mark. Crop damage is widespread across Germany where over 250,000 hectares have been flooded out.

The forecast for central Europe calls for some rain on Sunday, associated with a trough but these showers will be nothing near as significant as what was experienced last week.