Tag: Thunderstorms

Stormier Weather Set To Return

Brad Leave a comment

Southern Manitoba will be under an increasing risk of thunderstorms as the week progresses. Heat and humidity will slowly build back into the region as a deep upper trough begins to build over the Rocky Mountains before tracking eastwards across the Prairies later in the week.

GEM-REG 6-hour Precipitation for Thursday Afternoon

6-hour accumulated precipitation through Wednesday afternoon from the GEM-REG model.

We’ll see warmer temperatures today as warmer air pushes in behind a warm front that passed through overnight. Daytime highs should be near the 25°C mark through most of the RRV. By this afternoon a weak frontal wave will be positioned near the international border with a trough extending NW to a low pressure system tracking into Western Manitoba. Showers and thunderstorms will develop over SW Manitoba early this afternoon and slowly develop northeastwards into the Red River Valley. It will mainly be regions through the northern Red River Valley that face the risk for showers or thunderstorms (Portage la Prairie, Winnipeg, Selkirk; as seen in the image above). The showers and thunderstorms will lift northwards into the Interlake overnight while overnight lows drop to the mid-teens over most of Southern Manitoba.

12 hour accumulated precipitation through Thursday

12 hour accumulated precipitation through Thursday from the GFS model.

Opinions differ for Thursday, however it’s generally expected that a north-south band of showers with a chance of an embedded thunderstorm will develop over the Red River Valley or the Whiteshell in the afternoon. This line will slowly move eastwards and intensify into a band of thunderstorms. Again, there’s still quite a bit of uncertainty to where this line will develop, and the potential exists for fairly large (close to 1”) rainfall accumulations. We’ll be keeping close track of this system’s development.

Friday looks to be a fairly nice day with comfortable humdity and daytime highs in the mid-20’s. A large MCS is forecast to develop on Friday night in North Dakota, bringing the chance for a stormy and rainy Saturday. We’ll take a closer look at that system later this week.

Tornado Threat To Develop Over Southern Manitoba on Saturday

Brad Leave a comment

3km EHI Values

3km EHI Values. This measures the potential strength of a tornado should one develop. As can be seen, the GFS EHI values have gone off the chart over extreme SW Manitoba on Saturday afternoon.

A slow-moving low pressure system pushing into our region will set the stage this weekend for the potential of supercell thunderstorms capable of producing localized flooding, extremely large hail, damaging wind gusts and tornadoes. Read past the break to get all the details, our thoughts on the main threat areas, and to see updated information in the comments.

Jump to Live Twitter Feed

An extremely slow-moving long-wave trough has been slowly pushing it’s way eastwards this week. While it’s been a good distance from us, we’ve been able to enjoy the benefits of such a setup: plenty of nice, warm weather with comfortable humidity. Our friends in the Western Prairies haven’t had it quite as nicely; multiple rounds of storms have pushed into Southern Alberta & Southwestern Saskatchewan over the past couple days, bringing multiple tornadoes to Southern AB and torrential rain that caused localized flooding after 2-3” fell in a short period of time. Large hail was also reported in many storms across the Western Prairies, as well as with some severe thunderstorms that developed over SE Saskatchewan on Wednesday evening.

Entrance of this system in our region has been marked by the thunderstorms and showers that developed overnight. We should see most of these clear from the Red River Valley this morning or by early afternoon if they’re really tenacious. We’ll see a relatively pleasant afternoon, with some lingering cloud and temperatures in the low-to-mid 20’s. The dewpoint will be quite high, making it feel a little sticky, though.

The main surface low begins to move into our area on Saturday, pushing a warm front up from North Dakota into extreme Southern Manitoba. Using the basic MIST principles of thunderstorm forecasting:

  • Moisture: Plentiful. Surface dewpoints will be sitting near 20°C across Southern Manitoba, with 850mb dewpoints pushing up towards 15-17°C. This deep layer of moisture will provide plenty of energy for storms to work with.
  • Instability: The major inhibition to storms will be a layer of warm air at 700mb. Temperatures will climb to 10-13°C at 700mb on Saturday morning, however cooler air will push in later in the afternoon, helping destabilize the mid-levels. LI values of -8 to -11, combined with CAPE values anywhere from 2500 J/kg to 5500 J/kg are evidence of an extremely unstable atmosphere.
  • Shear: With a decent upper-level jet pushing in through the day, most areas across southwest and south-central Manitoba will see bulk shear values increase to 30-40kt by evening.
  • Trigger: A warm front draped across Southern Manitoba will be strong enough to initiate convection in the mid-to-late afternoon as the cap begins to erode.

Prog Tephi for SW MB

Prognosis tephigram for Southwestern Manitoba on Saturday afternoon. Note the extremely favorable veering wind profile present.

Models strongly disagree about the speed of this system, but agree that it has a very strong potential to produce damaging supercell thunderstorms capable of producing tornadoes. The greatest uncertainty, then, is where exactly the storms may form. Unfortunately, as I write this it’s still too early to tell exactly where the greatest threat lies. The slowest solutions would place the main risk over extreme SE Saskatchewan across SW Manitoba, while the quicker solutions would place the risk over SW Manitoba into the Red River Valley. Personally, I feel that the slower solutions are probably a little more true to what’s going to happen. With that in mind, here’s my threat area for Saturday:

Day 2 Storm Outlook

Day 2 Thunderstorm Outlook, valid Saturday afternoon through Sunday morning. This is subject to refinement as this system develops and more certainty exists on it’s track and speed.

A large MCS will likely develop as the whole system lifts northwards overnight, which will continue to provide a severe weather threat in the form of strong winds and large hail. It will push through the RRV by Sunday morning. We may see the threat for another round of thunderstorms on Sunday afternoon, however they are not expected to be severe. Things will finally cool off on Monday as the main upper low moves through and draws in cooler, dryer air from the west.

We’ll be sure to refine the forecast in the comments below as the day approaches. In addition, it looks like the AWM crew will be out chasing, so we’ll be sure to have some live updates should everything work out. Stay sky aware out there this weekend!

new TWTR.Widget({
version: 2,
type: ‘list’,
rpp: 30,
interval: 30000,
title: ‘June 9, 2012’,
subject: ‘AWM Storm Chase’,
width: ‘auto’,
height: 500,
theme: {
shell: {
background: ‘#3c3c3c’,
color: ‘#eeeeee’
},
tweets: {
background: ‘#eeeeee’,
color: ‘#2c2c2c’,
links: ‘#489ce1’
}
},
features: {
scrollbar: true,
loop: false,
live: true,
behavior: ‘all’
}
}).render().setList(‘buffaloseven’, ‘awm-team’).start();

A Scorching Week to End With A Bang

Brad Leave a comment

Temperatures are set to soar for the remainder of this week as heat sourced from the Gulf of Mexico builds into Southern Manitoba. Residents across all of Southern Manitoba should begin to prepare for a potentially dangerous end-of-week though, as a powerful low pressure system will threaten the first significant severe weather outbreak of the season.

850mb Theta-E Chart for 06Z Thursday

850mb theta-e (a form of measuring temperature) chart valid for 06Z Thursday 07 May. The light-red arrows depict the advection of heat from the Gulf of Mexico through Southern Manitoba.

A southerly flow of air aloft, aided by a long-wave trough over the Rocky Mountains to our west and a blocking high to our east, will bring us our hottest days of the year through the rest of this week. Temperatures at 850mb are expected to rise to nearly 20°C today, which will result in daytime highs between 25-30°C through the second half of this week.

A weak low will move through Southern Manitoba on Thursaday night ahead of the main upper trough and while parameters don’t look too great for severe weather, a band of thunderstorms will likely develop in the late afternoon or early evening, intensify, and slowly move east-northeast. While tornadoes aren’t a likely threat with these storms on Thursday afternoon/night, CAPE values in the range of 1250-1750 J/kg combined with LIs near -5 and 20-30kt of bulk shear should provide enough for a threat of large hail. The slow-moving nature of the line of storms could potentially also produce a risk of locally heavy rainfall, with as much as 0.75-1.25” falling over a relatively short period of time. While showers will be commonplace over southwest Manitoba throughout the day on Thursday, the risk for showers does extend eastwards through the western and central Red River Valley in the afternoon. The bulk of precipitation will occur with the thunderstorms that develop in the evening, though.

This is still about 36 hours away, though, and things could change quite a bit between now and then. Models are having a hard time degrading the blocking pattern that’s in place right now, and some are much more progressive with features and some are much slower. If things end up more progressive than they look right now, there may be minimal storm threat for Thursday night.

Night 2 Thunderstorm Outlook

Thunderstorm Outlook for Night 2 (00Z to 18Z June 08).

Taking into account the various speeds, the current area that might see storms on Thursday afternoon/evening looks to be the area bounded from the US border north to Brandon, up towards Dauphin/Swan River, then eastwards across the Interlake and southwards down the eastern Red River Valley. Storms will exit through the Central/Northern Whiteshell. While the potential for heavy rainfall exists, I do not feel enough confidence in it to justify any slight risk categorization on the outlook. The storms will likely be marginally severe, though, so it’s important that they are not ignored with the prospect of even bigger storms on the weekend.

Friday looks to be another warm day; debris cloud left behind from Thursday night’s convection should clear bout by lunch time or early afternoon which will allow the sunshine to warm us up to the mid-to-high 20’s. Dewpoints will build through the afternoon pushing up to 18 or 19°C, making it feel quite humid. The main upper trough is set to move in on the weekend, though, and what a system it looks to be.

SPC Day 4-8 Outlook

SPC Day 4-8 Severe Thunderstorm Outlook

I’m not going to talk too much about Saturday’s setup yet, as it’s still a ways out and in this particular setup, the exact specifics are sure to change with every model run until it’s much closer. We’ll be under the influence of two strong shortwaves that will push copious amounts of instability over Southern Manitoba. CAPE values look to exceed 2500 J/kg and potentially be as high as 5000-5500 J/kg; this, combined with a weak cap north of the warm front and favorable shear profiles looks to point at a potent setup for severe thunderstorms with high probabilities of (extremely) large hail, strong winds, and elevated risks of tornadoes. The setup is similar to other tornado-producing setups of years past, including the Pipestone tornado of 2007.

We’ll have plenty of discussion about the upcoming storm threats in the comments, so be sure to check back often for the latest information about this weekend’s potentially dangerous storm outbreak.

Cool, Wet Weather For The Weekend

Brad Leave a comment

Winnipeggers: get ready for a shock. The next few days are going to be startling chilly with daytime highs over 10°C below normal and overnight lows over 5°C below normal. Another thing that will be noticably absent other than warmth? The sun will make only a few rare appearances over the next several days as another system pushes into Southern Manitoba, bringing another round of rain and thunderstorms to the Red River Valley.

850mb Temperatures valid 00Z Friday

850mb temperatures vaild at 00Z Sat. May 26 (Friday evening). An elongated cold trough is sweeping across Southern Manitoba, bringing 850mb temperatures in the -2 to -5°C range.

This cool weather has brought late-season (or is it early-season now?) snow to several communities over Western Manitoba including The Pas, Flin Flon and higher elevations over SW Manitoba (Duck Mountain & Riding Mountain areas). A few leftover flurries will scoot across the Interlake this morning and exit out of the province. The Red River Valley wil be spared, however we’ll be stuck under low clouds with a daytime high that struggles to make it to 10°C.

Tonight, a widespread frost potential exists over the most of Southern Manitoba. As a surface ridge moves into our area, winds will abate and we’ll see the cloud begin to break up a bit this evening. The greatest potential for frost looks to be over Southwestern Manitoba in the Virden, Melita, Pilot Mound & Brandon regions. Further east, here in the Red River Valley, some scattered clouds and a bit of moisture trapped in the valley should help temperatures stay above freezing, with overnight lows in the 2-3°C range. Areas outside the City of Winnipeg in the RRV certainly have a slight risk of a light frost. Winnipeg will likely be frost-free, with an off-chance of patchy frost in outlying areas near the Perimeter Highway.

Saturday will be our transition day with temperatures reaching 13-14°C and cloud streaming northwards from the Dakotas with the next incoming system. Rain will push up towards the International Border by morning, likely staying in the States but certainly poses the chance of a few showers along the border. The rain will stay near the border until Sunday, when the next big northward push arrives.

24. hour precipitation accumulation Saturday morning to Monday morning](https://img.skitch.com/20120525-mkq1sh9w3aa3twa7r6stuq9j2q.png)

Precipitation accumulation from the GEM-GLB model for Saturday morning to Monday morning. A broad swath of rain is forecast to fall from extreme SW Saskatchewan through Southern Manitoba.

And what a push it will be! Showers and thunderstorms will rapidly develop into an expansive area of rain on Saturday night, slowly pushing northwards across the Red River Valley. Most regions across Southern Manitoba should expect rain to start fairly early on Sunday and last through most of the day. Rain will likely taper off from west to east overnight, with only a few wrap-around showers moving across the RRV on Monday. It’s still early to give accurate estimates of rainfall totals for this next system, however in general, most regions across Southern Mantioba look to see at least 10-20mm of rainfall, with the potential for nearly 30mm in some areas of the RRV if some embedded convection can get going. Regions of Southwestern Manitoba that end up north/northwest of the main upper low track will see higher amounts as well, with 20-30mm of rain likely. This isn’t the best news for this year’s Teddy Bears Picnic, but hopefully shouldn’t dampen spirits too much at an event that has, historically, had to deal with some pretty awful weather. Wait, I’m getting deja vu…

Conditions look to improve through the middle of next week, with temperatures pushing back towards the 20°C mark and some sun finally making an appearance. That’s a ways to go, though, so grab your slippers and heat up some soup! We have some great stay-inside weather coming up. We’ll be sure to keep a close eye on this system and provide updates in the comments.