Tag: Thunderstorms

Hot Weather Continues

Brad Leave a comment

The hot weather in place over the Red River Valley will stick around through the rest of the week, although a few more weak disturbances will bring in a little more cloud alongside the risk of a few showers or thunderstorms.

Wednesday

31°C / 18°C
A mix of sun and cloud. Humid.
Thursday

28°C / 18°C
A mix of sun and cloud. Humid. Slight chance a shower or thunderstorm.
Friday

27°C / 17°C
Mainly sunny. Chance showers or thunderstorms Friday night.

Today

We’ll see another hot and humid day today as temperatures climb into the low 30’s again with dew points hovering around 19–20°C. No precipitation is expected although we’ll see a mix of sun and cloud associated with a weak frontal system that wills be in the area.

Thursday

Tomorrow will be an interesting day; at this point it looks like we’ll see a fair amount of cloud in the morning before clearing out for the afternoon as an area of showers and thunderstorms moves across North Dakota and perhaps portions of the southern Red River Valley. Should this system push further north, there would be a slight chance of showers in the morning here in Winnipeg, but at this point I think that we’ll stay dry. Things will be pleasant in the afternoon as we climb to a high around 28°C before a weak upper-level cold front pushes into the Red River Valley. As it sweeps through in the evening, there will be a chance of some showers or thunderstorms pushing into the Red River Valley alongside it. Most regions in the RRV will see a chance of a shower or thunderstorm in the evening and overnight hours. Things will move out overnight as we drop to a low around 18°C.

Friday

Friday will be a beautiful day with mainly sunny skies and a high around 27°C. The humidity will drop off through the day as we heat up and are able to mix some of the remaining moisture near the surface out. There’s little threat of precipitation until the evening and overnight hours as low-pressure system pushes into Southern Manitoba, where thunderstorms will be possible with this system along a trough that will push through the Red River Valley. Depending on how things set up, there may be a slight risk of a severe thunderstorm with this system, so we’ll be sure to keep an eye on how things are setting up.

The Long Weekend

A preliminary look ahead through the long weekend looks beautiful. Skies should clear on Saturday morning and after that, it looks like nothing but sun, sun and more sun all the way through Monday. Highs look to be in the mid-to-upper 20’s, generally between 25–28°C with overnight lows dipping down to around the 12–13°C mark thanks to significantly less humidity in the air mass behind Friday night’s low pressure system.

Unsettled Weather Pattern Developing

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After a couple slightly cooler days across Southern Manitoba the heat is set to return as a southerly flow develops ahead of a upper trough pushing towards the Rocky Mountains. Unlike the potent upper ridge of earlier this week, this southerly flow will be peppered with disturbances ejecting northeastwards out of the west coast trough and we’ll see substantially more unsettled weather over the next week or so.

Today

Friday

30°C / 20°C
Sunny & increasingly windy. Chance of thunderstorms & increasing humidty overnight.

We’ll today start off pleasantly as we head towards a high of about 30°C, however by midday the winds will begin pickup up out of the south and will likely reach 40–50km/h with gusts as high as 70km/h by the end of the day, making it not quite as pleasant as 30°C can be. We’ll see a mix of sun and cloud as well as some mid-level cloud streams up from the southwest through the day. Fortunately it looks like the worst of the humidity will stay off to our south for the day and, with dewpoints only in the low teens, will help the day be a little more comfortable.

There will be a chance of thunderstorms overnight into the morning hours on Saturday though as the first of many impulses lifts northeastwards into Southern Manitoba, dragging up with it substantial amounts of humidity. Overnight we should see our dew point climb to nearly 20°C, which means we’ll only see our overnight low dip to close to that mark[1]. Regarding the thunderstorms, at this point it looks like the greatest threat for any activity will be over SW Manitoba then arcing NE through the Interlake region. There will be a chance of a thunderstorm through much of the Red River Valley, with the greatest risk at the north end – Winnipeg in particular could end up seeing the bulk of the action if things end up just a bit further south than currently forecast – and a decreasing risk towards the U.S. border. These storms are not expected to be severe, however given the ample moisture that they will be feeding off of, any storms that develop could produce substantial amounts of rainfall in short periods of time.

Saturday

Saturday

32°C / 18°C
A mix of sun and cloud; risk of thunderstorms in the morning and then the afternoon.

Saturday will start off cloudy, potentially with showers or thunderstorms in the region, and then begin gradually clearing. It will be very humid in the Red River Valley, with dew points in the low 20’s. We’ll climb towards a high of around 32°C which, with the humidty, will feel much more like 37–40°C. In the afternoon a sharp dryline[2] will begin working it’s way eastwards into the RRV associated with drier, westerly winds.

Thunderstorms are possible by late afternoon, but the exact location of them will depend on the entire synoptic setup and the placement of the dryline, which will be the feature that the storms will develop along. At this point, it appears that the western half of the RRV will be safe with an increasing risk through Winnipeg & the central RRV to a much greater chance over the eastern RRV into Sprague & the Whiteshell. These storms could easily become severe given the ample heating and surface moisture, 500mb jet core in the area providing 30–40kt of bulk shear, as well as a defined trigger in the dryline.

The storm potential does seem fairly dependant on the exact placement and strength of the dryline; if it doesn’t evolve to be strong enough or hangs back too long or blows through too early, then there will be almost no chance of any storms on Saturday. If storms develop, the main threats (particularly if they become severe) will be torrential rain and large hail. A tornado could not be ruled out either, but the flow may not be strong enough to support/sustain one. Strong winds would not be a widespread concern at this point.

And of course, since there has to be one more wrinkle in things, this will all be dependant on mid-level temperatures. The Canadian long-range model (GDPS) is forecasting cooler air at the mid-levels pushing over the RRV on Saturday afternoon, which would help destabilize things; if temperatures remain warmer at the mid-levels then we would likely remained capped and see have no thunderstorm activity. A lot of words for a conditional threat, but it could be a significant severe thunderstorm day for the Red River Valley and the Whiteshell, so I thought we should go over some of the possibilities and unknowns!

Sunday

Sunday

32°C / 18°C
Mainly sunny.

Sunday will be a very nice day with mainly sunny skies, light winds, and a high near 32°C. There will be little to no chance of any precipitation; at this point it looks like there may be a marginal chance of an isolated thunderstorm near the U.S. border in the Red River Valley, but even that is pretty unlikely. Humidity will actually be quite comfortable as well, with dew points in the low teens. Probably the nicest day of the weekend, so get out there and enjoy it!

Next Week

Without spending too many words on it, next week continues the warm trend with highs looking to be near 30°C much of the week; we’ll also see multiple disturbances move through bringing showers and thunderstorm threats to Southern Manitoba. It will likely be more pleasant than not, though, and our late-arriving summer will certainly continue!

  1. The dewpoint is often a good measure of what overnight lows will be as the temperature will often – but not always – dip just a couple degrees below it. When the dew point is high, such as the upper teens or low 20’s, often the temperature will only approach the dew point temperature, not dip below it.  ↩
  2. A dryline is similar conceptually to a warm or cold front, but instead of being warmer or colder on one side of the front, it’s more humid ahead of the dryline and substantially drier behind it.  ↩

Above-Normal Temperatures Continue

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The above-normal temperature streak we’ve seen the past few days will continue through the rest of the week – albiet at a slightly moderated level – until a more unsettled pattern develops for the weekend.

Today & Tomorrow

Wednesday

26°C / 11°C
Mainly sunny.
Thursday

26°C / 13°C
Sunny.

We’ll see mainly sunny skies the next couple days as a ridge of high pressure slides across the province in the wake of the cold front that pushed through last night.

This ridge of high pressure will bring a break from the 30°C+ weather we’ve had the past couple days, bringing us back down to closer-to-seasonal temperatures in the mid–20’s. We should reach about 26°C each day which is still a couple degrees warmer than the seasonal average of 24°C for this time of year. The evenings will be quite cool, generally near 10–12°C although temperatures could potentially dip into the single-digits tonight in some areas.

Friday

Friday

27°C / 17°C
A mix of sun and cloud; slight chance of showers or thunderstorms.

We’ll see a regime change come Friday as a leading impulse approaches the province ahead of a developing long-wave upper trough over the west coast. A southerly flow will redevelop ahead of this impulse pushing moisture northwards out of the Northern Plains back into Southern Manitoba; as such, we’ll see a noticable increase in humidity as temperatures climb to around 26–28°C.

Precipitation is a bit of a wildcard at this point; some models bring a wide area of rain and thundershowers into the Red River Valley in the morning and persisting through much of the day until the impulse moves into NW Ontario while others keep much of the rain north of the RRV in the Interlake and bring thunderstorms in during the evening hours.

I think that most of the precipitation will push north of the city, but I certainly can’t rule it out at this point. We’ll definitely see a mix of sun and clouds, though. It looks like a chance for thunderstorms will persist through much of the evening and into the overnight period as well.

Long-Range Outlook

This weekend we’ll see warm, humid and generally unsettled weekend ahead with showers and thunderstorms likely Saturday & Sunday in Southern Manitoba.

NAEFS 8-14 Day Outlook initialized 2013-08-20 12Z

The NAEFS 8–14 day outlook shows slightly above-normal temperatures persisting in the 1–2 week timeframe.

Looking to next week, we will continue to see above-normal temperatures as a slack or southerly flow persists. We’ll also see dew points in the high teens making it feel relatively humid as well. After a month of below-normal temperatures, it looks as if we get to enjoy a late summer after all!

This Week May Start with a Bang

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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.