Tag: Rain

Stormy Start to the Long Weekend

Brad Leave a comment

The August long weekend will be off to a stormy start today as the threat of severe thunderstorms bears down on the Interlake, Red River Valley and Whiteshell this afternoon.

Tornado near Lake Diefenbaker

One of a couple of tornadoes that the incoming system spawned in Saskatchewan yesterday. Photo by @TheMrsCogs.

A very powerful low pressure, responsible for at least two tornadoes in Saskatchewan yesterday, will move into Southern Manitoba today and push a cold front across the province through the day. Very strong dynamics will accompany this system, a stark contrast from the last few systems which have had comparatively strong thermodynamics instead. Despite the lack of strong thermodynamic parameters that are often looked at when diagnosing severe thunderstorm potential, such as CAPE, EHI or LIs, the strong dynamics will present a significant severe weather threat over south-central and southeast Manitoba.

Dynamics are physical, kinematic properties of the atmosphere, such as jets, shear and lift. Thermodynamics are thermal/energetic properties of the atmosphere such as temperatures, humidity and instability.

A band of showers will push into the western Red River Valley early in the afternoon ahead of the upper low. As the afternoon progresses, the upper low will begin to deepen and enhance the destabilization over the Red River Valley. By mid-to-late afternoon, despite the cool temperatures and cloudy skies, there should be rapid development of storms along the cold front. Tornadoes are unlikely, although not impossible, here in Southern Manitoba; that threat should be relegated to the Dakotas where even greater dynamics and substantially better thermodynamics are present. If any tornadoes do form tomorrow, it’s likely that they will be of the short-lived variety and relatively weak. The greatest threat from today’s storm will be extremely heavy rain giving rapid accumulations of 1-2” (25-50mm) given precipitable water values of 40-50mm and large, damaging hail given the cool temperatures aloft.

Thunderstorm Outlook

Day 1 thunderstorm outlook valid 18Z today through 12Z tomorrow morning.

The storms will exit the province overnight, and we’ll have a brief reprieve from precipitation. On Saturday, some showers will wrap down into the RRV on the back side of this system. Amounts will vary across the region, but in general less than 5mm is expected. Temperatures will struggle to climb to even 20°C; daytime highs of only 18 or 19°C are expected. Winds will be breezy from the NW.

This system will clear out Saturday night before nicer weather builds back in. The second half of the long weekend will see increasingly sunny skies and daytime highs near 25°C.

More Showers Than Thought?

Brad Leave a comment

A few systems are expected to bring chances for showers and thunderstorms to Southern Manitoba over the next few days as the upper ridge takes a few days longer to build in than previously thought.

30-Day Rolling % of Normal Precipitation for the Canadian Prairies

30-day % of normal precipitation for the Canadian Prairies. This map depicts the increasing drought conditions over much of the Red River Valley, with most areas only seeing only about 60% of the normal amount of precipitation over the last 30 days.

Offering a slight bit of relief to the dry conditions over the Red River Valley, an area of rain blossomed in North Dakota overnight and has pushed into Southern Manitoba this morning. Amounts are generally expected to be between 5-10mm along the International Border with amounts dropping off quickly to the north. This system will push into NW Ontario by late morning and skies will clear out behind it. Under sunshine our temperatures will soar to nearly 30°C in the afternoon.

The subtropical ridge that was previously progged to push into the Southern Prairies has instead decided to stay more or less where it was for a few extra days, which will leave us with a more zonal flow through this weekend. Fortunately, this means that we’ll have more chances for precipitation than previously thought.

The next chance for rain will come on Saturday afternoon/evening as a shortwave that will move across Saskatchewan today slumps southeastwards across the Interlake and Red River Valley. A couple showers and thunderstorms are likely to fire up underneath the shortwave as it crosses the RRV in the late afternoon. Currently all the convective parameters look to be fairly middling, so I don’t expect any severe weather to occur. Saturday will have a daytime high of 28°C before clouds move in in the afternoon. The low on Saturday night will be around 15°C.

Sunday should be a sunny day with a high near 28°C.

The next chance for rain will be Monday night as a shortwave slumps down the upper ridge that will build into the Western Prairies over the weekend. After that, it looks like the ridge will continue building into the Eastern Prairies, bringing us sweltering hot temperatures ove 30°C by the end of next week.

Unsettled Weather to Continue

Brad Leave a comment

This week will continue to be unsettled weather-wise. It appears that we will see the chance for rain virtually every day for the next several days.

A trough of low pressure over the Prairies

A trough of low pressure over the Prairies (the jet stream is in blue)

A trough of low pressure sitting over the Prairie provinces will be responsible for our unsettled weather over the coming days. This trough is created due to the fact that the jet stream will be to our south, allowing cooler air from the north to spill down into lower latitudes. As weather systems track along the jet stream they will create chances for rain in Southern Manitoba. It appears that rain is a possibility on every day from Monday through Thursday. At this time it looks as though rainfall amounts on Monday and Tuesday will be fairly light, if it rains in your location at all, but the precipitation forecast for later in the week is less clear.

Due to the cloudy and potentially wet conditions expected on Monday and Tuesday, temperatures won’t be very warm. Highs on Monday will generally be in the high teens over Southern Manitoba, except for border regions and parts of south-eastern Manitoba where temperatures should be closer to twenty degrees. Tuesday is likewise expected to remain cool, with highs in the mid to upper teens expected. Temperatures on Wednesday will be governed by when and if it rains, but it doesn’t look like it will be warmer than twenty for midweek (if it indeed gets that warm at all).

Too much uncertainty exists in the forecast at this point to talk about the weather much beyond Wednesday. However, at this time it doesn’t appear that we will be going back into a prolonged spell of nice weather in the short-term.

A Chance of Showers Today, Mild Weekend Ahead

Brad Leave a comment

A weak trough pushing across SW Manitoba today will push into the Red River Valley this evening, bringing with it some scattered showers or thundershowers. Things will clear out quickly, and we’ll be looking at temperatures in the mid-20’s for the weekend.

GEMREG QPF for Friday Afternoon

Total expected precipitation from teh GEMREG model this afternoon.

We’ll have a slightly more unsettled day today as a weak surface trough pushes into the Red River Valley this afternoon. Temperatures will climb up to just over the 20°C this afternoon before showers and thunderstorms develop over SW Manitoba and push eastwards into the Red River Valley. Dynamics begin to fall apart as the afternoon progresses, and any showers or thunderstorms will struggle to survive in an increasingly disorganized environment. It looks like the best chance of seeing some rain this afternoon will be through the Western Red River Valley, with diminishing chances east of the Red River. By the time the trough gets to the Whiteshell, the threat of precipitation will likely be over.

Saturday looks to be a gorgeous day as sunshine once again dominates across Southern Manitoba and highs climb to around 25°C. Things will turn a little more unsettled overnight on Saturday as an area of rain blossoms over Southern Saskatchewan and heads our way. The exact location of the rain is still uncertain, however best indications are that we’ll see a cloudy day across much of the Red River Valley, with the bulk of the rain passing north of Winnipeg through the interalke region, with only a chance of showers for Winnipeg and areas south. It will certainly be a system to keep an eye on as the weekend progresses.