A Chance of Showers Today, Mild Weekend Ahead

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.

Summer Returns to Southern Manitoba…For a Short While

Beautiful weather is on tap for Southern Manitoba with plenty of sunshine the next couple days and positively summer-like temperatures. Things will return back to normal on Friday, after a cold front sweeps across the province on Thursday night.

500mb Winds/Height for Wednesday Evening

500mb Winds & Heights from the GEMGLB, valid for 00Z Thursday 10 May. The upper ridge has been highlighted over Manitoba.

A deep southerly flow has moved into Southern Manitoba underneath an upper ridge sliding east over the Prairies, pushing warmth from the Central Plains of the United States into our area. Temperatures will climb to around 20°C today with winds increasing to 20-30km/h out of the south by the afternoon. Temperatures will only drop to around 10-12°C tonight as the southerly winds keep our temperatures up in this warmer air mass.

Tomorrow the real heat moves in, and we’ll see temperatures soar in the Red River Valley, with daytime highs between 24 – 27°C. We’ll see a bit more cloud, though, and dewpoints in the low teens will make it feel closer to 30°C.

Day 2 Thunderstorm Outlook valid 21Z May 10 to 12Z May 11

Day 2 thunderstorm outlook, valid from 21Z May 10 (Thursday afternoon) to 12Z May 11 (Friday morning). No severe thunderstorms are expected.

By tomorrow evening, a cold front sweeping across the province will move into the Red River Valley. With the extra moisture in the air from the higher dewpoints, CAPE values will be enhanced slightly, and we’ll be looking at 500-750J/kg of CAPE as the front pushes into the RRV. A band of showers and thunderstorms will fire along the cold front on Thursday afternoon over SW Manitoba and continue eastwards through the evening, crossing the RRV through the evening and pushing through the Whiteshell overnight.

Seasonal conditions are expected to return for Friday into the weekend.

Nice Today, Then Showers & Rain

Winnipeg and the Red River Valley will get a bit of a reprieve from the unsettled weather of late today with some sunshine and daytime highs in the mid-teens for Winnipeg and closer to 20°C for regions in the Southern Red River Valley. Conditions will deteriorate tonight, however, as Southern Manitoba deals with another low pressure system that will move through on Thursday.

12hr. QPF -- GEMREG

12 hour precipitation accumulation from the GEMREG model. Valid 12Z Thursday to 00Z Friday.

Clouds and showers will push into the Red River Valley tonight as a low pressure system makes it’s way through North Dakota. A very slight risk for a thundershower exists along the US border, however the odds aren’t very likely. For everyone else, just plain old rain will be pushing your way. Models disagree on how far northwards the precipitation will push: the American models keep the northern edge on a line that cuts from Morden to Bisset, south of Winnipeg, while the Canadian models push the precipitation as far north as Gimli. It seems fairly certain that the southern half of the Red River Valley will see showers tonight and Thursday; Winnipeg will likely see at least a few passing showers out of this next system, with a chance that we’ll see rain tonight through much of tomorrow.

12 Hour QPF -- NAM

12 hour precipitation accumulation from the NAM model. Valid 12Z Thursday to 00Z Friday. Notice how the NAM keeps the precipitation much further south; whereas the GEMREG has Winnipeg in the highest accumulations of the system, the NAM keeps us on the Northern fringe of the rain with very little accumulation.

For areas that do see steady rain, total accumulations should be in the 5-10mm range with localized areas that see some convective enhancement seeing as much as 15-20mm. My current feeling is that Winnipeg will see at least 5-10mm through Thursday evening.

Rainfall in systems like this is typically hard to predict because it is so dependent on the initiation of elevated convection at night; something that models do not have a great handle on and humans struggle with not because we don’t understand it, but because there’s simply so little data to work with. Small errors in the location or strength of initiation of the nocturnal convection can result in huge errors in the model for later times, which can cause the model to end up forecasting tons of rainfall for one location that ends up seeing nothing and completely missing other areas that might see plenty of rain. For this reason, working off of real data is often the best way to go; satellite & RADAR imagery can be a forecaster’s best friend in dealing with nocturnal convection. A drawback to this, though, is that you can’t make your forecast as early. As soon as things begin to take shape, a forecaster can act quickly and make a fairly accurate forecast for the next 12-24 hours. It’s crucial to make sure that the starting point is correct, though, which is why when dealing with convectively driven situations, it’s important to talk in terms of probabilities and likelihoods while still a ways away from the event actually happening.

Improving Weather

Southern Manitoba will see improving conditions today and round out the work week with nice conditions and near-normal temperatures.

Ridge Dominating Southern Manitoba

Model 3hr. QPF & MSLP w/Surface analysis valid 00Z Thursday April 19th

There will be a slight chance of some light snow this morning over the western half of the Red River Valley as a weak short wave slumps into North Dakota. As it exits the province, clouds will clear and we’ll be left with a sunny afternoon with a high near 8°C.

Clear skies will be the weather story for the rest of the week as a ridge of high pressure builds in from Northern Saskatchewan. We’ll have an overnight low near -6°C tonight and warm back up to a repeat of today on Thursday, with a high near 7°C. Rinse and repeat for Thursday night. As a system pushes into the NW United States, slightly warmer air pushes into Southern Manitoba and we’ll likely see our daytime high bumped up a few degrees to around 10°C.

Saturday brings with it a chance of rain as an upper trough swings across the Prairies. We’ll keep an eye on that as the week progresses!

In short, it’ll be a sunny, albeit a little cool, rest of the week!