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.

Showers Today to Give Way to a Beautiful Week

A well-developed upper low will blanket the Winnipeg & the Red River Valley with showers today as it slides southwards into the Northern Plains. Its exit will leave room for an upper ridge to build in from the Pacific Coast, flooding the southern Prairies with some beautiful warm and sunny days.

GEMREG 24hr. QPF valid Tuesday morning

24 hour accumulated rainfall from the GEMREG model valid for Tuesday morning.

Winnipeg will see showers off and on today with a cool daytime high of around 13°C. Winds will be in the 20-30km/h range, starting out of the SW and switching to the NW this afternoon. Conditions will be similar through much of the Red River Valley, with temperatures generally between 12-15°C and similar winds. Showers will clear from north to south overnight, with only a slight chance of some lingering showers or drizzle through the Morder/Winkler, Altona & Gretna areas first thing tomorrow morning. In total, most areas in the Red River Valley, including Winnipeg, will see 4-8mm of rain by the time the showers clear out.

We’ll see sunny skies tomorrow through the entire Red River Valley, with highs from 12-15°C again and northerly winds from 20-30km/h. For the rest of the week, we’ll see a big warm up as mild Pacific air pushes into our area. Currently, it looks like Wednesday will have high temperatures near 20°C and Thursday will push even higher towards the mid-20’s. Things will cool off for the end of the week as a cold front pushes through and brings with it showers and a slight chance of thunderstorms across the Red River Valley.

Cloudy With A Chance of Showers

A series of weak disturbances will bring more cloudy days for Winnipeg with a chance of showers across the entire Red River Valley overnight and through the weekend.

Total QPF for Friday Night

GEM-Global 12hr. QPF valid 00Z May 5 to 12Z May 5 (Friday night). Notice the relatively small amounts over Manitoba compared to the 2”+ rainfall accumulations near the North Dakota/South Dakota border.

A shortwave tracking northeastwards is pushing into Southern Saskatchewan this morning, supporting a band of rain in the associated trough over SW Manitoba. As this system pushes northeast, the upper-level support will weaken and the band of rain will begin to diminish and become more “shower-y”. As the weak upper trough passes through the Red River Valley overnight, an area of nocturnal convection will develop in southern North Dakota, centered around some slightly enhanced lift from a weak low pressure system.. Models want to initiate a band of showers all the way along the upper trough that will be positioned between the ND low and the SK shortwave; however, any showers that want to try and develop may have to contend against subsidence north of the nocturnal convection in ND. Should this happen, either the SK shortwave would need to track further south than currently forecast to provide enough lift to offset the increased subsidence from the storms or the storms would need to fire further south so that more instability remains over the RRV. Otherwise, we’ll likely see little to no precipitation in the Red River Valley tonight. Were I to produce a standard EC forecast, I’d say that the north half of the RRV has a 40% chance of showers tonight and the southern half of the RRV has a 60% chance of showers.

Another system is forecast to track through on Saturday night into Sunday, bringing with it another chance of showers for Southern Manitoba. Once again it’s a binary system: the band of precipitation will be supported by two shortwaves, one in Canada and one in the US. As the system moves into the Red River Valley, the northern shortwave pulls northwards and the southern shortwave slides SE a bit, resulting in a good chance that the main band of rain will split apart and miss much of the RRV with the northern half pulling into the Interlake and the southern half sliding into North Dakota.

Again, with these convective systems, forecasting is a challenge. Over the next few days, expect more cloud than sun, daytime highs between 10 and 15°C, and a chance of showers tonight, Saturday night and Sunday. We’ll be providing updated forecasts when possible in the comments below, so be sure to check them over the next couple days.

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.