Hottest Day of the Year to Give Way to Unsettled Weather

Winnipeg may see the warmest day of the year today as temperatures soar into the mid-30’s under the influence of an upper ridge and southwest wind. The upper ridge that has brought us our sunny weather will then be weakend by multiple upper disturbances tracking across the Prairies, bringing us a few days of more unsettled weather across Southern Manitoba.

850mb Temperatures for this afternoon.

850mb temperatures from the NAM for this afternoon.

A southwest wind, combined with significantly warmer temperatures under the upper ridge (around 22 or 23°C at 850mb) today will help Winnipeg’s temperature soar to a scorching 35°C if we can stick to sunny skies. Today will be the warmest day of the week, with temperatures returning to near 30°C for Thursday and Friday. Overnight lows will be mild with the temperature bottoming out at only around 19°C.

Several disturbances are set to track through the southern portion of the province beginning this afternoon/evening, which will bring us a risk of thunderstorms late this afternoon and this evening as well as tomorrow afternoon/evening. While some storm parameters will be significant given the heat, a distinct lack of wind shear will ensure that any storms that form will likely be relatively slow moving pulse-type storms. They may strengthen to severe levels, but they will likely be scattered and it will be quite hit and miss as to who sees them and who doesn’t. The main threat from the storms would be large hail and heavy rain. Strong winds area also a possibility. Extremely weak wind shear will likely preclude the development of tornadoes, but it’s important to remember that any thunderstorm has the potential to produce a tornado; some are just more likely than others.

Things clear up a bit for Friday (although a few hit and miss storms are possible through the Red River Valley) before another system pushes in for the weekend and we’ll see more significant chances for thunderstorms return.

Surprise! More Hot Weather

This week will be another hot one in Southern Manitoba and indeed all over Western Canada. The potential for thunderstorms during the week may temper the heat somewhat.

A large ridge of high pressure will reside over Western Canada this week

A large ridge of high pressure will reside over Western Canada this week

The weather forecast for this week will be rather tricky. What we do know for sure is that it will be hot all week, with high temperatures being near 30C every day. However, what is somewhat unclear is the risk of thunderstorms during the week. Let’s start with the easy part – the heat.

Temperatures will start out the week in the upper twenties or near thirty on Monday and Tuesday in Southern Manitoba. Humidity levels should remain low on these day making conditions hot, but not excessively so. By Wednesday high temperatures should be be in the low thirties with the humidity making it feel closer to 40. It currently appears that temperatures for late week will remain around the 30C mark, with humidity levels remaining elevated.

A shortwave will move toward the Eastern Prairies on Wednesday, potentially helping to trigger thunderstorms

A shortwave will move toward the Eastern Prairies on Wednesday, potentially helping to trigger thunderstorms

The presence of heat and humidity over the Prairies this week will cause the atmosphere to become unstable, creating the risk of thunderstorms on many days. Unfortunately, the thunderstorm forecast is not entirely certain. The issue is that a large region of high pressure, such as the one we’ll be under, does not typically promote widespread thunderstorm activity. In fact high pressure usually suppresses convective activity. It looks like this ridge will not be very good at suppressing thunderstorms, which complicates the forecast significantly.

At this point it looks most likely that Southern Manitoba will see thunderstorms mainly during the second half of this week, from Wednesday onward. During that time period the atmosphere will be most unstable and there will be some weather features moving through the region which may trigger storms. The jet stream has weakened significantly over the Prairies as of late, meaning that most storms will be non-severe in nature. Heavy rain will likely still be a concern though due to slow storm motion. Some severe storms will also be possible just simply due to the instability present in the atmosphere. Although stronger storms will certainly be less widespread than weaker ones. As the week progresses we’ll have to reassess the thunderstorm risk one day at a time.

While my forecast for this week might seem a bit equivocal, that will just be the nature of the weather in the short-term. Unfortunately thunderstorms are just simply unpredictable a frustrating but unavoidable aspect of mother nature.

More Showers Than Thought?

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.

One Last Shot at Some Rain

Another frontal system tracking across Southern Manitoba today will bring one last shot at precipitation before the sub-tropical high begins to edge northwards and push us back into a hot, dry pattern.

15Z GEM-REG Analysis

Analysis of the GEM-REG model for this morning. The red and blue lines represent warm and cold fronts, respectively.

A cold front that brough severe thunderstorms and numerous tornadoes to Saskatchewan yesterday will push across the Red River Valley late this morning into the early afternoon. What sort of weather we’ll see from this depends highly on how much sunshine we’re able to see beforehand.

A rather large MCS will slowly decay as it moves through SW Manitoba this morning on approach to the Red River Valley. Some uncertainty exists as to what this system will do, however, and the result is dramtically different outcomes.

The NAM wants to keep this system quite progressive and push it eastwards fairly consistently. Under this solution, we’ll see a cloudy morning with some showers and thundershowers pushing through late morning/early afternoon. There’s a chance that rain could be fairly heavy under some of the thundershowers. Westerly winds would build in this afternoon flushing out the moisture in the Red River Valley and returning us to much more comfortable dewpoints in the low teens.

The growing trend in allh the other models, though, is for this system to stall out for a while over SW MB / extreme western RRV. If this is indeed what happens, things could be a little more interesting. Should the sun be able to poke through even a bit, that heating combined with the high surface dewpoints (should be in the 20-23°C range tomorrow morning) would build our CAPE values into the 2000 – 3000 J/kg range. That, combined with good deep shear and a SE wind at the surface veering to SW aloft, could provide an environment favorable for strong storms. The main threats would be heavy rainfall due to the slow-moving nature of the system (this threat would be centralized over the Western Red River Valley), strong winds and large hail. Stronger winds pushing in on the backside could favor the development of a squall-line type feature, but if they’re late to the party, a few isolated supercells certainly aren’t out of the question.

My take on all this? I think we’ll see some middle-ground solution play out. I think we’ll have a chance at seeing a bit of sun this morning, and by late morning some showers and thunderstorms will start pushing through the RRV. One can’t ignore the potential that exists for strong convection, and in that regard I would agree with the SPC’s “See Text” analysis for ND into Southern MB. The potential is there, but I wouldn’t say it’s likely. I hope that many places across the RRV see some rain as this front comes through, because it may be our last chance for a while…

8-14 Day Temperature Anomoly Outlook

NAEFS 8-14 Day Temperature Anomoly Outlook. The large area of red over the Canadian Prairies indicates a high probability of warmer than seasonal temperatures through the 8-14 day time period.

After this system, the sub-tropical high will begin to build northwards again, pushing plenty of heat into Southern Manitoba. Daytime highs will remain in the high 20’s to low 30’s through much of the next 7-10 days, with nary a drop of rain in sight for the Red River Valley. After many places have gone two weeks without any measureable precipitation, perhaps not the best of news.

We’ll keep a close eye on the storms this morning and post updates in the comments as the system develops!