Author: Brad

Brad lives in Winnipeg with his wife and two children and is the founder of A Weather Moment. He has loved weather from a very young age and has followed that passion through his life so far. He received a B.Sc. in Earth Sciences with Specialization in Atmospheric Sciences and is currently employed in the field of meteorology. You can find the author as WeatherInThePeg on Mastodon.

Potent Fall Storm Brings Strong to Severe Winds to Winnipeg

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Strong to severe westerly winds will be out in full force today behind a cold front now pushing into Ontario. These winds are being created by a very potent fall storm over Northern Manitoba which is also bringing up to 25 cm of snow and blizzard conditions to the most northern regions of the province. The remainder of the week looks beautiful, however, with temperatures rebounding quickly back to well above-seasonal values.

Early morning cloud will quickly push eastwards this morning as very strong westerly winds move into the Red River Valley behind a cold front racing eastwards into Ontario. While skies will be sunny, it won’t be a particularly pleasant day out there as winds quickly increase to 50-60 km/h with gusts of 85-95 km/h. Winds will be just a bit lighter to the south of Winnipeg and a bit stronger to the north of Winnipeg. There will be a few areas that may see wind gusts in excess of 100 km/h: areas just downwind of the Riding Mountains and the Turtle Mountains, the Manitoba Lakes (Manitoba, Winnipegosis, Winnipeg), and across portions of the southern Interlake. These strong to severe winds will diminish quickly in the evening hours as temperatures cool and the low pushes off to the northwest.

RDPS Forecast 10m Wind Speed valid 18Z Wednesday October 18, 2017
Strong to severe (darker purple, red) westerly winds will move across southern Manitoba today behind a cold front associated with a potent fall storm moving through northern Manitoba.

All in all, about 9-12 hours of strong to severe winds are expected, so it will not be surprising if damage to buildings occurs. While the sustained winds may be below the EC³ warning criteria, once winds reach the 60 km/h, the stress incurred on buildings across numerous hours can cause structural failures. Hopefully the worst will just be some missing shingles, but recalling the May 18, 2015 wind storm, significant damage can occur with gusts to 90+ km/h. In that storm, winds were over 50 km/h for 20 hours, which we won’t see this time, but the strongest winds occurred in a 6-hour stretch where winds were maintained in excess of 60 km/h. While this isn’t the same storm, and thus we can’t expect the same outcome, it’s entirely possible that we may see damage that looks familiar.

So, other than the wind, temperatures will fall to around 13°C today as cooler air surges in from the northwest. That said, I don’t think there’s any room for complaints when temperatures remain above-seasonal behind a cold front in October. Lows will dip down to around 3°C with light winds and just a few clouds.

Tuesday will be just a tad breezy by comparison, as another warm front pushes into the region and brings southerly winds of 20 gusting to 40 km/h. Temperatures will climb to a high near 18°C under partly cloudy skies. Winds will remain out of the south at 20-30 km/h on Thursday night as skies become mixed and temperatures dip to a low near 8°C.

GDPS Forecast 2m Temperature Anomaly valid 00Z Saturday October 21, 2017
Temperatures will climb around 15°C above seasonal values on Friday as another surge of very mild air pushes through the province.

Friday will be a late-season “scorcher” in Winnipeg. Despite mixed skies, temperatures will soar to a high near 21°C on Friday afternoon. While we probably won’t be challenging the record high of 23.9°C set in 1958, it may end up coming close if we get enough sunshine. Winds will once again be in place out of the south at 30-40 km/h with some gustiness on top. Expect a low near 13°C on Friday night with winds continuing out of the south to southwest and increasing cloudiness.

Long Range

A second low pressure system will move through Friday night into Saturday, bringing more cloud, cooler temperatures, and a slight chance of showers on Saturday afternoon. While there may be some clearing on Saturday evening/night, more cloud is expected to move in on Sunday ahead of the next low pressure system cross the Prairies. Temperatures will remain above-seasonal throughout the weekend, but after a cold front pushes through on Sunday evening, a west to northwesterly flow will set up for the next few days, bringing seasonal temperatures back to the region.

The extended forecast looks relatively dry, but one wildcard is Saturday and Sunday. Overall, it seems models have having a hard time resolving exactly what kind of low will move through the region, the timing of it, and how much precipitation it will produce. Some models produce little rain with the low coming through — the GFS has essentially no precipitation for much of the Red River Valley — others, such as the GDPS, produce as much as 10-15 mm of rain. The solutions seem to be flipping around quite a bit right now, so it’s hard to pin down exactly what to expect. We’ll certainly be keeping an eye on it and have more details in Friday’s forecast.

Otherwise, next week looks like it will bring variable cloudiness to Winnipeg and the Red River Valley with the occasional chance for some rain showers.

Winnipeg’s seasonal daytime high is currently 9°C while the seasonal overnight low is -1°C.

Dry and Mild Conditions Ahead

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A series of low pressure systems tracking along the 60th parallel will spread mild Pacific air eastwards over the Prairies throughout the week, bringing warm and dry weather to Winnipeg for much of the coming week.

Breezy south-southwest winds of 20 km/h strengthening to 30 gusting to 50 km/h westerlies will bring above-seasonal high temperatures near 16°C to Winnipeg today as another warm front pushes across the Red River Valley. The front will bring partly cloudy to mixed skies in the morning, giving way to more sunshine in the afternoon. The clouds will completely clear out tonight as the winds taper off. Temperatures will dip down to a low near 4°C.

Even warmer temperatures are on the way Tuesday as even milder air pushes eastwards across the Prairies. Winnipeg and the Red River Valley can expect daytime high temperatures in the 18-21°C range under mainly sunny skies, but a moderate south-southwesterly wind of 30 gusting to 50 km/h will develop for the afternoon hours. These winds will persist into Tuesday night in the 20 to 30 km/h range as temperatures drop to a low near 9°C under partly cloudy skies.

GDPS Forecast 850mb Temperature Anomalies valid 00Z Wednesday October 18, 2017
Seen easily in this 850mb temperature anomaly forecast for Tuesday evening, significantly warmer-than-normal temperatures will be moving through the southern Prairies.

Slightly cooler temperatures return for Wednesday as a cold front sweeps through the Red River Valley early in the day, ushering northwesterly winds of 40 gusting to 60 km/h that will draw cooler air back into the region. Temperatures will reach a high in the low teens under partly cloudy skies. The “cooler” weather will be short lived, though, as another warm front pushes into Manitoba Wednesday night. This will bring more cloud to the region and keep overnight lows slightly warmer than Tuesday night at around 5°C.

Long Range

The remainder of the week looks quite warm with temperatures climbing back towards 20°C by the end of the week as yet another surge of mild air spreads eastwards across the Prairies.

GDPS Forecast 850mb Temperature Anomalies valid 00Z Wednesday Friday 20, 2017
An even warmer surge of mild air will return to southern Manitoba on Thursday into Friday

Slightly cooler conditions will move in for the weekend, as a disturbance moves through and brings a chance of showers, but temperatures are expected to remain above-seasonal until early next week.

Winnipeg’s seasonal daytime high is currently 10°C while the seasonal overnight low is -1°C.

September Brought Mild Temperatures, Wet Weather

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September brought mild weather to Winnipeg with above normal temperatures on about two-thirds of the days in the month. The month also started off extremely dry, but a change to a more unsettled pattern mid-way through the month ended up producing measurable rain on 9 of 13 days, including 25 mm of rain on September 22.

September is typically a month that brings a lot of cooling to the region; the daily mean temperature drops from 15.6°C at the start of the month to 9.3°C at the end of the month, a drop of 6.3°C. So while the average daytime high did drop considerably through the month in line with this trend, temperatures still remained generally above normal, with cool spells few and fair between. The warmest day of the month came on September 12, when Winnipeg set a new daily record high temperature of 34.8°C, beating the old record of 33.3°C set in 1952. That day was also the most “warmer than normal” day of the month with a daily mean temperature of 24.3°C, a full 11.3°C warmer than the normal daily mean of 13.0°C.

The coldest temperature of the month came on September 29th, where the temperature dipped to a chilly -1.2°C in the morning, 4.6°C below the normal seasonal low of 3.4°C.

September had a monthly mean temperature of 14.2°C, which was 1.9°C above the seasonal normal of 12.3°C. The mean daily high temperature was 20.1°C, which was 1.6°C above normal. Warmer than normal daily highs occurred on 20 out of 30 days. The mean daily low temperature was 8.2°C, which was 2.2°C above normal. Warmer than normal daily low temperatures occurred on 21 of 30 days.

The monthly temperature range was 36°C; from a maximum temperature of 34.8°C on September 12 to a minimum temperature of -1.2°C on September 29.

The longest stretch of above-seasonal days was 8, from September 7 to September 14. The longest stretch of below-seasonal daily mean temperatures was 3, which occurred on September 4-6, 15-17, and 24-26.

An Abrupt Mid-Month Change Brought Rainy Conditions

September begin with very dry conditions, continuing the trend from August, which saw dramatically lower than normal rainfall. Mid-month, however, a significant shift occurred which brought disturbance after disturbance across southern Manitoba, producing much rainier conditions.

As can be seen above, very little rain fell between September 1 to September 14, with just 1.8 mm over two rainfall events. Beginning September 15, however, came rain on 9 of 13 days, producing the wettest 10-day stretch of 2017. Between September 17-26, 61.5 mm of rain fell in Winnipeg, eclipsing the 60.8 mm of rain that fell between July 15-24. The largest rainfall event occurred on September 22, when 25.2 mm of rain fell. This was followed quickly by another 18.3 mm on September 24. These two events combined to make the highest 3-day rainfall total of 2017 as well at 43.5 mm, beating 32.2 mm between July 11-13 by 11.3 mm.

With a monthly total of 67.1 mm, Winnipeg exceeded the seasonal normal of 45.8 mm by 21.3 mm.

2017 Annual Precipitation Statistics – Updated October 1, 2017

By mid-September, Winnipeg had crept into having the driest year since 1980, however the rainfall through the second half of the month has eliminated that potential by raising our annual precipitation amounts above the driest on record. Winnipeg still remains well below-normal, outside 2 standard deviations from the 1981-2010 normal amounts.

All in all, September was a beautiful month. Exceptional warmth through the first half gave way to near-seasonal temperatures in the second half, but overnight lows that remained well above-normal through much of the month helped keep that fall chill away until near the very end. The rainfall through the second half of the moth helped alleviate some of the drought that the region has seen, although Winnipeg still sits in a significant precipitation deficit for the year.

October has continued September’s trend so far with most of the days bringing above-normal temperatures to the region. Precipitation has been sparse, though, and little is on the horizon. Although Winnipeg saw its first snowfall of the year on October 14, temperatures will rebound well above-normal with unseasonably warm temperatures expected to build into the region later this week. With daytime highs nearly 10°C above normal and mild overnight lows, it looks poised to offer one last stretch of summer-ish weather before jacket weather arrives for good.

Forecast Update for Friday Night and Saturday

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The disturbance that we wrote about in our forecast that went live early this morning is throwing a wrench into things as it has progressed eastwards much faster than models had anticipated, already spreading across southwestern Manitoba into the Red River Valley. This will dramatically change the forecast for Saturday morning and afternoon.

As of writing, the system is producing a line of precipitation extending from the Manitoba/Saskatchewan/North Dakota border east-northeast along a line that runs just through Boissevain and Deloraine into the Red River Valley. Much of the precipitation from this line is currently falling as rain, however snow is likely mixing in on the northern edge of the band, where temperatures have dropped towards the freezing mark.

HRRR Forecast Accumulated Precipitation valid 17Z Saturday October 14, 2017
The forecast total precipitation amounts from 9PM October 13 to 12PM October 14 reveal the narrow band that the rain/snow is expected to fall along.

Precipitation will push east-northeast throughout the night, however where it is expected to be heavy enough to accumulate in any meaningful way will lie along a very narrow band roughly located where the heaviest of the precipitation is as of this writing.

Much of this will likely remain as rain; there’s a fair amount of warm air aloft and temperatures are being maintained around 2-4°C underneath the precipitation. As mentioned before, some snow will likely mix through as it progresses eastwards, but no significant accumulations are expected.

Over the heaviest band in the southwest corner of the province, it will likely be a decent soaking, however, with 10-20 mm of rain possible.

Shift Southwards Spares Southwestern Manitoba From Snow

With the shift southwards, the southwest corner of the province will be spared from the 5 to 10 cm we suggested was possible in our earlier forecast. The closer proximity to the border has the precipitation falling in warmer conditions, causing that snow to fall as rain instead.

Winnipeg On The Edge

The forecast for Winnipeg continues to be difficult, with the city likely resting right on the northern edge of the precipitation. It seems most likely that the city will see some rain or snow beginning around 2 to 4AM and tapering off by 7 to 8AM. No significant accumulations are expected.

Still A Chance for Afternoon Showers

This disturbance won’t be completely gone for Saturday afternoon, with a chance for showers re-developing over the Red River Valley mid- to late-morning and persisting until mid-afternoon. Temperatures will be warm enough that snow won’t be a concern, but 2-4 mm of rain will be possible under the “heaviest” band of showers. The chance for rain should remain south of Winnipeg.

Slightly Warmer Highs Expected

With the shift in timing for this system, daytime highs will be slightly higher than we forecast earlier. With the higher intensity precipitation finished by mid-morning, highs will be able to climb a bit warmer into the 6 to 8°C range instead of near 5°C like we advertised before.

The faster and more southerly arrival of this system means that the daytime hours on Saturday will see less precipitation than expected and allow daytime highs to climb a bit warmer. The heaviest amounts will fall along a narrow band in the southwest corner of the province with 10 to 20 mm possible through the and Saturday morning. The precipitation is largely falling as rain instead of snow, thanks to the slightly warmer temperatures aloft due to the shift southwards of this disturbance’s track.

Hopefully this covers what to expect; sometimes these systems progress a bit unexpectedly and all model guidance just…fails. This is one of those cases. We think the newer runs of rapid-update models are getting a good handle on it, though, so hopefully this forecast is able to hold up a bit better than the last one.