Snow Tapering Off Today

Today’s post will be short as I’m occupied with some family-related business.

Moderate snow pushed into the Red River Valley yesterday evening, bringing reduced visibilities and slippery conditions. Snow will continue through much of the day before tapering off.

Accumulated Precipitation From 00Z Friday to 00Z Saturday

GEM-GLB Accumulated precipitation from 00Z Friday to 00Z Saturday

Snowfall accumulations will generally be close to 5cm, however there will be a swath near the Trans-Canada highway between Brandon and Winnipeg that will likely see total amounts in the 5-10cm range. Snow should taper off by evening, and we’ll see an overnight lows throughout the RRV around -15°C.

Over the weekend, we’ll see mostly sunny skies with daytime highs near between -10° and -5°C, with overnight lows between -20°C and -15°C. The next chance for precipitation will come Monday with a passage of a warm front that will push our temperature up into the plus mid-single digits.

Unsettled Weather into the Weekend

After a few sunny days, snowier weather will return to Southern Manitoba as a slow-moving system tracks from Southern Saskatchewan into Southern Manitoba along the international border. For today, we’ll see skies cloud over this morning, but we’ll still have beautiful conditions, with highs through the entire RRV sitting within a degree or two of 0°C and winds dying off by early afternoon.

Tonight will mark a transformation to a snowier pattern, however, as a complicated series of shortwaves begin to march across the Prairies associated with a strong upper low.

500mb Winds

500mb Winds from the GEM-REG valid 12Z Thursday morning, March 1st.

As the Colorado low that has brought severe winter weather to the Northern Plains progresses eastwards, an upper low will be pushing into Southern Alberta and inducing troughing eastwards across the Southern Prairies. As this troughing occurs, a series of smaller shortwaves will lift northwards and track across Southern Manitoba.

Tonight, an area of light snow will develop along the RRV in North Dakota and slowly lift northwards into Winnipeg. This area of snow will slowly fizzle out over the region before being replaced by a more organized area of snow that will push across Southern Manitoba as the main low tracks across the Southern Prairies. By Thursday night, we’ll be back under steady snowfall.

24hr. QPF

24hr. Precipitation Accumulation valid 12Z Friday morning, March 2nd.

The entire system will exit the region overnight on Friday. Snowfall totals west of the Trans-Canada highway will be general amounts near 5cm. Areas in the RRV and east into the Whiteshell will see more, with widespread accumulations of 5-10cm and localized amounts potentially reaching as high as 12-13cm. These amounts are estimates right now, and we’ll certainly see how things shape up over the next day and a bit.

After this system clears out we’ll have a bit of an unsettled weekend with the potential for some light flurries as a weak low pressure system tracks through Central Manitoba. The next potential for snow comes on Monday as another powerful low pressure system tracks through the Prairies. More on that on the weekend!

Calmer Weather On Tap (for Manitoba)

After a wild week of weather that featured heavy snowfall across many parts of Southern Manitoba conditions will begin to calm down. However, the same can’t be said for areas just to our south.

Surface Map Showing the Colorado Low

Surface map showing the forecast track of the Colorado Low

A major winter storm will impact portions of the North-Central United States just south of Manitoba. Areas such as Fargo, North Dakota, Minneapolis, Minnesota, and Aberdeen, South Dakota will be impacted by a Colorado Low system on Tuesday and Wednesday of this week. The hardest hit areas in South Dakota and Central Minnesota may see upwards of 30cm (1 foot) of snow. Wind speeds will also be high during this storm and as such the National Weather Service has issued blizzard watches for portions of the Northern U.S. Plains. Anyone who has travel plans to regions just south of the border may want to reconsider as this will be a significant and potentially life-threatening winter storm.

On our side of the border the weather will be considerably different this week. Temperatures for the first half of the week will be very reasonable. Highs on Monday will be in the -10 to -15C range in most of Southern Manitoba, which is unseasonably cold. Fortunately wind speeds will be light on Monday, making conditions fairly comfortable. By Tuesday and Wednesday temperatures will have increased with highs in most of Southern Manitoba reaching the minus single digits. Temperatures for the remainder of the week will remain mild as an approaching low pressure system develops a southerly flow over Southern Manitoba. The approaching low pressure system will probably reach Southern Manitoba on Friday, potentially bringing a bit of light snow along with it.

With meteorological winter nearly over many people are wondering what March has in store. Unfortunately, there is no clear signal as to how March will evolve at this time. Most models show generally seasonable conditions in Southern Manitoba for the first part of March with no signs of any major warm-ups or cool-downs. Nevertheless, with spring set to begin in just over 3 weeks you can certainly count on the fact that winter’s worst cold is behind us.

Meteorological winter is defined as December, January, and February. Solar (calendar) winter lags behind by about 3 weeks (December 21 – March 21). Meteorological seasons more accurately describe the type of weather that takes place in Southern Manitoba

Elsewhere in Weather News

Flash Flooding in Queensland, Australia

The southeast region of Queensland, Australia experienced flooding this week after more than 330mm of rain fell in some areas. Although heavy rainfalls are not that uncommon in the region, southeast Queensland was deluged with heavy rain the past couple weeks and the river system levels are quite high.

This week’s rainfall totals for Queensland, some areas topping 300mm in one week! (Source: Bureau of Meterology, Australia)

This week’s rainfall totals for Queensland, some areas topping 300mm in one week! (Source: Bureau of Meterology, Australia)

From Friday, February 24th to Saturday the 25th, a surface trough combined with an upper-level low intensifying over Queensland and slowly moving westward, caused the Bureau of Meteorology (BoM) to issue multiple warnings. (In the southern hemisphere low pressure systems spin clockwise and move westward as opposed to the northern hemisphere where lows spins counter-clockwise and generally move eastward.) The BoM had issued flash flood warnings, advising that some of the downpours could easily reach 150-200mm within a day. Severe weather bulletins had also been issued for storms associated with this system however the main threat was flash flooding.

Bridge leading into Cooroy has been destroyed by rising waters. (Source: The Courier-Mail)

Bridge leading into Cooroy has been destroyed by rising waters. (Source: The Courier-Mail)

The rainfall caused extensive damage to the road networks in the region, causing authorities to close more than 40 roads and urge residents to stay off roads and only travel for urgent reasons. More than 100 water rescues were made due to rapidly rising water levels and fast flowing streams turning into raging rivers in a matter of minutes. The town of Cooroy which had been impacted by very strong winds earlier in the week had now been cut off by rising waters as the roads heading in and out of town were flooded out. Since then, the water has receded and the town can now travel freely.

The weather should clear up though, as the forecast calls for minimal rain for the start of the work week, with only sporadic showers occurring every second day.

Elsewhere in Weather News has been provided by Matt

Another Significant Snowfall on the Way

After Manitobans dug out from as much as 21cm of snowfall, it looks like some portions of Southern Manitoba may need to keep the snow shovel ready as another significant weather system tracks across the Northern Plains, bringing significant snowfall to North Dakota. The question is, just how much snow will make it into Southern Manitoba? Read on for our best guess…

Winters Around - Photo by Jennifer Molnar

Winters Around – Photo by Jennifer Molnar

First: for today we’ll see a mix of sun and cloud and light flurries through much of the day as the shortwave that brought around 3cm of snow to Winnipeg yesterday slumps southwards into Minnesota. Temperatures will be cooler today than the past few days now that we’re on the back side of the cold front, with daytime highs around -10°C in Winnipeg and the Red River Valley. Overnight, skies will clear and temperatures will drop considerably; in Winnipeg the temperature should get down to around -22°C, while some regions in the Central RRV south of Winnipeg will see temperatures dipping just below -25°C. Saturday will see temperatures rebound back to around -10°C with increasing clouds late in the day.

Another system will bear down on Southern Manitoba by the end of the weekend, and this time we’ll be looking at a very strong snowfall gradient from north to south instead of east to west. A powerful low pressure system will make landfall on the British Columbia coast by this evening and then accelerate across the Rockies and slice through the Northern Plains, spreading an intensifying area of snow across North Dakota and Southern Manitoba.

The exact question to be asked is “How much snow?” In this case, that’s not quite so easy a question to answer. In the heart of the heaviest snowfall, this system will pack quite a wallop, dumping up to 20cm (~ 9”) of snow in North Dakota. The situation in Southern Manitoba will be complicated by our old friend, the deformation zone.

While with the last system the deformation zone set up in a north-south orientation, dramatically reducing snowfall amounts across an area as small as Winnipeg, this system’s deformation zone will have a more typical west-east(ish) orientation and will not be quite as strong. This will again produce a relatively sharp drop-off in snowfall amounts from the south side of the deformation zone to the north side. Currently, indications are that it will set up somewhere slightly north of the Trans-Canada highway. This will allow snow to push across Southern Manitoba and give areas along the Trans-Canada highway, such as Brandon and Portage La Prairie, roughly 5cm of snow. Areas north of the Trans-Canada would see a couple cm, but nothing significant. Current indications are that if things pan out as currently forecast, areas south of the Trans-Canada would receive 5-10cm of the white stuff, with the potential for isolated areas of 10-15cm within 50km or so of the International Border.

Any forecast for this system will be extremely sensitive to the track the system takes, which is essentially impossible right now, given the fact the low pressure system is still off the Pacific seaboard. The best way to approach a system like this is through the use of ensemble forecasting.

Ensemble forecasting is a technique where instead of outputting one “answer,” a forecast model produces many “answers,” each a result of slightly altered initial conditions. We then combine all that information to be able to produce probabilities of some weather condition at any given location. This technique produces *probabilistic forecasts compared to the traditional single-“answer” deterministic forecasts.*

We’ll use the NAEFS (North American Ensemble Forecast System) to look at this problem. It consists of output from two models, a Canadian one and an American one, each supplying 21 “answers” to the weather. This will help us find the most likely solution given the conditions we know right now. So, moving forward…

NAEFS Ensemble Snowfall - Probability of > 5cm

Ensemble probability of greater than 5cm of snowfall accumulation, valid for 06Z to 18Z Monday February 27.

This shows us the probability of any one location getting more than 5cm of snowfall. For various reasons, although it may not seem like it would be, anything above 50% is a pretty good chance of more than 5cm of snow. We can see that Winnipeg sits right on the border of the 30% probability, which means we’ll likely see at least 3 or 4cm for the time period covered by this image.

My best guess for storm-total snowfalls from Sunday through Monday evening, given the current information would be:

  • Winnipeg: 7-10cm
  • Brandon: 8-12cm
  • Portage la Prairie: 8-12cm
  • Steinbach: 8-12cm
  • Morden/Winkler: 10-13cm
  • Emerson: 12-15cm

With the very sharp drop-off visible immediately north of Winnipeg, it becomes quickly apparent how important the track will be for this system. A shift of even 50km could dramatically increase or decrease the amount of snow that ends up on the ground. We’ll have updates in the comments through the weekend as this system develops. I get a feeling that once we can actually see the low and where it’s heading I’ll be updating those numbers above, but hopefully not too much!