Category: Forecasts

Will Our First Snowfall of the Year Come This Week?

Scott Leave a comment

Will our first snowfall of the year come this week? That is the question that meteorologists are trying to answer as a complex weather system potentially brings accumulating snowfall to southern Manitoba tonight.

An inverted trough pattern associated with a strong system to our south may help bring snowfall to southern Manitoba
An inverted trough pattern associated with a strong system to our south may help bring snowfall to southern Manitoba

This Week

Today will start out cloudy and cool with temperatures hovering near the freezing mark. Change is coming, however, as a strong weather system moves off the mountains and begins to produce snow over the northern United States and southern Prairies. This is a complex system, with the strongest part well to our south over the midwestern US. A secondary part of this system will move across the southern Prairies and likely produce accumulating snowfall along part of its track. At this point it appears probable that snow will begin to develop over southern Manitoba on Monday night as moisture and lift begins to push into the region. The question is whether conditions will come together just right to produce significant snow over all of southern Manitoba, or whether the system will only begin to produce significant snow as it pushes into northwestern Ontario.

Weather model simulations generally begin to produce light snow over western Manitoba late on Monday afternoon, before the snowfall intensifies as it moves into the Red River Valley and southeastern Manitoba. This would likely result in 1-4 cm of snow over western Manitoba, 4-8 cm over the Red River Valley, and 5-10 cm over southeastern Manitoba. However, an alternative solution would have only minor snowfall (if any) over western Manitoba and the Red River Valley, with slight accumulations of 2-4 cm over southeastern Manitoba. The former solution is most favoured at this time, with about 5 cm expected in the Winnipeg region, with slightly higher amounts to the east and slightly lower amounts to the west. The most likely outcome may change as the system develops today, therefore you should stay tuned for more details.

A map of the currently favoured snowfall outcome is shown below, showing the probability of at least 5 cm of snow; note that Winnipeg has a 70% chance of receiving at least 5 cm. Some blowing snow is possible, due to southeasterly winds of 30 km/h gusting to 50 km/h today, however blizzard conditions are definitely not expected. Winds will taper off by Tuesday, alleviating any blowing snow that does develop. The first major snowfall of the year is always one of the most challenging as drivers adapt to the changing conditions. Regardless of whether it snows tonight, this is probably a sign that you should get those winter tires on if you haven’t already!

Probability of at least 5 cm of snow according to the NAEFS (ensemble)
Probability of at least 5 cm of snow according to the NAEFS (ensemble)

Snow will taper off on Tuesday morning, should it materialize in the first place, leaving Tuesday with cloudy and cool conditions. Temperatures will once again sit near the freezing mark under mainly cloudy skies. The odd flurry is possible during the day, but generally quiet weather is expected. Winds will be light from the west.

A quiet weather day is expected on Wednesday as well, with mainly cloudy skies and just a lingering chance of flurries. Temperatures are likely to be around or just above zero. Winds will be northwesterly at 20-30 km/h.

Long Range

The long range outlook will be partly shaped by how much snow falls this week. If we manage to avoid major snow, it is likely that the remainder of November will remain generally warmer than normal. Because a blanket of snow on the ground reflects most of the incoming sunlight, it is more difficult for us to heat up during the day. The longer we avoid snow the longer we’re able to keep that darker, exposed soil which helps to absorb the limited sunlight that we do receive at this time of year. Should we receive significant snow with this upcoming system, we’ll likely see normal conditions through month’s end. Regardless of how much snow falls this week, this November is likely to end up as one of the warmest, if not the warmest, Novembers on record in Winnipeg.

Cooler Weekend A Seasonal Reality Check for Winnipeg

Brad Leave a comment

Temperatures will be startlingly colder this weekend than we’ve seen through the first half of November, but despite the shock to the system, Winnipeg will simply be seeing temperatures closer to typical values for this time of year.

The weather through the weekend will be relatively benign overall, with the major storm system forecast once upon a time to slam the Manitoba Red River Valley now taking a significantly more southwards track, instead tracking across central Minnesota into Northern Ontario. With that major system moving through to our south, we’ll be left with cloudy skies and a brisk north wind to 30 gusting 50 km/h. Temperatures will be much cooler with a high near +1°C

As cooler air slumps southwards through the day, narrow bands of lake-effect snow will fire up off of the south basin of Lake Winnipeg. At this point, it appears that the line will run north-south and primarily impact a line between Selkirk and St. Clements southwards towards Springfield. Beausejour may end up just east of the main band, but slight shifts in the wind direction could shift the heaviest band east or westwards. Lighter flurries may make it all the way south of Steinbach. By the time the lake-effect tapers off on Saturday morning, anywhere from 5-15cm of snow may accumulate under the heaviest axis of snow.

If you look to the northwest of the massive Colorado Low blob, a narrow band of lake-effect snow accumulation can be seen east of Winnipeg.
If you look to the northwest of the massive Colorado Low blob, a narrow band of lake-effect snow accumulation can be seen east of Winnipeg.

Skies will begin to clear out on Saturday night, save for locations that see cloud streaming off the lakes. Winds will taper off and temperatures should dip to a low near -6°C.

Saturday will bring a ridge of high pressure to the province, quashing the lake-effect snow and bringing a bit of sunshine and light winds. Highs will reach around 0°C under mixed skies. Saturday night will be partly cloudy with a low near -5°C.

Sunday will bring increasing cloud ahead of a warm front pushing eastwards across the southern Prairies. Temperatures will climb to a high near -1°C with a brisk southeasterly wind at 20-30 km/h. Expect fairly cloudy skies with a chance of some light snow on Sunday night with a low near -4°C.

Back To Normal

As mentioned up top, while these cooler temperatures are a shock to the system, we’re simply in a rapid adjustment back towards seasonal temperatures.

November has been a phenomenally warm month so far, with an average high of 11.3°C, a whopping 9.8°C warmer than the typical average high of 1.4°C through the same 17-day period. Including overnight lows, mean temperatures have been over 6°C above normal, more typical of mid-October than November, and November 2016 has taken the crown with the warmest first half1 of November on record.

Top 6 warmest first halves of November in Winnipeg on record. Credit: Rob's Obs
Top 6 warmest first halves of November in Winnipeg on record. Credit: Rob’s Obs

And, while a brief seasonal snap is on the way, models indicate that by next weekend above-normal temperatures will be back in full force, which could enter the month into the competition for warmest November on record!

Long Range

The system pushing the warm front eastwards across the Prairies on Sunday will continue to push eastwards and bring another chance for snow to the region on Tuesday. After that, it appears that a series of low pressure systems will track to our north and begin building warmer air back into the Prairies.

Winnipeg’s seasonal daytime high is currently -3°C while the seasonal overnight low is -11°C.

  1. First half of November is November 1-15, inclusive. ↩

Coldest Weather So Far This Season Arrives In Big Pattern Shift

Brad 1 Comment

An increasingly active storm track will bring a major winter storm through the Northern Plains of the U.S., drawing colder arctic air southwards cross the Prairies and ushering in the coldest temperatures seen so far in the fall of 2016.

Today will start with a weak system pushing through the Red River Valley, bringing with it a band of showers that will lift northeastwards across the region through the first half of the morning. After that moves through, we’ll be left with fairly cloudy skies as temperatures climb to a high near 9°C. Winds will pick up out of the southeast this morning to around 20-30 km/h, then taper off for the afternoon. Expect the winds to pick back up out of the northwest later in the evening with a slight chance of some very light rain showers or snow flurries overnight as a cold front moves through and temperatures dip down to the 0°C mark.

Thursday will bring mainly cloudy skies as a Colorado Low strengthens south of the border. Winds will be breezy out of the north to northwest at around 20-30 km/h and temperatures will climb to a high of about 3°C.

This history of forecast precipitation for Friday's Colorado Low shows how the GDPS model has developed consistency only in the last day and a half.
This history of forecast precipitation for Friday’s Colorado Low shows how the GDPS model has developed consistency only in the last day and a half.

Since last weekend, it’s been quite clear that a major winter storm was possible on Friday, and that much it got right. However, what at one point looked like a major blizzard for the Red River Valley has since turned into a moderate-strength winter storm for the Dakotas and Minnesota into Wisconsin. There’s a whole discussion on long-range model forecasts, but we’ll leave it at this: while it may get the general pattern right, don’t trust it on the details.

So what will we see instead of a blizzard? Cloudy skies and a stiff north wind likely at 40 gusting to 60 km/h. The southeastern portion of the province may get clipped with some snow from this system, but here in the Red River Valley, the system snow should miss us. There may, however, be a sneak attack from the north as cooler air surges southwards and lake-effect snow fires up over the lakes. Areas in the lee of the lakes may see some light to moderate snow flurries, however these will occur in fairly narrow strips and be highly dependent on the wind direction.

Temperatures will climb to only -1 or 0°C for a high. Expect the cloud and potential lake-effect snow to continue overnight as temperatures fall to a low near -4°C.

Long Range

The weekend looks cool with a continued chance for lake-effect snow through the day on Saturday. Cloud cover will be a mixed bag and highs will be near 0°C with lows near -6°C or so. If we get completely clear skies one night, then temperatures could plummet quite severely, though, so an overnight low below -10°C may be possible if the cloud manages to be scoured out of the Valley.

November “Heat” Continues

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Our November “heatwave” will continue into early this week as temperatures remain well above normal. However, change is coming later this week as a strong low pressure system ushers in a much cooler air mass.

This Week

Today will be fairly nice in southern Manitoba. High temperatures will be near the 10C mark in most areas with mainly sunny skies to start the day. Clouds will begin rolling in as the day progresses, in association with a low pressure system pushing in from the west. This system may bring some light showers to southern Manitoba this evening and tonight, but no major accumulations are expected. Stiff southerly winds will be in place during the day with values of 30 km/h gusting to 50 km/h.

A nice Tuesday is expected, with mainly sunny conditions and “hot” temperatures yet again. The mercury should rise near the 10C mark, which is more than ten degrees warmer than normal for this time of year. Winds will be strong again though, with a westerly flow of 30 km/h gusting to 50 km/h.

Slightly cooler weather appears likely for Wednesday as another low pressure system begins pushing up from the south. As a result, skies will be mainly cloudy with a chance of showers or flurries throughout the day. Winds will be easterly at 20-30 km/h.

Long Range

Models have consistently advertised a strong low pressure system passing through the northern US later this week. This exact track of this system remains unclear, but it appears quite likely that it will usher in a much cooler pattern to southern Manitoba from late this week into the weekend.

While the current GDPS forecast has this storm completely missing Southern Manitoba, the GFS clobbers the region with heavy snow.
While the current GDPS forecast has this storm completely missing Southern Manitoba, the GFS clobbers the region with heavy snow.

Should the system take a northerly track we will also have to contend with heavy precipitation, in addition to the cooler temperatures.