Tag: Snow

Mild Weekend Then Into A Colder Stretch

Brad Leave a comment

A low pressure system crossing the Prairies will bring another wave of unseasonably mild air into Southern Manitoba and help temperatures climb above 0°C for the second time this week. Heading into the latter half of the weekend, unsettled weather will develop over Southern Manitoba bringing flurries as cooler air begins gradually slumping southwards out of the Arctic and across the Prairies.

Today will be a much nicer day for Winnipeg than it appeared like it would be earlier this week, all thanks to a more northern track for today’s low pressure system crossing the province. As a result of this trajectory, Winnipeg will still see the warmth we expected before, but much less of the precipitation, which will now mainly fall through Central Manitoba and the Interlake before heading off into Ontario.

For the city, today will start off with a chance of…well, just about anything—snow, freezing rain, or showers—as a warm front pushes through and brings our temperatures above zero. As the warm front pushes off to the east relatively early in the day, we’ll be left with skies on the cloudier side and temperatures in the +1-2°C range. Windswe will start out of the south at around 30-40km/h before shifting to westerly behind the warm front at similar speeds. The chance for showers will redevelop mid-day and through the afternoon as a little bit of cooling aloft moves across the region. Expect temperatures to drop to around -2°C tonight with a few clear breaks developing.

RDPS 12hr. QPF Forecast for Friday January 29, 2016
This RDPS forecast showing accumulated precipitation through Friday shows how most of the precipitation is expected to our north and east

Saturday will bring more warm weather cloudier skies once again, although a few sunny breaks are certainly possible and the southwestern Red River Valley may actually end up seeing a fair amount of sunshine. Temperatures will climb to around +1°C with lighter winds than Friday.

A cold front will begin slumping southwards through the region on Saturday night. This will bring cooler temperatures and send our overnight low down to around -11 or -12°C under cloudy skies. Alongside the cooling will be a chance of some light flurry activity.

Sunday will be a cooler day with a high in the near -6°C or so. Under mainly cloudy skies, Winnipeg will see a slight chance for flurries throughout the day thanks to favourable temperatures throughout the lower atmosphere. This cooler weather will mark the leading edge of a return to seasonal and below-seasonal temperatures for a short while.

Long Range: Colder, But For How Long?

Looking forward into next week, it looks like cooler weather will return to the Prairies as the conditions that have supplied the warmer weather to the region over the past week collapse southwards and allow cooler Arctic air to slump southwards.

GEPS Maximum Temperature Forecast valid February 1-6, 2016
GEPS maximum temperature forecasts valid for the February 1-6, 2016 time period

The GEPS[1] is showing a transition into slightly below normal conditions next week. This image shows the maximum temperature expected in each 6-hour time period from Monday through Saturday. Ensemble forecast systems produce numerous forecasts, and then statistical analysis can be done on the output to (in theory) produce more accurate forecasts, especially in the long range. In the image above, the easiest way to understand it is that the value along the line is a fairly reasonable "most likely" temperature, while the red shading on either line represents the certainty; if there’s little shading extending from the line that means there is high confidence in the values; if there’s a lot of shading extending above and below the line, it means that there’s more uncertainty associated with the forecast at that time.

The GEPS shows fairly reasonable confidence that daytime highs will be dropping into the -15 to -20°C range early next week, a fair amount below the seasonal highs of -11°C for this time of year. With daytime highs in that range, it’s likely overnight lows will dip into the mid-minus 20’s. Heading toward the end of the week, though, there begins to be a lot more uncertainty on the weather pattern, so we’ll just have to wait and see for when the warm-up returns!

  1. Global Ensemble Prediction System  ↩

Messy Wednesday Morning Leads to Wind & Warmth

Brad Leave a comment

Winnipeg will likely see a messy commute on Wednesday morning as a warm front pushes through and brings the potential for some rather intense snow. Behind the front, however, gusty westerly winds will bring very mild weather to the province with temperatures climbing above freezing. This transition will lead into a fairly warm spell that will persist throughout the remainder of the week as multiple disturbances roll through the region.

Snow & Freezing Rain Ahead of Milder Weather

The weather on Wednesday morning will be dominated by a low pressure system and associated warm front that will push through the province Wednesday morning, bringing with it snow, freezing rain and rain to the province. Over western & southwestern Manitoba, precipitation will be a wintery mix of rain, freezing rain and snow. The freezing rain may be fairly intense at times, with total ice accumulations of 2-3mm possible. This will be more than enough to make regional highways treacherous. The freezing rain threat will extend slightly into the southwestern Red River Valley, but will depend significantly on the exact low-level temperature profiles and track of this system. Anyone southwest of Winnipeg in the Red River Valley should stay alert of the potential expansion of freezing rain warnings eastwards.

Wednesday Storm-Total Snowfall Forecast valid at 6PM CST
Freezing Rain Threat for Wednesday January 27, 2016

While light freezing rain is possible throughout the remainder of the Red River Valley, it’s far more likely that the precipitation will fall as snow. To the east of the main band of freezing rain, a swath of fairly intense snow will slump southeastwards overnight and move into the Red River Valley in the morning.

Forecast Sounding for Winnipeg – Wednesday January 27 @ 1400Z
Forecast sounding for Winnipeg early Wednesday morning

This forecast sounding, which shows the forecasted temperature and moisture profile as you move upwards in the atmosphere, is rather telling regarding heavy snowfall:

  1. First is that there is a deep, deep layer of saturation (shown by the red and green lines being close together. Essentially the entire tropopause is forecasted to be saturated with ample synoptic lift moving in. This will provide plenty of moisture for snow generation.
  2. Also revealing is the moist adiabatic profile[1] throughout the mid-to-upper levels of the atmosphere coupled with the cooler advection occurring aloft. This is a fairly traditional profile that often produces widespread embedded convection within the precipitation area.

These two aspects reveal that intense bursts of snow will be likely with this system, resulting in abruptly reduced visibilities and rapid accumulations. The bulk of the snow is expected to fall between 6 and 9AM, with total amounts of 5-10cm possible in Winnipeg and much of the remainder of the Red River Valley. This will likely result in significant delays in the morning commute as drivers battle slippery roads and poor visibility.

The snow will taper off to flurries for the remainder of the morning and then the next phase of the system sets in…

Mild Weather, But Questionably Nice

Behind the warm front, temperatures will continue to climb in Winnipeg to a daytime high of around 2°C as gustier west-northwest to northwest winds move in. The winds will likely climb all the way to around 40-50km/h, making for not exactly pleasant outside weather. As we climb above 0°C, depending on a few different things, the flurries may either stop or transition to some isolated rain showers.

Heading into the evening, the new dominant weather feature will be a very slow-moving cold front gradually slumping southwards through the province. With ample moisture stuck in place and temperatures dropping back below zero, fog and drizzle/freezing drizzle will begin to become a concern. At this point, it looks like the winds will begin to taper off through the evening, becoming relatively light by midnight or so. Once the winds ease, it’s quite likely cloud bases will begin lowering throughout the region with the risk of fog or drizzle developing. The overnight low will sit around -5°C, so if drizzle materializes, it will do so as freezing drizzle.

Thursday will see the Winnipeg and much of the region stuck underneath that pokey front as it begins to stall and push back to the northeast as the next low pressure system begins developing over the western Prairies. Skies will remain mainly cloudy as a slack flow combines with the weak convergence aloft around the front to keep the moisture socked in over the region. With all that low-level moisture stuck in place, the risk for freezing drizzle and/or fog will also continue. Winds will be fairly light and the high will be around -4°C.

GDPS 6hr. QPF divided by precipitation type.
The GDPS model shows a mix of rain, snow and freezing rain over Southern Manitoba late Thursady night.

The next weather system will begin moving in on Thursday night, spreading warmer air eastwards. As a result, temperatures will climb to around -2°C by Friday morning alongside some light snow and a threat of another round of freezing rain, this one primarily for the Red River Valley.

Winter Mix for Friday

Friday will be another mild day with temperatures climbing to +1 or +2°C in the warm sector of the second disturbance impacting us this week. Freezing rain or snow will taper off to cloudy conditions with a chance of some drizzle. At this point there’s wide discrepancies in how much precipitation will fall through Thursday night and Friday morning, with everything from a relatively minor event to a chance for another 5-10cm of snow.

Late in the day as temperatures cool slightly, some lighter snow is possible. Temperatures will drop to around -1°C on Friday night.

Normal daytime highs for Winnipeg at this time of year currently sit at -12°C with typical overnight lows near -22°C.

  1. Moist adiabatic is the "temperature path"—how its temperature changes—that an imaginary parcel of air will follow as it moves up and down in the atmosphere if it is saturated.  ↩

A Stretch of Above-Seasonal Temperatures

Scott Leave a comment

The weather this week will remain well above seasonal with high temperatures generally in the minus single digits.

Today will be mainly cloudy with a good chance of flurries as a strong upper-level disturbance passes through southern Manitoba. No significant accumulations of snow are expected. Temperatures will be in the mid minus single digits with north-westerly winds at 20-30km/h.

Skies should clear on Tuesday as a drying north-west flow persists over the region. Temperatures will be slightly cooler than Monday, but still in the minus single digits. Winds will generally be light and variable.

A strong low pressure system will be the focus of Wednesday’s weather in southern Manitoba. A warm front will pass through during the day, bringing with it a small, but heavy band of snowfall. Given the warmth of the air associated with this front, there is a chance of some mixed phase precipitation in some areas, but it’s too early to discuss those details. It appears that 2-4 cm of snow is probable with this system, but again that total should be revisited closer to the event.

Long Range

CPC 6-10 Day Temperature Anomaly Forecast
The CPC’s 6-10 day temperature anomaly forecast shows a strong return to El Nino winter conditions.

In the longer range it appears we’ll see above-seasonal weather last for the rest of the week before more normal weather returns next week. Long range models aren’t showing a clear signal for February’s weather at this time, which suggests fluctuations between above and below normal conditions.

Milder Weather Ahead, But Deep Freeze Looms

Brad Leave a comment

A few morning flurries will mark the arrival of slightly milder air than has been in place over Southern Manitoba over the past several days, however the reprieve will be brief as another potent blast of Arctic air spills southwards for the weekend.

This morning will start off with a few flurries tapering off as a weak disturbance shunts by to the south of Winnipeg, leaving behind mainly cloudy skies for the day. There will be a slight chance of continue flurry activity through much of the day thanks to favourable snow-making temperatures throughout the depth of the cloud cover, but with the lack of any real focus for the snow, it will be very light if it occurs and pose no likelihood of any accumulation. Temperatures will be slightly milder than the highs near the -20°C mark that have been in place over the last few days; today’s high should climb to around -15°C with light southerly winds while the low tonight drops to around -19°C under mostly cloudy skies.

Thursday will bring a pair low pressure system through the province; the first skirting through the southwestern corner and the southern Red River Valley before exiting into Minnesota while the second drops down from Northern Manitoba, eventually merging into the first low near Lake Superior. This makes the forecast a little bit trickier, but fortunately neither system will bring particularly significant weather with it. The southern low will produce a swath of 2-3cm of fresh snow through southwestern Manitoba into the southwestern Red River Valley, while areas to the north and east see some light flurry activity.

RDPS 12hr. Precipitation Accumulation for Thursday
The RDPS is showing the main swath of snow from Thursday’s system well to our south…perhaps too far south.

Winnipeg appears to be near the edge of that, so throughout the day on Thursday we’ll likely see fairly cloudy skies with a chance of some flurries or perhaps even some light snow if the whole system pushes a little further to the east. Temperatures will climb a little higher than today, with a high temperature near -13°C expected.[1] Skies will remain fairly cloudy on Thursday night with a chance of flurries; the overnight low should be near -22°C.

With the low pressure systems off to our southeast, all that will be left is for the Arctic air to begin building back into the region unimpeded. This next shot of cold looks, at this point, to be colder than the last by a couple degrees. Friday will mark the entrance of that air, with northwest winds near 15-20km/h and a high near -19°C under partly cloudy skies. The overnight low on Friday night will sit near a very chilly -28 or 29°C.

Bitterly Cold Weekend Ahead

This weekend will be particularly cold thanks to a deep Arctic air mass that will slowly move through the region.

850mb Temperature Forecast for January 15-18, 2016
This animation of 850mb temperatures from Friday morning to Sunday morning shows the bitterly cold air moving over the province.

It will begin moving in on Friday, the core of it will be over Winnipeg on Saturday, and then it will begin shuffling off on Sunday. Unfortunately, as these systems move to the southeast, temperatures here at the surface tend to stay quite cold despite the warmer air moving in aloft thanks to an outflow of cold air out of the ridge to our south.

This will mean daytime highs likely around -24 or -23°C this weekend with overnight lows in the -28 to -30°C range. There’s also some indications that there will be 10 to 20 km/h winds through the weekend, which would likely mean Environment Canada would issue extreme cold warnings for wind chill values at night in the -38 to -44 range.

Temperatures will begin to moderate back towards -20°C or the low minus teens early next week.

  1. It’s worth noting that this system will have quite a sharp temperature boundary associated with it, so if everything were to shift east a bit we could see temperatures climbing above -10°C in Winnipeg; conversely, if it were to track further west, we could see daytime highs limited to around -17°C.  ↩