Tag: Freezing Rain

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.  ↩

Windy Transition to Mild Weather

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Warmer weather is on the way for the weekend with temperatures soaring close to the freezing mark, however not before a blustery day that will be rather miserable and may impact transportation throughout the Red River Valley.

Windy Weather Developing

Windy weather is on the way for Winnipeg today courtesy a developing low pressure system pushing eastwards across the Prairies. As this system moves towards Manitoba, a strong pressure gradient will develop over the Red River Valley between the incoming low pressure centre and departing ridge of high pressure. As the gradient strengthens in the afternoon, strong southerly winds will develop throughout the Red River Valley.

Strong winds are expected by Friday evening through Southern Manitoba and the Northern Plains
Strong winds are expected by Friday evening through Southern Manitoba and the Northern Plains (the highlighted area).

Sustained wind speeds will increase to 40-50 km/h by the early evening. It seems fairly probable given the near-constant light snow and ice crystals that have fallen over the last several days that blowing snow will become a transportation issue for Friday night into Saturday morning. In Winnipeg it shouldn’t be too bad, but in rural areas, particularly along west-east running highways, the potential for near-whiteout conditions exists. Be sure to give yourself extra time and carry a winter survival kit if you will be travelling on area highways.

Warmer Weather Brings Risk for Freezing Rain or Drizzle

Winds will begin tapering off on Saturday morning as the low pressure system arrives, bringing with it a blast of mild Pacific air. Despite the fact that skies will remain cloudy for most of the day, temperatures will soar to a high of -1°C.

Alongside the surge of warm air will come a risk of some freezing rain. An above-freezing level (AFL) will develop overnight, and by morning an area of precipitation is expected to slide through Parkland Manitoba, the Interlake and northern Red River Valley before sliding eastwards into Northern Ontario.

YWG Forecast Sounding valid Saturday morning from the NAM
This forecast sounding for Winnipeg from the NAM shows a well-defined AFL with Tw ≥ 0°C.

With sustained warm air advection and a wet-bulb temperature above 0°C in the AFL, the potential for organized freezing rain exists. The highest likelihood lies over the Swan River region and then southeastwards through the Interlake. The risk exists over the Red River Valley, but at this point it doesn’t appear that actual amounts will be particularly high. Nonetheless, it doesn’t take much freezing rain to make things slick, so we’ll monitor things and provide an update if the threat for the Red River Valley increases.

Behind the warm front, freezing drizzle will be possible throughout much of the day with saturated low-levels and the lift associated with the incoming low. Winds will be calm through the afternoon.

Winds will shift to the northwest in the evening as a cold front passes through. Skies will remain fairly cloudy and the threat for freezing drizzle will persist well behind the cold front and through much of the night. Temperatures will drop to around -8°C by Sunday morning.

Sunday will bring weak cold air advection through the day, resulting in temperatures rebounding only slightly if at all through the day. The chance for flurries will redevelop as temperature profiles become too cold for freezing drizzle and more favourable for snow. That said, overall moisture supply will be dwindling, so at this point it appears that there will be just a chance for some flurries.

Sunday night will bring cloudy skies and a low near -10°C.

IR Satellite Image of Late-March Storm over the Southern Prairies

Winter Storm Slams Manitoba

Brad Leave a comment

A potent spring storm is moving into Manitoba today and will likely exit the region known as one of the strongest of the Winter 2014/15 season. This storm has already brought drizzle, rain and freezing rain to southwestern Manitoba & the Red River Valley and will end up delivering the whole wintery mix by the time all is said and done. Environment Canada has issued a swath of heavy snowfall warnings and special weather statements across Manitoba in advance of this system.

Tuesday Night

Tuesday Night
-1°C
Rain changing to snow

Rain will redevelop this evening and persist through much of the overnight period until a cold front pushes through the Red River Valley and switches the precipitation over to snow. Many areas in the Red River Valley will see around 5-10mm of rain. Alongside the switchover to snow, strong northwesterly winds to 40-50km/h with gusts as high as 70km/h will begin to move into the Red River Valley. The combination of falling snow and strong winds, coupled with the temperature dropping below zero overnight after a day of melting, drizzle & rain will likely produce very poor driving conditions with slippery roads & poor visibilities in blowing snow by Wednesday morning.

Wednesday

Wednesday
⇒ -2°C / -11°C
Snow ending in the afternoon; windy

Snow will continue through Wednesday morning before beginning to taper off through the afternoon with a further 5-10cm possible for the City of Winnipeg and the Red River Valley. As mentioned before, the snow will be accompanied by strong northwesterly winds to 40-50km/h which will produce a fair amount of blowing snow as well. Temperatures will drop just barely to -2 or -3°C through the day. Given the relatively mild temperatures, it’s quite likely that as soon as the snow begins to taper off, the blowing snow will too; falling snow will be needed to produce it and it’s unlikely we’ll see much ground-based blowing snow after the fact. Winds will begin to taper off late in the afternoon or in the early evening as the storm moves off into Ontario. Left behind the storm will be partly cloudy skies as temperatures drop to around -11°C.

Storm Update

As expected, many regions across Manitoba saw a significant dump of snow overnight and into this morning. Snowfall totals to 10:30AM CDT across Manitoba are:

Location Snowfall Amount
Winnipeg 5cm
Portage la Prairie 5-10cm
Brandon 6cm
Steinbach 5cm
Dauphin 15-25cm
Rossburn 20cm
McCreary 18cm
Neepawa 15cm
Fisher Branch 15cm
Roblin 14cm
Elkhorn 10cm
Argyle 10cm
Swan River 8cm
Miami 6cm
Morris 2cm

In addition to the heavy snow, many areas through the Red River Valley saw several hours of rain last night. Here in Winnipeg, around 8mm fell overnight, and preliminary reports indicate that similar amounts were seen through much of the Red River Valley. In addition to the snow and rain, very strong winds to 50-60km/h moved into Red River Valley this morning producing blowing snow and helping make sure roads are slick.

The winter weather has wreaked havoc on area infrastructure with numerous accidents on highways as well as complications to power infrastructure with numerous pole fires & power line damage events reported. Many motor-vehicle collisions were reported on Manitoba Highways, with several resulting in sections of Highways 1 and 75 being closed. Two of the more significant ones, pictured above, involved a jackknifed semi-truck collision near Elie and a school bus rollover near Ste. Agathe on Highway 75.

Conditions have begun to improve in the Red River Valley; winds remain strong however with the snow finally moving off into Ontario, much of the blowing snow has stopped. Road conditions will continue to be poor through the remainder of the day, so if you are driving, especially on area highways, be sure to give yourself extra time and be cautious.

Thursday

Thursday
-6°C / -11°C
Partly cloudy

Thursday will be a mainly sunny day – perhaps just a few lingering clouds – with a cool high of just -6°C. Winds will be light, so with the increasingly strong March sun it may not actually feel all that bad outside. Even with the sub-zero temperatures, expect plenty of melting to happen. We head into Thursday night with clear skies and cool off to around -10 or -11°C again overnight, although that could be a couple degrees warmer depending on when cloud cover arrives from…

Friday

Friday
-3°C / -8°C
Mainly cloudy with a chance of light snow

Friday will bring mainly cloudy skies as clouds push in either early Friday morning or late overnight on Thursday thanks to a system rippling through Southern Manitoba from the northwest. It will most likely produce a band of snow through portions of the Parkland, Southwest and into the Western Red River Valley. Under this band, accumulations of 1-2cm look possible at this time. There’s a little uncertainty as to the exact track, given that it’s 3.5 days out at this point, so it may end up a little further west or east. With the current “most likely” track, Winnipeg sees a fairly decent chance at some flurries but little in the way of accumulations. Temperatures will climb to around -3°C with fairly light winds. Friday night looks pleasant with light winds again and a low near -8°C.

Long Range

It’s looking as if another storm is possible on Saturday night as a shortwave tracks across Manitoba.

GDPS 24hr. QPF Forecast valid 12Z Sunday March 29, 2015
The GDPS is forecasting a fair amount of precipitation associated with a significant storm moving through Manitoba this weekend.

Fortunately, it seems like it will be bringing enough warm air with it that precipitation would fall as rain. Either way, though, it looks like we’ll see plenty of cloud and wind this weekend. After a long spell of little in the way of weather, it looks like a typical, more active springtime pattern is setting up!