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Windy Transition to Mild Weather

January 22, 2016January 21, 2016 Brad Leave a comment

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 (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 T_w ≥ 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.

Seasonal Weather Leads To Blustery End of Week

January 20, 2016January 20, 2016 Brad Leave a comment

Winnipeg will see near-seasonal temperatures over the coming days with some light flurry activity mixed in before a big warm-up moves in for the weekend. The transition to warmer weather won’t be particularly graceful, however, as a howling southerly wind develops on Friday, making for a rather unpleasant shift.

The weather in Winnipeg through today and tomorrow will be dominated by the gradual arrival of a weak Arctic high that will slowly build southeastwards out of the Northwest Territories across Saskatchewan and Manitoba. Weak is the key descriptor of this ridge; it will bring with it little in the way of cold air nor will it be able to muster up much clearing either.

That said, today’s weather will be relatively pleasant, all things considered. Skies will be mainly cloudy through the day with some occasional light flurry activity. Temperatures will climb a little bit from where we start off to about -10°C with fairly light winds throughout the day. Tonight will continue to bring mainly cloudy skies—although a few clear breaks are possible—and temperatures dipping down to about -18 or -19°C. If more clearing develops than is expected at this point, the overnight lows could dip closer to about -23°C.

Tomorrow will bring very gradual clearing to Winnipeg with the morning likely starting off fairly cloudy and slowly becoming mixed to mainly clear throughout the day as the Arctic ridge slides into the Red River Valley. With the arrival of that system, the daytime high tomorrow will be cooler at around -15°C with a light northerly wind. There’s a slight chance of some flurries through the early morning, but for the most part no precipitation is expected on Thursday. Expect a low on Thursday night near -21°C under partly cloudy to mixed skies.

Friday will be…unpleasant. As many who have lived in Winnipeg for a while know, whenever a big warm-up is on the way there is often "the day" before the warm weather arrives; a day where it’s rarely as nice as it sounds like it’s going to be and those famous southerly winter winds make an appearance. Friday will be that day.

As the Arctic ridge pushes past and moves to our southeast, it is quickly replaced by a strengthening low pressure system moving across the Prairies. As the low moves into eastern Saskatchewan and begins spreading warmer air aloft over Southern Manitoba, its relatively close proximity to the Arctic ridge will result in a tight pressure gradient over the Red River Valley, oriented very favourably for the development of strong southerly winds. While starting the day off light, the winds through the Red River Valley will increase to around 30 gusting 50 km/h by noon, and then further strengthen to 40-50km/h gusting to 70km/h by the evening hours.

GDPS MSLP & Surface Wind Forecast for Friday — The GDPS shows the strong southerly winds (emphasized in yellow) expected over the Red River Valley on Saturday.

Temperatures will gradually climb to around -12 or -11°C by late in the afternoon—although it will feel closer to -25 throughout much of the day due to the wind chill. Temperatures will continue to rise overnight as the warmer air finally begins working its way into the valley; by Saturday morning the temperature is expected to climb to about -8°C in Winnipeg.

With strong warm air advection aloft and the surface flow dominated but the outflow from an Arctic ridge, it’s likely that Friday will be fairly cloudy as stratus streams northwards out of the ridge.

Warm Weekend Ahead

This weekend looks beautiful with temperatures well above seasonal expected throughout the Red River Valley. In Winnipeg, the temperature is expected to climb all the way to around the freezing mark under mainly cloudy skies. Sunday looks fairly nice, perhaps evening bringing some sun to the region, with daytime high closer to the -5°C mark.

Temperatures are expected to return to seasonal values for the start of next week.

Bitter Cold Returns to Manitoba

January 15, 2016January 14, 2016 Brad Leave a comment

Another shot of bitterly cold air is poised to crash through Manitoba this weekend with daytime highs plummeting back into the -20’s and overnight lows dipping close to -30°C.

The cold snap this weekend is looking slightly different from earlier in the week and now comes with some good news, some bad news, and a bit more uncertainty. The overall pattern has shifted further west, with the core of the coldest air now forecast to slump southwards over the Saskatchewan/Manitoba border instead of the Red River Valley. This will shift the coldest temperatures westwards, which results in the good news for Winnipeg: it likely won’t be quite as cold as it looked earlier in the week, but just by a couple degrees. The bad news, however, is that there will be a bit more wind throughout the Red River Valley as the light winds in the centre of the ridge shift west with the coldest air.

RDPS forecast of surface temperatures and wind, valid Saturday January 16, 2016 at 12Z — The RDPS forecast shows very cold temperatures across much of the Prairies on Saturday morning with the main ridge axis running from Northern Alberta through Southern Saskatchewan.

The cold air begins working in today; temperatures will climb to around -19°C today for the daytime high, and then top out between -23 and -21°C on Saturday and Sunday. Overnight lows over the coming days will likely be around -28 or -29°C for the coming 3 nights, depending on "the uncertainty."

The complicating factor with the ridge of high pressure pushing further west will be cloud cover. Two aspects complicate the fair sky forecast:

Uncertainty in how much cloud cover will remain on the east side of the ridge. Many of the Arctic ridges this winter have been "dirty ridges," that is, they are "polluted" by significant amounts of low-level cloud. There are some indications that this may be the case with this next system, but to a much lesser extent compared to others this winter based on satellite imagery of upstream conditions.
Complications with an inverted trough rotating through Central Manitoba. While much of the province will be under the influence of the Arctic ridge, several forecasts show a weak inverted trough associated with a system rotating through Ontario digging into the ridge through Central Manitoba. This feature could produce more cloud that would gradually slump southwards into the Red River Valley.

The biggest uncertainty with cloud cover is Saturday. My best guess at this point is that we’ll see a bit of cloud, however it will overall be a mixed-sky to sunny day. There is an off-chance, though, that we end up mainly cloudy. Cloud cover can marginally impact the daytime high (likely increasing it by around 2°C), and substantially impact overnight lows (keeping them significantly warmer than in clear skies).

That said, with winds likely between 10-20 km/h at night, wind chill values in the -35 to -40 range will be widespread over Southern Manitoba over the coming nights, with -40 or colder wind chills quite likely over southwestern Manitoba. Here in the Red River Valley, -40 wind chills seem unlikely, but could be seen if temperatures get a couple degrees colder than forecast at night or the winds are a tad stronger. Environment Canada issues extreme cold warnings when the wind chill *or* temperature is expected to drop below -40.

Sunday has more confidence in seeing mainly sunny skies.

Long-Range Outlook: Hints of Warming

The first half of the coming week still looks quite cold with daytime highs near -20°C and overnight lows in the -25 to -30°C range. By mid-week, however, it looks like a big change will be on the doorstep.

NAEFS 8-14 Day Temperature Anomaly Forecast – Valid January 22 - 29, 2016 — NAEFS 8-14 day temperature anomaly forecast, valid January 22 – 29, 2016

Current long-range forecast models are beginning to show with higher confidence that the polar vortex will finally be displaced allowing a milder zonal flow to develop. While it doesn’t look like a huge surge of warm air, seasonal to slightly above seasonal temperatures by the end of the week look fairly reasonable.

Right now, the average daytime high is -13°C and the average overnight low is -24°C.

Milder Weather Ahead, But Deep Freeze Looms

January 13, 2016January 12, 2016 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.

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. ↩

A Weather Moment

Author: Brad