Tag: Cooling Trend

Cooler Weather Rounds Out Weekend

Brad Leave a comment

The unseasonably warm weather that’s been in place over Southern Manitoba will remain for a couple more days before a big shift in the weather pattern behind a low pressure system passing through on Sunday that will bring cooler air back to the region for next week. The shift in conditions will be quite a shock to the system after a pleasant stretch of above-normal temperatures looks to be replaced with the potential of a return to…snowier conditions.

Today will be a fairly pleasant day in the Winnipeg area. On Wednesday we had mentioned the possibility that today might be another very windy day but, thankfully, it looks like the system that guidance suggested would be a bit of a trouble-maker has ended up weaker and further north than it appeared earlier in the week. As such, we’ll see slightly warmer temperatures with a high near 18°C with somewhat breezy northwesterlies developing to around 30 gusting 50km/h. Tonight will bring mainly clear skies and a low near 3°C with light winds.

Saturday is looking like another beautiful day as warm air surges northwards ahead of Sunday’s low pressure system. Winds will be a bit breezy out of the south to southeast at around 20–30km/h in the morning but will likely taper off a bit into the afternoon, making for an exceptionally pleasant sunny afternoon with a high near 20°C and fairly calm winds. Unfortunately, it’s all downhill from there. Cloud will move in on Saturday evening and through the overnight period as a low pressure system pushes northwards out of the Central Plains of the United States. Expect a low near 6°C.

Sunday Brings Showers & Transition to Cooler Weather

Forecast 1000–500mb Thickness Sunday into Monday
Forecast 1000–500mb Thickness Sunday into Monday

Sunday will mark the transition into a cooler air mass as a fairly complex pattern change gets underway. The weather will be dominated by two primary features: a low pressure system lifting north-northeast out of the Northern Plains of the US and a shortwave moving into Manitoba from Saskatchewan. The two systems will undergo a complex merging and look to stall out a bit over Northern Ontario. This stalling out will resulting in an amplification of the long-wave trough developing over the region resulting in a plunge of colder air southwards over the Eastern Prairies. This is reflected very nicely in the above graphic which shows the forecast 1000–500mb thicknesses[1] plunging behind the low pressure system.

So what does that mean for Sunday? Well, there’s a bit of ambiguity as to what will happen here in Winnipeg as a lot will depend on the exact timing of and how the two systems merge. We’ll definitely see cloudy skies, likely see a very good chance of showers through the day. Precipitation will fall as rain for most of the day, but likely switch over to snow sometime in the early evening. Snowfall amounts won’t be big, however a couple cm are certainly possible.

The high on Sunday will be near 10°C with a slight northwesterly breeze. Temperatures will drop just below freezing on Sunday night. Rainfall totals of 5–10mm are possible with 2–3cm of snow possible on Sunday night.

Long Range

Heading into Monday, it looks like the Red River Vally will see flurries, highs near the freezing mark and blustery northwest winds. After that, the rest of the week looks fairly quiet with little in the way of precipitation expected. Daytime highs through much of the week will be more than 5°C below the seasonal values of 11–12°C.

  1. The 1000–500mb thickness is the distance, or thickness, between the 1000mb level (near-surface) and 500mb level (averages around 18,000ft and is often considered the steering flow for weather systems). Higher thickness values correlate to warmer temperatures and lower thicknesses correlate to colder temperatures.  ↩

Wednesday? Beautiful, No Foolin’! Thursday? Not So Much…

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Some of the warmest weather so far this year will move into the region today, drawn eastwards by a fairly strong spring storm moving through the Central Prairies. The warmth is not meant to last, though, as a strong cold front pushes through and brings below-normal temperatures for the remainder of the week.

Wednesday
16°C / 2°C
Windy with sunny breaks this afternoon

Thursday
⇓ -2°C / -12°C
Cloudy & windy; chance of showers or flurries

Friday
0°C / -8°C
Mainly sunny & cool

Today will be quite a warm day thanks to very mild air over our region; 925mb temperatures are expected to climb to around 9°C, which should translate to daytime highs near 15 or 16°C once we sunshine this afternoon. Speaking of sunshine, while today is starting off cloudy, we should the cloud cover break up this afternoon as the dry slot associated with the Central Prairie low moves across Southern Manitoba. Alongside the sunshine and clearing will be fairly gusty westerly winds to 30–40km/h with gusts as high as 60km/h. The winds will taper off in the evening as we head to an overnight low of around +2°C.

RPDS 3hr. QPF & MSLP valid Thursday, April 2, 2015
The RPDS shows an area of light precipitation moving through the Red River Valley on Thursday with a relatively tight pressure gradient that will produce gusty northerly winds.

Thursday will be a significantly less pleasant day as a cold front pushes through Southern Manitoba, bringing with it cooler temperatures, gusty northerly winds and a fairly good chance for some shower or flurry activity. Temperatures in Winnipeg will slide through the morning, settling near –1 or –2°C for much of the afternoon as gusty northerly winds to around 40km/h tap cooler air from the north. The best chance for any shower or flurry activity would be through the morning & early afternoon. Skies will clear out Thursday evening as we head to a low near –12°C.

Friday will be a benign weather day for Winnipeg & the Red River Valley, but temperatures will be well below normal. Daytime highs will only be around +1 or +2°C through the Red River Valley, which is a few degrees below normal for this time of year. Fortunately, winds will be light and with that increasingly strong April sun shining, it won’t feel so bad. Expect temperatures to drop to around –8°C on Friday night with partly cloudy skies.

Quiet Weekend Ahead

The weekend is looking fairly quiet for Winnipeg with seasonal to slightly below-seasonal temperatures and a few clouds. A ridge of high pressure building in from the Arctic looks to keep most disturbances to the south of Winnipeg, however with the main frontal zone setting up near the U.S. border and a few shortwaves rippling along, areas along the U.S. border in Southern Manitoba may see a few showers or flurries through the weekend. Nothing significant is expected.

NAEFS 8-14 Day Temperature Anomaly Outlook (issued 12Z March 31, 2015)
The NAEFS 8-14 day temperature anomaly forecast show above-seasonal warmth returning to Manitoba.

In the longer range, it looks fairly likely that we’ll see a return to above normal temperatures through the second week of April as the storm track shifts back further north; while above normal temperatures will return, it looks like much of the warm weather will be associated with weather disturbances, making it likely that we’ll see more of a “roller coaster” temperature pattern than a prolonged period of warm, dry weather. Only time will tell, though! For now, expect a few cool days and then a stretch of near-seasonal temperatures.

Winter Returns With A Vengeance

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As we mentioned on Wednesday, a big cool-down is underway across Southern Manitoba. While we knew earlier that it was going to get cold[1], it’s beginning to become clear that it’s going to get quite a bit colder than that. Just how cold? Winnipeg might see daytime highs in the near future not seen since last January.

Friday
⇓ -13°C / -17°C
Cloudy with sunny breaks; chance of flurries
Saturday
-16°C / -26°C
Mainly cloudy with some flurries
Sunday
-21°C / -28°C
A few clouds

Today will be the coolest day in a little over a week as temperatures will slide towards –13°C by the end of the day. Skies will start out cloudy then gradually become more mixed through the day. With favourable temperature profiles, some patchy non-accumulating light snow is possible. Winds will be out of the northwest at around 15–20km/h. Temperatures will drop to near –17°C tonight.

Daytime highs will drop on Saturday to just –16 or –15°C with mixed skies. Some flurries or light snow is expected as a system slides from Saskatchewan into North Dakota, but amounts aren’t expected to be much more than a skiff at most. Temperatures will drop into the mid-minus 20’s on Saturday night.

Sunday will be a downright cold day a few clouds around. Highs will sit near –20°C through the Red River Valley and winds will be light. Expect lows dipping close to –30°C on Sunday night.

Cold Start to Next Week

The GDPS forecast shows Southern Manitoba embedded in a deep cold trough on Monday afternoon.
The GDPS forecast shows Southern Manitoba embedded in a deep cold trough on Monday afternoon.

Next week will begin with a substantial trough of cold air positioned over Southern Manitoba that will bring daytime highs in the mid-minus 20’s through the first half of the week. There may be a mid-week warm-up, but a return to colder weather would follow quickly behind. No big storms are on the horizon, so in general expect cold, dry weather to persist through the next week.

  1. On Wednesday’s post, we surmised that daytime highs would generally be near –20°C.  ↩

The Christmas Cool-Down

Brad Leave a comment

After a prolonged period of temperatures some 10 to 20°C above normal, Winnipeg & the Red River Valley is set for a rude awakening after Christmas as Arctic air plunges southwards and brings below normal temperatures to the region.

This graph of the daily average temperature compared to normal illustrates the dramatic warmth Winnipeg has seen in December.
This graph of the daily average temperature compared to normal illustrates the dramatic warmth Winnipeg has seen in December.

The crash to colder temperatures will be exceptionally jarring considering the abnormal warmth we’ve seen through much of December. Leading up to Christmas, mild weather will persist as an incoming low pressure system helps extend the stay of the warm air that’s been so common the past few weeks. As the system passes on Christmas Eve, though, a major pattern change is set to take place as our fairly weak is absorbed into the rather major East Coast “Santa Bomb” which in itself will induce a shift to the gradual re-establishment of the Polar Vortex over Hudson Bay.[1]

Christmas Eve

Wednesday
-3°C / -6°C
Cloudy with evening flurries

Today will be a pleasantly mild day with highs near –3°C through the Red River Valley and winds developing out of the south to around 20–30km/h. Skies will remain mainly cloudy in advance of the incoming low pressure system with some flurry activity finally pushing into the Red River Valley by late in the afternoon and reaching Winnipeg by evening. Little is expected as far as accumulations go; the main accumulating snowfall will remain north of the Trans-Canada corridor through the Parkland and Interlake regions eastwards into Ontario where around 2–4cm are expected.

Temperatures will drop to around –6°C tonight with winds shifting to the west-northwest at around 20km/h.
Freezing drizzle will once again be possible overnight into Christmas morning as saturated low-levels are left behind the departing low pressure system. Steep low-level lapse rates and only a relatively light wind from the NW may result in another batch of road-slicking freezing drizzle. Due to its nature, freezing drizzle requires a fairly delicate balance of factors to exist, so there will be unavoidable uncertainty until later tonight, but keep in mind that it is a distinct possibility.

Christmas Day

Thursday
⇒ -5°C / -12°C
Mainly cloudy with scattered flurries

Christmas Day will be a mixed bag in Winnipeg. Temperatures will remain above-seasonal, but the push of cold air will already have begun. As a result, temperatures will likely remain steady near –5°C as any potential daytime heating is offset by the cooler air moving in. Freezing drizzle is possible through the morning hours, while flurries are more likely through the afternoon.[2] Skies will remain mainly cloudy, although a brief glimpse of sunshine is possible.

Temperatures will head down to the –12°C mark or so overnight with a continued chance for flurries and gradually diminishing cloud.

Boxing Day

Friday
⇓ -16°C / -24°C
Mixed skies with a chance of flurries

Boxing day will be when the real surge of Arctic air begins pushing in. Expect mixed skies with a chance of flurries through much of the day. Temperatures will drop through the day to around –16°C by evening. Skies should clear out overnight as the Arctic ridge begins moving in and temperatures drop to around –24°C. This will be the coldest overnight low we’ve had since November 30th into December 1st when the temperature dipped to –27.1°C. Given that the normal overnight low for this time of year is –22°C, that’s not too bad.

Cold Pattern Persists

The cold weather will be here to stay for a while as a persistent northwesterly flow develops over the province thanks to gradually establishing polar vortex over Hudson Bay.

The NAEFS 8-14 day temperature outlook is foreacsting a good chance of below-normal temperatures for Southern Manitoba.
The NAEFS 8–14 day temperature outlook is foreacsting a good chance of below-normal temperatures for Southern Manitoba.

In the end, it means a relatively dry pattern with daytime highs generally in the –15 to –20°C range.[3] This pattern looks to continue at least until late next week, so dig out those real winter clothes again and get the block heater ready, winter’s on its way back.

$.bigfoot()

  1. The persistent vortex over Hudson Bay – for all intents and purposes a “polar vortex” – is a regular occurance over Hudson Bay in the winter months and is the most common cause for prolonged cold weather in Southern Mantioba.  ↩
  2. If things end up just a tad cooler, the freezing drizzle risk could be just a chance of flurries; if things end up a tad warmer, the freezing drizzle risk could persist through much of the day.  ↩
  3. …or a tad cooler.  ↩