Prairie Weather This Week

Prairie Weather (Rural Roots Canada) – Drought expands…will the Polar Vortex rescue us?

Late last week, there was a sobering update to the Canadian Drought Monitor. Heading into winter, well over 80 percent of the prairies are abnormally dry or in drought. The situation in the rest of the country is similarly dire. You’ll find more details in a story we posted Friday.

It is about to get considerably colder toward the end of the month. European meteorologists have brought attention to the likelihood of a Sudden Stratospheric Warming (SSW) event for the latter half of November. Long story short, high pressure over the Arctic will cause sudden warming in the stratosphere, which will destabilize the upper flow in the Arctic, unleashing the dreaded and often misunderstood Polar Vortex. That will bring cold and snowy weather to the prairies, the rest of Canada, and the northern United States. In the article linked above, it is suggested we’ll have a “December to remember”.

Latest model guidance shows the wintry weather will show up on the prairies in the last week of November.

Let’s go behind the scenes. It’s no secret that weather forecasters use computer models to come up with their outlooks. Some even report “what the models are saying” on their websites and broadcasts. Models are not forecasts. Models are tools to make a forecast. Just like a hammer is a tool to make a coffee table. The end user wants the table, not the hammer. The end weather user wants a forecast, not a model.

That said…..let’s look at some models!

The charts below are generated by the NAEFS, the North American Ensemble Forecast System.

Output from the NAEFS concur with the theory of polar cooling after stratospheric warming, beginning in the last week of November.

Here are some charts:

Calgary

Regina

Winnipeg

I could add many more charts to this page, but they all show the same thing- colder and snowier weather for the last week of November.

The colder weather arrives next week, on or about November 24h. Until then, a broad upper ridge over the Prairies will keep winter away this week, with only a couple of weak systems brushing the region. Expect generally mild conditions for mid-November, occasional fog, and only light or localized snow except in far northern areas.

Monday

Alberta, Saskatchewan, Manitoba

Other than snow sneaking into northern Alberta from a Low in central BC, the prairies will be dry on Monday. South of a line from Peace River to Fort McMurray, it will be mainly sunny in Alberta. North of that line, there will be snow. Manitoba and Saskatchewan will stay dry. In southern Saskatchewan, expect brisk wind from time to time, in the 20-30 km/h range, from the southeast. While the three provinces will experience similar weather, there will be big temperature differences. Southern Alberta will see double digit highs. Central Alberta and Southern Saskatchewan will reach the 5-10 degree range. Northern Alberta and Saskatchewan, along with all of Manitoba will remain below freeing, with highs between 0 and -10.

Tuesday

Alberta

A low pressure system will form in southwestern Saskatchewan, sending moisture back into southeastern Alberta. Early morning rain is likely from Lethbridge to Medicine Hat, and north to Coronation. At the same time, an upslope flow will produce some snow between Calgary and Banff, potentially affecting travel on the Trans Canada Highway. By midday, the rain and snow end, and in the afternoon, sunshine returns to the region.

Later in the day, in the afternoon and evening, snow will develop in central Alberta, including the Red Deer, Sundre, and Edmonton regions, as yet another low forms to the south, hear Longview. That same low will draw warm air into southeastern Alberta, and in the late evening, rain can be expected in southeastern Alberta, including Taber, Bow Island, Medicine Hat, Suffied, and Cypress Hills. South of Red Deer, highs will be in the low single digits. North of Red Deer, it will be cooler, with highs within a few degrees of -5.

Saskatchewan

A Low pressure system just southwest of Saskatoon will spread early morning rain across central Saskatchewan, and snow to the northeastern part of the province. About 5 mm of precipitation is expected. The low will weaken, and the rain tapers off, leaving behind a mainly cloudy sky for the remainder of the afternoon and evening. South of the Yellowhead highway, highs will be a few degrees above zero. North of the Yellowhead, highs will be a few degrees below zero.

Manitoba

While southern Manitoba stays dry and partly cloudy, a weak cold front will drag snow across the northern part of the province, and the northern Interlake, but well away from agricultural land. The result being that southern Manitoba will remain uncharacteristically snow-free going into the second half of November. In the south, expect some fog patches in the early morning. Southwestern Manitoba’s highs will be a few degrees above zero. In northern Manitoba, the Interlake, and the Red River Valley, highs will be a few degrees below zero.

Wednesday

The map shows the precipitation that will cross the southern prairies on Wednesday. Blue is snow, green is rain, pink is a mix.

Alberta

As the map above shows, a weak Low will form in the southwestern Alberta foothills earlier in the day, and quickly move east. Snow will begin in the early morning in central Alberta, cross the province quickly, with the sky clearing in the afternoon. Expect 5-10 cm in the Edmonton/Vegreville area, and similar amounts in east central Alberta, from Medicine Hat north to Lloydminster. By afternoon, the moisture will have moved into Saskatchewan, and high pressure will clear the sky. South of the Trans Canada highway, expect highs from 0 to 5. North of Highway one, temperatures will stay below the freezing point, with highs ranging from 0 to -6/

Saskatchewan

Referring to the map above, you’ll see a band of snow will move from west to east across south central Saskatchewan, just north of the Trans Canada Highway. That snow is generated by a weakening low as it crosses the southern part of the province. South of the Trans Canada Highway, some rain is possible, as highs in the area will reach the low single digits above zero. To the north, it will remain below freezing, with highs close to -5. Snowfall amounts will be near 5 cm.

Manitoba

Fog patches are possible again in the early morning Wednesday, followed by brief clearing. Expect rain to develop south of the Trans Canada Highway by midday. This is from a developing Low pressure system that will form near Portage La Prairie during the afternoon. As the low forms, the rain will intensify, and snow will spread into the Interlake.

As the Low moves east, the circulation will shift to the north and northwest, drawing colder air into the area, changing the rain to snow in southern Manitoba during the evening. The precipitation will continue into early Wednesday morning. 7-10 mm of rain or snow, or both, can be expected. Highs in the southern half of the province will rise a few degrees above zero. In the northern half, highs will come in cooler – a few degrees below zero.

Thursday

This map shows precipitation expected until the early evening of Sunday Nov 23. There’s just not a lot there….

Alberta

It will be a dry day across Alberta, but some areas will experience considerable wind, especially along the foothills, with gusts of 50 to 60 km.h. Due to a weak upper level disturbance, there will be some cloud for northern Alberta, with the rest of the province under a mainly sunny sky. The strong southern Alberta wind will bring warm weather to the region, with highs climbing above the melting point. North of the Trans Canada Highway, temperatures will remain below zero.

Saskatchewan

A low in northern Manitoba produces some light snow for the northern Saskatchewan forests, but that moisture will pull off to the east and taper off during the day. Agricultural regions will stay dry, and most of the province will have a mainly sunny day. It will be cool, with temperatures remaining below the freezing point.

Manitoba

Light snow will fall in northern and southeastern Manitoba during much of the day, tapering off as a Low pressure system crosses the northern part of the province, heading into Ontario by the end of the day. As the map below shows, accumulations will be minor to moderate, with agricultural areas remaining dry.

Temperatures across most of Manitoba will remain below zero Thursday, though south of the Trans Canada Highway, highs may be as warm as 0 to 5 degrees.

Friday

Alberta

Friday’s another quiet weather day in Alberta, though a weak surface trough is likely to produce plenty of cloud, especially during the midday. No precipitation is expected in Alberta. There will be a warm wind from the southwest, and temperatures will rise above the melting point in most of the province, the exception being low lying valleys, coulees, highway 9 northeast of Calgary, and the Yellowhead highway east of Edmonton. Those areas could remain below zero all day.

Saskatchewan

Warm westerlies will bring temperatures above zero in southern Saskatchewan, south of the Trans Canada Highway. The rest of the province will continue with sub-freezing temperatures. Most of Saskatchewan will be mainly sunny, however a weak disturbance late in the day will produce some light snow in the northern forests toward evening. Accumulations will be minor. There is a risk of freezing rain for the La Ronge area for a brief period in the early evening.

Manitoba

Manitoba’s Friday forecast is straightforward. Mainly sunny and dry. The wind will be light, and Manitoba will not catch the warm westerlies that will produce above zero highs to parts of Saskatchewan and most of Alberta. The southern half of Manitoba will achieve highs in the -2 to -7 range, while in the north, temperatures will be closer to -10.

Saturday

Alberta

A drying westerly wind will continue Saturday in Alberta, so the subsidence flow off the mountains will give the province another dry, warm, and windy day. There is upper level support as Saturday is the day the ridge reaches its peak. That said, most of the province will be slightly cooler than Friday, with highs within a few degrees of zero. South of the Trans Canada Hihgway, though, in the chinook belt, there is an opportunity for 5-10 degree highs.

Saskatchewan

It’s another dry day for Saskatchewan’s agricultural regions, and for most of the rest of the province. A weak disturbance could bring light snow near the boundary with the Northwest Territories. Otherwise, it will be another quiet day, with a westerly wind. In southern Saskatchewan, highs will be just above zero, and in the north, it will be mild, with highs between 0 and -5.

Manitoba

It will be a warm November day in Manitoba, with highs climbing above the melting point in most of the populated areas. It will be cooler to the north, but still relatively warm, with highs between 0 and -5. While the south will be mainly sunny with a westerly wind, a northern Low will produce some light snow through most of the day over the northern permafrost.

Sunday

Alberta

Sunday will be another dry, partly cloudy day in Alberta, but things are starting to happen. A low pressure clipper system will begin to develop in southern Alberta. The impact on Sunday’s weather will be minimal, with most of the province remaining dry. However, some late day snow is likely to form over the foothills and mountains, getting ready to move across the southern part of the province, spreading snow across the region on Monday. For Sunday, though, it will be dry and warm. Double digit highs can be expected Sunday south of the Trans Canada Highway. To the north, expect highs of only 0 to -5. There will be an abrupt change in the weather Sunday night as the wintry conditions develop, and could have a significant effect on travel through central and southern Alberta on Monday morning.

Saskatchewan and Manitoba

While we see change developing in Alberta Sunday, Saskatchewan and Manitoba will have another quiet day, under a partly cloudy sky. There is a chance of afternoon flurries or freezing rain near Prince Albert, but the remainder of the region stays dry. The map below shows temperatures for the late afternoon in Saskatchewan and Manitoba:

Nest Week:

There will be a return to active weather across the southern prairies next week, with a couple of snowy weather systems crossing the area. The first on Monday, the second on Saturday. The map below shows an animation of next week’s expected weather. Bear in mind, this is a long way out, and subject to change.