A Seasonal Start To The Week

Brad Leave a comment

Seasonal temperatures will be in place for Winnipeg & the Red River Valley for the start of the week as a continued weak southerly flow keeps the Arctic air locked up to our north.

The CMHR on a Snowy Winnipeg Morning

The Canadian Museum for Human Rights on a snowy Winnipeg morning.

Temperatures will sit near -10°C today through Winnipeg & the RRV, perhaps climbing up to -9 or -8°C briefly. We’ll see light snow through much of the morning with a chance for it to redevelop this evening for a few hours. Accumulations will sit around 2-4cm from this very light, fluffy snow, but it will likely have significant impact on roadways. Combined with the warmer temperatures, fog, and patchy freezing drizzle, some roads in Winnipeg and some provincial highways are already quite icy. As this light, fluffy snow is driven on, it tends to compact to a thin layer of ice; this will likely make it so that some highways, including the Perimeter Highway, side-streets and intersections are quite slippery by the evening commute. Be sure to leave yourself some extra time if you need to drive this evening.

Temperatures will remain fairly steady tonight or even climb a degree or two and another push of warmer air moves in. Once again we’ll likely see dense fog patches and patchy freezing drizzle redevelop tonight as this warm air advances towards the RRV.

Tomorrow, temperatures will climb to about -5°C with scattered flurries through the RRV. Winds will remain light, so it will be another great day to get outside. Some light snow will move through Winnipeg & the RRV tomorrow evening/night as a weak disturbance passes to our south. We’ll get another 1-2cm of snow as temperatures drop back towards -10°C.

Wednesday looks to be almost a carbon copy of today, with some light snow and highs around -9°C. The rest of the week is a little more uncertain; models all hint that the upper-level flow pattern will begin to break down, but how quickly that will happen is uncertain still. While the next few days will almost certainly be cloudy, we’ll probably see the sun start to make an appearance later in the week, if not having the clouds completely clear out. We’ll have more details on the second half of the week on Wednesday.

Elsewhere in Weather News: December 15th, 2012

Matthieu Leave a comment

Tropical cyclone Evan struck the Samoan Islands on December 13, bringing strong winds and heavy rain to the area.

NASA's Aqua satellite captured this image of Evan as it struck Samoa

NASA’s Aqua satellite captured this image of Evan as it struck Samoa (Source: http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=79989&src=nha)

Evan was a category 1 cyclone when it struck the Samoan Islands region on Thursday, with maximum sustained winds of 144km/h. The storm came onshore near Apia, the capital of Samoa, and the country’s largest city (population 37,708). The cyclone destroyed buildings, ripped up trees, and took down phone, internet, and electricity services across Samoa. In addition, the heavy rain generated by Evan caused widespread flooding. The death toll from Evan is at least 2, with the cyclone being called the worst in many years by local residents.

People walk over a destroyed bridge in Samoa's capital Apia, Friday, Dec. 14, 2012

People walk over a destroyed bridge in Samoa’s capital Apia, Friday, Dec. 14, 2012 (Source: http://www.wunderground.com/blog/JeffMasters/article.html?entrynum=2311)

Evan has taken an unusual track so far, first moving eastward toward Samoa, then making a 180 degree turn over the islands, with its track now taking it westward toward Figi. Evan is currently intensifying, with maximum sustained winds presently at 185km/h. That is high enough to make it a category 3 cyclone on the Saffir-Simpson scale. Current forecasts suggest that the cyclone could approach category 5 status (winds >252km/h) this weekend, before hopefully weakening somewhat prior to affecting Figi. Despite its expected weakening trend ahead of hitting Figi, Evan could become a major disaster for the country, with the country’s leader Commodore Frank Bainimarama’s quoted as saying the following “Fellow Fijians I cannot stress how serious this is, every Fijian will be affected”. Figi is a small country consisting of 332 islands with a population of approximately 850,000.

Pleasant Weekend Ahead

Brad Leave a comment

We’ll break out of the deep freeze today as things finally warm up a bit as we head into a mostly snow-free, pleasant weekend.

850mb Temperatures

850mb temperatures for this evening from the GEM-REG model. It’s clearly evident that a substantial area of warm air has pushed northwards over Southern Manitoba.

Yesterday’s 1-3cm of snow that fell across the city marked a shift in the long-wave pattern over the Prairies as the flow shifted from a west to northwest flow to a more southwesterly flow. This has allowed warmer air to flood over Southern Manitoba aloft, and as winds pick up this afternoon, we’ll get a chance to mix it down to the surface.

There will be a slight chance of flurries through the day today, but if they happen they’ll be quite light and very scattered about. Winds will pick up midday to around 20-30km/h, which will help mix down warmer air aloft and warm our temperatures up to around -6°C.

Skies will remain mainly cloudy tonight, and temperatures will remain steady near -6 or -7°C.

Winds will remain out of the south or southwest for most of the day tomorrow, keeping our temperatures around -6°C yet again. By late in the afternoon or tomorrow evening, the winds will shift around slightly to the northwest, which will allow our temperatures to drop to a low of -15°C overnight. We’ll be far from a deep freeze, though, as Sunday looks to bring sunshine back to Southern Manitoba as we climb to a daytime high around a more seasonal -10°C.

Light Snow Then A Return To Cold

Brad Leave a comment

Winnipeg seems to have found itself in the firm grip of winter as below-seasonal temperatures dominate the forecast. A low pressure system passing to our south today will bring snow and a slight moderation to our temperatures to near-normal values, but we’ll quickly drop back to well below-normal temperatures.

Storm-total liquid-equivalent precipitation accumulation

Liquid-equivalent (how much water there would be if you melted the snow) precipitation accumulation valid 18Z today.

A weak upper trough will swing through Southern Manitoba today, embedded within a strong northwesterly flow. While temperatures have warmed some 10-15°C aloft over the entirety of the Red River Valley, it looks like the surface warm front will halt part-way between Winnipeg and the U.S. border. Areas south of the warm front (probably areas south of Morris) will be able to tap into a southerly or even southwesterly flow, allowing temperatures to warm possibly as high as -5°C. Unfortunately for areas over the Northern Red River Valley, the warm front will likely remain well to our south, keeping our winds out of the southeast and slowly backing to northwesterly as the system passes by. These wind directions all favour the reinforcement of cold air as they tap into the colder air ahead and north of the low instead of the warmer air south of the low. That means that while there will be a slight increase in temperature from the advection (bringing in) of warm air aloft, a significant portion of the warming taking place over the Northern Red River Valley will be due to heat directed towards the surface from the clouds associated with this low. Highs north of the warm front will sit in the -12 to -15°C range.

Snow associated with this system pushed in overnight and will continue through the morning before tapering off around lunch time. Heaviest accumulations will lay north of the warm front with lighter accumulations south of the warm front. North of the warm front, including here in Winnipeg, we’ll see a total of 6-8cm of light, fluffy snow, while south of the warm front (the Southern Red River Valley) will probably only see a total of 2-4cm. There’s a slight chance that a few lingering flurries will hang on through the afternoon, but accumulations with those would be minimal should they happen.

Temperatures will drop down to around -25°C tonight as the clouds begin to break up and cold air filters southwards again in a northerly flow behind the low. Temperatures struggle to climb above -20°C tomorrow as we find ourselves deep in the cold air once again, some 8-10°C below normal for this time of year.

There are hints that temperatures may begin to moderate on Friday into the weekend, climbing as high as -9°C on Saturday, as a weak south/southwesterly flow develops. I’ll bite my tongue for now as models can sometimes be overly enthusiastic on moving the cold air out of the Red River Valley, but it does look like it’s at least a possibility. If that flow does develop, it’s likely we’ll see another batch of snow late this week as the warmer air pushes in. Until then, keep the long johns handy and be sure to check back in the comments below or follow along on Twitter for updates as the week progresses!