Cool and Calm

Monday through Wednesday

This week will start out cool and calm weather-wise. No significant precipitation or warm weather is expected.

Monday
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Clearing
-6°C / -21°C
Tuesday
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Mainly sunny
-1°C / -10°C
Wednesday
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Mainly sunny
-1°C / -10°C

Monday will be another ugly April day. Temperatures will be in the mid minus single digits with clearing skies. There will be a strong north wind as well, making it feel even worse than the temperature alone would indicate.

Tuesday and Wednesday will be very similar days. High temperatures will be just below zero in both cases, with the exception of urban and forested regions which will be a few degrees warmer than everyone else. The wind will also be from the north on both Tuesday and Wednesday, but it won’t be very noticeable except in open areas.

Long Range

The long range is looking slightly better than it has been for the last while. It looks like we may finally be moving into a pattern with more consistent melting temperatures by week’s end. It’s too early to say how warm it will get, but it looks like temperatures will still generally remain mainly below normal in the medium-term. The normal high for this time of year is +8C.

Elsewhere in Weather News: April 6th, 2013

Historic Flooding in Argentina

Major cleanup efforts are underway in Argentina this weekend after major flooding occurred in the city of La Plata (pop. 250,000), just east of Buenos Aires. In some areas of La Plata, over 150mm fell in less than a 24 hour period causing for some flash flooding when the city’s sewers simply could not keep up. The reason for so much rain over one area can be attributed to a nearly stationary low pressure system over Argentina, south-west of Buenos Aires. Moist air from the South Atlantic was drawn in and the near stationary thunderstorms stayed over La Plata for over ten hours, beginning April 1st, lasting through April 2nd.

La Plata flooding

Aerial image of one of La Plata’s hardest hit areas. (Source: Reuters)

Flooding caused whole neighbourhoods to be submerged and people had to escape from their houses through the roof as floodwaters rose up to three feet. At one point, three million people were without power across Argentina because of the heavy rains. Some 2,200 residents of La Plata had to be evacuated. Unfortunately, 54 people have died from this event and there are still around 20 people missing. The property damage is extensive and is still being calculated but is likely to be in the hundreds of millions.

Elsewhere around the world:

  • There has also been severe flooding in Eastern China and Taiwan due a series of low pressure systems that brought heavy rain to an already saturated soil base.

  • This week will likely bring another multi-day, severe weather outbreak in the southern half of the US; from the Southern Plains into Dixie Alley, as a large trough digs across the region and warm, moist air from the Gulf of Mexico clashes with it.

More Snow on the Way

sigh

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850mb wind forecast showing the deep southerly flow that will be providing the moisture and lift for today’s system.

Today

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0°C / -2°C
Snow beginning this afternoon. 2-4cm overnight.

A frontal wave sliding across the Prairies will push into Southern Manitoba this morning, spreading snow eastwards across the Red River Valley this afternoon. While southwestern Manitoba will see 5–10cm of the white stuff, we should fare a little better here in the RRV with 5cm expected near the US border tapering off to 2–4cm here in Winnipeg. The bulk of the snow will fall this evening into the overnight period before tapering off late overnight or early tomorrow morning.

Saturday & Sunday

Saturday
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1°C / -11°C
Cloudy with a chance of flurries. Clearing late in the day.
Sunday
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-4°C / -14°C
Increasing cloud. Light snow beginning in the afternoon.

Saturday will be a bit of a mixed bag with some lingering flurries in the morning and gradual clearing in the afternoon before skies clear late in the afternoon or evening. The high temperature on Saturday should be around 1°C and we’ll see temperatures drop to –11 or –12°C Saturday night.

More snow looks to be on the way for Sunday afternoon as an Alberta Clipper slides along the international border. At this point, it doesn’t look like a significant system, but it should pack enough of a punch that it will likely drop a couple cm through the RRV in the afternoon. After Sunday, it looks like we’ll slip back into another benign pattern with below-normal temperatures as a surface ridge keeps snowier weather to our west and to our south.

Warmest Day of Spring So Far Will Also Be Most Unpleasant

It’s almost a certainty that Winnipeg will record the warmest day so far this spring at it’s official reporting station at the airport, but it will without question be perhaps one of the most unpleasant feeling days of the past couple weeks as a low pressure system moves through.

3hr. QPF valid this afternoon.

RDPS output showing a weak band of flurries pushing across the RRV this afternoon.

Today


3°C / -9°C
Cloudy & windy. Chance of flurries midday onwards.

A low pressure system will be tracking through Southern Manitoba today, bringing with it a mass of very warm air. Temperatures at the surface will climb to around +3°C today despite our 850mb temperatures climbing nearly 20°C from yesterday’s values. Thanks to the significant push of warm air aloft moving into the Red River Valley, our winds will be blowing quite strong today out of the south. The winds should sit around 40km/h with gusts to 60km/h through much of the morning, although it’s possible that winds will strengthen beyond that with gusts as high as 70–75km/h.

In addition to the above-zero temperatures, our dewpoint is expected to climb above zero as well. The above-zero temperatures combined with above-zero dewpoints will prove to be one of the more effective melting days we’ve seen so far this year despite the absence of sun with substantial warming of the entire snowpack possible. We may see some flurries as the cold front pushes through in the afternoon, but current indications are that the air coming in is a little to dry to produce much precipitation. Before the cold front comes through, the thermodynamic profile looks relatively favourable for drizzle, but I think that the strong winds will prevent its development. All in all, despite the warmer temperatures, today will end up a cloudy, damp, windy chilly-feeling day.

Once the cold front pushes through mid-afternoon, we’ll see winds lighten and slowly shift to westerlies while gradual clearing occurs. Temperatures will drop to around –9°C tonight under clear skies.

Thursday & Friday

Thursday

-2°C / -14°C
Mainly sunny.
Friday

0°C / -8°C
Mainly sunny. Increasing cloud overnight with chance of flurries.

We’ll return to a benign pattern for the rest of the week as another Arctic ridge builds into the Prairies. We’ll see plenty of sunny skies and highs near or just under 0°C while overnight lows sit around –14°C on Thursday night and warm to just –8°C on Friday night as clouds begin to move in ahead of the next low pressure system. Winds will remain light through Thursday and Friday.

The Weekend

Models are having difficulty resolving exactly what is going to happen with the next system headed our way for late overnight Friday into Saturday. American models are keeping it well to our south, the Canadian models are clipping it through SW Manitoba and the far SW portions of the Red River Valley, while the European models are bringing it through the Trans-Canada corridor, including Winnipeg. While the European models tend to have higher skill than the North American models at long-range (primarily thanks to their relentless efforts to initialize the models as well as they possibly can), the solution doesn’t necessarily make a whole lot of sense to me.

We’ll be watching this system develop over the next few days, and while it seems likely that some snow will fall this weekend over SW Manitoba, it’s still too early to call for Winnipeg or the RRV; we may see nothing or another 5–10cm of the white stuff. At this point, regardless of where it goes, it doesn’t look like a major system that will drop too much water (ensemble solutions are pointing towards 5–10mm of liquid equivalent with this system).

Long-Range

This cool weather of late has many people asking when spring will arrive. Our snowpack is abnormally deep for this time of year, March started off warm but just got colder and colder as time went on, and we have yet to even start the widespread snowpack melt. All this is certainly compounded by memories of last March’s weather, where we had the warmest March on record at 2.2°C, 0.6°C above the previous record.[1] Fortunately, there is some hope on the horizon.

AO Graph

AO values over the past few months. A quick flip from negative to positive values is expected, denoted by the forecast red line.

The Arctic Oscillation (AO), a large-scale weather pattern that can impact the distribution of cold air through the Northern Hemisphere, has been locked below zero for quite some time now. When the AO value is negative, it usually results in a stationary pool of cold air over central continental North America, as we’ve seen over the past few weeks. This has brought below-normal temperatures to many locations across the Prairies and northern United States. The good news is that, as seen above, the AO values are expected to sharply shift into the positive over the next two weeks, which should allow the jet stream to start pushing northwards and bring warmer weather to our region. So while the cooler weather will likely be here for the next 7–10 days at least, a significant change in the weather pattern looks like it’s on it’s way in the near future.


  1. Check out the mentioned link for a list of the 9 significant records we broke in March 2012.  ↩