Week to Start Cool, but is Spring Coming?

Brad Leave a comment

This week will start out well below normal, but there are signs that we may begin to warm up towards week’s end. Is Spring finally set to arrive?

Monday and Tuesday

Monday
image
Mix of sun and cloud. Chance of flurries.
-3°C / -8°C
Tuesday
image
Mainly sunny.
2°C / -8°C

Monday will be a cold day by April standards. High temperatures are generally not expected to exceed the freezing mark in Southern Manitoba (except in cities and forests), which will make the day some 15 degrees below our normal high of 13C. There may be some isolated flurries on Monday, as weak low-level instability develops during the day.

Tuesday will be a bit warmer than Monday, but not by much. Temperatures should climb just above zero in most areas, but that will still put as well below normal.

Wednesday

Wednesday
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Mainly cloudy. Chance of flurries.
2°C / 2°C

Wednesday should be another above freezing day in Southern Manitoba, but we could see more snow as well. Flurries look to plague us for much of the day as the atmosphere once again destabilizes behind a passing weather system. Accumulations look to be minimal, but I doubt that will make the snow any more pleasant.

Long Range

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Forecast high temperatures on Friday

There are signs that we may finally see a return to near normal or just below normal conditions by late this week or into the weekend. Models are in fairly good agreement that temperatures will rise up into the high single digits or low DOUBLE digits by later in the week/weekend. Of course we have seen forecasts like this fall apart before this spring, but hopefully this time things will be different.

Elsewhere in Weather News: April 20th, 2013

Matthieu Leave a comment

Major Trough Moves through US

A trough of low pressure moving across a large swath of continental United States this week has been the cause for severe flash flooding, much wind damage, and a few tornadoes including Canada’s first of the year.

The first severe weather day occurred on Wednesday, April 17th, when a moderate risk was issued by the SPC for most of Oklahoma, parts of south-west Kansas and Missouri. Over 150 chasers (reporting) were scattered throughout Oklahoma, and at one time over 50 chasers could be seen on the same supercell! Severe thunderstorms fired along the warm front and further along the dryline that extended into Texas in early afternoon. The storms that had the largest tornado potential went up in south-western Oklahoma and moved towards the north-east. These storms along the warm front trailed each other and produced flash flooding in some localities. Also to note is that a few cities such as Lawton, OK who were lying along the warm front saw not one supercell that day, but three within four hours. One of these also dropped a tornado which caused some damage to an industrial area on the outskirts of the town.

Chasers

Incredible chaser convergence (red dots) in Lawton ahead of a supercell. Just about every single street in Lawton had a chaser on it! (Source: Spotter Network/RadarScope)

On Thursday and Friday the trough continued its push eastward, but it became less of a tornado threat and more of a severe wind and hail event. At one time, thunderstorms stretching from Ontario all the way down to Texas could be seen. A few states such as Illinois, Iowa, Alabama, and Missouri saw extremely heavy rain in a short period of time which was cause for flash flooding concerns. Air rescues took place in Oxford, Alabama to save stranded motorists caught in their partly submerged cars. Canada’s first tornado of 2013 was also recorded on Thursday, rated as an EF 1 it touched down near Melanchton, Ontario.

Tornado damage

Damage of a barn in Southern Ontario from the EF 1 tornado. (Source: Steve Murphy EMC via Caledon Enterprise)

The cooler weather is not expected to last this weekend as return flow sets up and southerly winds kick in for most of the Plains and Midwest. Later next week it appears as though yet another high pressure will slide down the Rockies, in turn bringing more unseasonably cold air to the Central United States.

Pleasant Weekend With Stormy End

Brad Leave a comment

Although temperatures will remain well below normal, we’ll see a pleasant weekend ahead when compared to the weather we’ve had as of late.

Friday

4°C / -14°C
Sunny.
Saturday

2°C / -4°C
Increasing cloudiness in the afternoon.
Sunday

2°C / -3·C
Cloudy; rain or snow beginning midday.

The next two days will be fairly nice despite the cool air that remains entrenched over the province. Both Friday and Saturday will provide plenty of sunshine and daytime highs climbing a few degrees above zero. We should see substantial snow-melt here in Winnipeg over the next two days thanks to that increasingly strong April sun. We’ll see a cooler night tonight as winds lighten up allowing us to radiate more heat away than the past couple nights. Temperatures will likely drop into the minus teens tonight while cloud cover will keep us substantially warmer on Saturday night.

Stormy Sunday

Precipitation totals for the daytime period on Sunday from the 00Z April 19 GDPS model.

For Sunday, an Alberta Clipper will make it’s way across Southern Manitoba and while many aspects of the system look to be relatively innocuous, it looks poised to pack a punch precipitation-wise. Snow will push into the Red River Valley midday, but the afternoon brings a particular challenge. Warm air will be advected northwards in the southeast flow ahead of this system, slowly warming the lower-levels of the atmosphere. Some indications are that preciptiation will switch over to rain in the afternoon, especially for the central Red River Valley and areas eastwards. It’s a very challenging problem and the phase of the precipitaiton will make a significant impact: around 10mm of liquid-equivalent precipitation and if it ends up falling as snow, that could quickly amount to another 6-10cm of the stuff. It’s almost a certainty that areas east of the Red River Valley will see mainly rain and areas west of the Red River Valley will see mainly snow.

At this point I think we’ll end up seeing a mix here in Winnipeg, with predominantly snow in heavier areas of precipitation. I’m not going to wager too much on accumulations right now; it’s likely that much of the snow will melt on contact with the ground as temperatures will likely remain just over the freezing mark. The system will move off overnight leaving clearing skies on Monday morning.

Cool Weather Breaks Records

Brad Leave a comment

Temperatures will remain well below normal this week in the wake of Monday’s snowstorm. Far from the 45cm of snow that fell in Bismark, only 5-10cm fell across Southern Manitoba while strong northerly winds coupled with near-0°C temperatures to spare no expense in turning highways into sheets of slush and ice. Unfortunately it looks like the cool weather reinforced by this system isn’t going anywhere anytime soon.

Snowfall Totals from Monday’s Storm

City Snowfall (cm)
Winnipeg 7.8
Oakbank 8.6
St. Alphonse 8.4
Miami 10.0
Winkler 12.0

Record Cool

As mentioned above, the cool weather is here for a while yet. A stable atmospheric structure called a high over low (or Rex) block has developed off the west coast of North America. This feature will produce persistant ridging over the Eastern Pacific which will in turn produce relatively persisitant troughing over western North America. This persistant troughing will tend to keep the storm track to our south and any warmer air shunted off towards the eastern half of the continent. The feature is expected to weaken towards the end of the week, but not enough to truly break down the rather stationary pattern. While troughs will weaken periodically over the next week, the general trend will be to reinforce and redevelop them instead of bringing any significant ridging onshore.

NAEFS 8-14 Day Temperature Outlook issued April 17, 2013 at 00Z

NAEFS 8-14 Day Temperature Outlook issued April 17, 2013 at 00Z.

The above image is the 8-14 Day Temperature Anomoly outlook from the NAEFS1; it’s an “at a glance” product that tells you whether the models think that it will warmer or cooler than normal next week2. As you can plainly see, a wide swath of cooler than normal temperatures is expected over much of the center of the continent.

Unfortunately, this is compounding on an already exceptionally long winter. Rob, over at Rob’s Blog, put together a plethora of interesting statistics about this spring:

[…] Today was the 36th consecutive day below normal in Winnipeg (March 9th was the last day above normal) and it appears that below-normal tmeperatures will continue into next week. […] With no prospect for +5°C the rest of the week, this year will mark the latest date in 141 years that Winnipeg has reached it’s first +5°C of the year (record back to 1872). The previous record latest date was April 15th 1950 (the year of the historic Red River flood).

— Rob’s Blog

Rob rubs salt in the wounds a little more by reminding us that on average Winnipeg sees at least 15 days with highs above 5°C and sees on average at least 10 days with highs above 10°C. It’s an excellent read on the stats for this spring and I recommend you go check it out.

Long-range models continue to pepper us with hope in the long, long range. There is growing consensus on a pattern break-down by the end of the month with temperatures beginning to warm in earnest through the start of May. That could just be the fact this cold air can only fight against the increasingly strong sun for so long.

This Week

Wednesday

2°C / -9°C
Cloudy; gradual clearing.
Thursday

2°C / -8°C
Mainly sunny.
Friday

2°C / -8°C
Sunny.

The weather through the rest of this week will be uneventful. The main storm track will remain well to our south, bringing severe thunderstorms to portions of the Southern Plains and more snow to the Dakotas. We’ll see cloudy skies today as overruning cloud pushes into Southern Manitoba from the system psuhing through the Dakotas with some flurry activity over Southern Manitoba. For the most part, the snow should stay out of Winnipeg while skies gradually clear through the evening and overnight period and we’ll be left with mainly sunny skies for Thursday and Friday as another Arctic ridge pushes into the Prairies. Daytime highs will remain steady near 2°C and overnight lows will be near -8 or -9°C.

Looking towards the weekend, it looks like we’ll see more of the same temperature-wise, and a chance for some light snow as a weak low pressure system moves across the Prairies. At this point it does not look like this system will bring any significant accumulations with it.

  1. North American Ensemble Forecast System ↩
  2. A Day 1-7 outlook would be for the coming week, Days 8-14 would be the week after. ↩