Normal Weather Continues; 5th Hottest July in the Books

“Normal” weather will continue over the next few days as a ridge of high pressure builds into the Eastern Prairies, bringing us plenty of sun and daytime highs in the mid-to-upper 20’s. Before that, though, we’ll see a slight chance of showers this afternoon. A trough of low pressure is forecast to push into Manitoba on Saturday, bringing with it a chance of rain.

GEM-GLB Forecast of Prominent Ridge

GEM-GLB surface winds valid on Thursday morning. A very large ridge is the dominant feature over the Eastern Prairies.

There is a very slight chance of a shower or two over the Red River Valley this afternoon as a trough of cold air digs southwards as it heads east out of the province; the best chances should remain to our east, through the Whiteshell and Berens River regions, but it certainly can’t be ruled out for us. Accumulations will be minimal and the showers will dissipate fairly early in the evening.

A strong ridge will continue building in across the Northern/Eastern Prairies, forecast to strengthen to a 1028mb high by tomorrow morning, with the ridge axis extending from the Red River Valley NE into Hudson Bay/James Bay. This feature will ensure fairly sunny skies over the next couple days, limiting clouds to just some shallow fair-weather cumulus, as well as induce a broad southerly flow over Manitoba. This would normally result in hot temperatures and high humidity, but in this case, it’s actually going to result in…well, more of the same. The reason for this is significant: instead of being a high pressure system created by an upper ridge, this will be a high pressure system created by a cold trough of air descending from the Arctic. The southerly flow that will develop over the province, instead of being a flow of warm, moist air from the Gulf of Mexico, will be a return flow of air out of the high. So while we’ll have sunny skies, our temperatures will only creep up little by little, and our dewpoints will only climb into the low-to-mid teens.

It’s also worth noting that as crops mature, we’ll be significantly less likely to see days with very high dewpoints (20°C+) for two reasons:

  1. When plants mature, the evapotranspiration (ET) rate dramatically diminishes. Corn, for example, will ET up to 0.33“ per day at peak growth rate. That value then diminishes to 0.23” at maturity[1]. Mature trees may ET up to 50 gallons of water each day during the growing season. Again, this value diminishes in late-summer when all the growth has become mature. Most plants follow similar patterns.
  2. The crushing drought through the Central US will diminish pretty much any advection of moisture that may occur. There’s a long way between us and the Gulf of Mexico, and the normal ET contributions from plants through the Central Plains is missing this year.

One of the side effects to this is that our severe thunderstorm season will likely come to a fairly rapid halt over the coming weeks as good setups become moisture-starved.

Evapotranspiration is the process by which plants take up moisture from the soil and expel it as vapour into the atmosphere through the stomata on their leaves.

For Saturday, it currently looks like a trough of low pressure will work it’s way across the province, bringing with it a chance for showers. The track is highly dependent on the positioning of an upper low over the northwestern Prairies, so it’s a little early to say where exactly precipitation will fall. Either way, it doesn’t look to be very powerful, and any areas that see precipitation look to receive small amounts.

The next chance for rain looks to be not until the middle of next week.

July 2012 Closes Out as 5th Hottest

July 2012 closed out as an extremely warm month. The average temperature[2] for the month was 22.3°C, 2.7°C above the normal 19.6°C[3]. This places July 2012 in 5th place for all-time hottest July:

Warmest Julys on Record
Year Average
1 1936 24.2°C
2 1935 22.4°C
3 1916 22.4°C
4 1914 22.4°C
5 2012 22.3°C

The warmest day we had was July 11th, which reached 34.5°C. Our coolest day was July 15th, where the mercury topped out at only 19.4°C. Our warmest overnight low was 20.5°C on the night of July 10th/11th. Our coldest overnight low was 7.9°C on the night of July 26th/27th. In total, the Winnipeg Airport recorded 14 days with temperatures above 30°C in July. The hottest day in July on record is 42.2°C set in 1936. The coldest night on record in July is 1.1°C set in 1972.

The biggest story was, perhaps, the sheer lack of rainfall last month. The airport recorded 23.5mm of rain, which is the 11th driest July on record:

Driest Julys on Record
Year Amount
1 2006 10.5mm
2 1875 13.5mm
3 1925 15.5mm
4 1894 16.0mm
5 1886 17.0mm
6 1960 17.0mm
7 1920 19.3mm
8 1910 20.3mm
9 1964 22.4mm
10 1979 23.1mm
11 2012 23.5mm

July 2012 was the 7th driest July in the last 100 years. Fortunately, the drought wasn’t as hard hitting as areas further south, as Winnipeg had several months preceding July with above-normal precipitation.

As we covered on Monday, August looks to be off to a dry start with daytime highs sitting near-normal to just above normal[4].

  1.  ↩
  2. The average temperature is a mean of all the daytime highs and overnight lows. It is not an integrated parameter, so take that as you will.  ↩
  3. Normal average temperature calculated for the years 1981–2010.  ↩
  4. Normal daytime highs for the beginning of August in Winnipeg are generally around 27°C.  ↩

A Chance To Dry Out A Little Bit…

After a deluge of rain over the past 10 days, Winnipeg is finally set to see some sunny, dry weather. A high pressure system pushing through the area will provide sunny skies over the next couple days with daytime highs pushing back towards our normal high of about 22°C.

Winnipeg has had 46% more rain than normal since April 1

Winnipeg has had 46% more rain than normal since April 1. (KEN GIGLIOTTI / WINNIPEG FREE PRESS)

Winnipeg is absolutely soaked. So far this month, many areas of the city have seen over 100mm (3.94”) of rain, with some areas of the west end seeing closer to 125mm (4.92”). This is a huge amount of rain for a single month in Winnipeg; the Manitoba Agricultural Department released a report showing that Winnipeg has had 46% more rain than normal over the last 30 days. This wetter-than-normal month has broken a 9-month stretch of dryer-than-normal conditions for Winnipeg and the city has already shattered last year’s total summer precipitaiton. If summer is considered June, July and August, our 100-125mm of precipitation in Winnipeg this month trounces the 93mm we got through Summer 2011. In addition, through summer last year only 7 days had thunderstorms reported. So far in May alone, we’ve had 5 days with thunderstorms. All in all, we’re off to a wet start to the summer that’s already been more promising on the storm front than last year.

Over the next couple days, though, we’ll see the sun. A ridge of high pressure will move across the province today, bringing sunny skies, light winds and a high near 19°C. The high begins to move out of the region on Thursday, allowing a slight southwest flow to bring some warmer air for the day, allowing our daytime highs to climb just over 20°C under sunny skies.

We’ll see a slight chance of showers on Friday afternoon as a warm front pushes through the Red River Valley, bringing temperatures in the mid-20’s for the weekend.

Beautiful Week Ahead; Stormy Weekend

The Red River Valley will bask in the sunshine through the rest of the work week before a strong spring storm system moves into the area, bringing rain and snow for the weekend.

Unlike our friends to the west in Alberta, where a major winter storm is set to dump 15-25cm of snow through areas west of Highway 2 over the next two days, a ridge in place over Manitoba will keep skies clear and temperatures warm over the next few days, with plenty of sunshine and daytime highs of around 15°C and overnight lows around 2°C.

850mb Winds

850mb winds from the GEMGLB valid 06Z Saturday morning.

Our next weather system will move in this weekend, with an upper trough swinging eastwards across the Prairies. An area of rain will blossom in Saskatchewan through the day on Friday with rainfall intensifying through the day. Embedded thunderstorms may increase rainfall amounts for SK, but currently it looks like rainfall amounts of 20-40mm are possible for SE Saskatchewan, with some models painting as much as 75-85mm of rain! This system will track eastwards into Southern Manitoba through Friday night.

Southern Manitoba will be under the influence of this system through Saturday and Sunday, with some regions seeing rain changing over to snow on Sunday as cold air is wrapped into this system. Given the system’s intensity and its time out, we’ll wait to look at it in more detail on Friday when things are a bit clearer.

For now, get out there and enjoy that sunshine!

A Beautiful Weekend Ahead

Our left-over moisture will slowly clear out today and tonight ushering in a beautiful weekend with plenty of sunshine and warm temperatures. With Winnipeg’s average daytime high sitting at around -8°C right now, we can expect to see tempeatures nearly 10°C above normal by the end of the weekend!

Sunny Skies

Many areas in Southern Manitoba that are typically covered in snow at this time of year are completely bare. PHOTO BY ERIN GARDIN.

We’ll see a mix of sun and cloud here in Winnipeg today, with the ever-present chance of a few snowflakes, but any snow that does develop will be less significant than the few light flurries we saw yesterday in the city. The daytime high today will be cooler than yesterday, around -4°C, as a trough of cool air aloft swings over Southern Manitoba. The snow much of the Red River Valley recieved between 2 and 5cm of on Wednesday as a shortwave embedded in an upper trough swung across the province will not be sticking around for very long. An upper ridge has begun to build into the Prairies and will continue it’s trek into Southern Manitoba over the next two days. Here in Winnipeg, we’ll see winds switch around to southerly overnight tonight, which will usher in milder air and push our temperatures up for the weekend.

Upper Ridging

GEM-REG 500mb Winds valid 12Z Friday Feb. 17 (6AM CST)

We’ll see temperatures soar this weekend with a light south-southwest flow and mild air pushing in aloft. 850mb temperatures are expected to increase to slightly above 0°C by Sunday night, which will ensure that through the weekend we have daytime highs of 0°C – 3°C in Winnipeg.

Temperatures are expected to reach as high as +2°C this weekend; that’s 10°C above normal for Winnipeg at this time of year.

Any areas that manage to return to snow-free quickly will be able to add a couple degrees to those temperatures. Overnight lows will still be cool, with temperatures dropping down to around -11°C tonight and tomorrow night.

By Sunday, a low-pressure system will begin ambling it’s way out of Alberta into Saskatchewan. This will increase the southerly upper-level flow and provide the needed kick to really push those 850mb temperatures up. With the dramatically warmer 850mb temperatures in place, our overnight low on Sunday night will essentially be just a degree or two cooler whatever the daytime high makes it to.

The low will then track eastwards across Manitoba Monday into Tuesday. Models disagree significantly on what will happen happen for Winnipeg, with some giving us 5 to 10cm of snow and others keeping the precipitation 250 miles away from us. We’ll certainly keep our eyes on this system as it develops!