Seasonal Weekend Ahead

Seasonal weather will be in place over the Red River Valley this weekend with dry conditions and comparatively mild temperatures.

Friday
-9°C / -14°C
Mixed skies and breezy

Saturday
-6°C / -8°C
Increasing cloud with late-day wind

Sunday
-3°C / -9°C
Cloudy and mild

Today will be the least pleasant day of the weekend with temperatures climbing to around -9°C with somewhat gusty northwesterly winds – around 30km/h with gusts closer to the 40-50km/h mark – ushering cooler air than we had yesterday. While we’ll see a fair amount of cloud today clearing out in the afternoon, no snow is expected. Temperatures will dip to the mid-minus teens tonight as winds taper off.

Saturday looks like a fairly pleasant day. A ridge of high pressure over the region will bring mainly sunny skies and a high near -6°C. Winds will begin picking up out of the south a little later in the day, making it feel a bit colder but limiting our overnight low to just around -8°C or so. Some light snow is possible late Saturday afternoon into the evening hours ahead of a warm front gradually lifting northwards through the night.

Sunday will be a very mild day that starts off with somewhat unpleasant southeasterly winds. By late morning or early afternoon it looks like the winds will die off and the temperature will climb to a very balmy high of around -2 or -3°C. Some snow is possible in the afternoon, but it looks like the bulk of the precipitation will remain to the north and east of the Red River Valley, with just a light dusting of snow possible. Temperatures on Sunday night continue mild with lows near -9°C.

Pattern Change Next Week Brings More Mild Weather

As we mentioned earlier this week, a major pattern shift covering much of North America will occur through the early half of next week that will move most of the continent into an above-average temperature regime for an extended duration.

The general gist of the pattern evolution is this: over the next few days, a very strong frontal zone over the northern Pacific will shift eastwards alongside a train of upper-level disturbances reflected at the surface by a very intense low pressure system – bottoming out today at 950mb or so. This intense low will become stacked east of the Aleutians and absorb several weaker, more disorganized disturbances, becoming a very impressive, large storm over the northeastern Pacific. This intense system will build an upper-level ridge over western North America, beginning the push of warm air. The second key ingredient is the evolution of the polar vortex that has been anchored over Hudson Bay for the last few weeks.

By this weekend, shown here in the GDPS 500mb height & vorticty forecast, several very potent low pressure systems – marked by the letter L – will begin building a ridge over western North America while the polar vortex – shown by "PV" – begins a slow trek eastwards.
By this weekend, shown here in the GDPS 500mb height & vorticty forecast, several very potent low pressure systems – marked by the letter L – will begin building a ridge over western North America while the polar vortex – shown by “PV” – begins a slow trek eastwards.

Fortunately, a powerful low pressure system heading up the east coast with teleconnections to the polar vortex will help “push” the vortex from its resting place and rapidly shunt it eastwards over Greenland. This is the second key ingredient because the polar vortex over Hudson Bay[1] is what anchors the eastern Prairies into a northwesterly to northerly flow for such long periods of time, reinforcing colder air and shunting warmer air to our south. With the vortex skipping town, the arctic jet stream will retreat northwards and the warm air spreading northeastwards with the upper ridge will be able to spread eastwards across the Prairies unhindered.

It’s a very interesting situation that highlights how stable the ridge-trough pattern that is so common is; in order for us to be kicked out of this pattern that has brought us a very cold November, we need very potent, significant storms on both coasts at the same time disrupting the upper-level pattern enough to get things moving again.

Within the warming pattern, we’ll see relatively warm and cool spells as disturbances ripple across the Prairies , but overall it looks quite dry in the Red River Valley as daytime highs climb into the -5 to 0°C through the second half of next week with the possibility of above-zero temperatures late into the week through the weekend. different from


  1. Its worth noting given how much press the term “polar vortex” gets lately that this is a completely normal feature that is dominant over Hudson Bay for huge swaths of winter every single year.  ↩

State of The Climate – Meteorological Fall 2014

Wow, what a fall temperature-wise in southern Manitoba this year! From record July-like heat in late September to January-like cold in November, we saw the extremes of all seasons… Here are the average temperature and total precipitation rankings for fall 2014 in Winnipeg:

Meteorological Fall Rankings for Winnipeg
Category Fall 2014
Average/Total
Rank
High Temp. 9.1°C Tied 49th coldest
Mean Temp. 3.8°C Tied 48th coldest
Low Temp. -1.5°C Tied 53rd coldest
Rainfall 47.3 mm 24th least
Snowfall 18.2 cm Tied 46th least
Precipitation 59.7 mm (est.) 18th driest

The meteorological fall (Sep-Oct-Nov) averaged 3.8°C or 0.7°C below the 1981-2010 normal. The negative anomaly was due to a frigid second half of November. September and October actually averaged warmer than normal with anomalies of +0.6°C and +1.6°C respectively. November on the other hand finished 4.2°C colder than normal with an average of -8.8°C, the 22nd coldest November on record since 1872 and the coldest since 1996.

Record Heat & Humidity In Late September

The dramatic burst of July-like heat we had in late September was perhaps the top weather event of fall 2014. The bulk of the warmth occurred September 22 to 27 with 6 of those days seeing highs over 25°C, a good 10-15°C above normal for that time of year. Overnight lows remained well into the teens.

Fall colours as seen in Henteleff Park on September 13, 2014.
Fall colours as seen in Henteleff Park on September 13, 2014.

September 26 was the hottest day with a high of 30.2°C at Winnipeg Airport, just shy of the old record of 31.7°C in 1952. However, it was even hotter in southwestern Manitoba where the heat was literally unprecedented for so late in the season (at least since records began). In Brandon, highs of 34.0°C and 32.8°C on the 25th and 26th respectively were the hottest on record for so late in the season since 1890. The provincial hotspots during the hot spell were Swan River and Wawanesa with maximums of 35.1°C!

In Winnipeg, only 1 temperature record was broken; a record high minimum of 17.4°C on September 26. This was the warmest minimum temperature for so late in the year since 1872. Humidity was the main story with dewpoints in the teens and humidex values in the 30’s. In fact, 6 daily high dewpoint records were broken in Winnipeg during the warm spell, with a maximum dewpoint of 18.1°C on September 26. A maximum humidex value of 35.8 on the 26th was the latest occurrence of humidex over 35 on record since 1953.

October Warmth & January in November

After a brief cool down early October, things warmed up again mid-month with highs commonly in the teens. 2 days exceeded 20°C. A high of 20.6°C on October 24 was the warmest for so late in the year since 1990. Thanks to generally warm conditions in October, The Forks weather station did not report its first freeze until October 30!
Of course, winter came in viciously in mid November with a prolonged cold snap lasting until the beginning of December. A low of -29.6°C at Winnipeg Airport on November 26 was the coldest in November since 1996. We only reached a measly high of -19.3°C on the 26th and 30th, the coldest highs in November since 1985.

Dry Fall

It was also a fairly dry fall, as many of you have probably noticed. Only around 60 mm of precipitation fell in Winnipeg, making it about the 18th driest fall on record since 1872. October was driest with just 4.9 mm of precipitation (all rainfall), the 3rd driest October on record.

The Year So Far

2014’s standing in terms of temperature has improved (warmed) slightly since the summer summary in September, thanks to warmer conditions in September and October. This January to November period averaged 2.3°C or 2.1°C below the 1981-2010 normal for the period. It is the 22nd coldest since 1873 and coldest since 1996, which is an improvement from the 17th coldest January to August period.

Monthly & year-to-date temperature deviations through Fall 2014 in Winnipeg, MB.
Monthly & year-to-date temperature deviations through Fall 2014 in Winnipeg, MB.

391.4 mm of rain has fallen this year up to now, which is actually about 37 mm below normal for an entire year. The deficit in rainfall can be attributed to a very dry fall and below normal rainfall in the spring.

Warm-Up in Store

There’s no question about it: the biggest upcoming weather story is the big warm-up that’s in store not just for Winnipeg & the Red River Valley, but much of North America. After one more cold night tonight, temperatures will move towards seasonal values by the end of the week and then push towards above-normal by the end of the weekend. Given that November just finished up as the 22nd coldest on record that was some 4°C below normal[1], news of a prolonged warmer trend is likely very welcome news for many.

Wednesday
-15°C / -20°C
Mainly sunny; becoming partly cloudy in the evening

Thursday
-8°C / -15°C
Mix of sun and cloud

Friday
-9°C / -15°C
Mix of sun and cloud

Medium-range model consensus is showing high agreement in an above-normal temperature trend through the first half of December.
Medium-range model consensus is showing high agreement in an above-normal temperature trend through the first half of December.

Today will be a relatively cool day courtesy a cold front that passed through Southern Manitoba overnight. Daytime highs will sit near -15°C through the Red River Valley today under mainly sunny skies and relatively light west to northwesterly winds. A ridge of high pressure moving through the region tonight will help temperatures dip to a chilly -20°C overnight.

Southerly winds will develop through the Red River Valley in advance of an approaching warm front quickly advancing across the Prairies. The winds – climbing to only around 20-30km/h – will help our overnight low as relatively “mild” as it is as well as begin ushering in warmer air. Temperatures will climb to around -8°C by Thursday afternoon as the winds gradually diminish under mixed skies. Temperatures will dip to the -15°C on Thursday night.

Looking to the end of the week, Friday appears to be a near-copy of Thursday with light winds, mixed skies and a high of -9 or -8°C and a low once again near -15°C.

Seasonal to slightly above seasonal temperatures will continue through the weekend alongside a slight chance for some light snow.


  1. We’ll have our own climate summary on the fall of 2014 up later this month.  ↩

Scary Cold

This week will start out scary cold, as it continues to feel more like January than early December.

Monday morning will be extremely cold in southern Manitoba
Monday morning will be extremely cold in southern Manitoba

Monday

Monday
-20°C / → -20°C
Mainly Sunny

This morning will likely feature the coldest temperatures we’ve seen so far this winter. Temperatures will slowly climb toward minus twenty the day, but a gusty south wind will begin to develop as well. By the afternoon the wind will be 40km/h gusting to 60km/h, putting wind chill values in the mid to upper minus thirties. That gusty south wind will also generate patches of heavy blowing and drifting snow in open areas.

Tuesday

Tuesday
-12°C / -20°C
Mix of sun and cloud

Tuesday will be significantly nicer than Monday. Temperatures will be in the minus teens, but the wind will be light and from the west…just that fact alone will make it feel a lot warmer!

Wednesday

Wednesday
-12°C / -25°C
Mainly Sunny

Wednesday will feature much the same weather as Tuesday. Temperatures will once again be in the minus teens, but with a slightly stronger west wind. There may be a few flurries early on Wednesday morning, but nothing of great significance.

Long Range

Long range guidance suggests we’ll see less extreme conditions develop as we move into December. Models are hinting at an upper ridge building over the Prairies about a week or so into December. That doesn’t necessarily mean it will be warm, but conditions that are closer to normal, or perhaps even above-normal should become more prevalent.