Major Arctic Outbreak Next Week…But First, Milder Weather

Our shot of winter this week won’t look so bad by this time next week! Slightly warmer temperatures today will be followed by some light snow tonight and a dreary but milder weekend, before the coldest airmass we’ve seen this winter settles in over much of the Prairies.

Today will bring warmer temperatures as Pacific air pushes east-southeast across the Prairies. Temperatures should be able to make it up a little past the -15°C mark by early to mid-afternoon. Clouds will roll in by evening, and we should see some light snow in the evening and overnight with temperatures staying fairly steady overnight as warmer air continues to push into Southern Manitoba. Winnipeg will likely see 2-4cm of snow as relatively high snow to liquid water ratios (SLR) are expected, around 15:1 to 20:1.

Snow to Liquid Water Ratio (SLR) is a measure of how much snow is produced per millimetre of water. For example, a SLR of 20:1 would mean that for each 1mm of liquid water that fell, there would be 20mm, or 2cm. If someone received 10cm of snow, and that was melted and resulted in 4mm of water, then the SLR would be 25:1. The higher the SLR is, the ‘fluffier’ the snow.

Milder temperatures will be seen in the southwest and south-central portions of Manitoba on Saturday and Sunday. Temperatures will reach between -10°C and -5°C in the Red River Valley this weekend, with relatively light winds and plenty of cloud.

Surface Temperatures, Saturday Afternoon

Surface temperatures valid 12Z Saturday Morning (6AM)

We could see some light snow on both days as well, but significant accumulations (2+ cm) are unlikely. The days may be a little dreary, but enjoy the warmer temperatures while you can. Next week will be shockingly different.

Cold Front Passing Through Monday Morning

Surface analysis of forecasted temperature field valid 06Z Monday, Jan. 16. Warm front is represented by red line and cold front is represented by the blue line.

Early Monday morning, a cold front will sweep through Southern Manitoba, ushering in a completely different weather regime. We’ll see steady or dropping temperatures through the day Monday with some accumulating light snow through much of the RRV, especially north of Morris. Current indications show that 2-4cm looks reasonable, with 5-10cm possible for areas north of Winnipeg. Snowfall amounts in the City of Winnipeg will be sensitive to the exact track of the low, so we’ll keep an eye on that system as it develops.

The entire change will be driven by a long wave trough rotating southeast from Alaska into the Central Prairies. This will drive the jet stream south into the Northern U.S., allowing bitterly cold Arctic air to spill southwards into the Prairies. Just how cold is it going to get?

Bitterly Cold Temperatures Monday Night

Surface temperature prog valid early Tuesday morning, 12Z (6AM) January 17. Many areas in Southern Mantioba will see temperatures in the low -20’s with some spots in the southwest corner potentially reaching as cold as -32°C or -33°C. A wide swath of temperatures dipping below -40°C is forecast through Central Saskatchewan.

The coldest air we’ve seen all winter at 500mb will be pushing into the Prairies, with temperatures at that height forecast to be between -40°C and -45°C over most of the Prairies. What does this mean for temperatures at the surface? The GEM-GLB model is currently forecasting a swath through East-Central Alberta and Central Saskatchewan that will experience overnight lows between -40°C and -45°C!

For the third week of January, average daytime highs are around -13°C and average overnight lows are around -23°C. We will be several degrees below normal for a couple days next week.

This cold air will slump southeastwards bringing bitterly cold temperatures into Southern Manitoba, with overnight lows near -30°C and daytime highs struggling to climb above -20°C. By mid-week, temperatures may moderate into the mid-minus-teens as some cloud cover spills into the Southern Prairies associated with a system tracking through the Northern Plains. It may feel extremely cold, however, as we may be dealing with stiff northeast winds as the system moves through the area.

The cold air looks to be entrenched for the whole week, but we’ll have more on that on Monday. Get out and enjoy the weekend as best you can! It’s hot drinks and oatmeal weather next week!

Another Day of Record Highs, Then…Winter.

Winnipeg has enjoyed 32 consecutive days with above average temperatures, making this one of the more pleasant winters in recent memory. This is about to abruptly change as winter is making an ungraceful return tonight. Before that, however, is another beautiful day with a good chance that more daytime temperature high records will be broken.

2012-01-10 21Z Surface Prog.

Jan. 10, 2012: 21Z (3PM) surface prognosis from the GEM-REG. Blue line represents cold front, red line represents the warm front.

This afternoon will bring more record-setting temperatures to southern Manitoba as the area is drenched in one last shot of Pacific air. By mid-afternoon, Winnipeg will be firmly in the warm sector, and with 850mb temperatures of 2 or 3°C, temperatures should reach as high as 6 or 7°C through a majority of the RRV, Winnipeg included. There is a slight chance that some areas close to the western escarpment of the RRV could see another day of 9 or 10°C with the extra push from downslope winds and their continued lack of snow cover. That being said, I fully expect daytime high records to be broken in many communities in the RRV today.

Tonight, however, is a whole different story.

Winter Returns

After being held well to our north for over 4 weeks, Arctic air will surge across the Prairies today and tonight, bringing a drastic change to the weather. The cold front will sweep through Winnipeg between 00Z and 03Z (6PM & 9PM, respectively), ushering strong northwest winds and much colder air. Much of the southern Prairies will see snowfall with this system, with areas closer to the international border receiving 2-4cm. Winnipeg will be near the northern fringe of the snowfall, but I think that we’ll see at least 2cm of snow here. I think that 5cm is very unlikely, but there is still some uncertainty in how intense the band of snow will be. The most significant snowfalls will occur through the Northern Interlake, where they’ll be under the influence of a hang-back trough from the main low pressure system, bringing them snow for a longer period of time than us in the southern portions of the province.

2012-01-11 15Z 850 Wind Prog

Jan. 11, 2012: 15Z (9AM) 850 wind prognosis from the NAM

With winds at 850mb forecast to be 30-40kt, surface winds have the potential to gust as high as 70km/h overnight. Likely, we’ll see a period of sustained winds near 50km/h before things settle out with sustained winds near 40km/h with gusts to 60km/h. Combined with temperatures that should fall to near -15°C tomorrow morning, wind chill values will be as low as -25 overnight.

2012-01-12 06Z 850 Temp Prog

Jan. 12, 2012: 06Z (Midnight) 850mb temperature prognosis from the NAM

A second cold front will pass through the RRV between 15Z and 18Z tomorrow morning (9AM and Noon), reinforcing the strong winds and causing temperatures to either remain steady or drop through the afternoon. The gusty northwest winds should continue through the whole day, with some light flurries and temperatures that will start near -15°C and drop to close to -20°C by evening. These temperatures combined with the wind should result in wind chill values near -30 for most of the day.

Normal daytime highs for this time of year are around -13°C and normal overnight lows are around -24°C. For the first time in over a month, Winnipeg will experience below-normal temperatures.

Extremely cold air at 850mb will move over the southern portion of the province Wednesday night; with 850mb temperatures in the -25 to -30°C range, we can expect overnight lows close to -25°C for Wednesday and Thursday night, with a daytime high on Thursday barely above -20°C. The GEM-REG is a little warmer than the NAM on the cold air moving over the RRV, so there is a chance of temperatures being a couple degrees warmer than this, but I’ll always bet on the cold air.

Fortunately, it looks like the cold weather will be relatively short lived. Current indications are that another low tracking across the Prairies should push warmer air into Winnipeg for the weekend, with daytime highs near -5°C. More on that later in the week.

UPDATE: 6 records fell again today across Manitoba as most places enjoyed yet another mild day.
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Old Record
Fisher Branch4.92.42002
Winnipeg (Tie)5.15.11990

Changes Coming To Our Weather Pattern

Our remarkably warm January weather will continue for at least a couple more days before some large-scale changes begin to reshape our weather for the rest of January. The weather for the second half of January will certainly be colder than the first half, but just how much colder?

WRF Model Model Temperature Output for Monday, Jan. 9 at 12pm

WRF Model Temperature Forecast for Monday, Jan. 9 at 12pm

Temperatures will remain very warm to start the week. High temperatures on Monday will likely be in the mid single digits in much of Southern Manitoba. As a result, more temperature records will be threatened. Tuesday will also be unusually warm, but temperatures will be slightly lower, with highs closer to zero. The remainder of the week will be colder, with high temperatures for Wednesday through Friday being near to or slightly above normal (normal high being -13C). There is potential for some snow on Tuesday night into Wednesday with the passage of a low pressure system. Current indications suggest that we’ll see a few centimetres of snow from this system, but that could still change. We will continue to monitor this system and provide updates as we get more information.

Beyond this week the forecast becomes somewhat unclear. Most forecasts suggest that we’ll cool off significantly for the second half of January (see CPC outlook above). However, the extent of the cold weather is quite uncertain. We may have to deal with a so-called “roller-coaster pattern”, where big warm-ups are followed by big cool-downs. These roller-coaster patterns tend to bring a fair bit of snow, along with many days with gusty winds. As we move further into January the details will become clearer.

CPC Outlook for late January 2012

Climate Prediction Center’s Forecast for mid January 2012

Many people are wondering what is causing this spell of remarkably warm weather in Southern Manitoba. The main reason for the really warm weather this past December (and early January) is the Arctic Oscillation. The AO, for short, is a cycle which helps forecasters determine whether cold air will be bottled up in the north, or be allowed to spill down into Central North America. For most of December the AO was strongly positive, meaning that arctic air was kept well to our north. Current modelling suggests that a switch to a negative phase of the AO is likely by mid to late January. Once the AO switches to negative, Southern Manitoba will finally be able to get some real winter weather.

UPDATE: 6 records fell across Manitoba today as most places enjoyed yet another mild day.
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Old Record
Island Lake-0.2-0.62002

All in all, 29 records were broken across the Prairies, with a majority of them happening in Alberta and Saskatchewan. Tomorrow will see another day of above-average temperatures in Southern Manitoba before cooler weather arrives on Wednesday.

Slight Cool Down Before Mild Temperatures Return

26 temperature records were broken across the Southern Prairies yesterday as warm Pacific air flooded the region tied to a low pressure system tracking through central SK/MB. The RRV will see a cooler weekend as colder air is creeping southwards on the backside of this system, however the deep freeze is still a little ways off.

Overnight Snow along a weak trough in NW flow

3hr. QPF from the 12Z Jan 06 GEM-REG valid at 09Z Saturday Jan. 7

An area of snow will slowly push southwards through the RRV today, brining only minor accumulations to the region. The system should clear out by this evening, with the chance of a few light flurries through the night in a weak northwest flow. A ridge of high pressure will then work across Southern Manitoba Saturday & Sunday, brining cooler temperatures to the area with daytime highs in the -10 to -5°C range and overnight lows in the -10 to -15°C range through the region.

By Monday, another low pressure system tracking through the northern Prairies will drag more Pacific air over the Prairies once again pushing temperatures above 0°C. Many areas in Southern Manitoba should see daytime highs Monday near 5°C. Currently, it doesn’t look like temperatures will reach nearly as high as some places did yesterday, but things will become a little clearer closer to the day (naturally). It’s quite likely we’ll more daytime high record temperatures broken on Monday.

850MB temperatures from the GEM-GLB

850mb temperature from the 00Z Jan 6 GEM-GLB valid at 00Z Thurs. Jan 12

After that, it looks like we’ll be seeing a bit of a cold snap. On the back side of the system, a fairly strong push of Arctic air will flood through the Prairies, bringing us our coldest temperatures in a while. It looks reasonable, as temperatures in Oymyakon, RU have dropped below -50°C (-55°C when I checked last night), with daytime highs only around -35°C, which is a good indicator for colder weather pushing over the poles towards the Prairies. We won’t get nearly as cold as they are, but by the middle of next week, daytime highs around -15°C with overnight lows around -25°C are certainly possible, as 850mb temperatures are forecast to dip down to -25 to -30°C over Souther Manitoba . This system looks relatively dry, however we may shift into a pattern that will favour clippers tracking along the international border which may bring long-awaited snow to southern portions of the Prairies and the Northern Plains.