Category: Forecasts

Going Into the Deep Freeze

Brad Leave a comment

After an extraordinarily warm start to January, our weather is about to take an abrupt turn toward very cold conditions. It was only last Tuesday that temperatures were well above zero in Southern Manitoba. By the time this Tuesday rolls around, conditions will be starkly different.

Surface Pressure Map of the Prairies for Monday, Jan 16/12

Map of Surface Pressure Over the Prairies – valid Monday, January 16, 2012

The colder weather that is currently overtaking the Prairies is the result of a low pressure system that crossed the region on Sunday. As the low raced across the Prairies, it dragged down an arctic air mass in its wake. This arctic air mass will be centred around a 1040mb high pressure system, which is currently in the process of breaking away from a much larger 1063mb high over the Yukon. While in summer high pressure usually means warm and sunny conditions, in winter a large high pressure system usually means sunny but very cold weather.

Surface Temperature Map of the Prairies for Tuesday, Jan 17/12

Map of Surface Temperatures Over the Prairies – valid Tuesday, January 17, 2012

Temperatures in Southern Manitoba on Monday will be in the mid to high minus teens, which is slightly below normal for this time of year (normal high is -13C). However, by Tuesday it looks unlikely that temperatures will rise above -20C during the day. Despite the very cold high temperatures that are expected this week, overnight lows will not be that extreme in Southern Manitoba. Currently it doesn’t look like we’ll get much below -30C in most areas (save for Thursday, when we might see an extremely cold morning). Wind chill values toward -40 are entirely possible this week, especially in the morning hours when actual temperatures are still very cold. Our neighbours to the west in Alberta and Saskatchewan will be much worse off, as low temperatures in those provinces are expected to hit -40C this week.

In the longer range it appears unlikely that we will return to the very warm conditions that we experienced earlier this month. However, that doesn’t mean the rest of January will be extremely cold. We don’t yet know how long this cold spell will last, though bear in mind that arctic air is very dense and does not like to move quickly. In terms of snow, weather models are showing a return to a stormier pattern for the rest of January. It looks as though a minor weather system may give Southern Manitoba a couple centimetres of snow on Tuesday. Other than that, it doesn’t look like we’ll see any snow until next weekend at the earliest. Typically colder patterns tend to bring more snow than warmer patterns. This explains why our winter has been fairly snow-free thus far.

Elsewhere in Weather News

US Tornado Season Kicks Off Early in 2012

One of the Unites States’ first significant tornadoes of the 2012 storm season has caused quite a bit of damage in western North Carolina on January 11th 2012. What caused the tornado was a potent cold front pushing across the region coupled with just the right amount of instability and shear. This storm system was associated with a low pressure system moving up the east coast and bringing unseasonably warm and moist air to the south-east states. The EF-2 tornado (about 115mph wind speeds) caused major structural damage to at least 50 homes and knocked out power to 800 homes in the North Carolina area. Thankfully no fatalities were related to this tornado.

Tornado Damage

North Carolina Tornado Damage – Photo source WBTV news

Ironically on the back side of this low (where the high pressure dome is moving in) winter is set to arrive with gusty winds and snowfall. The tornado’s cleanup will have to be done in wintery conditions.

2012 Starts Off With Extremes in Australia and Europe

Australia’s summer has started off as a sizzler in 2012 and Europe has had record snowfalls. Both these cases are examples of how extremes have already shown up in 2012. Southern Australia has produced some extreme averages; lows of 30ºC and continuous highs of 45ºC or more (7ºC+ above average). These extremely warm temperatures are causing brushfires to spring up almost anywhere in Australia’s southern counties, keeping firefighters on the go.

Meanwhile parts of Europe have had snowfalls that have buried them in snow which has left many ski resorts, including Zugspitze summit in Germany, covered. In this location there was less than a foot of snow a couple weeks ago, however now that several powerful systems have passed, more than 6 feet of snow have accumulated there!

CO2 Values

CO2 Values Graph – Courtesy of Arctic Warming (whyflies.org)

Many scientists believe that these extremes come down to how the Arctic sea ice has diminished significantly in the last couple years and how greenhouse gas levels (CO2) have been rising to an unprecedented level. One can also assume that these extremes happen naturally and the Earth is simply going through a warm cycle, as there is no exact proof that these could be the cause – it is for you to decide!

Elsewhere in Weather News has been provided by Matt.

Major Arctic Outbreak Next Week…But First, Milder Weather

Brad Leave a comment

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.

Brad Leave a comment

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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Location New
Record		 Old
Record		 Old Record
Year
Fisher Branch 4.9 2.4 2002
Gimli 4.7 3.0 1990
Gretna 7.5 2.6 2006
Melita 4.3 2.5 2002
Pinawa 6.5 3.5 1990
Winnipeg (Tie) 5.1 5.1 1990

Changes Coming To Our Weather Pattern

Brad Leave a comment

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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Location New
Record		 Old
Record		 Old Record
Year
Brandon 4.5 4.4 1986
Gretna 8.0 7.2 1958
Island Lake -0.2 -0.6 2002
Melita 8.6 3.9 2006
Sprague 5.9 5.0 1958
Thompson -3.3 -3.8 1983

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.