Brad, Author at A Weather Moment • Page 399 of 415

The End of The Arctic Deep Freeze

January 20, 2012April 3, 2015 Brad Leave a comment

After a couple days of bitterly cold temperatures, the end is already in sight for Southern Manitoba. Perhaps we shouldn’t complain, though, as Southern Manitoba got off pretty easy compared to the rest of Prairies, where temperatures plummeted to nearly -40°C through most areas, let alone considering the wind chill on top of that.

Pacific Analysis of Incoming System

Analysis of the Eastern Pacific, Jan. 12, 2012 02:45Z. A powerful low pressure system situated approximately 1000km off the British Columbia coast will bring a significant change to our weather pattern.

A powerful system pushing towards B.C. will bring a significant change to our weather pattern this weekend. As this system pushes into the western portions of the continent, the Arctic Vortex, currently situated near Baker Lake, NU, that has been pushing extremely cold air over the Prairies will begin to collapse and retrograde back towards the Gulf of Alaska.

As this happens, the large-scale flow over the Prairies will shift from northwest to southwest, and what a difference 60 degrees can make.

Temperatures will begin to rise on Saturday, as the arctic air begins to be pushed back northwards, and most areas in Southern Manitoba should see temperatures rise to around -12°C. Temperatures will continue to rise overnight and through Sunday up to around -5°C over the RRV as the actual low approaches.

We’ll likely see a couple of cm of light snow Friday night through Saturday as the warm front slowly lifts from North Dakota into the Interlake region. Past that, it gets a little tricky, as some models are forecasting substantial snowfall through Sunday while others keep all snowfall well north of the Trans-Canada Highway. Best case scenarios bring only light snow to the RRV on Sunday night in the wrap around for this system, while more pessimistic approaches bring close to 10cm of snow to our area through light-to-moderate snow through Sunday and Sunday night. It should start to become a little clearer over the next day or two, as the low approaches the coast. Currently, ensemble models predict that we’ll see little snow, and that accumulations should occur through the Interlake, and not as far south as Winnipeg.

After Sunday, we’ll cool back down to seasonal to slightly-above seasonal temperatures through much of next week, with daytime highs generally between -15°C and -10°C. All in all, next week looks quite pleasant. We’ll be sure to provide updates in the comments on how much snow we can expect for Sunday through the coming days!

Continued Cold This Week

January 18, 2012April 3, 2015 Brad Leave a comment

Cold air will remain entrenched over Southern Manitoba for the remainder of this week, until a large scale pattern shift once again brings warmer than normal temperatures to our area.

January 18, 1800Z (Noon) MSLP & Snow Accumulation Prog

January 18, 1800Z (Noon) MSLP & Snow Accumulation Prognosis

Snow will taper off by early afternoon today as an arctic high pressure system builds into Southern Manitoba as it pushes across Southern Alberta and Saskatchewan. Much of Southern Manitoba will see a total of around 2cm of snow when all is said and done, with a few localities along the international border seeing 2-4cm.

The big story over the next couple days will be the ridge building across the Prairies. Southern Manitoba will see the coldest temperatures of the winter with daytime highs continuing to be well below normal.

The average daytime high for the 18th of January is -13°C. The average overnight low for the same day is -23°C. Winnipeg will experience temperatures close to 10°C colder than average over the next few days.

This high pressure system has brought bitterly cold temperatures to Alberta & Saskatchewan, with daytime highs of only -29°C in Calgary, -28°C in Edmonton and Saskatoon, and -27°C in Regina yesterday. This air mass will push into our region today, which will limit our daytime high to about -23°C and bring us our first overnight low below -30°C tonight.

January 19, 1500Z (9AM) Wind Chill Prognosis

Attached to this cold arctic air mass will be increasing northwest winds to 20km/h, which will produce bitter wind chill values below -40 overnight Wednesday and through much of Thursday morning. At those values, exposed skin can freeze in 5 to 10 minutes, so be sure to dress warm!

Why don’t wind chill values have a °C attached?

Wind Chill is a value calculated from a complex equation that takes the air temperature, the wind speed, and some empirically calculated values for heat transfer through skin into account. When the calculations are done, the units cancel out, and you’re left with a unit-less number. So while the equation was tweaked to produce numbers that resemble temperatures, they aren’t!

If the current forecast works out, it’s likely that we’ll see a large portion of the Prairies covered with wind chill warnings Thursday morning. Little changes for Friday, so there’s a good chance we’ll see another repeat of exceptionally cold daytime highs and bitter wind chills at night.

Current forecasts show a pretty substantial area of warm air pushing into the Southern Prairies on the weekend, bringing daytime highs up by 10 to 15°C. Combined with the CPC’s new forecast of above normal temperatures returning to Southern Manitoba, it doesn’t seem like this winter spell is long to stay.

Going Into the Deep Freeze

January 16, 2012April 3, 2015 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

January 13, 2012April 3, 2015 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!

A Weather Moment

Author: Brad