A Mixed Bag On The Way

Brad Leave a comment

Today will bring warm temperatures along with a bit of light rain or snow as a Pacific system tracks through the Interlake towards Hudson Bay. Temperatures will climb above 0°C today before they gradually cool down by the end of the week to more seasonal values.

Probability of Snowfall >= 2cm

Probability of 12 hour snowfall accumulation exceeding 2cm, valid overnight Wednesday into Thursday morning.

A low pressure system tracking across the extreme Southern Prairies will arc northwards through Southern Manitoba today, lifting northwards through the Interlake region then exiting towards Hudson Bay. This system will intensify as it pushes into Manitoba and precipitation should blossom as it approaches the RRV. Two challenges exist with this system:

  1. When exactly will the precipitation develop/intensify?
  2. How far north with the system be?
  3. What will the phase of the precipitation be, snow or rain?

We’ll likely see some precipitation early this afternoon in the form of snow as the warm front pushes through the RRV. The Western RRV has a risk of some freezing rain if temperatures can stay below 0°C for long enough with this batch of precipitation. Any freezing rain that does develop will be short-lived, though. The snow will likely stop for the short period we’re in the warm sector of this system, but will return by late-afternoon/early evening with some rain or wet snow as the cold front passes through the area. The precipitation will end later in the evening. Snowfall accumulations today should be quite low in the RRV given the warm temperatures, however areas further east in the Whiteshell have a decent chance of getting around 2cm.

Temperatures should reach the 3-4°C range through most areas south of the Trans-Canada Highway today and drop only a little below 0°C overnight.

For Thursday, temperatures will reach close to 0°C as an elongated trough moves across the RRV, bringing with it a slight chance of flurries. It should pass by lunch, after which the NW winds will bring in cooler air and drop the temperature slowly through the afternoon.

The rest of the week will be relatively quiet, with temperatures gradually returning to more seasonal values (daytime highs moving from the low minus single digits to the high minus teens). The next chance for significant weather looks to be early next week.

Since it will likely be quiet on the weekend, I plan on having a bit of a special post on Friday! We’ll look at how warm this winter has actually been, and I’ll be unveiling a great new tool (barring no more problems…) that I’m really excited to let everybody get their hands on!

Much Nicer This Week

Brad Leave a comment

Temperatures this week will be a big improvement over last week. By mid-week we might even take a run at the zero mark.

GEM-GLB Temperatures on Wednesday, January 25, 2012

High temperature forecast for Wednesday, January 25, 2012 – areas south of black line are forecast to be 0°C or warmer

Temperatures through the first few days of the week are expected to be around or above normal (normal high being -13°C). Monday will be around normal, with highs in the mid minus teens in Southern Manitoba. However, Tuesday and Wednesday will be much warmer. Highs on Tuesday will likely break into the minus single digits in most areas, while highs on Wednesday will be near the zero mark. The GEM model is showing high temperatures reaching (or exceeding) the zero mark on Wednesday in much of Southern Manitoba. The GFS model likewise shows highs around zero on Wednesday. After a really warm Wednesday, the last two days of the work-week will be cooler.

The warmer weather is a result of upper-level ridging building into the Western Prairies, which will return our milder, west-to-southwest flow through the upper atmosphere, instead of the cold northwest-to-northerly flow we’ve been influenced by over the past week.

Our next chance for snow will likely come with the same system that will bring us the warm temperatures this week. A frontal boundary will sweep the warm air from Southern Manitoba later on Wednesday and may generate some snow in its wake. If we do see snow under this scenario, amounts will generally be light…but blowing snow could be an issue as the cold front is expected to usher in gusty north-west winds.

NAEFS Long-range Prediction

NAEFS Long-range prediction – January 19 to February 5

In the longer range I don’t see an immediate return to extremely cold weather. On the other hand, don’t expect early January type warmth either. Most indications suggest that we’ll end January with weather that is right around normal. The ensemble model, as shown above, gives a good indication of what type of weather to expect in the longer range. For most of the winter it has done a pretty good job in providing advance warning when major warm-ups or cool-downs are coming. Right now it doesn’t show much of anything, a sign that we’re likely to cruise into February without any highly abnormal weather.

Elsewhere in Weather News

Large Low Hits US Northwest

This past week a major snowstorm took hold of the US northwest, bringing a mixed bag of precipitation across the region. Various parts of Washington State were paralyzed, especially the west coast, by freezing rain initially (Wednesday/Thursday). The freezing rain brought down power lines and left about 200,000 people in the dark. It also wrecked havoc on the roads, forcing the state to shut down a couple major interstates and prompting Governor Gregoire to issue a state of emergency.

Weather Warnings across the northwest US

US Northwest littered with snowfall, freezing rain, and flood warnings. (Source: US National Weather Service)

Following the freezing rain, the storm brought heavy snow where totals topped 15cm in many locations across the Northwest. Here’s a short list of some of the higher snow accumulations throughout the region (Monday-Thursday):

  • 127cm – Mount Hood Meadows, OR
  • 60cm – Covington Mills, CA
  • 18cm – Seattle, WA

Many locations in Oregon and California also received significant rainfall with this low as well as strong wind gusts. A complete storm summary, made available by NCEP is available here.

Moisture arriving along the western coast of the US

Atmospheric river arriving inland on the US Northwest coast. (Source: SPC)

This unusually strong system resulted from a large amount of moisture being drawn with south-west winds from as far south as Hawaii. The so called “atmospheric river” then flows inland, in this case in Northwest US, and subsequently drops large amounts of precipitation.

Tropical Storm Funso Spins Up

Satellite image of tropical storm Funso

Cyclonic storm between Mozambique coast and Madagascar January 22. (Source: Meteosat 7; CIMSS)

A strong tropical storm has spun up on Mozambique’s east coast (African coast) in the last couple days. The storm is located in the Mozambique Channel and is predicted to intensify with the formation of a cyclonic eye. The warm sea surface temperatures (SST’s) and moist air trapped in the channel are contributing largely to the strengthening of the cyclone. It is expected to evolve into a strong cyclonic storm by Monday afternoon after the main center of the storm moves back over water. The main worries with this cyclone are the strong winds associated with it and flooding due to the slow moving nature of the storm. Mozambique’s coast will be affected significantly before the storm gets steered towards the south-west later in the week.

Elsewhere in Weather News has been provided by Matt

The End of The Arctic Deep Freeze

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

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

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.