Thursday, December 04, 2014

Major warm-up expected across Prairies, much of North America next week..

6-10 day outlook valid Dec 10-14
showing massive warmup over
central North America (CPC)
For those already tired of the mid winter-like cold that has gripped southern MB and the Prairies much of the past 3 weeks, some good news is on the way. A major shift in the weather pattern next week is expected to bring a prolonged period of above normal temperatures across much of the southern Prairies and central North America through next week. We'll get a taste of the milder weather on Sunday as a weather system tracks across southern Manitoba bringing a southerly flow of milder air across the south, with temperatures likely climbing towards the freezing mark in Winnipeg and slightly above freezing over parts of western MB. We'll get into some briefly colder air on Monday behind this system, but the colder weather will be short lived as a massive influx of Pacific air spreads over the Prairies beginning Tuesday. This flow of warmer Pacific air will overspread southern Manitoba by mid to late week, sending temperatures in Winnipeg and the RRV above freezing from at least Thursday into Saturday. In fact, some downslope areas from Dauphin through McCreary to Portage La Prairie, Morden and Winkler may see temperatures of +7-10C by Friday.  That will result in considerable melting of the meager snowpack across southern Manitoba.. with areas of  bare ground likely re-appearing by the end of the week in parts of the RRV and SW Manitoba. So put away the block heater cords for awhile and stock up on the washer fluid.. warmer weather is on the way!

Friday, November 28, 2014

5-10 cm of snow on the way for Winnipeg

24 hr precip amounts in mm to noon Saturday
(add 50% for snowfall amounts in cm) 
Get those shovels ready.. snow is on the way across much of southern Manitoba today into tonight as a storm system over Montana tracks into the Dakotas. Snow from this system has spread into western Manitoba this morning and will continue to spread eastward into Winnipeg and the Red River valley this afternoon. Snow will pick up in intensity by the afternoon rush hour, with 2 cm possible by evening. Snow will continue tonight into Saturday morning with another 5 cm possible in Winnipeg by the time it tapers off by midday Saturday. In total, about 5-10 cm of snow is possible across Winnipeg and the northern RRV, with less to the south of Winnipeg and more to the north. Heaviest snowfall for this system is expected over western MB Parklands and central Interlake regions (Riding Mtns, Dauphin, Arborg, Ashern, etc) where 15-20 cm is forecast by Saturday. In behind this system, winds will shift into the northwest Saturday tapping cold Arctic air once again, with temperatures falling from morning values of -10C towards -20C by Saturday evening. Cold but dry weather is on tap for Sunday and Monday with a moderating trend the rest of the week as the arctic airmass relaxes its grip over southern MB.  

Tuesday, November 25, 2014

Ready or not.. here comes some mid winter cold..

NAM model showing surface temperatures (F)
Wed morning. Arctic high building in from Saskatchewan
will bring in mid winter cold over southern MB  
Uggh. Not the news we want to hear, but the coldest weather of the season will be moving into southern MB over the next couple of days as a mass of Arctic air over the north spills southward. This airmass will be ushered in by a large Arctic ridge of high pressure over northern Saskatchewan that will build southward into southern Manitoba overnight into Wednesday bringing temperatures more typical of mid January than late November.

For tonight, a weak clipper system that has been bringing some light snow across southern MB today will exit the province, with gradually clearing skies tonight from the north. This will allow temperatures to drop well into the minus 20s by Wednesday morning, with some spots in the northern Interlake likely hitting the -30C mark (Moosehorn, Grand Rapids, Berens River, Swan River, etc)  In Winnipeg, temperatures are forecast to drop to -26C overnight with light northwest winds creating wind chills near -35 for the morning commute. Temperatures will recover only to around -18C Wednesday under sunny skies, some 13C below normal for late November. Wednesday night into early Thursday will be downright frigid in Winnipeg and the RRV as the core of Arctic ridge crosses the region. That will allow temperatures to plummet towards the -30C mark even in Winnipeg Wednesday night into early Thursday morning.. so make sure you have those block heater cords ready and working! (For the record, the earliest that Winnipeg has hit -30C or lower was on November 19th in 1896 with a reading of -33.9C. Record low for Thursday (Nov 27th) in Winnipeg is -36.1C in 1891, and more recently in Nov 1985, the airport had 5 days of -30C or lower over the last week of November. So believe it or not, it has been worse at this time of year)

A slight moderation is expected by Friday as the next clipper system moves in with some light snow, and high temperatures near minus 10C. Unfortunately, it looks like we're back into the deep freeze over the weekend into early next week behind the clipper system. There are some signs that the abnormally cold pattern will relax a bit by the middle to end of next week, but we'll have to see if those moderating signs continue over the next few days. Until then, bundle up and get prepared for some mid winter cold.. in November!

Friday, November 21, 2014

Mild weekend ahead.. but turning snowy and colder Sunday night. Tricky Monday morning commute likely..

After 2 weeks of well below normal temperatures, southern MB will be getting a brief break this weekend with some milder temperatures as a couple of weather systems track across the central Prairies drawing milder air across the south.  Southwest winds ahead of the first system today have pushed temperatures well above freezing over snow-free SW Manitoba with Brandon up to +7C this afternoon and +9C in Pierson. A brisk southerly wind over the snow covered Red River valley was keeping temperatures slightly colder in Winnipeg at -2C this afternoon.  For Saturday, a weak ridge of high pressure will cross southern MB giving dry weather and light winds, with temperatures above freezing. By Sunday, a storm system will track across southern MB bringing snow through the Interlake and western MB parklands with 10-15 cm possible by Sunday night. As this system tracks east of the RRV later Sunday, winds will shift into the north and draw colder air into Winnipeg and the Red River valley with snow developing. Snow will continue Sunday night into early Monday along with gusty north winds producing local blowing and drifting snow. It's possible we may see 5-10 cm of snow by the Monday morning commute in Winnipeg although there is still considerable uncertainty on snowfall amounts at this point. Regardless, residents should plan for a slow commute to work or school Monday morning due to sharply colder temperatures, gusty north winds giving local blowing and drifting snow, and slippery road conditions.

Friday, November 14, 2014

Manitoba lakes freezing up quickly

MODIS satellite image of MB lakes
Saturday Nov 8 2014
MODIS satellite image of MB lakes
Thursday Nov 13 2014

Well below freezing temperatures over the past week has brought the first snows of the season over much of southern MB as well as a rapid freeze up of the Manitoba lakes. The two "false colour" MODIS satellite images above were taken just five days apart between Nov 8th (left) and Nov 13th (right)  The images show a much different landscape over southern MB over that time with more extensive snow cover (shown in light blue) and a rapid freeze up of the western MB lakes, with Lake Manitoba and Lake Winnipegosis now mainly ice covered. Lake Winnipeg still remains generally ice free except along the shores and some bays.. which is allowing lake effect cloud and flurries to persist as cold winds blow over the open water (open water seen as dark blue on satellite imagery with clouds seen in white)  In fact, you can see the bands of heavier lake effect snow over the past day or two immediately south of Lake Winnipeg and Lake Manitoba, with less snow cover elsewhere over southern MB (bare land shows up as light brown) 

With a continuation of well below freezing weather over the next 5 to 10 days, ice cover will continue to grow rapidly on the lakes, with Lake Winnipeg likely freezing up by the middle to end of next week. This will effectively shut off the lake effect machine for the season, and will also allow invasions of cold air to spread into southern Manitoba unmoderated by the lakes. Like it or not, winter is here folks!