Environment Canada Dates Changes to Warning Program

Environment Canada released a notice today that dates some significant changes to the weather warning program in Canada. The notice touches on several key areas, however the most noticeable will be the changes to watch/warning types:








Several warnings are being downgraded to “advisory” status: blowing snow warnings, freezing drizzle warnings and frost warnings. It’s unclear whether these advisories will be handled through a Special Weather Statement (SWS) or if a new bulletin type will be started. I’m guessing they’ll be addressed as a SWS which could be problematic since SWS visibility has always been a bit of an issue. I can’t complain too much about the changes, although I feel that the blowing snow warning is being mishandled.

In 2012, Environment Canada tightened up the requirements for blizzards[1] to the point where warning-eligible events rarely ever happen on the Prairies. As a seeming acknowledgement of this fact, the blowing snow warning was introduced with slightly more lax requirements[2]. The blowing snow warning has been used substantially in Southern Manitoba where ground blizzards – blizzards that occur with no falling snow – are relatively frequent through the winter months. They generally don’t qualify for blizzard warnings because they are too short-lived or difficult to verify – especially since no weather sites along/south of the Trans-Canada Highway other than Winnipeg, Portage la Prairie and Brandon have visibility sensors.

These events can be quite significant and end up closing major highways. The idea that they’ll be regulated to a special weather statement seems disingenuous to their potential impact. Granted, this is mostly speculation at this point, so it will be interesting to see how they decide to handle advisories going forward[3].

Regarding Extreme Cold Warnings replacing wind chill warnings, I recently wrote a lengthy post that addresses this change and explores, in depth, the problems with wind chill and wind chill warnings.

The Extreme Heat Warning looks like an attempt to unify the way extreme heat is handled across the country. Currently some regions do humidex advisories (we use those here in the Prairies), some use high heat and humidity warnings, some use humidex and health advisories and some use extreme heat-wave advisories. The unification into a single banner for hot, humid weather seems like smart housekeeping.

Lastly, Fog Advisories and Weather Advisories will be added to the repertoire. Fog advisories will be great since there’s currently no official way to highlight significant fog events that can have dramatic impacts on transportation. I’m not entirely sure what a “weather advisory” will be, and as such I imagine we won’t see it much.

One of the other small changes which will likely be most obvious in severe thunderstorm warnings will be the inclusion of certainty of predicted severe weather hazards. This means that in a warning they could tell you that 2” of rain is certain, nickel-sized hail is likely and that there’s a slight chance of a tornado; or they could say that a tornado is certain and there’s a slight chance for dime-sized hail. This is a great step forwards into beginning to convey context in the weather forecast.

All of these changes will be implemented on April 8, 2014.

  1. Changed the required visibility from 1/2SM or less to 1/4SM or less. The requirements of sustained winds ≥ 40km/h and a duration of 6hr. or longer remained unchanged.  ↩
  2. A blowing snow warning requires visibilities of 1/2SM or lower (as opposed to 1/4SM for a blizzard), winds ≥ 30km/h (as opposed to 40km/h for a blizzard) for at least 3 consecutive hours (as opposed to 6 for a blizzard).  ↩
  3. From a developer standpoint, there’s no easy way to even check to see if a special weather statement is in effect for a site. It would be nice if Environment Canada included them in the same feeds for watches and warnings.  ↩

Snow For Much of Southern Manitoba Today Into Tomorrow

A system moving through the Northern Plains of the United States will push snow northward across the international border into much of Southern Manitoba, with warning-level amounts in some areas close to the International Border.

Heavy snowfall occurring in Montana is pushing east-northeastward into southeastern Saskatchewan and Southern Manitoba. Heavy snow giving near zero visibilities at times is expected to develop in southern regions near the international border, including the Melita, Pilot Mound, Morden/Winkler, and Emerson regions. Environment Canada has issued Snowfall warnings for the Melita and Pilot Mound/Kilarney regions, with 10cm of snow expected in areas close to the border, and the potential for amounts in excess of 15cm in upslope snowfall areas of Pilot Mound. All sorts of warnings exist for most of North Dakota, so anybody who has to travel south today should take extra precautions and prepare for extremely poor driving conditions.

For Winnipeg, the snow will push into the city mid-to-late afternoon and stick around for 18-24 hours. Thoughts based of previous model runs would have been for just some light non-accumulating snow, even taking into account that all models were keeping this system too far south. The new GEM-REG run has, however, pushed the system (in my opinion, correctly) further North and is bringing more substantial snow into the Winnipeg area.

GEM-REG 24H Cumulative Precipitation valid 12Z Tuesday 21 Dec. The heavier snow expected along the International Border and through North Dakota is the dark-ish green shading, indicating 7-10mm of liquid equivalent precipitation. This covers Monday morning to Tuesday Morning.

While we won’t deal with the extremely poor traveling conditions of our neighbours to the south, we will see accumulations of 2-4cm when all is said and done. South of the city, amounts of 5-10cm should pile up. The bulk of the precipitation will pull out of the province overnight, however there will be a weak trough that hangs back through the RRV and southeastern Manitoba that will continue to produce light snow through much of the day tomorrow.

GEM-REG 24H Cumulative Precipitation valid 00Z Wednesday 22 Dec. This shows the precipitation expected to occur Monday evening through Tuesday evening. Light snow, without significant accumulation, is expected to occur through much of southern Manitoba through the day on Tuesday.

After this system, we should have a fairly pleasant rest of the week, with highs just above or near -10C and lows in the low minus teens.

Another small point of significance to this event is that it may be one of Winnipeg’s last chance to break the record for wettest year ever. The current record is 723.6mm from 1962. We currently sit in 3rd wettest year ever at 716.0mm, with second place only a hair ahead of us at 718.4mm (which was from 1953). We need only another 7.7mm to break the record, and this system, in a worst case scenario could give us something in the 4-6mm range.

Worth noting, is that in many of the wettest years ever, a major flood did not occur in the following spring; just shows how the melt rate and spring precipitation are the most crucial aspects in our annual floods.