Here is where the latest medium-range forecast will be kept, for quick access.

Generally, a medium-range forecast is 5 days – 1 month.

A big cold shot is coming…

(Posted Dec 6)

After Thursday, this week has been quite cold. Temperatures have gone down quite a lot, and snow is here as well. Today when the sun was up, the temperature varied from -17.2 to -15.7. A high of -15.7 is definitely quite abnormally low. Current forecasts suggest this is only the beginning.

Here are the current temperatures, with a bunch of numbers sprayed all over it so you make sense of it:

Those -40s up at the top are a big mass of cold air anchored there. Winds are sweeping this air across the country. The 5s and 10 you see in the bottom left are an area of upper-level ridging. If you take a close look, you can see winds coming out of that area currently extending all the way to the eastern edge of the Rocky Mountains.

As we can see here, we somewhat have a battle of warm and cold: Warm air is trying to move north from the ridge, and cold air is trying to move south from the mass of it in YK/NT/NU. The actual systems that are moving that cold air down are the lows on the very active storm track we currently have. This is expected to be the pattern for the next little while for southern Alberta and BC. Warmer, but when a low moves through, temperatures drop. Thus, an alternation of above and below normal. We, however, are far enough north that the warmth is not the dominant factor. For us, it more of an alternation of mildly below normal and record territory. Yes, record territory.

This brings me to the forecast. The actual large-scale system behind this is pretty boring, basically a continuation of what I just explained in the last paragraph. For the forecast for specifically us, things get quite interesting. To start, here’s Environment Canada:

Like I said, a wave of mildly below normal (Sun/Mon), and record territory (Thu/Fri). Those highs are definitely record territory, but a low of -28 isn’t. Other forecasts have -30s for Wednesday night-Friday night.

Now let’s look at an ensemble model:

This is the Canadian one, GEPS. Ensembles wash things out as they go on, so I’ve drawn arrows for the likely temperature patterns. It has the 25-75 percentile actually getting quite close to -35 Thursday night. Even ensembles amplify temperature events as they near, so we might have a shot at getting it. -35 is definitely record territory.

Operational models also have extreme cold, and the most extreme of them, ECMWF, has us getting within a few degrees of -40. I would say we have good chances at both a minimum low and minimum high records, with temperatures to beat being around -35 and -25.

The very interesting thing about this cold wave is that we will still stay active, and the semi-clippers that we have (semi because they are tracking over us quite slow, then speed up as they exit Alberta) will continue to ring good amounts of snow repeatedly.

One more thing, we have no idea when this cold wave will end. The best thing I can say is that there is about a 90% chance of us still being in it in 10 days.