Last week’s forecast got the big weather picture not too badly, but it was off on the timing. The cold air took a little longer than forecast to move in and ended up being a little colder than expected. As often is the case, when the general movement of weather systems slows down, we often see either warm or cold air stick around for longer than expected.
This is how this forecast period is going to start off — with cold air sticking around for longer than we really want. The weather models show a large area of low pressure developing over Hudson Bay, which will help to “open the door” — allowing a series of arctic highs to build southward. The first of these highs built in late last weekend and into the early part of this week, bringing with it the coldest air so far this winter. By Wednesday, a second reinforcing area of arctic high pressure will build in to replace the first high that will be sliding off to our southeast. This second high will keep our skies clear and will continue to keep our temperatures on the cold side. Expect daytime highs to only reach about -16 C, with overnight lows dropping to around -25 C.
This second arctic high will begin sliding off to the east on Friday, which will allow our temperatures to begin to warm back up toward more seasonal values of around -10 C in the day and -20 C at night. Over the weekend and into the early part of next week, the weather models show an area of low pressure moving in off of the Pacific and through southern B.C. This low is forecast to track eastward across the southern Prairies and strengthen slightly as it moves into Manitoba. Confidence in this system is not that high, but there is a chance to see some measurable snow as it tracks through.
Behind this system we will see a weak area of arctic high pressure build in, bringing a return to sunny skies and temperatures right around average for mid-December.
Usual temperature range for this period: Highs, -18 to -2 C; lows, -28 to -11 C.