If you were getting used to the temperatures that have been averaging more like late October or early November lately, you may want to prepare yourself for some weather more in keeping with the middle of December as we move into next week.
Is this a major change to the weather pattern? Most likely not and most signs indicate a return of mild conditions by the time the final week of December rolls around.
During the past few write-ups we have indicated that while the winter as a whole looks to be quite mild, there will be a few -- mostly short -- periods when a more wintry scene will overspread the Prairies. It looks like one of those periods is going to be next week.
The seemingly endless flow coming inland from the Pacific Ocean across Western Canada looks like it will weaken and shift southward along the West Coast of the U.S. later this weekend into next week. This will produce a trough through the interior western U.S. northward to the Prairies. This change with the upper air flow should allow a little bit of a ridge through the eastern Gulf of Alaska for a few days that will cut off the flow of mild Pacific air.
High pressure at the surface is expected to develop and expand across central and Western Canada and allow a pretty big drop in temperatures. Some of the colder air that has been in place across far northern Canada may also get involved for a brief time as well. Temperatures should drop back to normal and even a little lower than normal for a few days next week. This will also lead to light to moderate snowfall Monday as the cooling process gets going.
The establishment of a fresh snow cover will only help the air mass cool down more as heat is radiated to space more quickly than with bare ground or old snow cover. We also have the longest nights of the year to help the process along.
Nearly all of the computer tools we use to forecast weather out into the few weeks to a couple of months indicate that this interruption to the very mild weather we have had so far in December will probably be short-lived. The trough across western North America may become history before we reach Christmas and the flow of Pacific air will most likely send temperatures back up to above- if not well-above-normal levels for the final week of December.
As we go into January, we continue to see a higher-than-normal temperature scenario for Western Canada which may again match the chart from Environment Canada from November. Above-normal temperatures are expected for a large portion of southern Canada with some areas of not so mild readings for possibly British Columbia and through northeastern Canada.
As we are likely to see, next week a couple of short-lived periods of colder weather can and probably will show up along the way, but on average nearly all indications point toward a very mild winter for the Prairies. If by chance any high latitude blocking were to take place, we could see some major changes to this forecast, but to date there continue to be no signs of blocking.
Doug Webster can be reached at firstname.lastname@example.org
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