Forecast: Split flow brings mild weather

Covering the period from January 29 to February 5

This graph helps to illustrate the top global weather story of 2019: the warming planet. Since the 1970s, each successive decade has been warmer than the last, with temperature increases of about 0.2 C above each previous decade over the last three decades.

Once again, the weather models have been doing a decent job with the short- to medium-term forecasts. As usual, some of the smaller details are getting missed, but the models are handling the overall pattern quite well.

For most of the last forecast period and the first part of this forecast period we have been in what’s known as a slip flow. This is when the jet stream splits into two paths, one tracking across the southern Arctic and the second cutting through the central U.S. This places us in between these two features, resulting in a rather weak flow across our region. The northern jet stream is keeping the cold air trapped to our north and the southern jet is keeping most of the moisture and storm systems to our south. What we’re left with is a stagnant airflow which, in the winter, will often result in cloudy skies and above-average temperatures, especially at night.

The first few days of this forecast period will see cloudy to partly cloudy skies along with temperatures around -6 C for daytime highs and -12 C for daytime lows. Over the weekend the models show an area of low pressure forming over Alberta and tracking into northern Manitoba by Sunday. This will bring increasing southerly winds along with milder temperatures to both southern and central regions over the weekend. I wouldn’t be surprised to see daytime highs climb above 0 C.

Once the low passes by we will see a push of cooler air as the flow becomes northwesterly. These cooler conditions only look like they will last for a couple of days before another area of low-pressure tracks across the southern Arctic, allowing milder Pacific air to move back into our region by the middle of the week.

Usual temperature range for this period: Highs, -21 to -6 C; lows, -31 to -14 C.

About the author

Co-operator contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.



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