Two weather regimes have been covering the Prairies during April thus far with winter very much in control for the eastern half of the Prairies while the west has seen very mild weather, sometimes reaching record high temperature levels. It appears that the pattern of two seasons will continue on average for another week or so.
The snow cover chart from Environment Canada shows an interesting pattern with snow cover still in place across the northeast half of the Prairies while the southwest half has bare ground. Of interest is the dotted line which is the climatological normal location for the southern extent of snow cover at this time and how close it is to what is being observed.
It just so happens that the snow cover line is also quite close to where weather shifts from cold to warm with the snow-covered eastern Prairies quite cold, while warmth covers the bare ground regions. This pattern is being produced by an upper level jet stream pattern where a strong ridge lies along the west coast of Canada and an unseasonably strong trough covers central and eastern Canada.
Winter was on vacation for most of the winter across central and eastern Canada but recently has made a strong resurgence with unseasonable cold and some snow as well. A blocking upper level high developing across Greenland is bringing about a weather pattern familiar to us from a couple of the previous cold winters.
It does not appear that this weather regime will have lasting power but may remain with us into the middle of April before weakening or possibly even going away completely. High latitude blocking is a difficult event to forecast from both the development stage to how long it will last. We also have to consider that El Nino remains in place and is still a formidable event, though not as strong as it was a few months ago.
The El Nino is likely having influence on the intensity of the warmth across the west where temperatures more like in May or early June have popped up at times. We should expect to see more of the February weather east and May weather west during the next week as the West Coast Canadian ridge holds fast and the strong trough through eastern Canada sends polar and arctic air southward into Manitoba, possibly making brief visits into Saskatchewan at times, too.
It is not out of the question that Alberta sees cold air back door into the province Sunday or Monday, sending temperatures tumbling before sky-rocketing again by Tuesday or Wednesday of next week.
A clipper low pressure area crossing from northwest to southeast cutting the Prairies in half during the weekend may supply a moderate snowfall to areas that already have snow cover, while little or no precipitation falls where snow cover is gone. With the current pattern in place we generally will not see deep Pacific moisture able to reach a large portion of the Prairies keeping the threat of drier soil moisture conditions in place as we move closer to the seeding season.
Western areas are likely to be more prone to increasing dryness during the next week or two while eastern parts of the Prairies may be able to rely on the melting snow cover as well as a couple of clipper low pressure areas to provide better soil moisture by the time May rolls around.
Doug Webster can be reached at email@example.com
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