Thursday, May 31, 2007

Weekend forecast flips

Quite the change in the Winnipeg area forecast for the upcoming weekend.. Yesterday, the forecast was calling for straight rain Saturday through Sunday. Today's forecast now calls for nothing but sunshine all weekend! Why the major flip? The short answer is that there was a significant change in EC's computer model solution for the upcoming weekend over southern MB. Yesterday's solution had a slow moving upper low hanging around the Dakotas all weekend long, putting Southern MB in a moist unsettled cyclonic flow with rain through the period. Today's model solution now is pushing that upper low further south and east into Minnesota over the weekend, taking the wet weather with it and leaving southern MB with a sunny dry forecast now. Remember, forecasts for the Prairies beyond tomorrow are no longer produced locally in Winnipeg, but are automatically generated from model output from Montreal. That's why long range forecasts can swing wildly from day to day, depending on how stable the model solution is for a particular period.

So, as far as this weekend is concerned, which solution do you believe, rain or sun? Well, probably neither solution is completely right.. and the best guess is probably something in between the two. Looking at the pattern, it looks like we'll still be seeing a lot of cloud on Saturday along with a chance of showers as the remnants of that upper low over the Dakotas starts moving out. Sunday looks like the nicer day with a better chance of sunshine and warmer temperatures as the upper low finally pulls away. As always though, only Mother Nature knows for sure...

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