Tuesday, March 06, 2007

+7C on Thursday? Don't count on it...

I see exceptionally mild temperatures are still forecast for Thursday, with a forecast high of +7C (up from +4C yesterday) While milder temperatures are likely for Thursday, highs of +7C are overly optimistic given that there's still 30 to 60 cm of snow on the ground throughout Southern MB and SK, and northern ND which will cool any warm sector crossing Southern MB. Looking at Thursday, the setup for an exceptionally warm day is unimpressive. A low pressure trough is forecast to lie across the MB/SK border by late Thursday, putting southern MB in a southerly flow. Southerly flows are not conducive to rapid warming in the Red River valley, especially with extensive snow cover. The best setup for warm wintertime temperatures in Winnipeg is with a westerly flow tapping milder air from southern SK and southern AB. This is not likely on Thursday. As a result, temperatures on Thursday in Winnipeg will likely only struggle up to the freezing mark, or maybe +1 or +2C at best. (Note that Accuweather and Weather Network are forecasting highs on Thursday of zero and +2C respectively. Even Grand Forks is calling for highs only around zero) I suppose with sunshine and light winds, it may FEEL like +7C, but the actual air temperature will be several degrees colder. So don't be surprised to see that forecast high of +7c drop significantly over the next day or so. (recall that for February 18th, the forecast high of +4C in the long range forecast was eventually scaled back to a high of -7C!)
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3 comments:

  1. Anonymous11:57 AM, March 06, 2007

    With the huge snowpack that exsists all the way down to Southern Iowa, a SSE fetch on Thursday is not likely to bring temps so far above zero. If this was happening 2 weeks ago when there was little snow in the north central US the forecast would have a better chance of verifying. Having said that..areas in the lee of the Manitoba/Pembina esccarpment always tap into warm air aloft and their winds veer west more easily.

    Friday and Saturday look to be slightly warmer with a west-WNW flow. Unfortunately we will not see a strong southwest flow from snow free areas in Southwestern North Dakota. Temps there will easy reach 15 C ... lucky them!

    Dan

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  2. rob1:06 PM, March 06, 2007

    The record high for Winnipeg today is 16.5C back in 2000.. but back then, we lost our snow cover by the end of February! Just goes to show you how mild it can get here in early March if we didn't have snow cover!

    But that snowcover is pretty deep this year, and extensive. Unless we get a prolonged warm spell this month, it'll likely be early to mid April before this snowpack is gone..

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  3. rob9:04 AM, March 07, 2007

    As expected, EC dramatically lowered the high for Thursday, now saying -2C , a drop of 10 degrees from yesterday's forecast high! Note that temperatures will likely rise above freezing Thursday evening as winds shift into the west and tap milder air from southern SK and southern AB. Temperatures from Friday through the weekend should remain mild over southern MB with highs of +2 to +5C.

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