Thursday, March 22, 2007

The Big Melt

An increasing southerly flow this weekend is forecast to spread a very mild airmass across the southern Prairies.. with double digit temperatures spreading over all areas including Southern MB. This will make a significant dent in the snowpack across southern MB over the next few days. Current forecast highs of 14C on Saturday and 17c on Sunday are likely about 5 degrees too warm for areas that are still snow covered such as Winnipeg and the Red River Valley. (Note that these extended forecasts are automated, and have been showing a 5 degree warm bias in warm southerly flows over snow covered terrain) However these higher temperatures are possible in the traditionally warmer downslope areas of southwestern MB from Dauphin to Portage and Morden where snow cover is considerably less, with bare ground becoming more evident in those areas.

Saturday will see southerly winds increasing through the day with highs of 10-14c likely over snowfree areas. Snow covered areas of the Red River valley including Winnipeg will likely be a few degrees cooler, with highs of 6-9c more likely. Saturday night will be quite mild with gusty southerly winds keeping temperatures well above freezing, with overnight lows likely not dropping below +5C. Sunday will be breezy and mild with scattered showers developing by the afternoon or evening, with even a chance for the season's first rumbles of thunder over parts of Southern MB. Highs should be 14-17c over snowfree areas, and about 10-12c for Winnipeg. The combination of sustained melting temperatures, gusty southerly winds, and increasing dewpoints will make for considerable melting of the snowpack this weekend with localized flooding possible, especially if we get some heavier shower or thunderstorm activity late Sunday.

1 comment:

  1. The big melt can't come soon enough for me...We have been plagued by a series of subtle disturbances bringing clouds and wet snow during the daylight hours only to clear during the night time.

    This has dramiticaly limited snowmelt for the past few days with snowdepths at the airport holding steady at 20 cm and 30 cm in more protected areas. Tomorrow looks like a repeat performance with another ill defined system tracking along the international border bringing precip and clouds during the day.

    Depeneding on when it clouds over and how heavy the precip is we could get stuck at zero with wet snow again :-(

    Finally by Saturday we will get into a very warm moist flow that should finish off the generalized snowpack in open country. Looks like a good chance for rain and even elevated type t-storms Sunday as a low approaches from the southwest.