Updraft: April 13, 2011 Archive

Putting the pieces together

Posted at 6:52 AM on April 13, 2011 by Craig Edwards
Filed under: Winter/spring 2011

Yes indeed, a cold front sliced through central MInnesota overnight. Temperatures will be some fifteen degrees cooler today in many locations. A narrow band of showers is creeping south through the southern third of the state, including the Metro area this morning.

Now we are working to put the puzzle pieces together for the much talked about weather system for Friday and Saturday.

Heres in the output of the NAM model for accumulated liquid precipitation for Friday ending at 7pm. The shaded yelllow is greater than a half inch of moisture.

Spring storms are a tough animal to deal with. Precipitation starting as snow in the middle layers of the atmosphere can change to liquid as it descends to ground level, sometimes in the last few hundred feet overhead. Then there is melting of the snow on the relatively mild ground. Throw in the filtered sunlight of mid April and it is a challenge to predict accumulations.

Here's the best guess at this time from NOAA's Environmental Prediction Center for snow to accumulate greater than four inches on Friday and Friday night.

One more piece you'd like to believe fits the center of the puzzle! Here's a critical layer where snow can sustain itself aloft at about five thousand feet. The blue region, banded over central Minnesota, is zero degrees Celsius; a zone that is favorable for snow production. Seasonally adjusted it would most likely be a mixture of cold rain and wet snow.

Let's get adjusted to today's return to seasonal temperatures. we'll have more on this weather-maker later today.

CE
naturesmessenger.com

Nothing simple about forecasting April snow

Posted at 4:25 PM on April 13, 2011 by Craig Edwards
Filed under: Winter/spring 2011

After crunching the model output with as much energy as I could muster, I can't come up with any conclusion much better than the one from the experts at NOAA's Environmental Prediction Center.

This weather-maker is a work in progress and doesn't fit the text book guidelines for synoptic winter storms. It really shouldn't since we are well into April. Moisture will fall in the Dakotas, Minnesota and Wisconsin from Friday through early Saturday. Snow falling during the cover of darkness in the eastern Dakotas has the best chance to accumulate four or more inches on Friday evening and night.

Here's the region outlined as the most probably area to accumulate four inches or more ending early Saturday.

That would translate to a cold rain, wet snow mix in portions of central Minnesota on Friday night with some accumulation possible by early Saturday morning. At this time it doesn't appear that there will be much accumulation about the Twin Cities region, but we reserve the opportunity to revise that by Thursday afternoon.

Here's how the accumulating snow probabilities pan out for more than four inches from late Friday night through Saturday, as the system churns eastward.

The models consensus track for the low pressue system is not ideally situated for a classic winter storm in Minnesota. But, again we are past winter.

Track the wintry weather potential on the Aberdeen NWS link.

Very dry air at low levels of the atmosphere in northeast and east central Minnesota may delay the onset of precipitation on Friday.

Bonus sunshine in the Twin Cities today helped to boost the temperatures into the lower 60s. Meanwhile a steady light rain fell in portions of the MInnesota River Valley around the New Ulm area.

CE
naturesmessenger.com