Monday, February 18, 2008

Freezing Rain Wednesday?

The models are starting to flip-flop a little . Yesterday, GFS starting shifting to this idea and I'm starting to buy into it. The above image is the overview window of BUFKIT. It's a program we use to analize model data. Simply put, red is not good. Red stands for freezing rain and/or sleet.

This is simple way to determine precipitation types, but you can also look at a forecast sounding of the GFS to check the precipitation type. Below is the forecast sounding for 3:00 pm Wednesday afternoon. That's when this mess may start. A sounding is like a vertical slice of the atmosphere. The red line is the temperature and the green line is the dewpoint. Both change as you go UP in the atmosphere, as seen in the mage. I have highlighted the freezing line. Everything to the left of the blue line is freezing.

If you notice, there is an area that is above freezing between 3900' and 7800'. Snowflakes that form above will melt in this area as they fall. The melted snowflakes (raindrops now) continue to fall and will go back into an area below freezing. One of two things can happen now... Either they will refreeze into sleet pellets OR they will freeze when they hit the ground as freezing rain. In either case, it's not good.

On last note, using the Cobb Algorithm also shows the precipitation as some type of snow or ice pellet and freezing rain..... The below numbers are mostly self-explanatory... As you'll notice, this is not being reflected in our current forecast, because we like to build some confidence in the forecast change. I will likely start talking more about it tonight... Stay tuned.


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