Wednesday, November 23, 2011

Week from now...snow?

The models have been hinting at a trough of cold air swinging through for the start of December. Now that that time frame is within shooting range it seems to be holding consistent from model to model, for the most part. The last couple rounds of models are showing a low pressure system getting lost from the flow of the jet stream and sitting over us early next week. This will allow cool temperatures and extended periods of rain for early next week and when a secondary cold blast of air arrives for the middle of next will pull the colder air into the area a little stronger. Soooo, what does this all mean. The image attached shows three important factors in our snow chances for next week. You may notice the blue and red lines. These are the temperatures just a short way above the surface of the earth. You can see the freezing line of 0 degrees Celsius hugging the plains and the Midwest. The -10 degree line taps into parts of Minnesota, Wisconsin, and the U.P. of that state up north. So the cold air will be in place. On to the black lines: these are the lines of pressure. The low pressure system that will begin lifting north by next Wednesday (according to the timing of today's model) will be a fairly strong system with a pressure of around 995 mb. The last and most important ingredient for us seeing snow...moisture. We are on the the third tier of amount of precipitation for the 12 hour window the model predicts. It appears there is plenty of moisture also higher in the atmosphere with cold air as well.

So here is what we are looking at for the forecast. The rain and clouds are on their way out of here. We will be dry all the way until Sunday. Today we will only get into the low 50's, but still on track to get into the mid 50's for Thanksgiving, tomorrow. Highs near 60 for Friday and Saturday before the big change in weather. The low pressure system will swing in on Sunday and put its brakes on and just sit around the Midwest for Monday. This will bring scattered showers for Sunday and Monday with highs in the upper 40's. The second cold blast of air is what we really need to time out to pinpoint our chance for snow. Right now it appears that the blast of cold air will arrive late Tuesday so we may see a few flakes of snow mixing with rain later Tuesday. If the cold air arrives at the predicted time we could see a switch over to mostly snow heading into Wednesday morning. Timing will be the deciding factor into when and where all of this happens so we still have a week to see what pans out. Remember, forecasting winter storms this far out is a lot like bowling down a lane that is about three times the normal length. It is especially difficult to forecast the first few systems...they typically pull north and we warm up at the last second, but with the Low already sitting over us a few days this is a little different. I will keep an eye on the situation and as always...keep ya posted because I have a feeling there will be changes by next week.

Andrew Buck Michael

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