After all the panic, no snow fell in DeKalb. Tuesday saw a rather nasty day of mist to light rain conditions. According to the National Weather Service out of Romeoville, Illinois (the Chicago office), there was some pea-sized hail in the region.
Throughout the day Tuesday, I mostly walked in light rain. On my way back from my morning class, I did see some snow-like precipitation, but very little. I saw a few small flakes (probably about 5-10 in total), and a little frozen precip, but for the most part it was rain.
Conditions are currently sunny and warming. Currently it is 59 degrees, and temperatures in the low 80's could be seen Friday and Saturday. I am getting this straight from the National Weather Service today, as I am a little time crunched. However, we will be entering a 500 mb ridge, which should keep our weather nice. I'd better wrap this up, because I still have a lot to do before the end of the week. I'll get another post up as soon as I can.
Wednesday, April 22, 2009
Monday, April 20, 2009
S-S-S-Snow!!!! In Late April?!
This seems to be a fairly popular topic in DeKalb lately. There is a fair chance of seeing some late April snow. This has left some people panicking, however, it seems to really be nothing.
As always, let's get ready to do some map analysis! Current 500 mb maps show an upper level low parked on top of DeKalb. This is sitting in a pretty nice trough. A look at the surface map shows a low pressure located in northern Michigan. Now it is time to look at more features. At 850 mb, We can see a freezing line in central Illinois. This level is around 1250-1500 meters above the surface. If we were to look at another upper air tool, called a sounding, we can look at temperatures in a vertical profile. I am going to use the Davenport, Iowa sounding from 0000Z, which is the evening sounding.
I have added a thick blue horizontal line to indicate the freezing line. The vertical red line indicates temperature with height, and the vertical green line indicates dew point with height. Where they are close, the atmosphere is moist. This is a pretty moist profile, extending up to about 600 mb. So, most of the moisture is above the freezing line in this profile, indicating that if precipitation falls, it will fall frozen. Below the freezing line, it will more than likely melt.
So, what is going to cause the snow? It appears that the low in Michigan will be the problem. Motion around a low is counterclockwise. So, the precipitation forming around a mid-latitude cyclone will follow this motion. Areas north of the warm front are cooler, in this case cool enough for snow. The snow will follow the motion around the low, driving the snow and cool temperatures towards DeKalb.
As for accumulation, I don't think we will see any. Forecast soundings indicate that surface temperatures will not reach freezing. Both the GFS and NAM models are in fair agreeement that the nighttime lows will be around 36 degrees into Tuesday morning. Tuesday highs should be around 46, with Tuesday night/Wednesday morning lows being around 36 again. There is about a 70-80% chance of precipitation. We will also be having northerly , turning into westerly, surface winds around 15-20 miles per hour Tuesday, which will keep the air feeling cooler. With highs expected in the 40's, I would expect to see some rain as well.
To sum it all up, yes we may see snow in DeKalb. However, it will proabably have rain mixing in as the day progresses, and we probably won't have an accumulation. If we do end up with accumulation, it will be minimal, and probably won't last long.
As always, let's get ready to do some map analysis! Current 500 mb maps show an upper level low parked on top of DeKalb. This is sitting in a pretty nice trough. A look at the surface map shows a low pressure located in northern Michigan. Now it is time to look at more features. At 850 mb, We can see a freezing line in central Illinois. This level is around 1250-1500 meters above the surface. If we were to look at another upper air tool, called a sounding, we can look at temperatures in a vertical profile. I am going to use the Davenport, Iowa sounding from 0000Z, which is the evening sounding.
I have added a thick blue horizontal line to indicate the freezing line. The vertical red line indicates temperature with height, and the vertical green line indicates dew point with height. Where they are close, the atmosphere is moist. This is a pretty moist profile, extending up to about 600 mb. So, most of the moisture is above the freezing line in this profile, indicating that if precipitation falls, it will fall frozen. Below the freezing line, it will more than likely melt.So, what is going to cause the snow? It appears that the low in Michigan will be the problem. Motion around a low is counterclockwise. So, the precipitation forming around a mid-latitude cyclone will follow this motion. Areas north of the warm front are cooler, in this case cool enough for snow. The snow will follow the motion around the low, driving the snow and cool temperatures towards DeKalb.
As for accumulation, I don't think we will see any. Forecast soundings indicate that surface temperatures will not reach freezing. Both the GFS and NAM models are in fair agreeement that the nighttime lows will be around 36 degrees into Tuesday morning. Tuesday highs should be around 46, with Tuesday night/Wednesday morning lows being around 36 again. There is about a 70-80% chance of precipitation. We will also be having northerly , turning into westerly, surface winds around 15-20 miles per hour Tuesday, which will keep the air feeling cooler. With highs expected in the 40's, I would expect to see some rain as well.
To sum it all up, yes we may see snow in DeKalb. However, it will proabably have rain mixing in as the day progresses, and we probably won't have an accumulation. If we do end up with accumulation, it will be minimal, and probably won't last long.
Sunday, April 19, 2009
Update
I know I have not posted in a while (almost a month). School has really kept me busy these past couple of weeks, and the next two to three weeks look pretty full, especially with the semester ending. It may be a little while more before I can post a forecast. I really want to do another forecast discussion, but time is not on my side right now. With any luck, a time slot may open for a forecast discussion. Thanks for the patience.
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