Thursday, February 21, 2013

Latest thoughts on Freezing Rain Tomorrow

There is no doubt that freezing rain is the nastiest of winter precip.  The picture above was from freezing rain that hit Ohio Feb 1, 2011.  Here is the blog entry from that day.  Our situation for tomorrow morning is similar, but also a little different... So here is the break down.
These are the temperatures from now until Sunday afternoon.  The Y axis is elevation based on pressure, the X axis is time though Sunday.  Later today and tomorrow will be the most interesting.  Just as a reminder, the times are in UTC time.  So 12z is 7AM and 0Z is 7PM.  The issue is the fact that there will be freezing temperatures at the surface and then above freezing temperatures a few thousand feet up.
If we stayed below freezing the entire time then we would stay snow, but the warm air will melt any of the falling snow.  The thin layer of below freezing temperatures at the surface will take the rain and make it freeze on contact of everything.
Not the next step is when will we be seeing precipitation... Even one degree difference in the warm air will mean snow versus freezing rain.  All of these models are based on Columbus, but they apply to most of Southwestern Ohio as well.  The precip will start after midnight and the models agree that it may start as a snow for an hour or so, then the warm air moves in above us.  The snow will transition to freezing rain.  I am still not confident in how much snow this is showing, I think we could be dealing with more freezing rain than snow.
To better show this, I made an overlay.  You can see where the models are showing the below freezing temperatures all the way up and that is where the snow arrives.  Then the warm air a few thousand feet up melts the snow, but it refreezes.  Then once we get into the afternoon it changes to rain because our temperatures at the surface warm up.
 And to wrap it all up, I wanted to show you the last 24 hours of models in comparison.  It is pretty much guaranteed that Ohio will get freezing rain tomorrow.  By noon we should arrive above freezing and hopefully melt a lot of the freezing rain, because the longer it stays on limbs and power lines the worse it will be.

NOW... you are probably asking "What about where I live?"  The atmosphere is water vapor.  So take a cake dish and fill it with water, now put a small amount of cooking oil on top.  Imagine that the oil is the above freezing temperatures.  Slosh the dish around.  The oil moves around and is pretty unpredictable.  The more oil you add, the more predictable it is.  Tomorrow will be similar to that.  The warm air will be slowly moving in from the south so the south will see the snow change to freezing rain first and they will be the first to see the freezing rain transition to rain.  In general it looks like the precip will start about 1-4AM and have switched over to freezing rain by 5-7AM and then finally switch over to rain by 9-11AM.  Keep in mind that even after we warm above freezing it will still take some time to melt the ice.  The good news is that we will will stay much drier and milder for the weekend.  Just make sure to stay safe out there.  Bill Kelly will be in later tonight for an update and Dana Turtle and Lisa Colbert will be tracking the storm tomorrow morning.  It is my day off tomorrow, but would not be surprised to get a phone call to come in. Here is a link to my work Facebook page if you haven't stopped by yet. Have a good one!

Andrew Buck Michael

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