Sunday, February 7, 2010

11:00am Weather Update: Tricky Forecast

Just as the title says, this is going to be a tricky forecast. I am referring to the upcoming winter storm.

Models are not in agreement for a lot of ingredients with the storm. I am feeling pretty confident with the timing of the storm. I think it will begin to impact the KFVS viewing area starting Monday afternoon. The storm will then spread east/northeast paralleling the Ohio River. The storm should be out of the area by Tuesday late-morning.

I posed a few questions yesterday morning that needed to be answered so we can forecast the storm.

  1. Track of the storm?
    Answer: There is not complete agreement as to the track of the storm in all of the models. The majority of the models seem to be shifting the storm a little further south. This means we should be able to draw in plenty of cold air. In fact, if this holds true, snow will be an issue further south than originally thought. This means there could be an accumulating snow from northeast Arkansas through the Missouri bootheel in to western Kentucky.

    There is one outlier. The NAM keeps the storm on more of a northerly track. If this were to pan out we would see more rain and the rain could slide further north.
  2. Temperature profile in the atmosphere?
    Answer: For the northern half of the KFVS viewing area (southeast Missouri, southern Illinois, western Kentucky, and northwest) all precipitation should fall as snow. The southern half is a little more tricky because of the answer to question 1. If the storm tracks further south then snow would be a problem for southern counties.
  3. Will dry air be in place?
    Answer: It will be dry but not as dry as the storm from two weeks ago. As of 11:00am CT, dew points are in the upper teens to lower 20's. Winds will be out of the northeast/east today. That means we will draw in air from southern Indiana and central Kentucky. Their dew points are in the upper teens. So there will be some dry air to overcome initially, but it should "eat" our snow like it did last time.
Now for the big question. How much? Extremely tricky especially since the models continue to flop back and forth as to how much liquid there will be to work with. For example, last night's 0z run of the NAM model put down around 0.6" of liquid for Cape Girardeau. This morning's run is showing 0.25". Potentially, that is a huge difference. That is the difference between at a minimum 4" of snow.

Here is what this morning's NAM run is showing for snow accumulation.


To contrast the above numbers with the NAM I decided to take a look at a couple of other models that most don't look at. The Canadian weather agency's model and the United Kingdom's model.

0z Canadian run:
Liquid:
  • Cape Girardeau: 0.59"
  • Farmington: 0.51"
  • Harrisburg: 0.43"
Snow:
  • Cape Girardeau: 5.9"
  • Farmington: 5.5"
  • Harrisburg: 4.2"
12z Canadian Run:
Liquid:
  • Cape Girardeau: 0.55"
  • Farmington: 0.59"
  • Harrisburg: 0.39"
Snow:
  • Cape Girardeau: 5.3"
  • Farmington: 5.9"
  • Harrisburg: 3.5"
0z UKMET Run:
Liquid:
  • Cape Girardeau: 0.11"
  • Farmington: 0.17"
  • Harrisburg: 0.08"
Snow:
  • Cape Girardeau: 1.2"
  • Farmington: 3.1"
  • Harrisbug: 0.8"
This gives you an idea as to how models are all over the place right now. So confidence in any given amount is not very great at this time. It still appears to me that a 4"-8" snow is possible. Where exactly? Still too tough to call. It will depend on where the rain/snow line sets up. The heaviest snow should occur just to the north of the rain/snow line.

Here is a look at what the forecasters with the Hydrometeorological Prediction Center are thinking. This is a probabilities forecast.


I will try to update later today, but to be honest my attention is going to be on the Super Bowl airing on KFVS12. In case you haven't been following my blog, I am originally from Indiana and I am a HUGE Indianapolis Colts fan. Needless to say, I have interest in this evening's game.

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