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Thursday, February 21, 2008


The net result of Wednesday's storm was very close to my forecast (you can see in the post below).
Here you see 2 distinct bands of moderate snow. Unfortunately for most in the Baltimore metro area, it was just around 1 inch. That is in tune with my original forecast, yet the increased range did verify north and south. Annapolis was the big winner with 4 inches of the fluffy stuff. However DC and Chantily, VA barely got a dusting... Just bad luck I guess.

As of 6am- here is Winter Storm Watch Map, and my First Call:

The overnight models are trying to push BWI up to around 34-36 on Friday which would turnover to plain rain. However the model trend has been to be too biased with storms, pushing them to far north.
Below is what I am looking at to factor into my forecast:

  1. Storm track verifies just a little south and east.
  2. Colder temps this morning, plus snow pack may establish a colder start for the storms arrival.
  3. NE wind= Cold air Damming. Most models are notorious for warming us up to fast. Take the Election Day storm for example... While it may not guarantee more snow, it could mean a longer duration of ice. That's not good for anyone! The freezing line often sets up near I-95 thanks to our geography and topography. The bay can warm up nearby areas, while the hills (500ft-1000ft) stay cooler, and lock cold dense air in the valleys longest.
  4. Warming at cloud level will make this more of a wet/heavy snow (compared to yesterday), and likely push sleet or freezing rain for most of central Maryland during Friday.
Here is a breakdown of wintry precipitation:

The red layer show warmer temperatures (above freezing), above the ground which can remain cold. It all depends on how thick that layer of warm air.
Sleet: A raindrop has a thicker layer of cold air to refreeze before reaching the ground.
Freezing Rain: A raindrop does not freeze until after it touches the ground/tree/power line, etc.

Mid Day Update:
I am having a hard time accepting the morning model package. While there is trend down in temps (especially the GFS), I still think it is too warm. The range is from 33F-36F. That is for BWI. Remember Election Day? That was also a set up with below freezing temps lasting most of the day from Towson north. As for maps and charts and stuff... They don't show much, but I will try to get back on later today to highlight something. However, it all breaks down to this... There is pretty much a guarantee that it will start as snow, and drop 1-2 inches by daybreak. There is also a guarantee of mid level warming, so sleet and extended freezing rain will be the mid day and afternoon story (north). The potential is for 1/2 inch of ice on top of the snow. That could allow it to stick better and cause the power problems late in the day.
So I am sticking with my initial forecast I have above. Depending on how fast and intense the snow builds in, will be the ultimate test for how much we end up with. For many, not much more than when you wake up- because of the change over.

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