Saturday, February 6, 2010

11:30am Weather Update: Upcoming Winter Storm

Forecast focus continues to be on Sunday night through Tuesday morning. This is when the next winter storm will impact southeast Missouri, southern Illinois, western Kentucky, northwest Tennessee, northeast Arkansas, and Indiana.

Computer models are developing a surface low pressure area over the southwest United States tonight. This low will move east through New Mexico --> southwest Texas --> Dallas --> northern Louisiana. After northern Louisiana, it begins to split the storm. One moving northeast. The other staying south along the gulf coast. Generally, this is a pretty good track for heavy snow for southeast Missouri and southern Illinois. However, the models are trending a little further north that could take the heaviest band just north of the KFVS viewing area. A more northerly track would also mean slightly warmer air being brought in to play.

Lets look at the data from the models. I always have to remind people reading the blog that the following information is data straight from the models. The below numbers are NOT the forecast. Often times the forecast will differ from one specific model.

Here is an overall look at NOAA's global forecast model (GFS):

The graphic shows accumulated snowfall through Tuesday evening. The GFS has handled things pretty well this winter with the exception being the winter storm to hit Indiana yesterday.

Here is a closer view of what the GFS is suggesting:

You note the grey box above. I believe that is a "burp" in the rendering of the graphic and is just missing data in that area.

Lets now move on to one of the other models run by NOAA. The NAM:

Something interesting to notice in this run of the NAM. It puts a heavy bulls-eye of snow over north central Arkansas. This doesn't look out of question to me as that would be the area where the surface low would be most concentrated before "splitting".

Here is a closer in view of the NAM model for the KFVS viewing area:

You can see in the NAM that it is taking more of a northerly track with the storm. This is noticeable due to the lack of snow over Tennessee and western Kentucky.

Specific locations.... Again, these numbers come straight from the computer models. These are not the forecast.
  • Cape Girardeau, Missouri: NAM = 5.5" GFS = 3.4"
  • Farmington, Missouri: NAM = 4.8" GFS = 6.0"
  • Paducah, Kentucky: NAM = 4.6" GFS = 3.4"
  • St. Louis: NAM = 5.2" GFS = 6.2"
  • Indianapolis*: NAM = 3.5" GFS = 9.0"

*The storm would impact Indianapolis late Monday through Wednesday.

There are still several questions in place as for the amount of snow we will get.
  • Track of the storm?
  • Temperature profile in the atmosphere?
  • Will dry air be in place?
The final question in the three above is an interesting one. The big storm in the KFVS viewing area had dry air in place to begin with. Dew points were in the single digits. As I type, dew points are in the middle 20's. So we should be in better shape (if you want snow) to start with as opposed to the last go around.

Stay tuned...

1 comment:

Bob said...

John, I really enjoy reading the posts on this blog. I appreciate your willingness to share this data and your analysis before you start making an "official" forecast. With the weather being like it has been, I find myself checking in there quite often. Thanks a lot for taking the time to write these posts, even if it's not in your official capacity with the station.