Sunday, December 18, 2011

Late Evening Winter Storm Update

The winter storm continues to develop and warnings are being extended. As always, let's start with the forecast precipitation with this storm:
Click to enlarge all graphics.

Severe Thunderstorm and Tornado Risk
While certainly not a situation where major tornadoes are likely to occur, tornadoes and thunderstorms with damaging winds are possible in the area marked "slight" risk. I suggest residents of these areas monitor the weather tomorrow for possible watches and warnings.

Blizzard and Winter Storm
Here is a map of the winter weather warnings and watches as of 8:50pm. The orange is a blizzard warning. Travel is strongly discouraged in these areas. Pink is a winter storm warning. Turquoise is a winter storm watch (mainly northeast Kansas) and the blue is a winter weather advisory.

This much is clear: Do not think about driving through the blizzard warning area -- roads will likely be closed and/or impassable. You could get stranded!  The amounts over southwest Kansas will be in excess of a foot with wind gusts of 35 mph. Note the blizzard warning now extends over a small part of Interstate 70 between Oakley and Ellsworth, KS.

The ARM model shows giant snowfalls over southwest Kansas and adjacent areas of Colorado and Oklahoma. This big issue with this storm is how far south and how fast the cold air will move. This model has six inches in Wichita because it shows the cold air moving just a little south of the other models. In theory, this should be the better model. 

How, the new NAM model this evening has the whole area of snow farther north. Scale same as above.

This model shows almost no snow falling in Wichita. I'm leaning toward the amounts and locations on this model. The important thing about this model, if I am right and it is the more accurate forecast, is that Interstate 70 would receive very heavy snow between roughly Salina and Colby, KS. 

Another way to play this is to consider the probability of snow accumulation thresholds at your location. These combine a variety of the models. So, here are the probability maps, the first is the probability of 2" or more:

This is the probability of 8 inches or more:
So, this update has been based on the very latest information. If you live in the area where heavy snow is forecast, please take this storm seriously.

So, where is the storm at 9:30pm? Via AccuWeather regional radar, it is over the Southwest. Note the bright red echoes (thunderstorms) W and SW of El Paso. This indicates it is a strong storm in the upper atmosphere.

Finally, thunderstorms have developed rapidly in southern Oklahoma which demonstrates that very moist air (more than adequate moisture for heavy snow as the air mass moves northwest) is in place and the instability exists for big thunderstorms tomorrow.


  1. Good stuff, Mike. Thanks.

  2. This is very useful, Mike, especially as I am meant to drive to Minnesota tomorrow! What do you think? We're flipping coins & models here. :)

  3. Jenna, if you leave during the day today you should be fine.


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