December 20 Blizzard Event Update (Posted 12/18)

Confidence Level: High

The HPC is keeping tabs on the December 20th blizzard event closely, as are we, and we have many images to share. The image we have above is the HPC's forecast track for this storm. The storm is expected to eject from the Southwest From that point, the storm is expected to move in a northeast direction. Then the forecasting gets tricky. We see the HPC going into a sharp north-northeast direction, before going almost entirely north by the time of 6 AM Wednesday. I cannot say I am surprised. Throughout the day, the models and ensembles have been projecting this system farther north, likely due to the sampling of the storm now that it is on US soil. Because it is all happening today, I am hesitant to believe it, but now that the storm has been fully sampled, my confidence level has indeed risen. It is likely that the ridge we have been discussing in the Southeast is partially to blame for this more northward trend, as a stronger ridge would indeed force the storm farther north.

Here we have another view of the storm, this time with ensemble member's participation. By matching each dot with the time key on the lower lefthand corner, we can see where the storm is projected to be at what times. The ensembles are very split on this supposed northward movement into Lake Michigan, and that is seen as the blue dots are very spread out, indicating a lack of confidence. These members are likely taking into account the ridge in the southeast as well, bring into question just how strong this ridge will be, and exactly where it ends up.

24 Hour Forecast Snow Accumulation

24-48 Hour Forecast Snow Accumulation

(For both images, the order is as follows: top left is probability for 4 inches of snow. Top right is probability for 8 inches of snow. Bottom left is probability for 12 inches of snow, and the bottom right is probability for .25 inches of ice.)
The above images are impact based, showing an estimate and probabilities for where the heaviest snow is forecasted to fall. We see that the next several hours hold a good potential for over 8 inches of snow in Northern New Mexico. The 24-48 hour timeframe has a slight probability for 12 inches of snow in Kansas and the Oklahoma panhandle, and that is where the heaviest snowfall should occur for that time period. I do think that the heavy snow may have to be adjusted a bit south, but again, this is depending on the ridge's strength.

With all this talk of a northward shift, a question I know many of you are asking is if these northern areas will get hit with snow now. The answer is possibly. 

Read the caption for this image.

In all fairness, the chances for snow have greatly increased for areas like Michigan, Wisconsin and parts of Iowa. However, the storm may be too far north for snow to happen, and some ice may factor in. Basically, any colors that are not a dark asparagus color indicate the chance for precipitation other than snow. Since the storm has been sampled properly at this point, we are expecting this to work out in some way, unless something dramatically changes (which could happen, judging by the way this storm has been wobbling everywhere in the models).

If you have any questions, you can comment them below.