Huge snowstorm this weekend...but will it affect us? Also, next week...

From a forecasting standpoint, it can only get better from here, because this weekend's storm features almost everything that can give a meteorologist a nightmare - most notably a sharp cutoff to the north edge of the precipitation shield, and an uncertain low pressure track which will cause a lot of uncertainty in the precipitation forecast, particularly for our area.

Having said that, let's take a look at what the forecast models are showing, and what I think will happen for our area. The models have come to a much better consensus from yesterday, and it now appears that of my 5 options, the one that will happen is... (4) A primary low pressure system tracking through the Ohio Valley, and energy being transferred to a secondary low pressure system which would either track up the East Coast or out to sea.

The thing that will make or break this storm for us is exactly when the energy will transfer. I'll try to explain this as best as I can...basically, the primary low pressure system will produce much of the snow for the Ohio Valley and Midwest, while the secondary low pressure system will prodcue much of the snow for the Mid-Atlantic and Northeast. Therefore, we want the primary low pressure system to make it as far north as possible before the energy transfers, so the snow associated with it also makes it as far north as possible. Once the energy transfers, the band of snow associated with it will stop moving north, and start moving east, which results in a sharp cutoff of snow accumulations. A difference of 50 miles in the track could result in us gaining or losing 6" of snow from this system.

Truly a forecaster's nightmare. So, when do the different models show the energy transferring? Currently, the results don't look all that good for us. I'll explain why they may change in our favor, and why they may not, but first, let's see what they show...

The 12z GFS has the primary low getting up to SE Kentucky before the energy transfers. Snow makes it up to the Ohio Border, more or less.

Hard to tell with the 12z ECMWF, but it appears to be more or less similar to the GFS.

12z UKMET, I had a better image with this but lost it, sends it a little north of the GFS and ECMWF, but not enough to make much of a difference.

12z GGEM, this is the best solution for us, sends the low all the way up to SE Ohio before the energy transfers. Precipitation shield goes up to I-69.

So, obviously the consensus is for the precipitation shield to stop around the Ohio Border, with us only getting minor accumulations, if anything at all. Here's some reasons why that may be wrong, and reason why that may be right:

Wrong:

*As the NAM forecast model comes into range, it appears to be headed for a more northern solution than the current model consensus. As I have said in earlier posts the NAM has been a pretty good model this winter.
*Overall, the models have trended further northwest from yesterday.
*As I have mentioned before, models tend to continue trending storms further northwest almost all the way up until the actually happen. We'll see if they trend even further northwest tonight.
*Sometimes, with an energy transfer, the forecast models tend to overdo how early the energy actually transfers, resulting in a further north precipitation shield.

Right:

*There is a strong model consensus right now, with 3 of the 4 major models that are in range agreeing in the precipitation field stopping at the Ohio Border.
*Can't go against winter trends. Almost all winter, the trend has been for less phasing and a more supressed storm.
*This one is a bit complicated, but effectively what you need to know is that there is a strong blocking pattern in place that will limit how far north the primary low can trend.
*A dry easterly wind will limit how much the atmosphere can be saturated with moisture.

Preference: I am in favor of a further NW trend with this storm. The models have trended significantly northwest since this time yesterday, and even with the more supressed storms this winter, the northwest trend has still appeared (it gave Washington DC a surprise storm last weekend). Combine this with the tendency of models to often overdo how early the transfer of energy occurs, and I think this will go further NW than currently forecasted.

Still though, it's going to be a close call. Based on model consensus, it would have to go ~ 60-80 miles NW to put us in business for snow from this storm. And with the blocking pattern and dry easterly wind, I question just how much further NW this storm can come. Combine that with the sharp cutoff in accumulations, and I see this as being a storm where accumulation forecasts will not be completely sorted out until we get within 12-24 hours of the storm actually happening.

Still, I will give us some accumulations probabilities with this storm (obviously subject to change)

Nothing: 20%
Trace-1": 20%
1-3": 40%
3-6": 15%
6+": 5%

Finally I'd like to say that if you only care about a storm for the snow days, then this isn't a huge deal, as it would likely be a Friday Afternoon - Saturday Morning storm if it affects us, and even if it does affect us, snow day criteria snow is not very likely.

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Beyond this storm, I hate to be looking at another storm a week out, but with this winter so far, what else can you do? As with earlier this week when I called for a big storm to affect part of the U.S. this weekend, signals once again look good for another big storm to affect the part of the U.S. There are a wide range of possibilities for this storm again...will it affect us? Stay tuned, as I'll probably start talking about it more in the next few days, as long as it still has a chance to affect us.