© 2019 Terry Swails

BIG SNOW NUMBERS LATER THIS WEEK...

February 7, 2018

Plain and simple, the pattern looks ripe for more snow Thursday-Saturday. For several days now models have been focusing on the central Midwest (including my area) for the bulk of the heavier accumulations.

What's driving the bus is a persistent storm track cutting from the Pacific into central Missouri. North of the track you have well below normal temperatures fighting warmer air to the south...a classic set-up for over-running snows in my area. Energy rippling along the boundary provides the lift for the snow. 

You can see the temperature anomalies that are creating this situation above. If this were summer we'd be dealing with a ring of fire pattern producing strong thunderstorms and heavy rain instead of snow.

 

Timing the individual disturbances is a bit tricky but we are seeing some consistency in 2 major waves. The first arrives Thursday night/Friday. After a break Friday night a second round of snow quickly follows Saturday. While it is still too early to get fancy with amounts, the ensembles of the GEFS and EURO EPS (comprised of 51 members) are showing similar scenarios. That leads to pretty good confidence much of my area has a strong chance of seeing 6-12" of new snow before this all moves out Sunday.

 

Here's the GEFS mean snowfall forecast.

Below you can see the individual members that were averaged to create these results.

Now here's what the EURO EPS has for totals.

Comparing the two the EURO is further north but not by much. If you blend the GEFS and EPS you come up with a solution that puts the heavy snow band right through the heart of my area. If all goes well, we should get a pretty good idea Wednesday (Thursday at the latest) how this all totals up.

 

Whatever happens, it's a near certainty that advisories or warnings will be issued in the next 24-36 hours for the advent of this extended event. I'm sure the folks at the NWS are mulling that issue over as I post this.

 

To give you and idea of the potential that exists, I will show you what tonight's operational GFS indicated. Again, this is nothing more than guidance but if I didn't think it had merit and support from the ensembles I wouldn't show it.

 

Last but not least, I'll show you two versions of the GFS snowfall forecast. One is a straight 10:1 ratio. 1" of water for 10" of snow. It looks like this.

However, because of the cold nature of the temperatures this will be fluffier snow what will pile up more. It's likely most of the snow will fall in ratios of 15:1 or higher, perhaps even 20:1. The snowfall forecast with the higher ratios based on the Kuchera method look like this for the same amount of moisture.

THIS IS IMPORTANT TO NOTE: This is not a forecast!!!! It is model guidance that will change to some degree. By that I mean amounts could go down (or up) and the heavy band might shift north or south. These are typical revisions that are part of the process of forecasting snow. As confidence increases the necessary advisories go out and so do the official forecasts. Until then. we wait and see what the latest data dictates. Roll weather...TS  

 

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