GOOD TIDINGS I BRING....MAYBE!

December 13, 2017

For the first time in quite some time, I saw some signs in the long range pattern that could lead to storminess and even some snow, just in time for Christmas. Now most of what I talking about does not happen for a week so there are lots of details to iron out. However, there is enough consensus among models that I seriously have some optimism this can be achieved!

 

Here's what it call comes down to. The massive ridge over the west which has brought 2 months of northwest flow and dry weather is showing signs of breaking down. (total precip. in Cedar Rapids since October 22nd 0.79"). Here's the 500mb ridge we've seen so much of.

Now look at transition shown in the operational run of the GFS Christmas Day. The ridge is replaced by a huge trough. Some moisture is allowed to enter the Midwest and a fight is on along the baroclinic boundary that cuts from Texas into the Ohio Valley. That leads to precipitation. What a concept!

What will be vitally important is where the trough sets up and where waves develop and propagate. Additionally, the duration of the trough will determine how long the period of potential storminess lasts. As I mentioned earlier those are factors that are impossible to know at this distance so we'll need to monitor trends in coming days. I will also point out, the models we employ to see these changes have been very erratic in recent weeks so I'm still a bit skeptical about getting on the band wagon. Keep that in mind as you read on.

 

Assuming this new look comes to fruition, there is certainly improved chances for snow and perhaps even a white Christmas. Here's some snowfall forecasts. I will start with the ensembles because those forecasts are an average of 51 different solutions. At this point, nothing more than trend indicators! These forecasts end Christmas night. Most of the snow in my area comes near or after December 20th.

 

Here's the EURO EPS mean:

Now the EURO EPS control:

The GEFS ensemble:

Finally, the GFS operational which is not an ensemble and at this distance not nearly as accurate:

When you get down to the nitty gritty you can certainly see there is a measure of consistency in the mid-range forecast that brings hope for those of us who "dig" the snow. However, I urge restraint going forward until we see these trends confirmed in later runs. I've been disappointed too many times to say this is a done deal. Roll weather...TS

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© 2019 Terry Swails