A BIG PATTERN CHANGE IS IN THE WORKS...

November 28, 2017

It's Monday night and that means the latest EURO weeklies are in the house. After a 7 day period that looks like this (Including 71 and 61 degree days in Cedar Rapids) the search for winter continues.

Despite the fact we really haven't seen winter in person, the models are in agreement we will get a significant change in the pattern around December 7th, something I alluded to in my post Thanksgiving night. It's a given the change will include colder weather, the big question is will we ever get into a storm track that's got the potential to bring any relevant precipitation (ie. snow). It's been mighty lean times in my area since October 23rd.

 

It's been especially tough to get snow. Here's a tweet from the NWS in Des Moines that proves my point. Remarkably, Tuesday will be the 701st day in a row without a 3" snowfall in Des Moines. An all-time record that won't end anytime soon.

Moving on let's start with the upcoming transition from warmth to cold. Here's where we are forecast to be December 3rd at 500mb according to the EPS control of the weeklies.

This flow aloft translates to temperature departures that look like this. More unusual Midwest warmth.

However, by the 14th the 500mb flow has transitioned to this. A dramatic flip-flop (complete reversal). 

Look at the difference this makes in temperature departures. Night and day!!!

With the cold air returning to the Midwest, it at least sets up the possibility of snow getting back into the pattern. I certainly can't guarantee it but at least the control run shows a healthy storm in Indiana preceding the push of cold December 13th. About all I can hope for at this distance is that the trend of a strong storm somewhere in the Midwest or Ohio Valley comes to fruition around this time. Phasing will be a huge issue for this to have any chance of coming together

Here's the broadbrush approach of what the weeklies are showing for snowfall totals the next 46 days. 

First the control which includes the storm you see above. Note the heavy snow band it develops across Missouri into NE Illinois. That's the first time this entire fall I have seen anything that resembled a snowstorm anywhere in the Midwest even if it turns out to be fantasy. 

The mean of the weeklies does not show the storm as it smooths the 51 members which means this is far from a done deal. However, it still has the most snow for the Midwest as a whole I've seen since the snow season began back in October. It's depicted well into Arkansas and northern Mississippi.

The time table for the flip to cold has been consistent among models around December 7-9th. The really nasty stuff comes around the 14th! Mark that down as a time to watch...

The means of the weeklies also show that's about the time that snow becomes a possibility. In the graphic above you can see it's hinting at the potential of an inch about December 10th, is up to 4" by Christmas, and 9" by January 11th in Cedar Rapids. Again, the ability to predict snow at this distance is difficult at best but the average of 51 solutions produces this outcome.  I'm far more certain of the cold that enters the pattern by the second week of December. Meantime it's more of the same for the next week! Roll weather....TS

 

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© 2019 Terry Swails