Weekend Update for the Piedmont

Here’s the latest thinking on the approaching Gulf system this weekend for our area

Models are beginning to settle on a track which would bring the system out of the Gulf towards the NC/SC border then up the coast as a Nor’Easter. This is a CLASSIC setup for a major snow event in central North Carolina except for one thing…Cold air.

Typically we would like to see a High Pressure system over the eastern Great Lakes region of 1030 mb or greater. This would send cold Canadian air down the eastern side of the Appalachians. We are lacking such a feature this go around.

Surface Analysis for Saturday

Surface Analysis for Saturday December 20, 2014

In this image, we see the storm system approaching from the Gulf it is not particularly strong at 1012 mb but deepening will occur as it approaches the NC coast. There are several features that need highlighting. The High pressures over the Great Lakes are very interesting. They are also not particulary strong being only 1024 mb but their position has caught our attention.

We see the beginning of a small Cold Air Dam (red arrow and lines). This tells us that some cold air will filter into the region but will it be enough for a snow event?

Here is the thermal profile:

BUFKIT Sounding for Greensboro and Piedmont

BUFKIT Sounding for Greensboro and Piedmont

This simulated sounding from BUFKIT shows that Snow will be falling from the favored dendritic zone (where snow crystals form) and then fall through a warmer layer melting and falling as freezing rain…A funny term call a “warm nose”.

What this tells us is that cold air will be arriving on top of the storm system about the same time as it reaches our area. This will change in future model runs, but it gives a pretty convincing reason why we feel this will not be the intense snow event that the European model is suggesting.

While discussing the European model, the ensemble (51 independent models that make up the entire system) agree that it will snow! We just can’t get past this temperature profile for significant snow to hit the ground this far south.

Here is what we are seeing with some exceptions…

Hi Res GFS for Saturday

Hi Res GFS for Saturday

Yes this is the GFS, a traditionally poor model for long range, but it is coming together with the Euro this morning. The Hi Res (new GFS) depicts precipitation type better.

In this image, we see a rain/snow mix over the mountains of NC and Va. At this time, we feel this is a bit off as we expected to see more Snow in the higher elevations. We also feel that as we get closer to Saturday, we should see the Rain/Snow mix enter the Piedmont regions of NC. This will account for the thermal profiles Shown above in the BUFKIT Soundings.

The Bottom Line:

At this time (and we are still 4 days out) there is still this whacky model disagreement going on! Here is what we do know:

Some Cons:

  • There will be copious moisture arriving Friday night/Saturday morning.
  • Temperatures in our area will be in the low 30’s to near freezing. (also a pro)
  • The ground temperatures are in the 40’s
  • We do not see any long stretches of below freezing weather prior to the event.

Some Pros:

  • The 1024 mb High pressure over the Great Lakes bears watching as any strengthening WILL send cold air into the area and then all this changes.
  • The 1012 Low forecast to arrive here from the Gulf also bears watching as any strengthening WILL overrun any cold air in place turning this into a freezing rain event.
  • One more day before more reliable short range models sample these solutions.

So, What’s it going to do? Until we see evidence that more cold air from Canada can work its way here, this looks like a Wintry Mix and Saturday morning may cause some travel issues…we just need more information to say anything beyond that this morning.

This bears watching as you can see there are a lot of things that have to come together and as we all know, models can be wrong as can forecasters. We just want to keep you in the know.

Off Topic sort of:

On another note, a Jason T. asked: “Why is your weather discussion so simplistic and amateurish?” I’ll take that question as it’s a very good one.

While working with area Emergency Managers over the past 16 years, we have noticed that social media sites recently offered good forecasts but provided very intricate and heady discussions to back them up. We also noticed that the public at times, were left more confused by all the jargon and terminology, than they were before they entered the sites! At conferences with the National Weather Service, Broadcast Meteorologists, and Emergency Managers we discussed this very thing. Last year while attending a seminar at the American Meteorological Society, the topic was “Social Media, the Web, and the Weather”. The same thing came up over and over. That was when I decided to “hang out my own shingle” and make a personal investment in weather equipment and technology to bring simple to understand weather to whomever would listen. NC Weather Happens means literally that! You know our weather best and you know it can be sunny and 60 one day and next and ice storm! Shown in this article are but a few of the many tools we use to get an understanding of the weather…I hope this answers your question Jason, and I hope you will continue to follow NC Weather Happens…it’s going to be a very busy year for us!

NC Weather Happens. Enjoy it!

 

 

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