Mixed signals for March 

Posted: 4:57 pm Thursday, February 15th, 2018

By Kirk Mellish

Lets face it, just using climate normal (climatology) says snow or ice of any consequence in Atlanta is most common in January. December and February are not far behind though.

Yes, many long-time residents remember the March “Storm of the Century” blizzard of the 12/13th 1993 and I’ve been here long enough to remember MORE than one rare April snow measured in multiple inches. But these events fall outside the normal bell curve distribution of weather, hence called “outliers” or “tails” in statistical analysis.

On the other hand, there is an old saying in long-range weather rules of thumb that says “what happens in December, the weather will remember”.

Simply put, it is an acknowledgement that global weather patterns have cycles that repeat. Literally “Rosby Waves” in the jet stream move around the hemisphere over long periods of time… what goes around comes around.

What did the local and national Groundhog say again? It’s been warm ever since the 6 more weeks of winter proclamation.

It would be highly unusual for us, at the very least, to not have two more cold snaps that include frost and/or a freeze. Many times we get a multi-day to week long cold snap in March and April.

Models are mostly in conflict on if or to what extent the pattern may turn colder next month, while old time methods and non digital rules of thumb suggest the warm rubber band will snap. (Rubber band theory, or pendulum swings idea).

The GFS ENSEMBLE shows a shift that is similar to the past 3 cold March patterns:

Screen Shot 2018-02-15 at 11.40.13 AM

Which is quite a jet stream pattern change from the warm pattern we are in now:

Screen Shot 2018-02-15 at 4.45.53 PM

(500mb is mid-level jet stream, roughly 18,000 feet)

At least one run showed an eye-popping similarity to March of 1962:

Screen Shot 2018-02-15 at 11.43.48 AM

That March had quite the snowstorm in North and South Carolina and parts of Georgia, mostly North and East of Atlanta with a Trace at Hartsfield and the month was much colder than  than normal:


So it’s something to keep an eye on, although one model run does not a forecast make.

The European model has performed so poorly this winter that I am not even going to show it. The GFS ensemble has done better but is still unstable one run to the next. It was showing a drop to below normal, now just has a cool off to near-average for the early days of March:

Screen Shot 2018-02-15 at 9.46.18 AMScreen Shot 2018-02-15 at 9.47.00 AM

KATL_2018021512_nxa_384Screen Shot 2018-02-15 at 4.35.22 PM

However, you can see the cold building across all but the southern most tier of states so it could still be coming later.

Either way, any change follows more warmth, maybe near-record highs early next week.

Screen Shot 2018-02-16 at 8.46.37 AM

Meanwhile, tons of rain and flooding to our North and West next 5-10 days with just pesty hit and miss showers here:


Drier than normal for most of Georgia and much of the Southeast away from the flood potential NW:

Screen Shot 2018-02-15 at 6.44.52 PM

Screen Shot 2018-02-15 at 6.45.05 PM



(Chart: TWC)

I’ll keep monitoring for more definitive signs for what next month may hold.


Yes that’s me. The hair and technology are both dated lol.

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