Maybe a Little Snow, Definitely a Lot of Uncertainty

Posted on by David

A Nod to Mr. Bobby Boyd

You probably don’t know him. Mr. Boyd has worked over 50 years in public service to this community as a forecaster at the NWS office in Nashville. He didn’t want a big deal made of his retirement, so if I can presume to speak for Nashville and all of Middle Tennessee, I’ll leave this here simply with a sincere “thank you.”

Last Warm Day

Expect Light Showers Tonight

A cold front is on the way, pushing off and on showers our way this afternoon.

Rain chances increase tonight as the front nears.

HRRR model simulated radar illustrates:

The pink line at the end of the loop indicates freezing temperatures.

Arctic Air & First Real Chance of At Least a Little Snow

Snow Chances Exist Thursday through Saturday; Maybe a Dusting by Friday Morning

Very Low Forecast Certainty; Models Disagree Internally & With Each Other

Models continue to predict inconsistent snowfall amounts. The inconsistencies are internal — meaning each model disagrees with itself every time it is run — and external — the models disagree with each other.

NWS-Nashville illustrates the external disagreement here:

Here’s an example of internal model disagreement, using the last two runs of the GFS model:

A few takeaways from this.

1     Despite model differences, there have been enough solutions that indicate some snow that this is worth at least discussing in depth, rather than dismissing it all as common model speculation.

2     Tonight the regional models will come in range, and may prove useful to the forecast. Right now, those models suggest the snow will move north of us, but, again, we aren’t yet in range of the models through Friday morning to say for sure.

3     Both the GFS and Euro models — the two best we have at this range — suggest we wake up to some sort of minor dusting Friday morning.  Note that temps aren’t the reason the models are having a hard time. It will be plenty cold enough for snow. The issue is whether enough precip will squeeze out.

4     Sometimes it’s snowing overhead, but we never see it here on the ground because the snow is evaporated (or to use our analogy, eaten by the Dry Air Monster) on its way down.  There is uncertainty about whether the Dry Air Monster will be around Thursday night or Friday morning. The GFS model says the snow-eating monster won’t be around.

However, the NAM model says….

5     There are also timing differences. That precip/snow could be delayed by as much as 24 hours into Friday night or Saturday. Not only is this a quandary regarding “if”, but “when” is similarly uncertain.  This hazard graphic from NWS-Nashville lists the hazard levels not for a specific time, but from “Thursday through Saturday.”

6     This does not look like a sleddable, travel-snarling major snowstorm. Remember this from yesterday?

We described this model run as “wildly inaccurate” and not believed by any serious meteorologist. And, of course, 24 hours later, we see why:

You don’t have to get your weather info from us (we’re happy you do), but please do not get weather from a sports or media sensationalist source. Seek multiple credible opinions on this stuff (like local TV meteorologists).

My gut: maybe a dusting. Few/minimal travel impacts.

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