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Sn*w Update


Tonight/Overnight/Sunday Morning – Precip Arrives, Probably Not Any Freezy Stuff – Low 32°

Temps are going to very slowly dip from the upper 30°s, then the mid 30°s, and maybe even drop down to (but not below) freezing.

Maybe.

Meanwhile, clouds are beginning to build, with precipitation not that far behind. We might see a slight sleet/rain mix late tonight/early Sunday morning, but the lower levels of the atmosphere are very dry and any precipitation amounts will be inconsequential.

The NWS-Nashville produced the following graphic for tonight.

When the sun comes up Sunday morning, temperatures will rebound above freezing, on their way to a high temperature of 41°. Rain is expected during the day, and especially Sunday night. Expect 0.18″ by sundown Sunday night, and then about 0.5″ of precipitation through noon on Monday.

That leads us to the big question: will this rain change over to snow at any point Monday morning?

That depends on which weather model you believe. Let’s take a tour! All models will reference 6 AM Monday morning.

GFS

First, if you want snow, it’s important to see if the temperatures at 5,000 feet will be below freezing. The GFS model says they will be:

If this verifies, we will see some sleet or snow falling to the ground. However, temperatures at the surface may not coooperate:

We are on the wrong side of the freezing line to get any accumulating snow. However, this model has a pretty wide resolution, so I don’t think it’s meaningful to interpret too much into where the line is drawn right now. It could very easily wobble 10 or 20 miles northwest or southeast. Also note that if you are at higher elevation or driving across a bridge or overpass, you are more likely to face sleet/snow/ice or a slushy buildup than those who live at lower elevations.

However, it is suspected that this GFS model has a “cold bias,” meaning it’s saying it will be colder than it really will be. That’s bad news for snow fans.

Euro

This model thinks it will be cold enough at 5,000 feet to produce some wintry precipitation. It also predicts rain for most of the morning, but then a very brief changeover to sleet-then-snow before the precipitation moves quickly off to the east. (We are not allowed to post the actual model graphics here).

NAM4

This model does not think it will be cold enough at the surface to produce accumulating snow:

However, it looks like it might barely be cold enough to change some of it over to sleet/snow at 5,000 feet, then melt on contact. This solution is also preferred by the WRF-NMM and WRF-ARW.

All in all, NWS-Nashville produced the below graphic, which we feel like represents a consensus of all the models.

If we see the “dusting to half-inch,” and if the city survives, “any travel problems are expected to improve quickly before lunchtime Monday as the storm system moves away. Temperatures will climb above freezing quickly, and brisk Northwest winds will help dry the roads.” (NWS, Special Weather Statement). Monday’s high is 37°.

The biggest weather story of the week will probably be the temperatures on Tuesday, which are not expected to get above freezing. High 31°!

More here tomorrow and on Twitter @NashSevereWx.

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