A wintry forecast

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Main Threats

Tonight/Saturday morning: Wintry precipitation that could impact travel in the very early morning hours of Saturday (before 9:00 a.m.)

Sunday night: Wintry precipitation that could impact travel

Summary

Our beautiful, partly cloudy skies this morning will begin to become cloudier as we approach the afternoon and evening hours. These clouds are streaming in ahead of our next storm system. Like nearly every winter system we get in January and February, this one has some complicated caveats to it when it comes to precipitation.

Staying true to form, the plateau is right on the dividing line between rain and snow. Thankfully, we only have to deal with this wrestling match between temps vs precip for only a few hours late tonight. The precip will move in well after dark, closer to the midnight hour. That is when temps should be at or below freezing. The light precip will continue through the night, likely falling as a light snow/sleet mixture. That sleet mixing in will keep accumulations down, and I’m only expecting around a half inch or less (likely less).

Due to the track of the low pressure system going to our north, warmer air from the Gulf will quickly transition the mixed precip to all rain Saturday morning. That cold rain will continue Saturday and into Saturday night. A southerly flow will keep our temps above freezing Saturday night and Sunday.

By Sunday night, some more cold air works its way onto the plateau and that could lead to some light snow. There are numerous indications that temps will be 33-34 degrees, thought, which would prevent any accumulation. If that temp gets to 32, we could be looking at some light accumulation.

Monday looks cloudy and cold.

Below is a map showing the winter storm warnings (pink), with winter weather advisories surrounding the warned areas. The winter storm warning is for snowfall amounts between 4-9 inches.

Notice all the advisories are currently well to our north. I wouldn’t be too surprised to see some of those advisories dropped a bit farther south for late tonight/early Saturday morning. I’ll keep you posted.

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Discussion

You’ve probably heard me say it a lot and you’ve likely heard forecasters say it a lot…..”it all depends on the track of the low.” Indeed, your prospects for getting snow hinge on whether or not the track of the low is to your south, right over the top of ya, or to your north.

The flow around a low is counterclockwise, with northerly winds to the north and west of the low, and southerly winds to the east and south.

A southerly low pressure track keeps our winds from the north, which keeps us cold and allows it to snow. This is why a low that tracks from Birmingham, AL to Atlanta, GA is an ideal track for us to get snow. We get the moisture from the Gulf, but we get plenty of cold air staying in place to make that moisture fall as snow.

A track right very near to us, or even right over the top of us, gives us mixed precip. This is when we start as a wintry mix and transition to rain, only to have it all end as a few flurries. This is what we typically deal with in Tennessee.

A track to our north puts us in the “warm sector” of the system and gives us nearly all rain. No matter how cold you are the day before, if that low tracks to your north nearly all your precip will fall as rain. I’ve seen us have an overnight low, for example, of 15 on Monday night, only to see it rain all night Tuesday.

Looking at the map of winter storm warnings and advisories and you can tell where forecasters think the low is going to track. See the map below. This precip scenario works for nearly every low track, so always keep an eye on that forecast track!

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Records

The city of Nashville found itself digging out from 6.5 inches of snow on this day in 1918. Similar amounts of snow will fall today and tonight about 150 miles north of the city.

On this day in 1988, snow and high winds in Utah led to a 50-car pile-up along interstate 15. Winds gusted to 115 mph at Rendezvous Peak.

In 2008, Iraqis in Baghdad woke up to snowflakes falling from the sky. What’s unusual about that? Snow hadn’t fallen in Baghdad in nearly 100 years.

In 1972, down sloping winds off the eastern slopes of the Rockies hit speeds of 143 mph at Boulder, Colorado. The winds left 25 million dollars worth of damage in their wake.

Almanac

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Record high: 68 (2013)

Record low: -9 (1982)

Tomorrow’s Sunrise: 6:50

Today’s Sunset: 4:46

Day Length: 9 hrs 55 mins 40 secs

Tomorrow’s Day Length: 9 hrs 56 mins 48 secs

One Year Ago Today

A year ago today we had a high of 58 degrees, which is not half bad for the 11th of January! The morning low was only 52 degrees. As you probably know by now, when your high and low temperatures are that close together, it was probably raining that day. Indeed it was, though barely. Only 0.16″ of rain was recorded. Light rain was reported through noon, followed by cloudy skies. Winds were rather calm throughout the day, until they started gusting to around 20 mph around sunset.

News

Well, the good news is that I still get to watch the launch of Demo-1, with exclusive access to the launch via an invitation from NASA. The bad news is that the launch has been delayed until February because of the government shutdown. Let’s hope this shutdown ends with a good resolution soon!

You may have noticed some wintry weather on the radar this morning over toward West TN. That will stay away from us today, as it is moving more northward. We’ll be watching our radars later tonight for the mixed precip echoes. I’ll be tracking it all for ya!

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