Meteorologist Mark’s Wx Blog for Wed., Feb. 17

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Headlines 

Winter Storm Warning for tonight and tomorrow

Wrap up preparations this afternoon. Be home by dark, just to be safe.

A mixed bag of precip across the region

Warming trend next week!

Meteorologist Mark’s Wx Vlog 

48-Hour WX

Five-Day Forecast

Daily Forecast Summary

Today: Mostly cloudy. Areas of light sleet possible this afternoon and evening. Little to no accumulation.

Tonight: Winter storm conditions areawide.

Thursday: Winter storm conditions areawide.

Friday: Morning snow flurries possible.

Saturday: Mostly sunny.

Sunday: Mostly sunny and warmer.

48-Hour Precip Forecast

Meteorologist Mark’s Wx Concerns

I will begin by giving a map of Cumberland County, since this is the area of greatest precip variation for this event. You’ll see surrounding counties’ names to the sides. The red line is where I think the line between mostly snow and snow/ice will be. This is subject to change with additional data that comes in today. I included Crab Orchard in the mostly snow side of things, due to cold air tending to be a bit deeper there and giving them a bit different weather than some surrounding areas.

This is the updated timeline and precip type. I hope you find this helpful. Keep in mind that this could change with later updates today.

How far north you live will likely determine how much snow you get. The farther south of the interstate you are (ie Homestead, Big Lick, Grandview) the lower the snow totals may be. The farther north, especially around Livingston to Jamestown, the higher my confidence is that you will see heavier snow, which could top 6″ in localized locations.

How far north and south you are from the interstate will also determine ice impacts. Notice confidence is low for this, due to sleet mixing in and a lack of confidence that warm air will be deep enough to change snow to rain. Should your precip remain snow, you will be looking at higher snow totals.

Impacts from this event are not expected to affect trees and powerlines to a great degree, though all other surfaces will be highly impacted by any freezing rain, especially since surfaces are so cold right now. Again, those of you along and north of I-40 may never deal with any freezing rain, just snow and sleet.

Precip will change back over to snow for the end, although some of you may only get snow the duration of this event. That “back end” snow should stay light. I’ll keep an eye on that.

Meteorologist Mark’s Snow Day Forecast

I doubt anyone goes to school tomorrow in our region.

Meteorologist Mark’s Wx Discussion

There are several things I’ll be watching today.

  1. How warm will we get today? The colder we stay, the more wintry our precip will be.
  2. How dry is our air? Right now, dewpoints are very low. The dewpoint is the temperatures we need to reach for the air to be saturated (100% humidity). If air temp is 30 degres but dewpoint is 15 degrees, the dry air will eat up some of our wintry precip as it falls (evaporates it).
  3. The exact track of the low. Any deviation in the path will cause a wide variety of precip. The path of the low determines how far north the warmer air gets. The farther south the low stays, the colder we stay. In the last event, 20 miles made all the difference.
  4. Sleet potential. Sleet always cuts down on snow and ice totals. Sleet is a one of a forecaster’s biggest headaches.
  5. Finally, the amount of moisture the system brings up from the Gulf. Obviously more moisture means more precip.

We need cold air to get wintry precip but cold air is also drier air. That’s the point of #2 above. Drier air here at the surface can cause falling precip to evaporate. That’s not good if you want snow to come down. Eventually, the drier air will moisten up but figuring out how long that takes can be a challenge. How much snow will the drier air evaporate before it begins reaching the ground?

There’s a lot to watch and that’s just what I’ll be doing! Keep in mind that if you tend to be a colder spot on the plateau your precip will likely be more wintry. If you’re one of those areas that tends to get more snow and ice than everyone else I would expect the same with this storm.

NOTE: In the last storm conditions improved as you headed east to Knoxville. That will likely not be the case this time. Cold air will likely get trapped in the valley, leading to a decent shot at freezing rain for them. It’s not out of the question that they could have an ice storm. Be aware of this if you had planned to travel that direction on Thursday.

On This Day in Wx History

1956- A tornado, rated an F-2 (before EF scale), injured two people in Fentress County; The injured were between Jamestown and Allardt, along Highway 52.

Almanac

*30* Days until Spring!

Yesterday’s National Temperature Extremes

High: 87° at Fort Lauderdale, Atlantis, & West Palm Beach, Florida 

Low: -38° at Seagull Lake, Minnesota

Today’s National Wx Hazards

Another winter storm threatens the Southeast and southern plains, with a mixed bag of wintry precip. Snow will farther north. More snow can be found throughout the Rockies. A threat for severe storms will exist in the warmer sector of the storm, along the northern Gulf Coast.

Tomorrow’s National Wx Hazards

Another day of wintry weather across the Southeast, along with the continuing threat for severe storms across portions of the northern Gulf Coast, extending northeastward into southeast Georgia. Plenty of snowfall can be found across the Ohio Valley, Great Lakes, and Northeast. Still, another system moves into the Northwest, bringing more heavy snowfall to the Rockies. Notice another ice threat for southern Texas.

 Weather Shots

A powerful twister tore through Brunswick County, North Carolina late Monday night. This was part of the same storm system that brought our area a variety of wintry precipitation. This before and after picture shows the power of the storm. Three people died in this twister.

NASA Nerdology 

This is so cool! The Empire State Building is illuminated in red to celebrate this Thursday’s scheduled landing on Mars of the Persevere rover! I can’t wait to see what that rover finds!

You all have a great day and keep lookin’ up!

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