Icy North I-40 event January 5th

[Runman292]

Now that we have advisories in the northern parts of TN, it's as good of a time as any for this thread. 

MRX:

.LONG TERM...

(Sunday through Friday)

Issued at 340 AM EST Sat Jan 4 2025

 

Key Messages:

 

1. A winter storm will affect portions of the area Sunday into Monday. Ice accumulation is expected, mainly north of I-40 and west of I-81.

 

2. Potential for high winds for the mountains and foothills Sunday night into Monday.

 

3. Very cold air remains across the region next week.

 

Discussion:

Overall, not much has changed regarding the upcoming winter storm that will affect the area on Sunday into Monday. Winter impacts are expected across portions of our forecast area, especially in areas north of I-40 and west of I-81. Icing events are fairly uncommon in our area, unless there is a very cold air mass already in place before precipitation arrives. It appears we will have that setup for this winter event.

Strengthening isentropic ascent will produce light precipitation beginning Sunday morning, mainly west of Interstate 75, with precipitation gradually beginning to increase eastward throughout the day. At the onset of precip, very cold, dry air will be in place at the surface. Initially, precip will have a difficult time making it to the surface, and this evaporative cooling will help maintain sub-freezing surface temperatures into the afternoon as precip rates intensify. Temperatures will likely be slow to rise despite warm advection aloft, creating a setup for freezing rain. Models often tend to erode the shallow cold air too quickly in these situations. QPF totals are light Sunday, but even light amounts around 0.1 inch would result in hazardous, icy travel. With the southerly flow, downslope and warming conditions across the western mountain foothills will result in a warm nose west of the mountain chain across the foothills. This means that the highest probabilities of freezing rain ice accumulation greater than 0.1 inch will be north of Interstate 40 and northwest of Interstate 81. The highest ice accumulation is still expected near the Kentucky line and into southwest Virgina, where 0.1 to 0.25 inch of ice accumulation is expected.Temperatures will gradually rise above freezing as warm advection takes over Sunday evening as the surface low move northeast across the Ohio River Valley. By Monday morning, winds shift to the WNW/NW as cold advection begins in the wake of a cold front. Scattered light snow showers are likely on Monday, especially across the higher elevations, as orographic lift enhances snowfall across the mountains.

 

Based on the above, a Winter Weather Advisory will be issued for portions of the Cumberland Plateau and adjacent counties, where confidence is moderate that some ice accumulation will occur, beginning Sunday morning. In the SW VA counties, there will be more of a snow/freezing rain mix that complicates things, and lowers confidence that Warning criteria for ice (1/4 inch) will be met. The 06Z run of the HRRR is showing less ice and more snow for SW VA. With this lower confidence, and the timing of precip onset being mainly Sunday afternoon, the Winter Storm Watch will be maintained there. There is a potential for significant travel impacts on Sunday on I-75 and I-81 in SW VA.

[Holston_River_Rambler]

Thought I'd take a peek at the HREF ensemble this AM:

Here are the models that go into that mean: 

 

RGEM still insists that there will be a pocket of freezing rain in the central east TN valley, banked up against the mountains on the central plateau. 

 

3km NAM kinda tries to do the same thing:

but it is ultimately a bit slower, so I suppose it allows for more insolation? 

And of course the NBM is the most optimistic, if you don't want any ice. 

 

 

 

The other thing I am curious about with this system is the snow most models show some as the shortwave is forced southeast over NE TN as well as some possible front end snow. It just seems like you will sometimes get like 10 minutes of nice snow just as the precip. moves in. 

 

[Holston_River_Rambler]

Latest watches and warnings:

 

Sorry its blurry, I didn't want to go to each CWA to get individual pics. 

[Runman292]

20 minutes ago, Holston_River_Rambler said:

Thought I'd take a peek at the HREF ensemble this AM:

Here are the models that go into that mean: 

 

RGEM still insists that there will be a pocket of freezing rain in the central east TN valley, banked up against the mountains on the central plateau. 

 

3km NAM kinda tries to do the same thing:

but it is ultimately a bit slower, so I suppose it allows for more insolation? 

And of course the NBM is the most optimistic, if you don't want any ice. 

 

 

 

The other thing I am curious about with this system is the snow most models show some as the shortwave is forced southeast over NE TN as well as some possible front end snow. It just seems like you will sometimes get like 10 minutes of nice snow just as the precip. moves in. 

 

RGEM puts a bullseye right on Anderson County. I definitely don't want to see three tenths of an inch of ice.

[Holston_River_Rambler]

Oliver Springs may be one bullseye for this. I drive from Morgan County to Norris quite a bit and there seems to be a sink for cold there. Another would be from Rocky Top Lake City to Caryville. Notice below that there is alos a small area for the cold to get locked in to Dutch Valley

Here is a topography map of the areas in involved:

 

The top arrow shows a gap where the cold could funnel in and the other two arrows point at Dutch Valley.

 

I'd love to go around tomorrow afternoon and check these places out, but I also don't want to die doing it, lol. 

[matt9697]

Looks like could be kind of dicey in my area for at least a few hours tomorrow am; have not really seen much chatter about the wrap around snow potential Monday, have to think that this could be the bigger story, throw a half inch of snow on top of a thin layer of ice, not a good combo! 

[*Flash*]

1 hour ago, Holston_River_Rambler said:

Latest watches and warnings:

 

Sorry its blurry, I didn't want to go to each CWA to get individual pics. 

I'm curious as to the Benton County inclusion. Seems like a rogue addition. 

[*Flash*]

1 hour ago, matt9697 said:

Looks like could be kind of dicey in my area for at least a few hours tomorrow am; have not really seen much chatter about the wrap around snow potential Monday, have to think that this could be the bigger story, throw a half inch of snow on top of a thin layer of ice, not a good combo! 

Correct me if I'm wrong but I'd think the WAA/changeover to rain would eradicate the glaze ahead of any glorified dusting potential. I agree in theory though. Any snow accumulation on top of ice is a tough prospect wherever that occurs.

[*Flash*]

PAH with an excellent winter forecast briefing package. I wish OHX issued more of these: https://www.weather.gov/media/pah/DssPacket.pdf

[TellicoWx]

Sorry just noticed thread...mods feel free to move my other post here. Basically the lee side low effect on backend has me somewhat intrigued especially for the plateau counties.

[Scottie16]

Sorry just noticed thread...mods feel free to move my other post here. Basically the lee side low effect on backend has me somewhat intrigued especially for the plateau counties.

I agree


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[Bigbald]

58 minutes ago, Scottie16 said:

I agree


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Nam 12km res has been honking at that for days, I bet the ski resorts are loving this.

[Scottie16]

Cloud cover moving in quicker than anticipated. Some areas may not reach forecasted highs.


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[Grothar of Herndon]

2 hours ago, *Flash* said:

Anyone else think Chris Bailey defaults to being super bullish in these scenarios? 

His 0.35-0.75” ice forecast through Eastern Kentucky Southwest VA is much higher than any of the models are showing. Hoping for more snow and/or rain and less ice. 

[Runman292]

Areas along Interstate 40 and 81 have now been included into the Winter Weather Advisory. 

[John1122]

They extended the hours as well. It was 7am to 7pm here. Now it lasts until 11am Monday morning. 

[Holston_River_Rambler]

18z RGEM gives Kingsport 2” of snow tomorrow am. Somewhat lessened ice amounts 

[John1122]

The RGEM is one extreme and the NAM is the exact opposite extreme. 

[1234snow]

The RGEM is one extreme and the NAM is the exact opposite extreme. 

I was going to post something similar. They are completely different.

[Scottie16]

Would this be considered a type B storm system?


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[TellicoWx]

Temps here currently are closer to the RGEM than the NAM 3k...down to 29.

[TellicoWx]

Latest RAP is close...HRRR is too warm here with current temps. Both have the leading precipitation as snow along 40 and north in central valley.

[Scottie16]

Latest RAP is close...HRRR is too warm here with current temps. Both have the leading precipitation as snow along 40 and north in central valley.

Definitely looks a bit more south than models suggested.


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[Daniel Boone]

3 minutes ago, TellicoWx said:

Latest RAP is close...HRRR is too warm here with current temps. Both have the leading precipitation as snow along 40 and north in central valley.

HRRR and Nam 3k has nearly always had somewhat of a warm bias here. I think it has to do with the ingested Data ; the quality and siting of official repoting Station's. As far as here in Lee County, it is a Fact regarding the Station's. Neither official Station is within NWS official Guidelines irt Siting.  Both are within 10 feet of Metal Structures. 

     Also, the Airport Station's are governed by the FAA and are not as precise as NWS is irt Temperature accuracy guidelines. Allow 4 degree deviation either side of actual .

[John1122]

HRRR has a couple hours of snow here to start then precip backs off, then some light freezing rain or drizzle for a bit. 

[Grothar of Herndon]

24/12

clear sky

Forecast:

Winter Storm Warning

Weather Event Onset

11:00 AM (EST), January 5

Description

* WHAT...Heavy mixed precipitation expected. Total snow accumulations between 2 and 4 inches and ice accumulations up to two tenths of an inch.

* WHERE...Portions of southwest Virginia and southern West Virginia.

* WHEN...From 11 AM Sunday to 1 AM EST Tuesday.

* IMPACTS...Power outages and tree damage are likely due to the ice. Travel could be nearly impossible. The hazardous conditions could impact the Monday morning and evening commutes.

* ADDITIONAL DETAILS...A brief transition to rain is possible Sunday evening through early Monday, before a transition back to snow during the day Monday.

[Holston_River_Rambler]

3 hours ago, Scottie16 said:

Would this be considered a type B storm system?


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By the KU playbook, yes. 

[Holston_River_Rambler]

6 minutes ago, Holston_River_Rambler said:

By the KU playbook, yes. 

https://weatherworksinc.com/news/Miller-A-vs-Miller-B

[Daniel Boone]

10 minutes ago, Grothar of Herndon said:

24/12

clear sky

Forecast:

Winter Storm Warning

Weather Event Onset

11:00 AM (EST), January 5

Description

* WHAT...Heavy mixed precipitation expected. Total snow accumulations between 2 and 4 inches and ice accumulations up to two tenths of an inch.

* WHERE...Portions of southwest Virginia and southern West Virginia.

* WHEN...From 11 AM Sunday to 1 AM EST Tuesday.

* IMPACTS...Power outages and tree damage are likely due to the ice. Travel could be nearly impossible. The hazardous conditions could impact the Monday morning and evening commutes.

* ADDITIONAL DETAILS...A brief transition to rain is possible Sunday evening through early Monday, before a transition back to snow during the day Monday.

Looks like guidance showing Dickenson County getting hit pretty good. Just a small shift South would put us back in that Zone. Still wiggle room. In this case, I'm hoping it doesn't as can do without the heavy  Ice and it's effects. Hopefully, the whole area gets more snow with less Icing.

[Scottie16]

Wrap around looking good on the latest NAM run.


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