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January 15th-17th 2024 Arctic Blast/Snow Event


John1122
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I always enjoyed probability and statistics in college, even though I was horrible with numbers.  If they think there is a 40% chance of 3 or more inches, would they also accept a 5000$ bet to pay out equivalent odds that it does snow over 3 inches?
 
Screenshot_20240112_181323.thumb.jpg.fb2b3fc754625c4dbdd058530a5a84e0.jpg

I haven’t read much on the details of their % but is there a radius like the SPC uses for severe weather? Example: “10% chance of a tornado at a given location within a 50 mile radius”?


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While this may be my own forecasting “anti-bias” / cautious & pessimistic forecasting attitude taking hold, but I don’t like the look of the end of today’s 18z Nam for eastern areas if one wants snow. We haven’t had the actual arctic air yet arrive from behind the current system and it remains to be seen just how robust this arctic air is when it moves in Sunday. I feel pretty confident western and middle tn folks are on board to see some decent accumulation, but the potential is there for this swath of snow to shift 50-100 miles north of the current forecasted area for East Tennessee if deep cold thickness lines end up not being as far south and shift sw to ne like the end of the latest nam 12km is indicating. This is exactly what happened on January 5th, 2022 with the snow expected to hit pretty much all of East Tennessee with 3”-5” anticipated, however, in reality, all of East Tennessee barely received a trace or even 1/2” with most of the moderate to heavy snow going to our north and west with milder and drier air over all of East Tennessee. I’m not saying this is what will happen with this upcoming system because I’m sure different dynamics are at play and the Nam isn’t necessarily spot on at hr 84, but I did get a small dose of PTSD when I saw the end of the NAM and connected that to Jan 5th 2022.  

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While this may be my own forecasting “anti-bias” / cautious & pessimistic forecasting attitude taking hold, but I don’t like the look of the end of today’s 18z Nam for eastern areas if one wants snow. We haven’t had the actual arctic air yet arrive from behind the current system and it remains to be seen just how robust this arctic air is when it moves in Sunday. I feel pretty confident western and middle tn folks are on board to see some decent accumulation, but the potential is there for this swath of snow to shift 50-100 miles north of the current forecasted area for East Tennessee if deep cold thickness lines end up not being as far south and shift sw to ne like the end of the latest nam 12km is indicating. This is exactly what happened on January 5th, 2022 with the snow expected to hit pretty much all of East Tennessee with 3”-5” anticipated, however, in reality, all of East Tennessee barely received a trace or even 1/2” with most of the moderate to heavy snow going to our north and west with milder and drier air over all of East Tennessee. I’m not saying this is what will happen with this upcoming system because I’m sure different dynamics are at play and the Nam isn’t necessarily spot on at hr 84, but I did get a small dose of PTSD when I saw the end of the NAM and connected that to Jan 5th 2022.  

There’s no option off the table. We are excited about “what could be” but we know better than to count chickens at any point before nowcasting. However I do agree that the NAM at 84 is just something to look at or be used to verify other mods.


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While this may be my own forecasting “anti-bias” / cautious & pessimistic forecasting attitude taking hold, but I don’t like the look of the end of today’s 18z Nam for eastern areas if one wants snow. We haven’t had the actual arctic air yet arrive from behind the current system and it remains to be seen just how robust this arctic air is when it moves in Sunday. I feel pretty confident western and middle tn folks are on board to see some decent accumulation, but the potential is there for this swath of snow to shift 50-100 miles north of the current forecasted area for East Tennessee if deep cold thickness lines end up not being as far south and shift sw to ne like the end of the latest nam 12km is indicating. This is exactly what happened on January 5th, 2022 with the snow expected to hit pretty much all of East Tennessee with 3”-5” anticipated, however, in reality, all of East Tennessee barely received a trace or even 1/2” with most of the moderate to heavy snow going to our north and west with milder and drier air over all of East Tennessee. I’m not saying this is what will happen with this upcoming system because I’m sure different dynamics are at play and the Nam isn’t necessarily spot on at hr 84, but I did get a small dose of PTSD when I saw the end of the NAM and connected that to Jan 5th 2022.  
I understand this fear really really well. How many times over the years have we watch it take ages for cold air to filter over the plateau only to arrive when precip was ending. However I feel this is different primarily because of the initial cold front coming in now, and start time of precip especially for west and Middle as it will be at night likely, though even in Mid East Tennessee my forecast low Monday morning before precip start is 24 degrees. As sun comes up it will already be overcast and with dry air in place will likely start as virga which will help keep temperatures down through evaporative cooling. I don't really hold this as a great fear in this setup as I would if there weren't already seasonal cold in place. Many times we are above seasonal and then depending on the Arctic front to overcome above seasonal temps which just isn't the case this time with good cold air already entrenched. If I have a fear it's actually the dry air and not really over coming it quick enough. But with good Gulf connection that doesn't really spook me too much either. Just my thoughts.

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4 minutes ago, ShawnEastTN said:

I understand this fear really really well. How many times over the years have we watch it take ages for cold air to filter over the plateau only to arrive when precip was ending. However I feel this is different primarily because of the initial cold front coming in now, and start time of precip especially for west and Middle as it will be at night likely, though even in Mid East Tennessee my forecast low Monday morning before precip start is 24 degrees. As sun comes up it will already be overcast and with dry air in place will likely start as virga which will help keep temperatures down through evaporative cooling. I don't really hold this as a great fear in this setup as I would if there weren't already seasonal cold in place. Many times we are above seasonal and then depending on the Arctic front to overcome above seasonal temps which just isn't the case this time with good cold air already entrenched. If I have a fear it's actually the dry air and not really over coming it quick enough. But with good Gulf connection that doesn't really spook me too much either. Just my thoughts.

Sent from my Pixel 7 using Tapatalk
 

Really hope everyone can get some from this system, hope the overnight run of models don't disappoint 

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1 minute ago, Holston_River_Rambler said:

giphy.gif

E67kjR8.png

qpf may have ticked down a smidge

 

 

Actually QPF is up a bit. And looking at it versus snowfall, I actually have to wonder if the snow is under modeled. Looks like precipitation to snow on maps is roughly showing up as 10 to 1 ratio, even on the kuchera maps. 

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2 minutes ago, Silas Lang said:

Actually QPF is up a bit. And looking at it versus snowfall, I actually have to wonder if the snow is under modeled. Looks like precipitation to snow on maps is roughly showing up as 10 to 1 ratio, even on the kuchera maps. 

Anyone else see it or am I wish casting here? lol

ecmwf-deterministic-southapps-precip_24hr_inch-1705082400-1705384800-1705384800-40.gif

ecmwf-deterministic-se-precip_24hr_inch-5406400.png

ecmwf-deterministic-se-total_snow_kuchera-5406400.png

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14 minutes ago, EastTNWeatherAdmirer said:

While this may be my own forecasting “anti-bias” / cautious & pessimistic forecasting attitude taking hold, but I don’t like the look of the end of today’s 18z Nam for eastern areas if one wants snow. We haven’t had the actual arctic air yet arrive from behind the current system and it remains to be seen just how robust this arctic air is when it moves in Sunday. I feel pretty confident western and middle tn folks are on board to see some decent accumulation, but the potential is there for this swath of snow to shift 50-100 miles north of the current forecasted area for East Tennessee if deep cold thickness lines end up not being as far south and shift sw to ne like the end of the latest nam 12km is indicating. This is exactly what happened on January 5th, 2022 with the snow expected to hit pretty much all of East Tennessee with 3”-5” anticipated, however, in reality, all of East Tennessee barely received a trace or even 1/2” with most of the moderate to heavy snow going to our north and west with milder and drier air over all of East Tennessee. I’m not saying this is what will happen with this upcoming system because I’m sure different dynamics are at play and the Nam isn’t necessarily spot on at hr 84, but I did get a small dose of PTSD when I saw the end of the NAM and connected that to Jan 5th 2022.  

Quite a different set up this time vs then. That was a marginal event for the area with highs the day before in the 50s. The areas that got snow got it fast and it melted 48 hours later. Highs will be in the 30s the day before this system arrives with lows well into the 20s. 

This is a rare even where a system ushers in Arctic air and it's fresh for another system on its heels. If any areas see rain it would be in unfavorable downslope areas or a very deep system that has an epic warm nose, and even then you're probably looking at freezing rain. 

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8 minutes ago, Holston_River_Rambler said:

giphy.gif

E67kjR8.png

qpf may have ticked down a smidge

 

 

Models have been very consistent and I like it.  I know that there is a million ways we can get the screw job but it we do we will survive.  It is however time for us to get a storm like this, it has been a minute.

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1 minute ago, zippity said:

Winter Storm watch issued for parts of Mississippi. It's not Tennessee Valley, but imo still pertinent to size and scope of the developing system.

North Mississippi has been getting smoked almost every model run.  I really hope they cash in, they are overdue.

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1 minute ago, zippity said:

image.png.0cbc4164b1e58fc462cb9424b06d12c4.png.

 

Winter Storm watch issued for parts of Mississippi. It's not Tennessee Valley, but imo still pertinent to size and scope of the developing system.

I think Winter Storm Watches will hit tomorrow evening from Florence to Huntsville and points northeast to SWVA and points north of there. 

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1 minute ago, Holston_River_Rambler said:

I didn’t mean to spook anyone. I was just looking at the precip type fields and comparing to last run. I didn’t actually look at the qpf output. Sorry lol. 

Haha no worries! I just wanted to look for myself and noticed that the precipitation seems to be pretty much 10 to 1 or a little better. Wondering if with the cold air if we could squeeze some more out of it. 

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2 minutes ago, Holston_River_Rambler said:

I didn’t mean to spook anyone. I was just looking at the precip type fields and comparing to last run. I didn’t actually look at the qpf output. Sorry lol. 

The gif work is very much appreciated my man.  :guitar:

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I think Winter Storm Watches will hit tomorrow evening from Florence toHuntsville and points northeast to SWVA and points north of there.
 

Thanks. Huntsville NWS is always conservative as we are so often on the very edge of any snowfall, but they did state that there was a 57% chance of snow greater than one inch. That's a pretty optimistic statement for them, imo.

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Just now, ShawnEastTN said:

Someone got the DGEX for old time sake? I really miss it so much. I guarantee it would show the storm of the century right about now.

Sent from my Pixel 7 using Tapatalk
 

Not the DGEX but I've been fiddling with Earl Barker's page today trying to render some of his classic graphics.  Sadly no luck on my end yet.  If anybody can conjure an Earl NAMing please post it.

https://www.wxcaster.com/models_main.htm

 

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Not the DGEX but I've been fiddling with Earl Barker's page today trying to render some of his classic graphics.  Sadly no luck on my end yet.  If anybody can conjure an Earl NAMing please post it.
https://www.wxcaster.com/models_main.htm
 
Many many years ago so much it makes me feel really old, before I knew AmericanWX had forums those old DGEX outputs would set the old SouthEast forum on AccuWeather on fire! I swear sometimes it was a combination zoo & MMA sprinkled with a little weather.

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3 minutes ago, ShawnEastTN said:

Many many years ago so much it makes me feel really old, before I knew AmericanWX had forums those old DGEX outputs would set the old SouthEast forum on AccuWeather on fire! I swear sometimes it was a combination zoo & MMA sprinkled with a little weather.

Sent from my Pixel 7 using Tapatalk

 

Ha, those were my first weather forums, we probably interacted at some point!  I met John there around 2008-2009 I think.

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