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Cold Shot: Part Duex - January 18-20th Arctic Blast and Freezing Rain/Snow Event


John1122
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MRX Discussion this afternoon:

As the sun sets Wednesday night, temperatures will quickly fall into
the teens and into the single digits by Thursday morning. Hazardous
driving conditions remain possible across areas that have lingering
moisture/snow on roadways as they will see refreezing.

Heights rise on Thursday ahead of our next system and temperatures
climb back into the mid 30s to low 40s. Precip chances increase
Thursday afternoon into Thursday night areawide. This is in response
to a weak shortwave moving across the area. QPF hasn`t changed too
much since the previous forecast. QPF is still generally around 0.25
inches. Rain is still expected south of I-40, with mixed precip
along and north of I-40 and the Cumberland Plateau, and all snow
across northeast TN, southwest VA, and the east TN mountains. The
predominate precip type still looks like it will be rain/snow but
some light freezing rain can`t be ruled either based on sounding
data. Any freezing rain should be relatively light with ice
accretion averaging a few hundredths of an inch. Precip exits the
central TN valley by late Friday morning but will remain across
northeast TN and southwest VA into Friday evening. This is due to an
upper level trough moving through the Ohio River Valley that brings
additional moisture across the aforementioned areas. Storm total
snow still similar, with 1 to 2 inches possible across the east TN
mountains and southwest VA. Lighter accumulations up to half an inch
possible north of I-40 and along the I-81 corridor. NBM prob data
shows around a 40 to 50% probability of 1" of snow or more across
the east TN mountains and southwest VA.

Another bout of Arctic air moves in Friday night and lasts through
the weekend but no measurable precip is expected during this time.
Overnight lows on Friday and Saturday will be in the single digits
areawide. With low temperatures in the single digits, and breezy
northwest winds, windchill values below zero are likely across all
areas. In these conditions frostbite can begin in as little as 30
minutes with outdoor exposure. By Monday we are back into the low to
mid 40s as high pressure develops to our southeast behind the
departing trough. Our next shot of precip is on Tuesday but all rain
is expected for this round as temps will be in the upper 40s to low
50s during the day.
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16 minutes ago, Matthew70 said:

What does this mean?  Rain? Hopefully not ice.

Euro seems to be showing more of a inverted trough into Mid Tn compared to the GFS,thats why you dont see such a strong LLJ into Mid Tn,its snow to the north and mixing towards the AL/Tn line here in Mid Tn.GFS

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I expect the 18z GFS to back down or the other models to keep getting more frozen precip and less rain from here on. Kentucky looks pretty good for several inches of snow as do the mountains. More ice for everyone else per models but MRX is very confident in there not being much in the way of precip type other than rain/snow. 

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For these types of systems, we want them south and then have them work back north.  Roughly 80% of the time, these types of systems tend to trend north.  This is a little bit of a different animal in that it has such strong cold behind it.  In other words, this isn't your average clipper.  I would guess the qpf is under done.  I would tend to think the rain/snow line is too far south on the GFS.  But...there is snow on the ground and this appears to be at night.

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Man, he was awful with the storm we just finished. I hope he's off in a good way with this one. 

I mean……he DID work at WVLT!!! LOL!!!

To be fair, I do like Aldrich and the enthusiasm he brings to his forecasts. But, I almost always come to these pages in regards to weather forecasts


.
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2 minutes ago, Greyhound said:


I mean……he DID work at WVLT!!! LOL!!!

To be fair, I do like Aldrich and the enthusiasm he brings to his forecasts. But, I almost always come to these pages in regards to weather forecasts


.

He's just over the top with the "Captain Accurate" stuff. He had the heaviest snow yesterday over the areas that mix/rained. Todd Howell is about it for local TV mets that seem to be aware of meteorology and the microclimates here. 

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1 hour ago, John1122 said:

He's just over the top with the "Captain Accurate" stuff. He had the heaviest snow yesterday over the areas that mix/rained. Todd Howell is about it for local TV mets that seem to be aware of meteorology and the microclimates here. 

Great all around guy too ! 

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He's just over the top with the "Captain Accurate" stuff. He had the heaviest snow yesterday over the areas that mix/rained. Todd Howell is about it for local TV mets that seem to be aware of meteorology and the microclimates here. 
Yeah Todd is my fav local met. I swear most mets on local stations are just there for entertainment value and don't seem to study the topography of their forecast area aside from knowing the Smokies are generally colder.
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Someone updated the snow depth on the GFS to show a lot less than what is on the ground. Probably because of the feedback issues. 18z had Knoxville around -15 tonight and 00z is showing 3 tonight.

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55 minutes ago, Wurbus said:

Someone updated the snow depth on the GFS to show a lot less than what is on the ground. Probably because of the feedback issues. 18z had Knoxville around -15 tonight and 00z is showing 3 tonight.

I am at -4 now with 7" on the ground 

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11 hours ago, Wurbus said:

Someone updated the snow depth on the GFS to show a lot less than what is on the ground. Probably because of the feedback issues. 18z had Knoxville around -15 tonight and 00z is showing 3 tonight.

Speaking of models and temps, I noticed the NAM was about 10 degrees warmer than RGEM for this morning. I think the RGEM is doing better with temps and picking up snowpack. For this reason, I think I trust it more than the NAM for this event. Now, looks like for some areas that will be freezing rain, but still frozen. NAM wants cold rain for all. 

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Just now, Silas Lang said:

Speaking of models and temps, I noticed the NAM was about 10 degrees warmer than RGEM for this morning. I think the RGEM is doing better with temps and picking up snowpack. For this reason, I think I trust it more than the NAM for this event. Now, looks like for some areas that will be freezing rain, but still frozen. NAM wants cold rain for all. 

Also, would this event register for an advisory? Friday will have dropping temps even if they manage to get above freezing in the morning. I can imagine it will be a huge mess, even if precip is limited and rain...

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Also, would this event register for an advisory? Friday will have dropping temps even if they manage to get above freezing in the morning. I can imagine it will be a huge mess, even if precip is limited and rain...
This! Even if we get to 34 and rain where I am located there are piles of snow along the side of the road from plows. Those piles are not going to melt from the low QPF of this storm even above freezing with rain. There will be water trapped on the road surface unable to drain over the plow banks that will flash freeze and likely be worse than before at the peak of the 10 inch snow. I expect some hazard product to be issued likely advisory.


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12 minutes ago, Holston_River_Rambler said:

12z RGEM:

giphy.gif

 

4 run trend of RGEM is less qpf and a tick south:

giphy.gif

Yeah, I noticed the GFS went a little north. Almost like RGEM and GFS have met in the middle. If I had to guess, I assume places with a thick snowpack will hover just at or below freezing, resulting in freezing rain or snow. The valleys may fair better since they will pool cold air.

Wondering if MRX will pull the trigger on an advisory. I think it's needed if for precaution if nothing else. People may falsely believe that their roads are clear and not realize that it's just a sheet of ice. Temps should fall on Friday too. 

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We need that rain/snow line to get further south.  The good thing is it looks like this is at night for E TN.  Ideally, we want clear skies for a couple of hours before clouds cap the temp drop - we may not get that wish.  Snow cover is helpful, but the more important piece is the layers that snow would fall.  Snow gives a minor bump in our favor, but ultimately it will be the thermal profile of the incoming system which looks like a mess for lower elevations.  Maybe TRI and SW VA will have better thermals.  IDK.  My investment in this one is pretty low.  Looks like rain or a sloppiest.  The 12z GFS and CMC have steadily climbed north during the past several runs which is very normal w/ a northern stream system. 

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