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Potential Big Dog Snow Event February 15th


Stovepipe

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RGEM shows some mixing beginning around 7AM for East TN, with most of East TN switched over to rain by 10 to 11AM Monday morning for East TN, until then RGEM is snow.  Totals look realistic to me.

If it rolls in at night...could make things interesting. Still not sure the RGEM or GEM is handling the thermal profile well - might be too cold. But if it hits at night, that is a different variable. And the RGEM is a very respectable short-range model. The Euro always seems to have better physics, so have to lean towards it. But if the Euro is too slow...RGEM solution.

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Last years Feb 21 event was like pulling a magic rabbit out of the hat. That was some very unique and almost unexplainable set of circumstances that led to us, at least in my area getting almost 5in of snow. It just kept on and on and on. Meanwhile, areas to my east like Greeneville, and Johnson City were roasting around 39-40 degrees. Apparently there was enough cold air trapped, enough of a cold pocket aloft, and heavy enough precip, to keep the WAA at bay here, but the foothills got a direct hit of that warm air. So incredibly rare and odd. I could only hope for a miracle like that this time, but I won't hold my breath. Just gotta hope for good front end snow, and enjoy whatever we get.

Was this the midweek surprise system that had a convergence boundary draped across the valley?

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GFS doesn't start precip in East TN until around 7PM.  This could be the critical part.  We need early precip to rack up totals.  RGEM starts light snow at 7AM, GFS 12 hours later at 7PM for east TN.

 

Though the GFS wollops the Plateau and most of the central valley especially north and west central valley.  Cold air tends to get trapped longer from my experience in the valley nearer to plateau in this set up.  Generally if you are within 15 miles or so of the plateau in the valley usually keep the cold a little longer. 

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Am I seeing the snow amounts on the gfs has a bullseye at 69 on Knox county tn with 6-8 inches

Yep... With the trajectory of the flow if you are in the central valley away from the mountains closer to the plateau you keep the cold air longer.  The plateau does often act as a CAD in the valley if you are close enough to it.  It has a harder time eroding with the escarpment angle from about Rhea county north.

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I know it's the HRRR at the end of its run, but it also has precipitation coming into East TN tomorrow morning.

Thats what i'm leaning on.  The HRRR has been pretty accurate in depicting the precip that broke out already in Missouri and Illinois, where GFS hasn't even if it is virga.  I would like to see the HRRR and RGEM be correct on the very early start tomorrow morning, and then the GFS be accurate on its trapped cold depiction for the central valley.  With those two combined we could really over produce for an event such as this.

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Was this the midweek surprise system that had a convergence boundary draped across the valley?

The one I'm talking about was on the weekend, Saturday actually. Was supposed to switch quickly to rain, but instead it just snowed all morning up till about 2PM. I'm not sure it went much further south than the northern part of Jefferson Co. But the further North you went away from the mtns, the heavier it got. My in laws in Bristol VA got over a foot I remember. Places near Wise VA were just burried with huge amounts. It never changed to rain, but the temp did go up to 34 at the end, and even 38 after it was over. That night the temp came back down below freezing, but the drizzle that set up glazed everything over really bad. I don't think Greeneville, Johnson City, Newport, etc had any snow. The mtns were in the same boat. It's like it was a laser of warm air pointed at the mtns and we somehow escaped. Strange.

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The Gfs is actually picking up on a similar possible outcome as last February 21. Look at the snowfall projection. It has a small but, huge lolipop along the eastern rim of the plateau in Claiborne co. Tn. And neiboring county to sw(can't remember co. Name). Last year the lollipop area was Lee county , VA. It is possible the model is undergoing precip in Lee co. once again as years of bad precip. reported data from there has been ingested into the models.

The areas along the western valley/Eastern plateau rim actually get upslope with a ssw wind trajectory. Lee and Wise county, VA would be even more pronounce due to more elevation and a shift in rim orientation to more ene than ne.

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The Gfs is actually picking up on a similar possible outcome as last February 21. Look at the snowfall projection. It has a small but, huge lolipop along the eastern rim of the plateau in Claiborne co. Tn. And neiboring county to sw(can't remember co. Name). Last year the lollipop area was Lee county , VA. It is possible the model is undergoing precip in Lee co. once again as years of bad precip. reported data from there has been ingested into the models.

The areas along the western valley/Eastern plateau rim actually get upslope with a ssw wind trajectory. Lee and Wise county, VA would be even more pronounce due to more elevation and a shift in rim orientation to more ene than ne.

North Knoxville looks great on the GFS. Northwest Anderson for the second run in a row gets buried.

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Mid range models especially the GFS and NAM has one word to me"FAIL".They are WAYYYY to cold

That may be the case, but MRX said the other models are way to warm and said they were using GFS thermal profiles. Joe Bastardi mentioned that too, said that you're never going to see temps warm from the 20s to near 50 with heavy precip rates like the Euro has shown. I don't disagree with that at all based on my weather history. If heavy precip is falling I won't crack 40 degrees during this event even though the Euro had me at 47 under a band of extremely high precip rates.

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That may be the case, but MRX said the other models are way to warm and said they were using GFS thermal profiles. Joe Bastardi mentioned that too, said that you're never going to see temps warm from the 20s to near 50 with heavy precip rates like the Euro has shown. I don't disagree with that at all based on my weather history. If heavy precip is falling I won't crack 40 degrees during this event even though the Euro had me at 47 under a band of extremely high precip rates.

Good point John.After looking at the 2m's i looked aloft and this is colder than what the models show

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18z GFS is an inland runner, Miller A...barely. Big change from 0z... May be too late to help, but thought I'd throw that out there.

True!  Even though we are so close i'm still very interested to see 0Z tonight major models, though i'm really just watching obs of the northern stream and the short range models now for my take on the event.  

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Wish we could see some soundings from different sites.OHX is saying 19 degrees tonight,this makes me scratch my head and say WTH are you seeing

That is interesting...  Latests obs, though its an hour old is currently 29 at BNA, dewpoint 0, and wind out of the north at all regional terminals in the mid-state.

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