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Jan 6th-7th 2022 Second Chance Storm


John1122
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Definite trended southeast on that run - actually significant move by the 12z NAM.  Looks like freezing rain and sleet along the southern  border w/ moderate to heavy snow for a good portion of the state north of I-40. Not sure if it just got too amped at 6z or what.  There is likely going to be a minor to moderate problem with the rain shadow as they system comes off the Plateau....IF it is that flat.  Right now, I think modeling is having trouble with the strength/speed of the cold front.  Let's see where the RGEM goes.

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Morristown mentioned this in their disco but the air in front of this is extremely dry in the low levels.  We will have to moisten our column from the top down this time. This does help with surface temps east of the Plateau though. Hopefully it doesn't soak up all the precip.
 
282275925_dryair.thumb.png.62b3609aaea94ede55b248ee9ff1a691.png

The temperature rise is throwing me off. Unless there’s some strong WAA before hand, I’m not understanding my low temp of 27° rising to 37° during the day with elaborative cooling and dynamic cooling going on most of the day. Not sure how well mods handle that kind of thing. I think it’s more likely my low temps are modeled to low. It doesn’t make sense that my low temp tonight will be colder than it was last night with a system approaching. I can a situation where my low temp is around 32 but only rises to 34ish and then it starts to fall off when rain rates pick up.


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4 minutes ago, PowellVolz said:


The temperature rise is throwing me off. Unless there’s some strong WAA before hand, I’m not understanding my low temp of 27° rising to 37° during the day with elaborative cooling and dynamic cooling going on most of the day. Not sure how well mods handle that kind of thing. I think it’s more likely my low temps are modeled to low. It doesn’t make sense that my low temp tonight will be colder than it was last night with a system approaching. I can a situation where my low temp is around 32 but only rises to 34ish and then it starts to fall off when rain rates pick up.


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I know. Temps in extreme Eastern TN get into the 40s as the storm is moving in. Not sure if the low is forcing warm air up into the area or what. But it does seem strange. 

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Definite trended southeast on that run - actually significant move by the 12z NAM.  Looks like freezing rain and sleet along the southern  border w/ moderate to heavy snow for a good portion of the state north of I-40. Not sure if it just got too amped at 6z or what.  There is likely going to be a minor to moderate problem with the rain shadow as they system comes off the Plateau....IF it is that flat.  Right now, I think modeling is having trouble with the strength/speed of the cold front.  Let's see where the RGEM goes.

Think I remember a west to east slider/clipper quick hitter several years ago that was modeled to give Knoxville 2-4”. I only got some flurries but 5 miles north of me in Union Co got several inches. Dry air and downsloping killed the valley from Knox Co south down 40. Plateau, northern valley and mountains did well.


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6 minutes ago, fountainguy97 said:

I know. Temps in extreme Eastern TN get into the 40s as the storm is moving in. Not sure if the low is forcing warm air up into the area or what. But it does seem strange. 

Yeah down to 27 tonight, up to 41 then back down to 14 O.o  seems strange

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Southern Valley warm-nose risk is mainly because the vort max is still north. With less of a defined low level low, downslope will not be the deal killer. Plus the dry air will cool with precip. But that vort max.

HRRR is too amped though. We know it's always on steroids for severe. Well the physics of the model remains the same; therefore, one can deduce it's too amped. So the HRRR warm risk is too much. NAM is probably the worst case. 

Globals of course are all systems go! I feel pretty good about along and north of I-40 and I-81. South is TBD.

Note the MRX lowest case still gets Knoxville snow. Shows the classic Athens north. MRX highest case gets Chatt. Official fcst looks reasonable.

Nashville, Memphis, Paducah and Jackson, KY also have a public snow forecasts up. 

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1 hour ago, PowellVolz said:


Think I remember a west to east slider/clipper quick hitter several years ago that was modeled to give Knoxville 2-4”. I only got some flurries but 5 miles north of me in Union Co got several inches. Dry air and downsloping killed the valley from Knox Co south down 40. Plateau, northern valley and mountains did well.


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Yeah, happens all the time here on northwest flow or just west-to-east flow.  It will blank Kingsport and the line reform almost exactly at I-81.   The Sunday system is usually money here with bands moving in from the SE.  Just was unfortunate that go around. 95 times out of 100, that is money for Kingsport.  This system tomorrow is trick for those of us in the shadow of the Plateau.  Oddly, and I bet you have seen this in Knoxville at times, we get the opposite, and sometimes it roars of the Plateau.

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6 minutes ago, TellicoWx said:

Biggest thing I see is 1) Globals shear the 850 sooner vs HiRes...less time for the LLJ to nose up the valley. 2) Speed of the 850...some of the HiRes such as NAM has sped it up, while RGEM for example is the slowest. Globals have held steady. Faster solution/ less LLJ influence. 

Makes sense with the speed of the system and limited gulf interaction............

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12z(right) and 6z(left) GFS for comparison.  Incredible to see the GFS remain that steady.  At one time years ago, the GFS could be counted on for multiple northwest jogs as it was often too progressive.  There was once a saying that the GFS better have the system in Cuba in order to account for the northwest jog it was going to take.  The map below is the Kuchera snow algorithm.  Kuchera gives us more, so I picked the beefier look.  I firmly believe that taking that model that has the least is probably more correct once the system becomes reality.  However, when posting maps on the sub-forum it is the user's duty to post at least one map with the absolute most snow for that given run or suite.

This side-by-side is easier than making a gif.  Accumulation trends allow one to see the track .  @Holston_River_Rambleris the gif maker.   Please keep in mind there is ice/sleet along the southern edge of this precip shield, maybe a 100 mile band which is roughly two counties into Mississippi and Alabama(just south of the TN line).  

Screen_Shot_2022-01-05_at_11.07.57_AM.pn

 

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3 minutes ago, Carvers Gap said:

One thing to note @TellicoWx, I wonder if the GFS could be too progressive (as its bias) which allows for totals over the forum area to be higher.  The RGEM may be a bit less susceptible to that.  IDK which model is not either 1. too amped 2. too flat.

I think since last year that the old bias doesn't apply anymore...Euro seems to lost some of its shine, Ukie has turned into garbage, and somehow the GFS has found a way to be more steady (can remember it holding steady last year while the Euro caved to it). Believe there's a new set of bias that needs figured out. As far as this system, think the pieces are so weak that if you move them 1 county north or south, shear them 3 hrs sooner/later, or even the angle of the press from the northern stream..it has big changes to the final solution. Think the answer is somewhere in the middle.

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Regarding last post page 7. Chattanooga proper might score two busts in a row. Looks fine for the rest of East Tenn. Barring a hand-off debacle I think all of the TRI should be fine.

ICON follows GFS with Chatty winter precip. Prepare for disappointment in the valley. I'll double down. How about snow in Soddy and Ooltewah but not Downtown or East Brainerd? Signal and Lookout look solid though. 

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