Holston_River_Rambler

Yeah, was just about to post the image windspeed posted, no clear velocity couplets on the cells yet, but some of them are starting to hook.

Mesoscale Discussion 0257 NWS Storm Prediction Center Norman OK 0229 PM CDT Thu Mar 25 2021 Areas affected...far northern Mississippi into Middle Tennessee Concerning...Severe potential...Tornado Watch likely Valid 251929Z - 252130Z Probability of Watch Issuance...80 percent SUMMARY...The threat of severe storms including tornadoes will increase by late afternoon into Middle Tennessee and persist through the evening. A watch may be issued by 21Z. DISCUSSION...Surface analysis currently shows a warm front into far southwestern TN extending east/southeast into northern AL. Meanwhile, another warm front extended from the developing surface low from southern IL into central KY. In between these two fronts, gradual warming is taking place, with temperatures now into the low 70s F. MUCAPE currently remains below 1000 J/kg as a result of dewpoints near 60 F. Strengthening 850 mb winds out of the southwest later today should aid moisture advection out of MS into Middle TN, with areas of heating helping to destabilize as well. Shear will become increasingly favorable for tornadic supercells in the 21-03Z time frame, and a few tornadoes are anticipated as the mid 60s F dewpoints arrive later today. With the more unstable air in place, effective SRH may reach 400-500 m2/s2. ..Jewell/Hart.. 03/25/2021

MRX AM update: Wanted to talk about the environment expected this afternoon and evening. The main mid/upper lvl trough continues to dominate much of the CONUS this morning with the main shortwave showing up clearly in moisture channels. This shortwave and associated speed max will translate east as this shortwave digs into the MS river valley. Impressive kinematics will overspread much of the southeast this afternoon with 80-100 kt mid level winds. An associated low level jet is expected to develop late this morning peaking near 60-70 knots. This LLJ is already starting to be seen in the HTX Vad wind profile with strengthening flow just above 4kft. From a more mesoscale picture, a warm front is currently just to our south and west generally from northern MS through northern AL and into central GA. Plenty of showers continue to overspread along and north of this boundary. MUCAPE increases just south of this boundary where an increase in lightning activity can be seen. This front will continue its northerly motion thorugh the morning and into the afternoon. All available hi-res guidance suggests showers and embedded thunderstorms will increase in areal coverage through the morning and afternoon. While this normally will keep boundary layer instability on the lower side, I think the impressive LLJ will aid in advection and should overcome this. Also, guidance is pointing at some clearing taking place late this afternoon. If some sun can come out then this heating could encourage further increases in instability. The shear/CAPE parameter space is concerning to say the least. Deep layer shear will only increase by the afternoon and into the evening hours. 0-0.5km/0-1km/0-3km shear near 35/45/70 knots respectively suggest that the environment will be more than conducive for rotating updrafts today. SRH between 400-600m2/s2 leading to large looping hodographs combined with >300j/kg of MLCAPE suggests tornado potential increases late this afternoon and into the early evening for the southern valley and portions of the Cumberland Plateau. The threat of long-tracked supercellular structures and long-track tornadoes are also possible given the low LCL`s, 0-3km CAPE, and impressive near surface shear. Again this window seems to be from 00z-03z. HREF and HRRR continue to show several updraft helicity tracks through the area further increasing confidence of the above. Further severe weather hazards will be damaging winds and large hail with any of these supercell structures or any semi-linear convective structures.

MRX seems to think the real question is surface instability that any discrete cells could take advantage of. Is that determined by just sunshine warming the boundary layer? They also mention a 850 warm layer limiting instability. So my take is that for Cumberland plateau and areas east a lot depends on how quickly the atmo recovers after the AM warm front? Clouds and rain = more stability and more likely that everything consolidates into a line before it gets here?

If nothing else, this one does not have the upper low getting shunted east like last week, but racing off to the lakes. IMO that is a stronger signal for the possibility (not guarantee) of some of the more unstable atmo. making into east TN and plateau areas.

And another one. These are fun little storms that keep training over my house lol.

Got some even larger hail with another storm that just rolled through. Still pea-sized, but the hail with this one was much more intense than the last storm that rolled through:

Getting some very small hail with this line that is moving through Morgan county.

Getting some sunshine here in Morgan County, now.

This chaser is almost on the Selma/ Autauga county tornado: https://livestormchasing.com/chasers/brett.adair

Warned storm near Selma looks rough on radar:

Already a Watch through 1 PM Central and a warned cell in west central MS:

Warm front looks pretty healthy this AM: High Risk in effect now:

So..... BINGO card time for the storm chasers this Wednesday?? I was going to say Reed Trimmer sighting was the freebie and sure enough, he's already been sighted. I think my wxtwitter feed is just now getting some of the storm chaser shenanigans in it (previously, mostly winter wx stuff). If they're having trouble chasing tornados in western KS and TX, they may be in more trouble in the Upper SE, lol. I didn't quite catch everything that happened with the latest high plains chase session, (other than the now ubiquitous Dodge City windmill farm "No"), but are we about to get a bunch of the chaser newbies in the Upper SE (probably S and W of Eastern TN)? If we're gonna get some severe (not in this thread to talk about the likelihood or lack of it), might as well have the drama and comedy of wxtwitter pay a visit. Some BINGO card suggestions...... 1. Reed Trimmer is the free space 2. somebody tweets "where is the tornado??!!" with a Radarscope image of them next to a velocity couplet 3. somebody drives down a private gravel road and gets chased off with a shotgun 4. somebody from another forum area posts in the TN valley severe thread at 2 AM asking why only 2 people are awake digitally chasing the event as it is consolidating into a line of convection 5. We figure out someway to include the Johnny Cash image or birthday cake doodle dog images in a severe wx meme that only 10 - 13 people will understand and appreciate 6. another chaser mocks #3 on twitter 7. 2011 mention on twitter 8. Jeff Piotrowski sighting (another free space of your choice if he finds something like the infamous blue shed) That's all I can think of for now. PS, this is not me hating on storm chasers. I was just more interested in the interpersonal interactions I saw on wxtwitter after the latest high plains chase/ event, than the actual event, though I always love the hi res satellite imagery of the convective trains horizontal rotation getting lifted vertically. And this:

GFS v 16 brought my baby back:

Wild GFS v16 6z storm:

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Euro Control I40 special:

The 850 low isn't over Des Moines this time, I don't know what to think

John, you just got quasi NAM'd, what are you gonna do with more snow? MRX is rather encouraged, for precip at least, with a variety no not even a variety, a veritable smorgasbord of exciting forcing mechanisms For Tuesday night and Wednesday, a compact short-wave will move across the Tennessee valley, Gulf Coast states, and southern Appalachians. Jet structure is complex but northern stream jet over the mid-Atlantic and southern stream jet with the upper trough will produce upper divergence. The Ageostrophic Circulations with the jets will enhance the dynamic forcing over the area. Models show decent QG forcing which will help cool the column. This system will produce widespread showers beginning in the evening south, then lift northeast into much of the area overnight. Temperature profile tricky with the NAM colder. The GEFS and ensemble mean from the ECMWF suggest temperatures will be cold enough for snow across the higher elevations. Snow accumulations of a dusting (at or above 4kft) and 2 inches (at or above 5kft) are anticipated. Locally heavier amounts over the peaks of the Smoky and Roane Mountains. This lines up well with the WPC snow accumulations. They didn't even mention the WAA, meager though it may be: almost guarantees a NW trend with precip.

Rut roh Rorge (from MRX): Within this high shear, low CAPE environment, there will be a very low chance of a QLCS tornado within the convective line across our western and southwestern counties on tonight. While the risk of a QLCS tornado is very low, it is a risk that will need to be considered and monitored closely tonight.

Here comes bowling ball #1: Will it be a gutter ball or a strike? One of the big problems we had with the past systems during the arctic outbreak, is that the energy has never truly taken the low road. That we were even getting any frozen east of BNA was a testament to how cold the air was at the surface, while the 850 lows were running into the midwest.

I’ve had my 3 days of sun. I’m recharged for one more run until April, lol.

Already 40 in Mossy Grove. I'm thinking 72ish up here today.