18z nam rolling out, should get a better look at Friday into Saturday with the secondary lows evolution
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Severe Weather Threat January 8-10, 2026
- Thread starter CheeselandSkies
- Start date
- Thread starter
- #102
CheeselandSkies
Member
Compact warm sector in Mississippi late Friday into early Saturday on the NAM at the end of its range, maybe a little mismatch on best parameters. But it's rather good imo. Can't wait too see mesoscale models key in on this areas in a couple days.
Can anyone explain why Northern OK would be producing a sounding like this AFTER the initial line of storms moves through? It's presenting like the system is leaving SB CAPE directly in its wake. Does this have something to do with outflow boundaries?
GFS is showing something similar but in a different area and to a lesser extent.
GFS is showing something similar but in a different area and to a lesser extent.
jiharris0220
Member
It’s important to keep in mind that dew point is measurement of moisture RELATIVE to temperature. Dew points at or below 60 by itself doesn’t indicate lack of moisture.
A dew point of 13 with a temp of 20 is just as moist as a dew point of 70 over 77.
Models aren’t showing a lack of instability due low moisture, but rather because the vertical temperature profile is rather flat, temps don’t go below freezing until around 650mb, which wouldn’t be a big deal if it wasn’t combined with the mid level inversion layer and it’s no surprise cape doesn’t even break 500j/kg.
This can largely be negated if surface temps are at least in the mid 70s to 80s, this will depend on how cloud free the warm sector is. Obviously, low cape doesn’t thwart tornadoes, but the full potential will definitely be limited if the cumulus field doesn’t evaporate quickly.
A dew point of 13 with a temp of 20 is just as moist as a dew point of 70 over 77.
Models aren’t showing a lack of instability due low moisture, but rather because the vertical temperature profile is rather flat, temps don’t go below freezing until around 650mb, which wouldn’t be a big deal if it wasn’t combined with the mid level inversion layer and it’s no surprise cape doesn’t even break 500j/kg.
This can largely be negated if surface temps are at least in the mid 70s to 80s, this will depend on how cloud free the warm sector is. Obviously, low cape doesn’t thwart tornadoes, but the full potential will definitely be limited if the cumulus field doesn’t evaporate quickly.
jiharris0220
Member
The dry line is lagging back behind the initial line of storms it initiated, the reason why there’s higher cape is because of the colder air above the surface behind the line of storms.
On the right sounding you can see the dryline is slanted in height (normal), and again, theres higher cape due to the steeper temp profile and slightly warmer surface temps due to WAA being stronger near the dryline.
@jiharris0220 already nailed the answer for this, but on your second part:
Outflow boundaries can (and sometimes greatly) enhance shear and also act as a focal point for storm initiation. As you know as well, they can also undercut ongoing convection.
I’m sure there are scenarios where outflow boundaries can focus existing CAPE, but CAPE is always going to be more related to the temperature profile throughout the atmosphere at the vertical.
WeathermanLeprechaun
Member
You're one of few in the US to have a tornado shelter. Stay alert!
WeathermanLeprechaun
Member
That NAM quirk in S KS/N OK honestly would be a decent early cold core eque event if it were to verify. If that trend maintains, I might start watching that area.
A quick note about CAPE is while low level thermodynamics do matter, it is how it is distributed vertically throughout the atmosphere. There's reasons events like 3/5/2022 worked. You had fairly cold temps for a significant event, but the nice mid level thermodynamics contributed to strong instability above. If it was all focused in the low levels or depended on, then events where storms would need to break a stable layer or inversion, they wouldn't really happen. Strong instability above the stable layer is key in those nocturnal events. 2/26/23, 5/4/07, 5/18/25, 6/20/25. A few events of note where storms had a strong inversion to deal with but rapidly became mature so they sustained due to well mixed mid levels aloft allowing a balance of shear. That's a bit steering from the main question at hand. A profile like that, even if 62/59, would be pretty nice to sustain convection out of
A quick note about CAPE is while low level thermodynamics do matter, it is how it is distributed vertically throughout the atmosphere. There's reasons events like 3/5/2022 worked. You had fairly cold temps for a significant event, but the nice mid level thermodynamics contributed to strong instability above. If it was all focused in the low levels or depended on, then events where storms would need to break a stable layer or inversion, they wouldn't really happen. Strong instability above the stable layer is key in those nocturnal events. 2/26/23, 5/4/07, 5/18/25, 6/20/25. A few events of note where storms had a strong inversion to deal with but rapidly became mature so they sustained due to well mixed mid levels aloft allowing a balance of shear. That's a bit steering from the main question at hand. A profile like that, even if 62/59, would be pretty nice to sustain convection out of
WeathermanLeprechaun
Member
Yeah, admittedly i became WXTwitter that whole day and pretty much dismissed even professional offices opinions just because i simply couldn't see a reason why the high risk was warranted. It wasn't really due to the surface low, but more so a reliance on CAMs which o have lessened since then. They're more a guidance or potential depiction, and they do not forecast CFs well. I got proven wrong that day very hard. It's a reason why i try to be straight to the point but trying not to overdo my opinion of certain setups. I, called a pretty obvious bait setup in November in SE MO potential for a strong tornado lol.
Surface low placement does matter but as you said, outbreaks happen in all sort of variability. Always differently combined ingredients but they work to beat a certain factor and overcome it, whereas other times the combination doesn't work and the event underperforms.
Kds86z
Member
WeathermanLeprechaun
Member
Exactly why you just don't call a event off 5 days out lol. Definitely looking at a spinup risk around there like he says
WeathermanLeprechaun
Member
slenker
Member
Supercell printer go brrrrrr
WeathermanLeprechaun
Member
I feel like the RRFS is literally just that one guy on YouTube who calls every storm the "largest he's ever seen" mixed in with a little sprinkle of WXTwitter weenies. Genuinely trying to take that run seriously, I'm very curious WHY the RRFS depicts such a robust supercell in Eastern AR. Seems to be riding some sort of boundary on that run or something at least. It may be a major outlier but always fun to pick apart anyways
slenker
Member
In all seriousness, though, I do honestly question why the RRFS is always extremely bullish on supercells and helicity tracks. It’s so funny to me that it just always spits out the highest end solution 99% of the time.
WeathermanLeprechaun
Member
It's something to do with its parameter scheme, I'd bet. They can also mean hail tracks but that's a stupidly large UH track LOL. Definitely gives a idea of what maybe more instability up north could do...
Kds86z
Member
Totally forgot the 18Z HRRR goes to 18Z Thursday. It's actually more extreme than the Nam in terms of MU cape and (rear flank?) Supercells. Never seen anything like that before.
It actually has MUCAPE peaking at 1500 J/kg as the first line passes over.
Very interested in what the 00Z says in a couple hours.
Must be the model trey is looking at when he said widespread severe and all hazard potential threat for Friday lol.