rolltide_130 Posted February 22, 2018 Share Posted February 22, 2018 Okay, it may be time to start sounding the alarm bells for a significant severe weather threat across the eastern portion of the subforum for this Saturday.. The Euro has been slowly trending towards a more active solution over the last 48 hours, with the warm sector rapidly becoming more favorable across the Mississippi Valley in addition to kinematics that have been strong from the start. SBCAPE has been on a massive uptick, with values of well over 2000 J/KG now in place across the region. Put that below over 60 knots of deep layer shear, and well.. problems may start arising.. Link to comment Share on other sites More sharing options...
andyhb Posted February 22, 2018 Share Posted February 22, 2018 I'll be rather surprised if I don't see a 30% in the upcoming D3 outlook (at least for the damaging wind threat) given the strength of the wind fields associated with this and a seeming uptick in instability with each new model run across the suite. There's certainly potential for a notable event here, the 12z/00z Euro runs emphasize that with what appear to be several supercells breaking out across the Arklamiss and Mid-South, which would certainly be capable of tornadoes given the large hodographs and 35-45+ kts of low level shear in place. In addition, a mid level dry slot seems to be showing up through the morning/early afternoon in these areas that may allow clearing and fairly rapid destabilization given the degree of low level moisture. 500 mb temperatures have also been coming down a bit with a bit of an increase in 700 mb temperatures leading to steeper lapse rates in that layer. In other words, this looks to be trending up thermodynamically and it was always quite strong kinematically. Edit: No enhanced, but definitely expanded the slight and added a mention of a possible upgrade. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted February 22, 2018 Share Posted February 22, 2018 Not part of this subforum, but slight now includes much of northwest AL and clips the ABC 33/40 market. Will be interesting to hear James Spann or Brian Peters' take in today's Weather Xtreme Video.Sent from my SM-G955U using Tapatalk Link to comment Share on other sites More sharing options...
CheeselandSkies Posted February 22, 2018 Share Posted February 22, 2018 EHI and STP values ticking up on forecast soundings off both GFS and NAM, especially across AR, southern MO and western MS around 0Z Sunday. Hodos have that sickle shaped look in the lower levels. I think if lapse rates were steeper they'd be showing the PDS TOR hazard type.Sent from my SM-G955U using Tapatalk Link to comment Share on other sites More sharing options...
Jim Martin Posted February 23, 2018 Share Posted February 23, 2018 Highest tornado risk right there in Dixie Alley and the Mid South for Saturday evening. Link to comment Share on other sites More sharing options...
monsoonman1 Posted February 23, 2018 Share Posted February 23, 2018 This is a pretty classic cold-season setup for the area. CIPS analogs have some big events (#2 event from 12z NAM was 03/01/1997) mixed in with some lesser ones, but pretty much all of them had some tornadoes. Analogs aren't perfect, but I like to use them to get an idea of the ceiling and floor of an event. The 18z NAM maxed out around 1000 MLCAPE in east AR, which would be sufficient for tornadoes, maybe even a strong one or two. Any increase in lapse rates would really help this setup. With all that said, this is definitely the best setup so far this year, so I'll be paying close attention. Link to comment Share on other sites More sharing options...
JPOracle Posted February 23, 2018 Share Posted February 23, 2018 11 minutes ago, monsoonman1 said: This is a pretty classic cold-season setup for the area. CIPS analogs have some big events (#2 event from 12z NAM was 03/01/1997) mixed in with some lesser ones, but pretty much all of them had some tornadoes. Analogs aren't perfect, but I like to use them to get an idea of the ceiling and floor of an event. The 18z NAM maxed out around 1000 MLCAPE in east AR, which would be sufficient for tornadoes, maybe even a strong one or two. Any increase in lapse rates would really help this setup. With all that said, this is definitely the best setup so far this year, so I'll be paying close attention. I agree Link to comment Share on other sites More sharing options...
JPOracle Posted February 23, 2018 Share Posted February 23, 2018 Large cold season winter time set up at play Saturday into Sunday Morning as storms move northeast Link to comment Share on other sites More sharing options...
Quincy Posted February 23, 2018 Share Posted February 23, 2018 Can't rule out QLCS tornadoes on Saturday, and/or a few embedded supercell structures, but the storm mode looks largely linear. Low level instability does not look as impressive as some of the more severe analogs and issues in the mid-level wind fields suggest the window for any discrete supercells will be minimal at best. Even the agressive 3km NAM shows a linear storm mode, with some cellular elements within the larger scale line. Essentially it shows no open warm sector activity, where the parameter space and backing of near-surface winds are maximized. A typical forecast sounding ahead of the line (late afternoon in southern/eastern Arkansas) looks like this: The 0-2km wind fields are quite favorable, but then above that it gets junky looking. With all of that said, such considerable low level shear, combined with seasonably impressive low-level moisture and <1km LCLs suggest an elevated potential for tornadoes, although they'll probably be short-lived and embedded within a line. Link to comment Share on other sites More sharing options...
monsoonman1 Posted February 23, 2018 Share Posted February 23, 2018 Enhanced risk out for day 2 from NE TX to MS/TN with strong tornadoes mentioned. Sent from my SM-G920V using Tapatalk Link to comment Share on other sites More sharing options...
andyhb Posted February 23, 2018 Share Posted February 23, 2018 And in contrary to all of what Quincy posted lol, SPC (Broyles) goes with supercells and a 30% hatched. Link to comment Share on other sites More sharing options...
monsoonman1 Posted February 23, 2018 Share Posted February 23, 2018 And in contrary to all of what Quincy posted lol, SPC (Broyles) goes with supercells and a 30% hatched.Nothing like some Broyles to bring some enthusiasm. Lots of things still up in the air, I'd say.Sent from my SM-G920V using Tapatalk Link to comment Share on other sites More sharing options...
bjc3395 Posted February 23, 2018 Share Posted February 23, 2018 I'm on Quincy's side here. I don't see any reason to believe that there will be much in terms of supercellular activity. Typically what makes or breaks these cold season events is whether you get open warm sector development. Sure, the parameters may bring with them some impressive analogues, but they also bring some mediocre ones, and that's the problem with these events. The difference between a memorable tornado event and one that sucks is small. I'm not surprised in the 30%/hatched but I'm surprised definitely in the wording. That said, the forecaster has me less surprised. Link to comment Share on other sites More sharing options...
monsoonman1 Posted February 23, 2018 Share Posted February 23, 2018 SHEAR PROFILES SHOULD ENCOURAGE SEVERAL BOWING/LEWP STRUCTURES, WITH EMBEDDED SUPERCELLS POSSIBLE. FURTHERMORE, FORECAST SOUNDINGS AND HIGH-RES GUIDANCE DEPICT A CONSIDERABLE COMPONENT OF LOW-LEVEL SHEAR PERPENDICULAR TO SEVERAL BOWING SEGMENTS, ENHANCING THE POTENTIAL FOR TORNADOES -- A FEW OF WHICH COULD BE STRONG -- DURING THE AFTERNOON AND EVENING HOURS. Good tidbit from the new Day 2. Interesting that they would use the "strong tornado" wording for what is essentially a QLCS forecast. Not that you can't get strong tors from a QLCS, but typically SPC doesn't use that wording for this kind of setup. Also this: OUTSIDE OF THE MAIN BAND OF CONVECTION, ALTHOUGH FORCING FOR ASCENT WILL NOT BE PARTICULARLY STRONG EARLIER IN THE DAY, AN ISOLATED DISCRETE SUPERCELL OR TWO MAY FORM ACROSS THE MID-SOUTH WITHIN WARM/MOIST LOW-LEVEL CONFLUENCE SATURDAY AFTERNOON. FAVORABLE STORM-RELATIVE HELICITY AND EFFECTIVE SHEAR WOULD SUPPORT A CONDITIONAL DAMAGING WIND AND TORNADO THREAT DURING THIS TIME FRAME AS WELL. Link to comment Share on other sites More sharing options...
Quincy Posted February 23, 2018 Share Posted February 23, 2018 Can't say I strongly disagree with the 30% hatched, as a robust low-level jet (increasing to 55-65+ knots) would support a significant damaging wind threat with an evolving squall line. The potential for strong tornadoes seems more conditional. Despite some issues in the wind fields, just looking at LCLs, most of the region highlighted is progged to stay below 500m, so it won't take much at all for tornadogenesis, especially with the degree of 0-1km shear. One cannot completely rule out warm sector storm development given the magnitude of shear, especially if some of the low level cloudiness can be eroded to boost buoyancy. If anything, weak forcing would favor only isolated activity. Reference 12z HRRRX for a scenario where an isolated supercell could form in such an environment. The 3km NAM doesn't show this and the NSSL WRF tries to, but struggles to form any deep, robust convection ahead of the line. Stay tuned. Link to comment Share on other sites More sharing options...
Sydney Claridge Posted February 24, 2018 Share Posted February 24, 2018 18z GFS, 18z NAM, 18z 3k NAM, and 00z HRRR are all suggesting that the warm sector might move into (at least part of) the DFW metroplex area, most of which has been under a slight risk for tomorrow due to what seems to be a hail risk from elevated thunderstorms. It would be interesting to see if we can get surface-based convection in the vicinity of a warm front; the 18z 3k NAM and HRRR suggest that convection will develop just as the warm air moves in. However, the more recent 00z NAM and 00z 3k NAM are keeping DFW in the cool sector, though the 01z HRRR is moving the warm sector into DFW. So we'll see what happens. Link to comment Share on other sites More sharing options...
Jim Martin Posted February 24, 2018 Share Posted February 24, 2018 Memphis TN 0z NAM sounding valid 6 PM CST tomorrow evening. Link to comment Share on other sites More sharing options...
monsoonman1 Posted February 24, 2018 Share Posted February 24, 2018 I'm a fan of the HREF so far (it's only been around since October IIRC) as it did pretty well on 01/22 and it nailed that weird stuff in TX on the morning of 02/20. The 00z run has a messy convective mode tomorrow but it has some decent UH in good parameters with the line, so it points to a decent QLCS tornado day for AR, maybe into TN/MS. Link to comment Share on other sites More sharing options...
monsoonman1 Posted February 24, 2018 Share Posted February 24, 2018 10% hatched tornado probs for AR/TN/MS/MO/KY. Pretty large area of 5% probs too.Sent from my SM-G920V using Tapatalk Link to comment Share on other sites More sharing options...
Sydney Claridge Posted February 24, 2018 Share Posted February 24, 2018 First severe thunderstorm warnings now out for ping pong ball-sized hail from two elevated thunderstorms, one northeast of Wichita Falls and the other northwest of Bowie, TX. Link to comment Share on other sites More sharing options...
Upper Level LOL Posted February 24, 2018 Share Posted February 24, 2018 37 degrees here in Edmond and we've got a thunderstorm with some rain rates and thunder and lightning on par with storms in the summer. Crazy. Link to comment Share on other sites More sharing options...
Indystorm Posted February 24, 2018 Share Posted February 24, 2018 Starting to get some breaks in cloud cover in East TX now that will only help CAPE values later on today if this trend continues. Link to comment Share on other sites More sharing options...
Jim Martin Posted February 24, 2018 Share Posted February 24, 2018 Tornado Watch forthcoming. Link to comment Share on other sites More sharing options...
JPOracle Posted February 24, 2018 Share Posted February 24, 2018 I'm already seeing some supercells mixed in there already, i think this is a good call Link to comment Share on other sites More sharing options...
Jim Martin Posted February 24, 2018 Share Posted February 24, 2018 Possible tornado on radar already west of Y City, Arkansas, moving northeast at 50 MPH. Link to comment Share on other sites More sharing options...
Jim Martin Posted February 24, 2018 Share Posted February 24, 2018 Link to comment Share on other sites More sharing options...
Indystorm Posted February 24, 2018 Share Posted February 24, 2018 65/65 in Hot Springs. Play the game of where's the warm front. In all seriousness we may have a good chance of WF action today. Link to comment Share on other sites More sharing options...
Indystorm Posted February 24, 2018 Share Posted February 24, 2018 70/40 probs on that Arkansas/Texas tornado watch. Did not expect things to be that high today in all honesty. Link to comment Share on other sites More sharing options...
jojo762 Posted February 24, 2018 Share Posted February 24, 2018 Very impressive hodograph out of KSRX. Critical angle leaves a lot to be desired, but can't get much better than 0-1KM Shear of 45kts and 0-1km SRH of 360+ m2/s2. Definitely going to have a fairly significant QLCS threat later on... In addition to any discrete cells that might be able to develop and mature. Link to comment Share on other sites More sharing options...
JPOracle Posted February 24, 2018 Share Posted February 24, 2018 Likely tornado just northwest of Fort Smith Arkansas in Oklahoma, no warning on it, its an QLCS Link to comment Share on other sites More sharing options...
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