Quincy Posted April 10, 2014 Share Posted April 10, 2014 While the setup on Saturday will likely be mitigated by capping, Sunday has the potential to feature at least isolated severe thunderstorms. A positively tilted trough approaches a neutral tilt across the southern Plains on Sunday. The GFS and Euro have come into better agreement with this now, showing favorable instability coupling with increased wind shear. The 12z guidance alone seems to suggest the eastern half of Texas and portions of Oklahoma could be at the greatest risk. Timing is crucial here, as a faster cold frontal passage could minimize the threat. As it is, the 12z and 18z GFS looked impressive in and around the Dallas area. Dew-points in the upper 60s to near 70, CAPE of around 2000 J/kg, increasing jet dynamics and a dryline ahead of the cold front during the mid to late afternoon hours. The surface low matures in far north Texas before occlusion takes place Sunday night. Any activity from that point forward would probably consolidate into a large squall line as it moves toward AR/LA. If the 00z suite shows a similar setup, I think we'll see a day 4 outlook posted by the SPC overnight. Link to comment Share on other sites More sharing options...
1900hurricane Posted April 10, 2014 Share Posted April 10, 2014 Unless the 00Z suite really lights things up, I'm kinda thinking the SPC will forgo a Day 4 risk area. There are still a great many things that can throw a wrench into this setup, so the predictability might not be where the SPC is comfortable with putting out a risk area just yet. In addition to possible timing issues (cold front too fast and/or delayed shortwave ejection), capping issues may rear their head yet again. Looking at the GFS, 850 mb winds veer to the SW over north Texas by 00Z Monday, which really ramps up helicites, but could also put the area under an iron-clad cap, as those SW winds advect in an elevated mixed layer originating from the Texas/New Mexico high plains. Despite my apparent pessimism, I'm really hoping things come together though. Sunday is actually a vacant day for me, and with north Texas easily within my cruising range, the potential is there for a nice chase day. Link to comment Share on other sites More sharing options...
Quincy Posted April 10, 2014 Author Share Posted April 10, 2014 Day 4 outlook includes the Arklatex region, as far east as the MS border: All hazard types are included. Link to comment Share on other sites More sharing options...
andyhb Posted April 10, 2014 Share Posted April 10, 2014 Wording to go along with it, this is likely spurred on by the Euro coming in more robust tonight with the low level wind fields and also breaking out quite a bit of precip on the dryline. While the cold front does surge south pretty quickly, it is too late to really cut off the action for central/eastern TX and perhaps into the Arklatex later on as storms advance eastward. DAY 4-8 CONVECTIVE OUTLOOKNWS STORM PREDICTION CENTER NORMAN OK0334 AM CDT THU APR 10 2014VALID 131200Z - 181200Z...DISCUSSION...THE SWRN U.S. SHORTWAVE TROUGH IS FORECAST TO RAPIDLY MOVE EWDACROSS THE SRN PLAINS AND LOWER MS VALLEY ON D4/SUN...WITH NUMEROUSTHUNDERSTORMS EVOLVING THROUGH THE PERIOD. A SURFACE LOW SHOULDEXIST SOMEWHERE BETWEEN WRN OK AND NWRN TX DURING THE DAY...SHIFTINGSEWD AS A COLD FRONT DEVELOPS RAPIDLY SWD. AHEAD OF THE LOW...SLYWINDS WILL BRING MID TO UPPER 60S F BOUNDARY LAYER DEWPOINTS TO THELOW/FRONT. MEANWHILE...RAPID COOLING ALOFT WILL OCCUR WITH THE UPPERTROUGH WITH WARMER AIR ACROSS SWRN TX SPREADING NEWD HELPING TOERODE CAPPING.WIND PROFILES WILL BECOME INCREASINGLY FAVORABLE FOR SEVERE STORMSINCLUDING SUPERCELLS AHEAD OF THE COLD FRONT WITH A BROAD AREA OFSWLY 40-50 KT 850 MB FLOW AND SUBSTANTIAL SPEED SHEAR WITH HEIGHT.TIMING ISSUES EXIST REGARDING LEADING IMPULSES PRIOR TO THE COLDFRONT ARRIVING WHICH WILL AFFECT WHERE THE STRONGEST FORCING FORASCENT WILL BE. MODELS SUGGEST A FEATURE MOVING ACROSS THE ARKLATEXIN THE 18-21Z TIME FRAME...THEN THE MAIN COLD FRONT LATER IN THEDAY. TORNADOES...HAIL AND WIND WILL ALL BE POSSIBLE BEGINNING EARLYAFTERNOON...WITH MORE OF A WIND AND HEAVY RAIN THREAT OVERNIGHT IFAN MCS FORMS.FOR THE MON/D5 PERIOD...THE AFOREMENTIONED SHORTWAVE TROUGH WILLRAPIDLY CONTINUE EWD ACROSS THE GULF COAST STATES WITH COLD FRONT TOTHE W FROM THE MIDDLE OH VALLEY SWWD TO THE SABINE RIVER. MUCH OFTHE AIR MASS IS EXPECTED TO BECOME OVERTURNED BY PREVIOUS DAYSCONVECTION...THEREFORE...PREDICTABILITY IS TOO LOW FOR D5.RAIN AND STORMS WILL PERSIST ALONG THE FRONT INTO THE TUE/D6 PERIODALONG THE E COAST...BUT THE SEVERE THREAT SHOULD BE MINIMAL BY THISTIME...JEWELL.. 04/10/2014 Link to comment Share on other sites More sharing options...
1900hurricane Posted April 10, 2014 Share Posted April 10, 2014 Already a swing and a miss on my part regarding whether the SPC would put out a Day 4 risk area or not. Still feeling a bit on the pessimistic side, but it's definitely safe to say that my attention has been garnered. Link to comment Share on other sites More sharing options...
brettjrob Posted April 10, 2014 Share Posted April 10, 2014 With the shortwave timing for Sunday afternoon, I'm concerned that veer-back-veer may be a significant issue over much of the warm sector. If you put that aside, the tornado potential looks substantial over N TX/S OK. I really hate VBV because it's so difficult to pin down in advance what effect it will have. It would be foolish to write the day off at this early juncture because of VBV, but at the same time, it's conceivable that this one issue could more or less wreck storm organization and tornado potential. If anything, it may favor the afternoon (18-22z) as the prime show before mode becomes increasingly messy into the evening. Already tired of badly-timed waves and we're not even halfway through April. Link to comment Share on other sites More sharing options...
tornadotony Posted April 10, 2014 Share Posted April 10, 2014 With the shortwave timing for Sunday afternoon, I'm concerned that veer-back-veer may be a significant issue over much of the warm sector. If you put that aside, the tornado potential looks substantial over N TX/S OK. I really hate VBV because it's so difficult to pin down in advance what effect it will have. It would be foolish to write the day off at this early juncture because of VBV, but at the same time, it's conceivable that this one issue could more or less wreck storm organization and tornado potential. If anything, it may favor the afternoon (18-22z) as the prime show before mode becomes increasingly messy into the evening. Already tired of badly-timed waves and we're not even halfway through April. It's a much more subtle shortwave than, say, 5/24/11. I could see VBV being a problem N of the Red River, but I'm not sure about S. The GFS has no hint of VBV S of I-20 yet at 00z (and I mean absolutely none), and has a phenomenal shear/instability balance. This would be a formidable tornado threat if it verifies. Link to comment Share on other sites More sharing options...
thewxmann Posted April 10, 2014 Share Posted April 10, 2014 With the shortwave timing for Sunday afternoon, I'm concerned that veer-back-veer may be a significant issue over much of the warm sector. If you put that aside, the tornado potential looks substantial over N TX/S OK. I really hate VBV because it's so difficult to pin down in advance what effect it will have. It would be foolish to write the day off at this early juncture because of VBV, but at the same time, it's conceivable that this one issue could more or less wreck storm organization and tornado potential. If anything, it may favor the afternoon (18-22z) as the prime show before mode becomes increasingly messy into the evening. Already tired of badly-timed waves and we're not even halfway through April. VBV is terrible because the models are bad at predicting the winds at every level to the tee this far out. Sometimes VBV shows up last minute, sometimes it disappears last minute... and convection itself can subtly influence the wind flow. It's a pain to forecast. The issue you cited -- too many storms too early -- is clearly going to be a problem if the GFS is correct. Hopefully the issue that screwed us over last time -- slower ejection than progged -- will help us this time around. Then again by Murphy's Law that's probably not going to happen, lol. Link to comment Share on other sites More sharing options...
1900hurricane Posted April 10, 2014 Share Posted April 10, 2014 CIPS Analogs for the 12Z GFS at hour 84 features a great multitude of severe weather reports, but not really that many tornadoes. Link to comment Share on other sites More sharing options...
tornadotony Posted April 10, 2014 Share Posted April 10, 2014 CIPS Analogs for the 12Z GFS at hour 84 features a great multitude of severe weather reports, but not really that many tornadoes. It also had runs of >250 tornadoes for last Thursday, so... Link to comment Share on other sites More sharing options...
Thundersnow12 Posted April 10, 2014 Share Posted April 10, 2014 It also had runs of >250 tornadoes for last Thursday, so... He must still be pessimistic. Link to comment Share on other sites More sharing options...
tornadotony Posted April 10, 2014 Share Posted April 10, 2014 He must still be pessimistic. CIPS generally performed better w/in 48h or so of the last event (it was still running hot compared to verification but it started toning it down). We'll see where it goes from here. Link to comment Share on other sites More sharing options...
1900hurricane Posted April 10, 2014 Share Posted April 10, 2014 It also had runs of >250 tornadoes for last Thursday, so... Wow, that bad? I know analogs aren't the best forecasting tool to use most of the time, but I figured it would be interesting enough to talk about. Link to comment Share on other sites More sharing options...
NTXYankee Posted April 10, 2014 Share Posted April 10, 2014 Well the AFD from FWD is confusing to me. They say severe weather will be east of I-35 due to strong cap in western and central zones, but say storms will develop on dryline which will be on the I-35 corridor. Looking at the models it seems dryline is still west of DFW in the afternoon, actually in a very similar location to this last event. Granted several days away still and will change I am sure but seems like eastern Texas is more at risk than DFW. Link to comment Share on other sites More sharing options...
Quincy Posted April 10, 2014 Author Share Posted April 10, 2014 The CIPS analogs for Saturday also look impressive, but once you break down the individual analogs with the best 500mb and MSLP match and they become much less impressive. I have not, however, looked at the individual analogs for Sunday. Link to comment Share on other sites More sharing options...
brettjrob Posted April 10, 2014 Share Posted April 10, 2014 It wouldn't be too surprising if the combined analogs for Saturday/Sunday are far more impressive than how this weekend actually unfolds. As usual, this system is timed in such a way that its potential (in a very abstract sense, I guess) won't be maximized, likely not by a long shot. Twelve hours faster with the upper-air features and this would probably be a pretty big deal Saturday over much of KS/OK/TX. Link to comment Share on other sites More sharing options...
tornadotony Posted April 11, 2014 Share Posted April 11, 2014 It wouldn't be too surprising if the combined analogs for Saturday/Sunday are far more impressive than how this weekend actually unfolds. As usual, this system is timed in such a way that its potential (in a very abstract sense, I guess) won't be maximized, likely not by a long shot. Twelve hours faster with the upper-air features and this would probably be a pretty big deal Saturday over much of KS/OK/TX. Unless it slows a bit and Sunday becomes a big day. Yeah, you have the front, but it won't make it to TX in time to prevent a big day there... Link to comment Share on other sites More sharing options...
brettjrob Posted April 11, 2014 Share Posted April 11, 2014 Unless it slows a bit and Sunday becomes a big day. Yeah, you have the front, but it won't make it to TX in time to prevent a big day there... Right. I'm not writing Sunday off at all, but if nothing else, the areal extent of the threat isn't what it could've been Saturday. First SREF SigTor plot for Sunday: Link to comment Share on other sites More sharing options...
Quincy Posted April 11, 2014 Author Share Posted April 11, 2014 Right. I'm not writing Sunday off at all, but if nothing else, the areal extent of the threat isn't what it could've been Saturday.Speaking of the areal extent, it's really a relatively small piece of real estate that sees the best overlap of instability and shear. That's not to say that a few intense supercells aren't possible, but that the overall size of the "more significant" threat is limited to a segment of NE Texas into extreme SE OK. Link to comment Share on other sites More sharing options...
ZackH Posted April 11, 2014 Share Posted April 11, 2014 00z NAM took a step forward for Saturday and Sunday, IMO... I'm resigned to the fact that Saturday is not a tornado day, but maybe an elevated mothership is possible. The NAM keeps trying to break a cell out in central KS near the dryline bulge. It also seems like the front slowed a bit and now paints a possible dangerous situation for south central OK into north and NE TX depending on development ahead of the front. Also, northern IL sure is an interesting play for Saturday based on this run... but the 00z GFS says no Link to comment Share on other sites More sharing options...
tornadotony Posted April 11, 2014 Share Posted April 11, 2014 00z NAM took a step forward for Saturday and Sunday, IMO... I'm resigned to the fact that Saturday is not a tornado day, but maybe an elevated mothership is possible. The NAM keeps trying to break a cell out in central KS near the dryline bulge. It also seems like the front slowed a bit and now paints a possible dangerous situation for south central OK into north and NE TX depending on development ahead of the front. Also, northern IL sure is an interesting play for Saturday based on this run... but the 00z GFS says no It's not going to be 64°F at 21z in nrn IL on Saturday. Link to comment Share on other sites More sharing options...
ZackH Posted April 11, 2014 Share Posted April 11, 2014 Agreed... not to mention this is first time we've seen such a solution in any model Sent from my LG-LS980 using Tapatalk Link to comment Share on other sites More sharing options...
Hoosier Posted April 11, 2014 Share Posted April 11, 2014 It's not going to be 64°F at 21z in nrn IL on Saturday. Gotta say I'm a bit intrigued regarding Illinois on Saturday. NAM forecast soundings have MLCAPE exceeding 1000 in a fairly strongly sheared environment and no capping issues. Day 3 outlook was pretty bearish but we'll see what the new day 2 says. Link to comment Share on other sites More sharing options...
Stebo Posted April 11, 2014 Share Posted April 11, 2014 It's not going to be 64°F at 21z in nrn IL on Saturday. Yeah maybe 74 but definitely not 64. I would outright toss the GFS at this point up this way. Link to comment Share on other sites More sharing options...
brettjrob Posted April 11, 2014 Share Posted April 11, 2014 On average, I'm seeing a de-amplifying trend in the guidance over the past 24 h for Sunday's shortwave. A fair number of models imply a cap bust away from the surging cold front in OK, and a faster, weaker shortwave would not help in that regard. With another significant shortwave so close upstream (near the Four Corners by 00z Mon), the flow evolution is very complex and could still shift back and forth over these final 60 h. Assuming it doesn't speed up even more, the LLJ over N TX and S OK on Sunday afternoon should be highly impressive and ready to make things happen with any discrete supercells that can develop. Uncertainty reigns for Sunday, but what looks certain is we'll have to wait at least a week for anything else after that, as this Gulf-blasting winter-like front may bring a borderline ice storm threat to the southern Plains on Monday. March-April 2014: just to spite those who said 2013 was as bad as it could get! Link to comment Share on other sites More sharing options...
andyhb Posted April 12, 2014 Share Posted April 12, 2014 00z NAM is looking pretty nasty parameter-wise in E OK if we can get storms fired there. That said, the surface low is getting squashed by the leeside cold intrusion/high. Link to comment Share on other sites More sharing options...
tornadotony Posted April 12, 2014 Share Posted April 12, 2014 The 00z high-res NAM run is very, very interesting for Sunday in N TX. Link to comment Share on other sites More sharing options...
tornadotony Posted April 12, 2014 Share Posted April 12, 2014 Also, something to watch in future runs as we get into the NAM's "more reliable" range is the fact that it's had a secondary sfc low develop on almost every run since Sunday night/Monday morning came into its range (at least since yesterday's 06z run). That would likely drive an overnight and Monday threat (not sure of the degree) from the Arklatex to the TN Valley. Link to comment Share on other sites More sharing options...
brettjrob Posted April 12, 2014 Share Posted April 12, 2014 Synthesizing the 00z data thus far suggests to me a cap bust is more probable than not for N TX. I continue to agree the environment is fairly impressive if something can sustain itself away from the cold front. Link to comment Share on other sites More sharing options...
somethingfunny Posted April 12, 2014 Share Posted April 12, 2014 Is it really a wasted trip to Texas if the cap bust happens during bluebonnet season?? Link to comment Share on other sites More sharing options...
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