andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 That is one massive severe threat area... DAY 4-8 CONVECTIVE OUTLOOKNWS STORM PREDICTION CENTER NORMAN OK0351 AM CDT WED APR 23 2014VALID 261200Z - 011200Z...DISCUSSION.....SIGNIFICANT MULTI-DAY SEVERE EVENT EXPECTED ACROSS PORTIONS OF THECENTRAL AND SOUTHERN PLAINS SATURDAY AND SUNDAY AND ACROSS THE MSVALLEY AND MID SOUTH ON MONDAY...STRONG TORNADOES ARE POSSIBLE...MEDIUM RANGE FORECAST CONTINUES TO BE HEAVILY WEIGHTED TOWARD THEECMWF DUE TO RUN-TO-RUN CONSISTENCY REGARDING THE 500MB EVOLUTION OFWRN U.S. TROUGH. CONCERNS REGARDING POLAR FRONT UNDERCUTTING STRONGSWLY FLOW ALOFT HAVE ABATED THIS MORNING. LATEST GUIDANCE DEEPENSLEE CYCLONE OVER SERN CO SATURDAY AFTERNOON WITH SUBSEQUENT MOVEMENTINTO WRN KS ON SUNDAY. INTENSE 500MB SPEED MAX APPROACHING 90KTSHOULD ROUND THE BASE OF THE TROUGH ALONG THE AZ/MEXICAN BORDER THENEJECT INTO SWRN KS EARLY SUNDAY. AS A RESULT SFC LOW IS NOTEXPECTED TO ADVANCE APPRECIABLY EWD UNTIL LATER MONDAY AS SECONDARYMID-LEVEL SPEED MAX DEVELOPS FROM NORTH TX INTO THE LOWER OH RIVERVALLEY.MODERATE TO EXTREME INSTABILITY SHOULD DEVELOP EAST OF THE DRYLINESATURDAY AFTERNOON ALONG ERN PLUME OF STEEP LAPSE RATES. STRONGLYDIFLUENT FLOW ALOFT SHOULD ENCOURAGE VIGOROUS SUPERCELL DEVELOPMENTFROM PORTIONS OF WCNTRL TX...NWD INTO KS. VERY LARGE HAIL ANDTORNADOES CAN BE EXPECTED WITH THIS ACTIVITY.IT/S NOT ENTIRELY CLEAR HOW FAR EAST THE DRYLINE WILL MIX SUNDAY ASLOWEST PRESSURES WILL REMAIN FOCUSED ACROSS THE HIGH PLAINS OF WRNKS. MODELS MIX DRYLINE EAST OF I-35 CORRIDOR ACROSS OK BY 18ZSUNDAY BUT THE DAY5 FORECAST WILL ACCOUNT FOR DRYLINE NOT MIXINGACROSS THE PLAINS AS FAST AS MODELS CURRENTLY DEPICT. AS ARESULT...SUBSTANTIAL MID-LEVEL FLOW SHOULD OVERSPREAD THEMOIST/BUOYANT WARM SECTOR AND ANOTHER DIURNALLY-INITIATED ROUND OFPOTENTIALLY TORNADIC SUPERCELLS COULD EVOLVE.LATER MONDAY IT APPEARS THE SFC FRONT/DRYLINE SHOULD ADVANCE INTOTHE MS VALLEY. SCATTERED-NUMEROUS SUPERCELLS SHOULD EVOLVE AHEAD OFTHE FRONT FROM LA...NWD INTO MO AND POSSIBLY AS FAR EAST AS MIDDLETN. TORNADOES AND LARGE HAIL REMAIN POSSIBLE WITH WARM-SECTORCONVECTION...DARROW.. 04/23/2014 Link to comment Share on other sites More sharing options...
Ground Scouring Posted April 23, 2014 Share Posted April 23, 2014 Saturday afternoon looks to face increasing capping problems due to the slower movement as progged by the GFS and ECMWF. If the trend doesn't stop or reverse a possible bust may be coming, no matter how much the LLJ strengthens after sundown. Everything favors supercellular mode in wrn OK and swrn KS--deep-layer shear, instability, etc. that have already been mentioned elsewhere in this thread. We need to see some more model shifts, but if trends don't change, Monday evening over the Dixie Alley might be the best time/place for significant tornadoes--something that area doesn't need. It's a shame that the rural Plains of the TX / OK panhandles might get shut out of such a great set-up synoptically. The 12Z GFS and its ensembles today will be interesting, though not crucial, to watch. Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 Saturday afternoon looks to face increasing capping problems due to the slower movement as progged by the GFS and ECMWF. If the trend doesn't stop or reverse a possible bust may be coming, no matter how much the LLJ strengthens after sundown. Everything favors supercellular mode in wrn OK and swrn KS--deep-layer shear, instability, etc. that have already been mentioned elsewhere in this thread. We need to see some more model shifts, but if trends don't change, Monday evening over the Dixie Alley might be the best time/place for significant tornadoes--something that area doesn't need. It's a shame that the rural Plains of the TX / OK panhandles might get shut out of such a great set-up synoptically. The 12Z GFS and its ensembles today will be interesting, though not crucial, to watch. The 12z NAM still seems interesting for West Central and Central KS and OK (even though nothing is indeicated on the simulated CR)... Still showing CAPE to be in extreme values, along with LI of -6 and below. Helicity seemed OK, and then not much shear at any level, only about 30 kts, which is still meaningful enough... Link to comment Share on other sites More sharing options...
bdgwx Posted April 23, 2014 Share Posted April 23, 2014 I found the SAILS rollout schedule. It does not look like any additional radars will be updated in time for this outbreak...bummer. Link to comment Share on other sites More sharing options...
natecast Posted April 23, 2014 Share Posted April 23, 2014 Still learning, bear with me.... The new 12z GFS now coming in has some interesting, subtle differences from the 0z run. The 5H trough orientation is not as deep on the most recent run, and appears to be ejecting out in a negative tilt fashion quicker than last night's run of the GFS. In response, the 850mb low and surface low is shown farther east in Colorado. Thus, the most recent GFS run shows a stronger LLJ, stronger surface winds, and more backing surface winds across western OK/KS. Obviously we are still 72+ hours out from the Saturday event, so getting any more detailed than this would be futile. But, I believe the depiction on the latest GPS op run would be a significant event. Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 I'm still thinking that Saturday could end up at least a Moderate by Friday's D2 outlook... I'm also still flickering back and forth with which day (out of Saturday and Sunday) will be the highest severe threat day. I'm going with Sunday ATTM... although i'm not sure what I'll think once the 12z GFS and the 18z NAM come out. Link to comment Share on other sites More sharing options...
tornadotony Posted April 23, 2014 Share Posted April 23, 2014 The 12z GFS run is still significantly convectively contaminated for Saturday and Sunday. Link to comment Share on other sites More sharing options...
andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 Even with that, the GFS is coming closer to the Euro with a broader trough/more diffuse forcing for Monday. Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 12z GFS at 84h shows high to extreme instability over an area that's actually to the east of the threat area on Saturday... By Sunday the CAPE has diminished significantly over the threat area. The SPC is mostly going off of the ECMWF with their outlooks, so I'll be concentrating more on those products. Link to comment Share on other sites More sharing options...
andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 12z GFS at 84h shows high to extreme instability over an area that's actually to the east of the threat area on Saturday... By Sunday the CAPE has diminished significantly over the threat area. The SPC is mostly going off of the ECMWF with their outlooks, so I'll be concentrating more on those products. No it isn't, it is directly within the risk area. The warm sector does look like it broadened over KS though. Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 The 12z GFS run is still significantly convectively contaminated for Saturday and Sunday. I'm a little unexperienced with forecasting at this range... What do you think about Sunday vs. Saturday it terms of highest severe threat? Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 No it isn't, it is directly within the risk area. The warm sector does look like it broadened over KS though. Sorry, not exactly what I meant. I meant that the biggest area of high CAPE is more centered over East KS. And agreed about the warm sector's expansion. Once again, I'm very new to forecasting at this range Link to comment Share on other sites More sharing options...
andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 I'm a little unexperienced with forecasting at this range... What do you think about Sunday vs. Saturday it terms of highest severe threat? Saturday is definitely higher potential currently than Sunday, as Sunday could turn messy with the occluded upper low and the second vort max that rotates around for Monday hasn't matured yet. That's not to say that Sunday will likely be a total bust, although for chasers it likely won't be over the best terrain and situations like this where the ULL occludes and the main surface cyclone becomes vertically stacked usually result in messy convective modes. That changes on Monday though, with secondary surface cyclone development possible and also the main/original low moving east. Link to comment Share on other sites More sharing options...
tornadotony Posted April 23, 2014 Share Posted April 23, 2014 I'm a little unexperienced with forecasting at this range... What do you think about Sunday vs. Saturday it terms of highest severe threat? Sunday looks messy to me, be it on the GFS or the Euro. Saturday looks like a big day IF the forcing makes it to the warm sector in time. So in other words, neither right now. I'm going with Monday. Link to comment Share on other sites More sharing options...
andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 Sunday looks messy to me, be it on the GFS or the Euro. Saturday looks like a big day IF the forcing makes it to the warm sector in time. So in other words, neither right now. I'm going with Monday. This, especially on the Euro, Monday has the greatest potential to be a more widespread outbreak. This is somewhat hinted at in the D6 snippet with the mention of scattered/numerous warm sector supercells. If that happens, look out. Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 Saturday is definitely higher potential currently than Sunday, as Sunday could turn messy with the occluded upper low and the second vort max that rotates around for Monday hasn't matured yet. That's not to say that Sunday will likely be a total bust, although for chasers it likely won't be over the best terrain and situations like this where the ULL occludes and the main surface cyclone becomes vertically stacked usually result in messy convective modes. That changes on Monday though, with secondary surface cyclone development possible and also the main/original low moving east. Yep... I'm thinking the same for Monday, and if I have the ability to chase there, I would do it. Also, being in East Central KS, Sunday for here could turn even messier depending on how much of Saturday's convection can sustain overnight (that's assuming it moved close enough to here). I'm thinking Sunday has a bigger threat for multicell or line development, which does contradict the SPC's wording in their discussion. Link to comment Share on other sites More sharing options...
thewxmann Posted April 23, 2014 Share Posted April 23, 2014 Still learning, bear with me.... The new 12z GFS now coming in has some interesting, subtle differences from the 0z run. The 5H trough orientation is not as deep on the most recent run, and appears to be ejecting out in a negative tilt fashion quicker than last night's run of the GFS. In response, the 850mb low and surface low is shown farther east in Colorado. Thus, the most recent GFS run shows a stronger LLJ, stronger surface winds, and more backing surface winds across western OK/KS. Obviously we are still 72+ hours out from the Saturday event, so getting any more detailed than this would be futile. But, I believe the depiction on the latest GPS op run would be a significant event. It's a lot more than subtle, 12Z GFS is much faster than 0Z run, and occludes a little slower. In terms of sensible weather that could make a big difference. Link to comment Share on other sites More sharing options...
thewxmann Posted April 23, 2014 Share Posted April 23, 2014 Sunday looks messy to me, be it on the GFS or the Euro. Saturday looks like a big day IF the forcing makes it to the warm sector in time. So in other words, neither right now. I'm going with Monday. This. Neither Saturday nor Sunday look as impressive as Monday does for the Dixie. Link to comment Share on other sites More sharing options...
Ground Scouring Posted April 23, 2014 Share Posted April 23, 2014 This. Neither Saturday nor Sunday look as impressive as Monday does for the Dixie. If (as I and others have said before) Monday is to be the big day, then a lot is going to hinge on the mesoscale evolution, as is often the case in Dixie Alley. The ECMWF and the 12Z GFS hint at secondary cyclogenesis, but it's still just a hint, and both models ad verbatim show veered low-level winds over the western half of the warm sector Monday afternoon. Has the overall pattern this year favored secondary cyclogenesis a lot or a little? Link to comment Share on other sites More sharing options...
andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 If (as I and others have said before) Monday is to be the big day, then a lot is going to hinge on the mesoscale evolution, as is often the case in Dixie Alley. The ECMWF and the 12Z GFS hint at secondary cyclogenesis, but it's still just a hint, and both models ad verbatim show veered low-level winds over the warm sector Monday afternoon. Has the overall pattern this year favored secondary cyclogenesis a lot or a little? What? No they do not, especially the Euro. And even if they did, you don't need the type of backing in Dixie that you do in the Plains for supercells. Often, some of the worst Dixie Alley setups feature large amounts of speed shear with more subtle directional shear. SSW surface winds can work perfectly fine. Link to comment Share on other sites More sharing options...
andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 Euro is coming in way, way slower through 96, likely a day slower frankly. Assuming the wind fields are favorable over some area of the Plains, I think Sunday is back with this run, with the original ULL taking much longer to occlude. Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 I'm still holding out hope that something interesting will happen over Saturday and Sunday. Wish I could see the ECMWF for those days... does anybody have access to that? Link to comment Share on other sites More sharing options...
OUGrad05 Posted April 23, 2014 Share Posted April 23, 2014 Euro is coming in way, way slower through 96, likely a day slower frankly. Assuming the wind fields are favorable over some area of the Plains, I think Sunday is back with this run, with the original ULL taking much longer to occlude. need some run to run repeatability. I am losing confidence for this weekend because of all the inconsistencies. Sent from my SM-N900V using Tapatalk Link to comment Share on other sites More sharing options...
chase_stormz Posted April 23, 2014 Share Posted April 23, 2014 Euro is coming in way, way slower through 96, likely a day slower frankly. Assuming the wind fields are favorable over some area of the Plains, I think Sunday is back with this run, with the original ULL taking much longer to occlude. While a slower arrival of the sw trough hinders development Saturday, it could mean something big for Sunday as it times right with little to no convection in the warm sector. Link to comment Share on other sites More sharing options...
andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 Real strange run of the Euro, it still looks like Monday is the day in Dixie Alley, going by how the LLJ progresses through the day. Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 While a slower arrival of the sw trough hinders development Saturday, it could mean something big for Sunday as it times right with little to no convection in the warm sector. Agreed, although at this point... that's just one possible scenario out of the many that are becoming apparent... Link to comment Share on other sites More sharing options...
FHSC Sam Posted April 23, 2014 Share Posted April 23, 2014 Real strange run of the Euro, it still looks like Monday is the day in Dixie Alley, going by how the LLJ progresses through the day. What's the Euro showing it terms on instability there? EDIT- My bad... forgot ECMWF doesn't show that. Link to comment Share on other sites More sharing options...
andyhb Posted April 23, 2014 Author Share Posted April 23, 2014 I am becoming even more concerned with this, considering how different this evolution is, it still yields a likely outbreak in Dixie on Monday. The LL shear is also very high this run with the surface winds more backed than 00z. Link to comment Share on other sites More sharing options...
Superstorm93 Posted April 23, 2014 Share Posted April 23, 2014 What's the Euro showing it terms on instability there? EDIT- My bad... forgot ECMWF doesn't show that. If you have the paid sources, instability and many other variables are offered. By 132 hours, the ECMWF has a 993mb low over KTUL with 1500 joules or greater of SBCAPE with the LLJ ripping over TN/LA/MS/AL. Gulf is obviously wide open and moisture is abundant (to say the least) Link to comment Share on other sites More sharing options...
ZackH Posted April 23, 2014 Share Posted April 23, 2014 From a chaser perspective, I'm much more wishy washy about this setup now. Especially, if this new Euro slow trend is correct. Best case scenario, this makes Sunday a good chaseable day in good chaseable terrain (kind of like Saturday was a couple days ago). Also, there could still be an isolated monster on the dryline Saturday. When it gets to Monday, the biggest day, its generally in rough chasing terrain and those aren't the type of storms I really want to chase. Crazy storm motions in the jungle, no thank you. I did enough of that on 4/27/2011 and don't care to again. I am growing more concerned for the mid south and SE on Monday and beyond, however from a forecasting perspective. Could be a serious event. Either way, I will be out for the Plains setups Sat/Sun... already have confirmed the trip... I just hope that we get more certain about one potential big day while I'm out. Link to comment Share on other sites More sharing options...
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