David Reimer Posted April 25, 2012 Share Posted April 25, 2012 AY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1227 PM CDT WED APR 25 2012 VALID 261200Z - 271200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CNTRL/SRN HIGH PLAINS... ...CNTRL/SRN HIGH PLAINS... WELL DEFINED UPPER LOW OFF THE SRN CA/NRN BAJA COAST...CENTERED NEAR 29N/127W...WILL EJECT INLAND EARLY IN THE DAY2 PERIOD BEFORE LIFTING NEWD INTO CO/NM BY 27/00Z. THIS FEATURE WILL THEN SHIFT INTO THE HIGH PLAINS DURING THE OVERNIGHT PERIOD. AS THE TROUGH SHIFTS ACROSS THE ROCKIES LOW LEVEL FLOW WILL UNDOUBTEDLY RESPOND AND BECOME DECIDEDLY SELY ACROSS THE HIGH PLAINS. WHILE THE LATEST SHORT RANGE MODELS HAVE STRUGGLED RECENTLY REGARDING THE AGGRESSIVE BOUNDARY LAYER MOISTURE RETURN...IT APPEARS A LEGITIMATE MOISTURE SURGE WILL SPREAD ACROSS THE SRN PLAINS WARM SECTOR OVER THE NEXT 24-48HR AND 60-65 SFC DEW POINTS MAY BE IN PLACE ACROSS THE ERN TX/OK PANHANDLE REGION BY PEAK HEATING. TIMING OF THE UPPER TROUGH WILL FAVOR OVERNIGHT CONVECTION THOUGH STRONG BOUNDARY LAYER HEATING SHOULD CONTRIBUTE TO DESTABILIZATION WITHIN THE UPSLOPE REGION FROM THE TX PANHANDLE INTO EXTREME SERN CO. FOR THIS REASON IT APPEARS SCATTERED THUNDERSTORMS WILL BEGIN DEVELOPING AROUND 21-22Z. FORECAST SOUNDINGS SUGGEST SBCAPE COULD EASILY EXCEED 2000 J/KG WITHIN A SHEARED ENVIRONMENT THAT WILL STRONGLY SUPPORT SUPERCELLS. FAVORABLY SHEARED AND BACKED LOW LEVEL FLOW ALSO LENDS CREDENCE TO THE POSSIBILITY OF TORNADOES. HAVE INCREASED THE SEVERE PROBS ACROSS THE HIGH PLAINS TO ACCOUNT FOR THE LIKELIHOOD OF POTENTIALLY TORNADIC SUPERCELLS IN ADDITION TO VERY LARGE HAIL. LATE AFTERNOON/EVENING SUPERCELLS WILL ALSO DEVELOP FARTHER NORTH ACROSS ERN CO WITHIN STRONGER ZONE OF FORCED ASCENT. THIS ACTIVITY COULD EASILY SPREAD INTO SWRN NEB/NWRN KS BY MIDNIGHT AS LLJ INCREASES DURING THE OVERNIGHT PERIOD. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted April 25, 2012 Share Posted April 25, 2012 I have been watching this event for days now, and I still don't know what to think. Guidance always struggles with these cutoffs kicking out then deamplifying, but it has been worse than normal here it seems. It does seem like there will be some amount of PV stretching once this wave ejects the Rockies...even then most guidance now holds off ejection until after 00-03z. Going to be an interesting event nonetheless since elevated convection is going to be more than severe, but the question remains on surface based initiation during the early evening given the much discussed cap...going to take significant low level convergence to break through that...and it seems the forcing may be coming a tad late. Link to comment Share on other sites More sharing options...
brettjrob Posted April 25, 2012 Share Posted April 25, 2012 Yeah, this could very well end up being one of those absolute worst-case scenarios WRT timing. When I look at the H5 forecast for 12z Fri, it looks like a great setup for tornadic supercells across W KS. If the wave could either slow down or speed up by even 6 hr., then one of the two days would have more serious potential. The NAM had been fast enough to salvage Thursday up until this morning, when it really backed off toward the global model consensus, which places the shortwave trough axis over E AZ tomorrow evening. Given how compact it is, I don't see much PVA occurring during the daylight hours, so we'll be left to rely on convergence and any more subtle energy propagating through the SW flow. Quite a shame, since the medium range does not currently look promising for big convective potential on a wide scale. Link to comment Share on other sites More sharing options...
Chinook Posted April 25, 2012 Share Posted April 25, 2012 How many jet streaks are there? Link to comment Share on other sites More sharing options...
wxsniss Posted April 26, 2012 Share Posted April 26, 2012 noob / it's-dead-here questions: - have all major tornado outbreaks occurred east of a trough (ie is the strong southwesterly flow aloft a requirement)? - scheduled to chase may 5-12 in the plains... any thoughts on Day10+ outlooks for the ridge over the west shifting east / other large-scale features improving by then? thanks! Link to comment Share on other sites More sharing options...
reber500 Posted April 26, 2012 Share Posted April 26, 2012 Also, Friday appears to be rather interesting... Basing off of the most recent runs of the NAM, and GFS... ALTHOUGH uncertainty is still pretty high for this event, and the SPC didn't really pay much attention in the Day 3 Outlook... http://www.twisterda...e&archive=false This is 60-Hour NAM model for 500mb winds, although it's not particularly strong, it is there... http://www.twisterda...e&archive=false Although, the GFS appears a bit more promising in the 500mb winds... Although the CAPE isn't expected to be to strong on Friday basing off of the GFS, and NAM with AOA 1000-2500 J/KG... However, I did notice that the 3KM EHI is Extremely High (Granted it's not as high as April 14 but its still high...) http://www.twisterda...e&archive=false On another related note the WFO in ICT did give a "Significant" Threat to Life on the Day 3 HWO.. http://www.crh.noaa....o/hwo.php?day=3 All images can be found at twisterdata.com . . . Link to comment Share on other sites More sharing options...
reber500 Posted April 26, 2012 Share Posted April 26, 2012 I have been watching this event for days now, and I still don't know what to think. Guidance always struggles with these cutoffs kicking out then deamplifying, but it has been worse than normal here it seems. It does seem like there will be some amount of PV stretching once this wave ejects the Rockies...even then most guidance now holds off ejection until after 00-03z. Going to be an interesting event nonetheless since elevated convection is going to be more than severe, but the question remains on surface based initiation during the early evening given the much discussed cap...going to take significant low level convergence to break through that...and it seems the forcing may be coming a tad late. Same here... I'm thinking if storms DO form than this could be a pretty interesting event... It's just the Models have been changing quite a bit about where Storm initiation would occur, and where "Key" Ingredients are going to be... Link to comment Share on other sites More sharing options...
Buckeye05 Posted April 26, 2012 Share Posted April 26, 2012 From what I can tell, Saturday looks interesting as well. Link to comment Share on other sites More sharing options...
andyhb Posted April 26, 2012 Share Posted April 26, 2012 Friday looking fairly favorable in the Eastern portions of OK/KS perhaps into the Ozarks on both the 00z NAM and GFS. Both models show weakening of the CINH in this area between 18z and 00z Friday afternoon/evening, with a strengthening LLJ enlarging the hodographs with probably somewhere around 1500-3500 J/kg SBCAPE in place. Link to comment Share on other sites More sharing options...
It's Always Sunny Posted April 26, 2012 Share Posted April 26, 2012 noob / it's-dead-here questions: - have all major tornado outbreaks occurred east of a trough (ie is the strong southwesterly flow aloft a requirement)? - scheduled to chase may 5-12 in the plains... any thoughts on Day10+ outlooks for the ridge over the west shifting east / other large-scale features improving by then? thanks! Most outbreaks occur on the downstream side of a trough (aka "east side"), and mainly any sort of westerly flow is good. SW flow is nice because it provides that nice warm, dry air mass which typically lies behind the dry line. I hope you're ready to chase if you're asking questions like these. As far as the Day 10 outlook goes, flow looks mainly zonal without much amplification to really support severe weather outbreaks. Link to comment Share on other sites More sharing options...
David Reimer Posted April 26, 2012 Author Share Posted April 26, 2012 12Z NAM looks pretty sweet in Eastern Kansas on Friday. Looks like it's come in with a deeper surface low, resulting in a increased flow in the low levels. The hodographs actually look pretty sweet now. Sadly, I have to get through today first. I'll be heading west on Interstate 40 out of OKC to the Texas Panhandle where I'm promised I'll see a turkey tower before the cap smashes in. Link to comment Share on other sites More sharing options...
JoMo Posted April 26, 2012 Share Posted April 26, 2012 12Z NAM looks pretty sweet in Eastern Kansas on Friday. Looks like it's come in with a deeper surface low, resulting in a increased flow in the low levels. The hodographs actually look pretty sweet now. Sadly, I have to get through today first. I'll be heading west on Interstate 40 out of OKC to the Texas Panhandle where I'm promised I'll see a turkey tower before the cap smashes in. yeah I saw the SPC's newest outlook on that tomorrow. Hope that mess is north of me. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted April 26, 2012 Share Posted April 26, 2012 12Z NAM looks pretty sweet in Eastern Kansas on Friday. Looks like it's come in with a deeper surface low, resulting in a increased flow in the low levels. The hodographs actually look pretty sweet now. Sadly, I have to get through today first. I'll be heading west on Interstate 40 out of OKC to the Texas Panhandle where I'm promised I'll see a turkey tower before the cap smashes in. Have fun today...the OK/TX panhandles look good for big hailers and slow moving discrete supercells. Cap will be a problem, but it does seem PV advection will create an environment favorable for decreasing cinh/increased dryline convergence for initiation before dark...at least a few supercells. Link to comment Share on other sites More sharing options...
Chinook Posted April 26, 2012 Share Posted April 26, 2012 Looks like Eastern Colorado is about to have some storms. We have a few showers on the radar over the mountains, which should hit my area with brief rain. We have CAPE building up in all areas of the urban corridor, and 1500 J/kg CAPE near Sterling CO. Shear looks to be 30 knots at the urban corridor and 40 knots near Kansas, so possible severe storms in several areas, and much more likely over near the Colorado eastern border. Link to comment Share on other sites More sharing options...
andyhb Posted April 26, 2012 Share Posted April 26, 2012 As David mentioned, the 12z NAM's verbatim has some impressive parameters supporting a possible regional severe wx/tornado outbreak tomorrow across portions of NE OK, E KS and W MO, with capping weakening substantially/breaking. While they mentioned a potential upgrade, I'm a bit surprised the SPC didn't place a 30% and/or hatched area within the latest D2. Link to comment Share on other sites More sharing options...
JoMo Posted April 26, 2012 Share Posted April 26, 2012 New MCD for SE CO down into the TX Panhandle. Says main threat hail/winds due to high LCL's and boundary layer mixing. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted April 26, 2012 Share Posted April 26, 2012 New MCD for SE CO down into the TX Panhandle. Says main threat hail/winds due to high LCL's and boundary layer mixing. Yeah just saw that. I think today would be a fun chase day out near the OK Panhandle. Relatively slow moving storm motions and a decent likelihood any initiation is discrete...at least for a while. Nice high LCLs should make for pleasant viewing. MESOSCALE DISCUSSION 0592 NWS STORM PREDICTION CENTER NORMAN OK 0253 PM CDT THU APR 26 2012 AREAS AFFECTED...NERN NM...SERN CO...FAR SWRN KS...WRN TX/OK PANHANDLES CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 261953Z - 262100Z CONVECTIVE INITIATION WILL BE POSSIBLE BY 21-22Z ACROSS THE SRN/CNTRL HIGH PLAINS. THE ENVIRONMENT WILL SUPPORT A PRIMARY THREAT OF LARGE HAIL AND DMGG WINDS. COVERAGE IS EXPECTED TO REMAIN ISOLATED THROUGH LATE AFTERNOON...BUT CONVECTIVE TRENDS ARE BEING MONITORED FOR A POSSIBLE WW. VISIBLE/WATER VAPOR SATELLITE LOOPS SHOW INFERRED LARGE-SCALE ASCENT SPREADING EWD INTO THE HIGH PLAINS /DENOTED BY AN INCREASE IN MID/HIGH-LEVEL CLOUDINESS/...AHEAD OF A COMPACT SHORTWAVE UPPER TROUGH CURRENTLY POSITIONED OVER AZ. A WEAKLY CONFLUENT SFC TROUGH WAS ANALYZED AT 19Z FROM 20 E PUB...SWD TO CVS...ARCING BACK TO THE ESE TO 20 N BGS. RICHER BOUNDARY LAYER MOISTURE WAS LOCATED E OF THIS FEATURE...AS REFLECTED IN SFC OBS BY MID 50S TO LOWER 60S F SFC DEWPOINTS. ANALYZED PRESSURE FALLS OF -2 TO -4 MB PER 2 HRS SUGGEST SFC LOW WILL CONTINUE TO DEEPEN THIS AFTERNOON OVER ERN CO...AND IS EXPECTED TO RESULT IN INCREASING BOUNDARY LAYER FLOW AND LOW-LEVEL CONVERGENCE ALONG THE SFC TROUGH. AS LARGE-SCALE ASCENT CONTINUES TO OVERSPREAD THE AREA AND TEMPERATURES WARM INTO THE LOW 80S...CINH SHOULD ERODE AND SUPPORT THE DEVELOPMENT OF ISOLATED TSTMS...INITIALLY FOCUSED ALONG THE AFOREMENTIONED LEE SFC TROUGH. MODERATE MIDLEVEL FLOW /SAMPLED 30-40 KTS AT 6 KM AGL/ ATOP ESELY LOW-LEVEL FLOW WILL BE FAVORABLE FOR SUPERCELLS. PRIMARY THREATS APPEAR TO INITIALLY BE LARGE HAIL AND DMGG WINDS...WHILE TOR THREAT SHOULD BE LIMITED THIS AFTERNOON BY DEEP BOUNDARY LAYER MIXING/HIGH LCL HEIGHTS. Link to comment Share on other sites More sharing options...
JoMo Posted April 26, 2012 Share Posted April 26, 2012 As David mentioned, the 12z NAM's verbatim has some impressive parameters supporting a possible regional severe wx/tornado outbreak tomorrow across portions of NE OK, E KS and W MO, with capping weakening substantially/breaking. While they mentioned a potential upgrade, I'm a bit surprised the SPC didn't place a 30% and/or hatched area within the latest D2. I'm trying to pinpoint what's missing tomorrow. 18z NAM indicated no CIN across SE KS all the way down into OK by 00z. I guess there is a lack of convergence along the dryline as the winds are veering to the SW ahead of it. The triple point area north of those areas does have convection that tries to or does fire though but it looks like it outruns the warm front. Link to comment Share on other sites More sharing options...
wxsniss Posted April 26, 2012 Share Posted April 26, 2012 Most outbreaks occur on the downstream side of a trough (aka "east side"), and mainly any sort of westerly flow is good. SW flow is nice because it provides that nice warm, dry air mass which typically lies behind the dry line. I hope you're ready to chase if you're asking questions like these. As far as the Day 10 outlook goes, flow looks mainly zonal without much amplification to really support severe weather outbreaks. thanks of course would never go alone, but hoping to get some formal teaching so i can one day schedule a trip a day before a high-risk outbreak going with a group including pro mets may 5-12... unfortunately this was scheduled far in advance, and this jet pattern isn't look favorable through at least first week of may Link to comment Share on other sites More sharing options...
SluggerWx Posted April 26, 2012 Share Posted April 26, 2012 By the way - decent looking set of isolated cells in KY/TN right now. Although SPC says hail is the primary threat - they look nasty. Four of these cells are over 40,000 feet in elevation... Link to comment Share on other sites More sharing options...
Buckeye05 Posted April 26, 2012 Share Posted April 26, 2012 Decent couplet bearing down on Barbourville Link to comment Share on other sites More sharing options...
Superstorm93 Posted April 26, 2012 Share Posted April 26, 2012 Decent couplet bearing down on Barbourville By the way - decent looking set of isolated cells in KY/TN right now. Although SPC says hail is the primary threat - they look nasty. Four of these cells are over 40,000 feet in elevation... Wrong thread. Link to comment Share on other sites More sharing options...
SouthernNJ Posted April 26, 2012 Share Posted April 26, 2012 Very good chance of damaging winds between Masterson and Amarillo. Highway 87/287 not a good place for travel. Link to comment Share on other sites More sharing options...
Buckeye05 Posted April 26, 2012 Share Posted April 26, 2012 Boise City area cell exploding now. Moving into favorable, untapped environment too. Link to comment Share on other sites More sharing options...
JoMo Posted April 27, 2012 Share Posted April 27, 2012 00z NAM is rolling in. I am somewhat concerned because Springfield, MO NWS has been increasing their wording today and have now put up a Severe briefing. http://www.crh.noaa.gov/sgf/?n=webbriefing Link to comment Share on other sites More sharing options...
Buckeye05 Posted April 27, 2012 Share Posted April 27, 2012 I have heard people on multiple forums say that a surprise event could occur tomorrow. Interesting. Link to comment Share on other sites More sharing options...
JoMo Posted April 27, 2012 Share Posted April 27, 2012 NAM4 has me right on the southern end of the system tomorrow. Looks like SPC is going with a Watch for E CO later tonight. http://www.spc.noaa.gov/products/md/md0599.html Link to comment Share on other sites More sharing options...
Indystorm Posted April 27, 2012 Share Posted April 27, 2012 The rich dewpoints (mid to upper 60's) currently residing over the southern half of Oklahoma and Arkansas at this hour do concern me as that moisture advects northward into the system for the Springfield MO area tomorrow evening. Link to comment Share on other sites More sharing options...
Superstorm93 Posted April 27, 2012 Share Posted April 27, 2012 Potent little system... Link to comment Share on other sites More sharing options...
baroclinic_instability Posted April 27, 2012 Share Posted April 27, 2012 I have heard people on multiple forums say that a surprise event could occur tomorrow. Interesting. I don't know why anyone would be calling tomorrow a "surprise". There certainly is tornado potential if the NAM is correct with its depiction of a bent-back surface low, mid/upper 60s dewpoints, and strong cap breaking convergence along the Pacific front. There are a couple of warm layers evident in the NAM across the low level warm sector...so that may limit low level buoyancy as well. Nonetheless a threat is there and I don't think anyone is surprised by any depictions. Link to comment Share on other sites More sharing options...
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