andyhb Posted September 15, 2017 Share Posted September 15, 2017 I get the sense that there may be a surprise or two in E SD (perhaps somewhere in the Mitchell vicinity) this afternoon/evening looking at the overall synoptic setup. Pretty healthy dynamically in the low levels with favorable proximity to the triple point, although deep layer shear is a bit marginal for supercells. Link to comment Share on other sites More sharing options...
andyhb Posted September 16, 2017 Share Posted September 16, 2017 Not a bad call. Initiated about 15 miles E of Mitchell. 1 Link to comment Share on other sites More sharing options...
nrgjeff Posted September 18, 2017 Share Posted September 18, 2017 Tuesday looks like a short window of opportunity in eastern SD and adjacent areas of southwest Minnesota. Though the NAM has amped up CAPE and LI, lapse rates may not be quite that high. However, a local area of excellent turning of wind with height is forecast. An isolated cell ahead of the line could get going along the boundary intersection with the polar front/dry line hybrid. Another option for rotation is early in the life cycle of the main line. SPC touches on rotation but seems somewhat of an after thought. Mostly cloudy skies are forecast through early to mid-afternoon. Quicker clearing would allow greater heating and perhaps more tornado risk. Link to comment Share on other sites More sharing options...
Jim Martin Posted September 19, 2017 Share Posted September 19, 2017 Looking like an active weather day across portions of North Dakota, South Dakota, and Minnesota. Link to comment Share on other sites More sharing options...
Chinook Posted September 19, 2017 Share Posted September 19, 2017 The latest HRRR shows several storms developing in this area. Many of them seem to be linear-- there are no highly intense updraft helicity tracks. I think tornadoes are possible, but there probably won't be many. I think there will be few reports of 2"-3" hail, probably several reports of 1"-2" hail and wind damage. Link to comment Share on other sites More sharing options...
Chinook Posted September 20, 2017 Share Posted September 20, 2017 One confirmation of a tornado in the last few minutes * Tornado Warning for... Southwestern Spink County in northeastern South Dakota... * Until 815 PM CDT * At 740 PM CDT, a confirmed tornado was located near Spottswood, or 12 miles south of Redfield, moving northeast at 35 mph. HAZARD...Damaging tornado and quarter size hail. SOURCE...Weather spotters confirmed tornado. Link to comment Share on other sites More sharing options...
andyhb Posted September 30, 2017 Share Posted September 30, 2017 Could be a window for a nice sup or two in the central High Plains (specifically NW KS and SW NE) late tomorrow afternoon/evening. Strong flow aloft and good veering in the lowest 3 km will make for favorable shear profiles, although moisture may be a bit on the marginal side for tornadic potential especially if mixing is more than forecast. There is a fairly strong signal amongst the CAMs for supercell development and modest upsloping associated with the backed low level flow near the lee cyclone should allow for it along with moderate large scale forcing for ascent. Link to comment Share on other sites More sharing options...
andyhb Posted September 30, 2017 Share Posted September 30, 2017 Also, couple of potentially tornadic supercells W of the ABQ metro right now. Link to comment Share on other sites More sharing options...
monsoonman1 Posted October 1, 2017 Share Posted October 1, 2017 5% tornado probs for the CO/KS/NE area. Pretty nice setup for this time of year. Link to comment Share on other sites More sharing options...
Jim Martin Posted October 1, 2017 Share Posted October 1, 2017 Link to comment Share on other sites More sharing options...
Chinook Posted October 1, 2017 Share Posted October 1, 2017 Smallest enhanced outlook evar? (maybe?) Regarding the mathematics of saying there's a 30% chance of severe within any single point: Most of the enhanced outlook is within 25 miles of every other point. Link to comment Share on other sites More sharing options...
andyhb Posted October 1, 2017 Share Posted October 1, 2017 MCD out for an imminent tornado watch in the High Plains. Mesoscale Discussion 1678 NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Oct 01 2017 Areas affected...Central High Plains Concerning...Severe potential...Tornado Watch likely Valid 011939Z - 012045Z Probability of Watch Issuance...95 percent SUMMARY...Severe threat is increasing across the central High Plains. Tornado Watch is warranted for this region and will likely be issued by 2030z. DISCUSSION...Large-scale forcing for ascent is spreading across the central Rockies with high-based convection increasing across the northern CO Rockies into the High Plains where boundary-layer moisture is somewhat limited at the time. This activity is expected to mature over the next few hours as it encounters increasingly moist air mass from extreme northeast CO into southwest NE. Bow-type structures may ultimately evolve from this activity as it propagates northeast along a boundary draped across this region. Farther south, strong boundary-layer heating has contributed to a substantial dry line surge into northwest KS. CU field is increasing in areal coverage both west and east of the dry line, indicative of convective temperatures being breached. It appears thunderstorms will evolve across northwest KS over the next few hours and shear/instability favor discrete supercells. Latest HRRR model guidance supports this idea with two distinct scenarios evolving this evening. While storm mode may favor wind/hail with activity spreading across northeast CO into southwest NE, higher moisture/instability across northwest KS into south-central NE suggests a few tornadoes may evolve from supercells across this region. Tornado watch will likely be issued within the hour to account for this threat. ..Darrow/Guyer.. 10/01/2017 Link to comment Share on other sites More sharing options...
Quincy Posted October 1, 2017 Author Share Posted October 1, 2017 Watch two areas this afternoon: 1. Far northeastern CO into SW NE. The environment appears unimpressive given a dearth of low level moisture (dews in the 40s), but shear is highly favorable to support rotating updrafts given sufficient buoyancy. Any cells that remain discrete/semi-discrete into SW NE may pose the greatest risk to produce very large hail and an isolated tornado. 2. West-central to NW KS. Stronger low-level flow resides here, along with much more favorable low level thermodynamic profiles. CAMs have more or less shown one robust updraft going up near what appears to be faint boundary in the vicinity of Leoti. If a sustained cell can form here, a long-lived supercell would seem possible, if not probable, continuing into north-central KS early this evening. The parameter space around 23-02z would easily support a tornado given boundary layer dews in the lower 60s, lowering LCLs (already lower than areas to the NW this afternoon) and a low-level jet strengthening to 40-50+ knots at 850mb. Link to comment Share on other sites More sharing options...
Jim Martin Posted October 1, 2017 Share Posted October 1, 2017 Tornado Watch forthcoming. Link to comment Share on other sites More sharing options...
Jim Martin Posted October 1, 2017 Share Posted October 1, 2017 Link to comment Share on other sites More sharing options...
Jim Martin Posted October 2, 2017 Share Posted October 2, 2017 Link to comment Share on other sites More sharing options...
andyhb Posted October 2, 2017 Share Posted October 2, 2017 70-80 kts of effective shear and 400-500+ m2/s2 ESRH for that storm SW of Leoti to work with. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2017 Share Posted October 3, 2017 Wedge tornado reported N of Scott City per SN moving NE. Link to comment Share on other sites More sharing options...
hlcater Posted October 3, 2017 Share Posted October 3, 2017 That storm is sitting on an area of 500+ eSRH not surprised there's reports of a large tornado. Link to comment Share on other sites More sharing options...
Jim Martin Posted October 3, 2017 Share Posted October 3, 2017 This supercell has recycled itself multiple times so far tonight. It could be going through the cycle again. Link to comment Share on other sites More sharing options...
Chinook Posted October 3, 2017 Share Posted October 3, 2017 That's a lot of red (50dBz) for October Link to comment Share on other sites More sharing options...
monsoonman1 Posted October 5, 2017 Share Posted October 5, 2017 Enhanced risk tomorrow for SW KS into the OK panhandle. Link to comment Share on other sites More sharing options...
andyhb Posted October 5, 2017 Share Posted October 5, 2017 Pretty strongly worded AFD coming out of DDC with regards to tomorrow's severe threat. Quote National Weather Service Dodge City KS 355 PM CDT Thu Oct 5 2017 ...Updated Short Term and Long Term Section... .SHORT TERM...(This evening through Friday) Issued at 354 PM CDT Thu Oct 5 2017 The main interest in the forecast is severe weather potential tomorrow. This may be the best fall severe weather setup for southwest Kansas this year (and perhaps the last several years). A compact mid level potential vorticity anomaly will be at the base of a sharp trough over Colorado late in the day, and this will induce low level cyclogenesis just out ahead of it over far southeast Colorado. Intense low level convergence will develop at the surface low as well by late afternoon. Initially veered out surface winds will slowly back to due south, if not slightly east of due south in a very small area just ahead of the low. This is clearly the area of greatest concern for the most vigorous severe local storm anytime after 21z. This could be as far west as the Colorado border, initially. All ingredients from available moisture, convergence, deep layer shear, low level shear, mid level cold advection, etc. are pointing to aggressive severe storms, including supercells. The most vigorous supercell storm could produce baseball size hail. Tornado potential would be greatest early in the event, through about 00z or so, as 0- 1km bulk shear will be about 20-25 knots. Early CAMs runs of WRF-ARW and WRF-NMM show supercell development at the greatest surface convergence in southwest Kansas, not far from Dodge City. A supercell may very well be underway, as mentioned earlier, well to the west of Dodge City and even Garden City. The main question will be how long supercell phase would last. Link to comment Share on other sites More sharing options...
Jim Martin Posted October 6, 2017 Share Posted October 6, 2017 23 hours ago, andyhb said: Pretty strongly worded AFD coming out of DDC with regards to tomorrow's severe threat. Link to comment Share on other sites More sharing options...
monsoonman1 Posted October 9, 2017 Share Posted October 9, 2017 5% tornado risk for SE KS and NE OK. Might head down towards Eureka, KS today to see what happens. Link to comment Share on other sites More sharing options...
andyhb Posted October 19, 2017 Share Posted October 19, 2017 D3 ENH, partially hatched for N TX and a good chunk of OK. Given the forcing near the cold front and it's rather fast motion, convection will almost certainly be linear/undercut with time in that area (damaging winds, etc.). I'm a bit curious to see if we can get a few discrete cells popping out ahead given the degree of forecast low level shear and considerable BL moisture content (into the upper percentile for this time of year in this area) across guidance. This prospect would be more likely in a case where a more well developed secondary surface low can develop along the low pressure trough extending southward from the primary low over the Prairies, which would then amplify low level convergence/surface backing ahead of the front. Such a low is spurned on by the southern in a pair of vorticity maxima that emerges from the Four Corners region through the morning and afternoon Saturday. There is also a bit of a coupled upper jet structure overhead enhancing divergence aloft, which would also imply increased large scale ascent ahead of the front. 3 Link to comment Share on other sites More sharing options...
rolltide_130 Posted October 19, 2017 Share Posted October 19, 2017 7 hours ago, andyhb said: D3 ENH, partially hatched for N TX and a good chunk of OK. Given the forcing near the cold front and it's rather fast motion, convection will almost certainly be linear/undercut with time in that area (damaging winds, etc.). I'm a bit curious to see if we can get a few discrete cells popping out ahead given the degree of forecast low level shear and considerable BL moisture content (into the upper percentile for this time of year in this area) across guidance. This prospect would be more likely in a case where a more well developed secondary surface low can develop along the low pressure trough extending southward from the primary low over the Prairies, which would then amplify low level convergence/surface backing ahead of the front. Such a low is spurned on by the southern in a pair of vorticity maxima that emerges from the Four Corners region through the morning and afternoon Saturday. There is also a bit of a coupled upper jet structure overhead enhancing divergence aloft, which would also imply increased large scale ascent ahead of the front. The 12z GFS is showing a hint of a possible secondary low developing perhaps along the I-40 corridor near Elk City by 0z Saturday evening. If that comes to fruition, there could be a locally enhanced area in central and southern/SW OK. Link to comment Share on other sites More sharing options...
Indystorm Posted October 21, 2017 Share Posted October 21, 2017 Confirmed tornado over Fort Sill this Sat. evening Oct. 21 shortly after 6 p.m. central time. 1 Link to comment Share on other sites More sharing options...
hlcater Posted November 25, 2017 Share Posted November 25, 2017 Coming to a May 2018 near you! Link to comment Share on other sites More sharing options...
CheeselandSkies Posted November 26, 2017 Share Posted November 26, 2017 On 11/25/2017 at 0:11 AM, NWLinnCountyIA said: Coming to a May 2018 near you! If this forum had that "exploding head" smiley I've seen on others, I'd use that. Link to comment Share on other sites More sharing options...
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