TexasWeatherSpotter Posted March 14 Share Posted March 14 SPC AC 141257 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Thu Mar 14 2024 Valid 141300Z - 151200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF EASTERN OKLAHOMA...ARKANSAS...EXTREME NORTHEAST TEXAS...AND SOUTHERN MISSOURI... ...SUMMARY... Tornadoes, large to very large hail, and strong to locally severe thunderstorm gusts are expected from parts of north-central Texas into the Midwest and Mid-South. The greatest overall severe threat still appears to be across eastern Oklahoma into Arkansas and southern Missouri. ...Synopsis... In mid/upper levels, the pattern will slow considerably and become blocky over the western CONUS, as a closed cyclone continues to retrograde south-southwestward across the southern Great Basin and southern CA. The associated/cut-off 500-mb low should stall near the Imperial Valley by 12Z tomorrow, with troughing southward over Baja and northeastward over southwestern WY. A broad swath of southwest flow aloft will extend downstream of the cyclone, across the southern Plains, lower/mid Mississippi Valley and lower Ohio Valley. Weak synoptic-scale height rises are expected over much of OK, AR, east/north TX, and LA, in response to the cyclonic retrogression farther west. At the surface, 11Z analysis showed a low near TOP with cold front southwestward across northwestern OK to the TX Panhandle, and warm front over northern portions of MO/IL/IN to central OH. A dryline was drawn from central OK across west-central TX. The dryline is expected to move only slightly eastward through the day, being positioned over central/east-central to south-central OK and north- central/central TX during mid/late afternoon. A combination of the cold front and convective outflow will overtake the dryline over MO and OK by late afternoon and evening, and the front should catch the dryline over north TX overnight. Meanwhile, a sequence of convective outflows -- already underway across parts of the Midwest and forecast to continue through the day -- will shunt the effective baroclinic zone and best regional convective foci south of the synoptic warm-frontal position. ...Ozarks to north TX and Mid-South... Scattered thunderstorms should develop as early as midday along and east of the OK/TX dryline, and increase in coverage/intensity through the evening, while shifting eastward into AR, perhaps reaching parts of the Mid-South and Tennessee Valley regions overnight. Supercells with tornadoes (some strong), locally very large/destructive hail, and severe gusts will be possible this afternoon into early evening. Activity should evolve into one or two dominant quasi-linear segments with the threat trending more toward wind and sporadic QLCS/embedded tornadoes with time this evening and overnight. Continued theta-e advection east of the dryline, amidst strong diurnal heating, will erode MLCINH, which already did not appear particularly strong in the 12Z OUN sounding. Modified RAOBs and forecast soundings over eastern OK this afternoon suggest peak/ preconvective MLCAPE reaching the 2500-3000 J/kg range. Increasing inflow-layer moisture beneath favorable deep shear (effective-shear magnitudes 45-55 kt) yield hail over 3 inches in diameter when 2D hail models and historical analogs are applied. The duration of the threat, as well as the potential for tornadoes once hodographs enlarge greatly in late afternoon/evening, will depend on the number of relatively discrete supercells remaining. That is uncertain, given a substantial component of deep-layer flow parallel to the likely corridor of greatest forcing, which suggest a transition to messier convective modes. However, at least a few tornadoes are possible, including those with strong damage potential. Upscale evolution to an MCS appears possible this evening into tonight, spreading toward the Mid-South/Tennessee Valley regions. A separate area of convection also may develop this afternoon into early evening east of the modest EML plume, over parts of the Mid- South/Delta region. The environment will be characterized by rich low-level moisture (dewpoints increasing into the upper 60s to low 70s F), subtle mass confluence/convergence, and weak CINH. While low-level flow/shear will be modest, enough mid/upper-level flow will spread over the area to support a mix of multicell and supercell modes, with damaging gusts, large hail possible, and a marginal tornado threat. Forecast soundings reasonably depict a deep troposphere occupied by MLCAPE increasing into the 2000-3000 J/kg range, and around 30-40 kt effective-shear magnitudes. Ultimately, the main area of convection from the west and northwest also may shift into this area overnight, overtaking any remaining warm-sector activity and bringing severe probabilities as well. ...Midwest/Ohio Valley region... Bands of thunderstorms with trailing, progressive outflows are ongoing across portions of IL/MO. This activity should continue offering sporadic severe gusts and isolated potential for an embedded tornado or two, while moving rapidly east-northeastward this morning. Severe-gust and tornado threats may focus best along the warm front and leading outflow boundary. Those boundaries are where low-level convergence/vorticity will be maximized. However, severe potential also may be tempered regionally by the early- morning instability minimum in the boundary layer. See SPC severe thunderstorm watches 39-40 and related mesoscale discussions for near-term details. Some re-intensification of the combined complex may occur in parts of IN and perhaps KY today, as it encounters a plume of diurnal and warm-advection-related destabilization, before outrunning that plume. Farther west and southwest across portions of eastern/southeastern MO and up the lower Ohio Valley, a conditionally concerning threat is apparent for tornadoes, large to very large hail and severe wind from another potential round of convection this afternoon and evening. Where the environment is undisturbed by (or can recover at least mostly from) morning convection, strong deep-layer shear and favorable moisture/destabilization will support potential for long- lasting supercells and bowing clusters. Along and within an ill- defined distance north of the residual, diurnally destabilized outflow boundary, enlarged low-level hodographs and maximized boundary-layer shear/vorticity should concentrate tornado potential. At this time, however, with 1. Outflow still being newly produced, and 2. Its depth/character not well-resolved yet by higher-resolution convective guidance, mesoscale uncertainties over the position and character of the boundary remain too great to assign larger unconditional risk at this point. A focused corridor of enhanced- level probabilities may need to be introduced once the timing and location of the near-boundary threat become clearer. ..Edwards/Dean.. 03/14/2024 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z CURRENT UTC TIME: 1524Z (10:24AM), RELOAD THIS PAGE TO UPDATE THE TIME Top/Latest Day 2 Outlook/Today's Outlooks/Forecast Products/Home Weather Topics: Watches, Mesoscale Discussions, Outlooks, Fire Weather, All Products, Contact Us Link to comment Share on other sites More sharing options...
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