Severe Storm Outlook Narrative (AC)
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Issued by NWS
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291 ACUS01 KWNS 291627 SWODY1 SPC AC 291625 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Wed May 29 2024 Valid 291630Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHERN AND CENTRAL HIGH PLAINS AS WELL AS THE TRANS PECOS REGION IN TEXAS... ...SUMMARY... Scattered strong storms posing a risk for severe hail and wind still appear likely across the northern and central High Plains late this afternoon and evening. Isolated large hail will also remain possible in southwest Texas. ...Synopsis... A mid-level trough will traverse the northern Rockies as an embedded impulse overspreads the southern High Plains and a second mid-level trough meanders over the Northeast today. Along the East Coast and High Plains regions, surface lee troughing will result, that in tandem with moisture advection, supports the potential for at least scattered thunderstorm development through the afternoon and evening hours. Over the High Plains, modest mid-level flow overspreading a developing low-level jet (especially over the northern High Plains during the evening hours) will provide enough vertical wind shear to support strong to potentially severe thunderstorms. ...Northern and Central High Plains... Diurnal heating ahead of the surface lee trough will assist in deepening/mixing the boundary layer by afternoon. MLCAPE should reach 1500-2500 J/kg by afternoon peak heating as 8-9 C/km mid-level lapse rates overspreads low to mid 50s F. As the mid-level trough begins to overspread the region and convective temperatures are reached, convective initiation should occur along the higher terrain. Deep-layer shear will not be overly strong from the MT/ND border southward, so mainly multicell clusters (perhaps outflow dominant) are expected. Given the degree of buoyancy available, at least a few severe gusts or instances of large hail are possible with the initial storms. Locally stronger mid-level flow/deep-layer shear will overspread eastern MT, where a deep boundary layer will exist. Fast moving, high-based storms may quickly merge their cold pools, promoting a relatively concentrated threat of strong wind gusts (some of which may be severe). These storms should track eastward and merge with the High Plains convection, supporting one or more MCSs with a severe gust threat into the evening. ...Trans Pecos Region in Texas... Though deep-layer ascent will be relatively weak, enough lift will be provided by a subtle passing mid-level impulse, along with strong diurnal heating and orographic lift over the Davis Mountains, to support convective initiation ahead of the dryline. 2000+ J/kg MLCAPE will become commonplace as a 8-9 C/km mid-level lapse rates plume overspreads the Trans Pecos area, with over 35 kts of effective bulk shear also likely given modestly curved, elongated hodographs. Splitting supercells are expected to be the main mode of convection, accompanied by primarily a large hail threat (some instances of which may exceed 2 inches in diameter). ...Southeastern Texas... A remnant MCV continues to meander over eastern TX today, serving as a source of lift for convective initiation this afternoon as convective temperatures are reached. Surface dewpoints well over 70 F, overspread by 7 C/km mid-level lapse rates, will boost MLCAPE to 2500 J/kg. The presence of the MCV will also locally boost deep-layer shear in the absence of other synoptic foci to support elongated hodographs. Stronger multicells and perhaps a supercell could pose an isolated severe hail/wind risk through afternoon. ...Portions of the Mid Atlantic... Scattered thunderstorms (perhaps a few briefly becoming strong) will be possible this afternoon as a 60+ kt 500 mb jet streak overspreads the Mid Atlantic. Mid-level lapse rates should remain poor over the region, with expected 250-500 J/kg of MLCAPE constrained to short and thin profiles. When also considering modest deep-layer shear, the severe threat should remain too sparse to support the introduction of Category 1/Marginal risk probabilities. Nonetheless, a strong wind gust capable of tree or powerline damage cannot be completely ruled out. ...Far southern Florida Peninsula... Surface temperatures exceeding 90 F by afternoon peak heating will support convective initiation along sea-breeze boundaries, particularly south and east of Lake Okeechobee. The relatively hot temperatures will mix the boundary layer, and when considering poor mid-level lapse rates, 1500-2000 J/kg of the expected MLCAPE should be constrained to tall and thin profiles. Since deep-layer shear should also be weak, the severe threat should remain too limited for the introduction of severe probabilities. Nonetheless, a stronger and longer lasting storm could produce a severe gust. ..Squitieri/Guyer.. 05/29/2024 $$