Severe Storm Outlook Narrative (AC)
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Issued by NWS
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793 ACUS01 KWNS 290556 SWODY1 SPC AC 290555 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1255 AM CDT Wed May 29 2024 Valid 291200Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN AND CENTRAL HIGH PLAINS... ...SUMMARY... Scattered strong storms posing a risk for severe hail and wind appear likely across the northern and central High Plains late this afternoon and evening. Isolated strong storms will also be possible over parts of the southern Plains to lower Mississippi Valley, into the middle Rio Grande Valley. ...Synopsis... Early morning satellite imagery shows a pair of shortwave troughs within the northern stream, one moving southeastward across the Upper Midwest and another progressing eastward through the Pacific Northwest. Full-latitude shortwave ridging exists between these two features, extending from northern Mexico into central Saskatchewan. Eastern shortwave trough is forecast to pivot more eastward as it moves into the OH Valley before then continuing eastward throughout the day through the northern Mid-Atlantic States. Thunderstorm development is anticipated ahead of this system from the middle OH Valley through the northern Mid-Atlantic and southern New England. A damaging gust or two is possible with these storms, but a predominantly multicellular mode and weak vertical shear is expected to limit the overall severe coverage. Farther west, the Pacific Northwest shortwave is expected to continue eastward across the northern Rockies into the northern Plains. As it does, lee troughing will sharpen across the northern High Plains, with eventual cyclogenesis anticipated. The resultant surface low is then forecast to track northeastward across eastern MT and western ND late Wednesday night/early Thursday morning. Thunderstorms are anticipated ahead of this shortwave and attendant surface low as well as down the lee trough across the central and southern High Plains. ...Northern Rockies into the Northern High Plains... Afternoon thunderstorm development is anticipated ahead of the approaching shortwave trough from southwest MT into northwest/north-central WY and southeast MT. In this region, strong boundary-layer mixing and increasing mid-level moisture will contribute to airmass destabilization ahead of the approaching wave. Buoyancy will be modest, but the high-based character of the storms could still result in strong outflow capable of producing damaging gusts. Afternoon thunderstorm development is anticipated ahead of the shortwave trough as well, where strong heating, moderate low-level moisture and low-level convergence will support convective initiation. A relatively narrow axis of destabilization is anticipated across the western Dakotas, where a storm could become strong enough to produce hail and/or damaging gusts. The eastern extent of the severe threat will be limited by diminishing buoyancy into the central Dakotas. ...Central/Southern High Plains... Strong heating and low-level moisture advection will support airmass destabilization across the central and southern High Plains. Persistent low-level convergence coupled with glancing large-scale ascent is expected to result in convective initiation by the late afternoon/early evening. Highest coverage is expected across the central High Plains, with weakening large-scale ascent with southern extent likely limiting coverage. Large hail is possible with initial development, but outflow-dominant storm structures are likely, with damaging gusts as the primary risk. ...Central/Southeast TX into Lower MS Valley... Thunderstorms may still be ongoing across central TX this morning, supported by persistent warm-air advection across remnant outflow. Given the weak large-scale ascent and potential presence of a convectively generated vorticity maximum, the evolution of these early morning storms is uncertain. Some guidance suggests there is potential for an MCS to develop as the vorticity maximum moves into the moist airmass across central TX. Other guidance shows development along the northeast and southern periphery of the vorticity maximum, but with little linear organization. Modest westerly flow aloft atop southeasterly surface winds along with moderate instability will favor hail and areas of strong gusts with any mature convection. However, the uncertainty on convective evolution and resulting coverage precludes upgrading probabilities across the region with this outlook. ..Mosier/Barnes.. 05/29/2024 $$