Severe Storm Outlook Narrative (AC)
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Issued by NWS
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097 ACUS01 KWNS 260556 SWODY1 SPC AC 260554 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1254 AM CDT Wed Jun 26 2024 Valid 261200Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY INTO TONIGHT ACROSS PARTS OF THE MID AND UPPER OHIO VALLEY INTO THE NORTHERN MID ATLANTIC REGION...ACROSS PARTS OF THE OZARK PLATEAU INTO LOWER OHIO VALLEY AND ACROSS THE FRONT RANGE INTO ADJACENT GREAT PLAINS... ...SUMMARY... Clusters of thunderstorms accompanied by potentially damaging wind gusts are possible today into tonight from the Ohio Valley into northern Mid Atlantic, across parts of the Ozark Plateau into lower Mississippi Valley, and to the lee of the Front Range and Sangre de Cristo Mountains. ...Synopsis... To the south of a broad vortex centered over the higher latitudes of northeastern Canada, models indicate some further amplification of large-scale mid-level troughing east of the upper Mississippi Valley through the northern Mid Atlantic and Northeast during this period. Upstream, a broad low embedded within larger-scale mid-level troughing is forecast to progress inland across the Pacific Northwest. As it does, initially prominent ridging appears likely to become suppressed from the northern into southern Rockies by late tonight. A number of smaller-scale perturbations, including some convectively generated or enhanced, are embedded within the weaker flow around the Western ridging, and on the southern periphery of the stronger westerlies across the central Great Plains into Ohio Valley. As these progress through the evolving flow, they are expected to provide the primary focus for developing clusters of thunderstorms today into tonight. The predictability of these features is still relatively low at this forecast time frame, and it remains unclear how outflow associated with ongoing convection across the central Great Plains into lower Missouri and Ohio Valleys may impact convective development later today through tonight. Although a plume of elevated mixed-layer air emanating from the Intermountain West is in the process of becoming suppressed to the east of the Rockies, by late this afternoon it still appears that boundary-layer moisture and daytime heating will still be sufficient to contribute to moderate to large CAPE across parts of the central and southern Great Plains, the lower Mississippi Valley into eastern Gulf States, and across the Ohio Valley into Mid Atlantic. ...Ohio Valley into northern Mid Atlantic... Ahead of digging mid-level troughing, one or more convectively generated perturbations may contribute to increasing thunderstorm development across the mid into upper Ohio Valley by this afternoon, beneath modest west-southwesterly mid-level flow (on the order of 30+ kt). Although lower-level wind fields may be initially more modest, various model output suggests that convection could become fairly widespread and contribute to strengthening conglomerate surface cold pools accompanied by potentially damaging wind gusts. Potential instability across and east of the Allegheny Mountains remains a little more unclear, but it is possible that vigorous convection may be maintained along the leading edge of the outflows as they spread eastward into northern Mid Atlantic coastal areas by early this evening. While the magnitude of the convective surface gusts may be mostly marginally severe in nature, one or more swaths of potentially damaging gusts are possible, and severe wind probabilities may still need to be increased once sub-synoptic developments become more unclear. ...Ozark Plateau into and east of lower Mississippi Valley... Potential convective evolution remains uncertain. However, there is a substantive signal within at least some model guidance that a notable convective perturbation will be in the process of progressing into the Ozark Plateau at the outset of the period. This may still be accompanied by continuing vigorous convective development and a southeastward propagating cold pool, which may persist or contribute to renewed strong convective development across Arkansas into Mississippi and adjacent portions of the Gulf states by this evening. If this occurs, it probably will be accompanied by one or more swaths of strong to severe surface gusts. ...Front Range into adjacent Great Plains... Beneath modest westerly to northwesterly mid-level flow, destabilization may become supportive of scattered strong to severe storm development off the higher terrain. Models suggestive that destabilization will become sufficient across the adjacent plains to support considerable upscale growth and potential for strong to severe gusts along strengthening cold pools late this afternoon into this evening. ..Kerr/Barnes.. 06/26/2024 $$