Severe Storm Outlook Narrative (AC)
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Issued by NWS
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331 ACUS01 KWNS 030602 SWODY1 SPC AC 030600 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Mon Jun 03 2024 Valid 031200Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE SOUTHERN PLAINS...THE UPPER MIDWEST AND THE LOWER MISSISSIPPI RIVER VALLEY... ...SUMMARY... Strong to severe thunderstorms are possible from much of the Mississippi Valley into the Ozark Plateau and southern Plains today. A more concentrated area of severe thunderstorm risk may become focused across southern Oklahoma into the ArkLaTex vicinity, where a swath of damaging gusts is possible. ...Synopsis... Within a weak and predominately zonal mid-level flow regime, a complex series of mesoscale features will dictate the potential for severe thunderstorms today and tonight. A subtle, convectively enhanced shortwave trough currently over the mid Missouri Valley will move into parts of the upper Midwest by early afternoon. A second remnant MCS appears likely to be ongoing at the start of the period over the southern/central Plains. The potential outflow from this system may serve as a focus for secondary initiation later in the afternoon across parts of TX and OK. Additional storms are also possible along the dryline in Southwest TX. ...Upper Midwest and mid MS Valley... Rich low-level moisture advection is expected to be ongoing with southerly low-level flow across much of the Midwest ahead of the remnant MCV early this morning. Some clearing should allow diurnal heating to support moderate destabilization ahead of the MCV from eastern IA into southern WI and far northern IL despite relatively poor mid-level lapse rates. Weak convergence and some ascent from the convectively enhanced shortwave should allow for scattered thunderstorms to develop by early afternoon. Deep-layer shear profiles are not particularly strong (20-30 kt), though some low and mid-level enhancement from the MCV may be enough to support organized multicells and a few transient supercells structures. Damaging wind gusts, hail and a brief tornado or two will be possible. More isolated storms are also possible along a subtle wind shift/ surface pressure trough farther south across parts of eastern MO and western IL. However, confidence in storm development here is low owing to the potential disruption of diurnal heating from cloud debris or remnant convection from the overnight central Plains MCS. Still, a few instances of hail or damaging winds are possible should an organized multicell cluster or two develop. ...Southern Plains to the ArkLaMs... Short-term CAM and regional model guidance has come into fairly strong agreement on the presence of an overnight MCS across parts of the central Plains. By 12z convection will most likely be located across parts of southern KS, to as far as northeast OK. Relatively clear skies and strong low-level moisture advection (low to mid 70s F surface dewpoints) will likely be in place ahead of the early morning storms. This, along with numerous CAM solutions, suggests intensification of this cluster is likely from late morning through the early afternoon hours as it tracks east/southeastward into AR. Despite modest forcing for ascent, a broad swath of moderate to large buoyancy (3000+ J/kg of MLCAPE) and a fairly organized cold pool may support storms farther east into parts of the lower MS valley with a risk for damaging winds and hail into the evening hours. In the wake of the morning cluster of storms, a trailing outflow boundary is likely to be located somewhere over the southern Plains from central/southern OK into the Panhandle/western north TX. With very rich low-level moisture moving in from central TX (mean W of 16-18 G/kg), modification of this outflow boundary may serve as a focus for additional storm development through the afternoon and evening hours ahead of a subtle shortwave trough embedded within the mostly zonal flow. This appears especially likely where the boundary could intersect with the dryline over parts of the eastern TX Panhandle, far western OK and western north TX. Model soundings here show very large buoyancy (4500-6000 J/kg of MLCAPE) and sufficient deep-layer shear for supercells. Should storms form (pending the location of the outflow) large buoyancy and sufficient shear would support a risk for large to very large hail, damaging gusts and potentially a couple of tornadoes. Eventual upscale growth into a cluster or MCS may also support a risk for damaging winds downstream into parts of central TX later into the evening. ...Southwest TX... Along the southern portions of the dryline, very hot temperatures 95-105F are likely along with rich boundary-layer dewpoints in the 70s F. While large-scale ascent appears rather nebulous, the diurnal dryline circulation and weak upslope flow may support isolated thunderstorm development near the international border. While modest, 25-30 kt of mid-level flow within the sub-tropical jet may support some organization into isolated supercell structures. While uncertain, a few instances of hail and damaging winds are possible. ..Lyons/Darrow.. 06/03/2024 $$