Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
482 ACUS02 KWNS 171709 SWODY2 SPC AC 171708 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1208 PM CDT Tue Sep 17 2024 Valid 181200Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE GREAT PLAINS... ...SUMMARY... Isolated severe wind and hail are possible across a portion of the Great Plains during the late afternoon and evening on Wednesday. ...Great Plains... A stacked cyclone will slowly shift east/northeast from eastern MT to southern SK/MB on Wednesday into early Thursday. At the surface, a dryline will be oriented from the eastern Dakotas into western/central NE, then southward across western KS and into the OK/TX Panhandle vicinity. With time, a cold front will merge with this feature on the northern end across the Dakotas during the nighttime hours. Deep-layer south/southwesterly flow will remain somewhat enhanced across the northern/central Plains toward the Upper Midwest as the mid/upper trough shifts east. Around 30-35 kt effective shear magnitudes are forecast along the extent of the dryline. Meanwhile, surface dewpoints in the 60s will be maintained ahead of the surface boundary in a persistent southerly low-level warm advection regime. Midlevel temperatures are forecast to be somewhat warm, precluding steeper lapse rates. Nevertheless, 1000-2000 J/kg MLCAPE is expected, with the greatest instability expected near/north of the Mid-MO Valley. Weakening convection may be ongoing Wednesday morning in the vicinity of the Mid-MO valley, with areas of cloud cover extending northward into MN. Where stronger heating occurs, low-level convergence along the surface dryline and any remnant outflow boundaries may focus thunderstorm development during the afternoon. Large-scale ascent will be nebulous, with stronger forcing focused near/north of the international border. Instability and shear will decrease with southward extent into KS and the southern Plains. This will limit coverage and intensity of convection to some degree. Nevertheless, isolated strong to severe storms may pose a risk for locally damaging gusts and hail. Additional thunderstorms may develop overnight as the surface cold front overtakes the dryline from the far eastern Dakotas into MN. This activity will be driven by warm advection and likely be elevated. Severe potential currently appears low beyond the 03-06z time frame. ..Leitman.. 09/17/2024 $$