SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0802 PM CDT Wed May 14 2025 Valid 150100Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS... ...SUMMARY... Scattered strong to severe thunderstorms will occur over parts of the Dakotas and Nebraska this evening, and across far western Iowa and southwestern Minnesota overnight. Very large hail, severe wind gusts, and a couple of tornadoes will be possible. A few marginally severe storms may also occur from the Lower Ohio Valley into the Carolinas. ...Central and Northern Plains... The latest water vapor imagery shows a mid-level trough in the Rockies, with a diffluent pattern over the central and northern Plains. A pronounced dry slot is evident from the southern Rockies into the central Plains, with multiple bands of convection ongoing to the north of this feature. At the surface, a dual-centered 991 mb low is over far southwest Kansas and southern Nebraska, with an inverted trough extending north-northeastward into the eastern Dakotas. To the west of the trough, a cold front is moving east-southeastward across the central and northern Plains. Thunderstorms across the Dakotas are post-frontal, while the storms in Nebraska are straddling the boundary on both sides. These storms are located along an axis of low-level moisture, where surface dewpoints are in the mid to upper 50s F. The strongest instability is located across southwestern and central Nebraska, where temperatures have reached the lower 80s F. Across southern Nebraska, the RAP has MLCAPE in the 2000 to 3000 J/kg range. So far, several semi-discrete supercells have developed along the northern edge of the strongest instability, from near North Platte, northward into Cherry County, Nebraska. This activity is expected to become more linear with time, as it moves east-northeastward across the remainder of northern Nebraska and into southeastern South Dakota. The greatest tornado potential will exist over the next couple hours in central and northern Nebraska, before convection becomes more linear. The latest WSR-88D VWP at North Platte has 0-3km storm-relative helicity near 230 m2/s2. Low-level shear should strengthen some this evening, helping to maintain a tornado threat with supercells that remain semi-discrete. In addition, a plume of steep mid-level lapse rates is analyzed by the RAP from eastern Colorado into central Nebraska. Supercells at the northeastern edge of this plume will have a large hail threat, and hailstones of greater than 2 inches in diameter will be possible. The wind-damage threat will likely increase as a line segments becomes more organized later this evening. Several short-term models suggest that a small-scale bow echo will develop over parts of the central Plains this evening into early tonight, where severe gusts exceeding 70 knots will be possible. The severe threat is expected to move northeastward into parts of Iowa and southwest Minnesota tonight. ...Lower Ohio Valley/Southern Appalachians/Carolinas... A positively-tilted mid-level trough is currently located from the central Appalachians southeastward into the Carolinas. At the surface, a moist airmass is in place across much of the region, with surface dewpoints mostly in the 60s F. Across the moist airmass, the RAP has moderate instability analyzed from the lower Ohio Valley southeastward into the Carolinas. Along this corridor, moderate deep-layer shear is present according to WSR-88D VWPs, which should be enough for a marginal severe threat for a couple more hours this evening. Isolated severe gusts and hail will be the primary threats. ..Broyles.. 05/15/2025