Severe Storm Outlook Narrative (AC)
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Issued by NWS
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072 ACUS01 KWNS 170602 SWODY1 SPC AC 170600 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Tue Sep 17 2024 Valid 171200Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Thunderstorms capable of severe wind gusts and isolated large hail will be possible this afternoon and evening across parts of the central and northern High Plains. Wind gusts greater than 70 mph are likely in parts of northeast Colorado, far northwest Kansas and western Nebraska. A marginal potential for severe wind gusts is also expected to develop in parts of the southern and central Rockies, and in parts of eastern Florida. ...High Plains/Central and Southern Rockies... A mid-level low will move across the Intermountain West today, as an associated upper-level trough becomes negatively tilted. A 50 to 65 knot mid-level jet in the base of the trough will move into the central Rockies. Ahead of the system, a lee trough will deepen across the central and northern High Plains. The western edge of a moist airmass will be located just to the east of the surface trough from eastern Colorado into the western Dakotas and eastern Montana. During the day, thunderstorms are expected to develop ahead of the mid-level trough across the central and northern Rockies, with these storms moving east-northeasteastward across the central and northern High Plains during the afternoon and evening. A severe threat will likely accompany many of the stronger storms. Ahead of the approaching trough, partial clearing will result in strong surface heating this afternoon over the central High Plains. MLCAPE is expected to peak near 1500 J/kg from eastern Colorado northward into western Nebraska. A slab of strong large-scale ascent, and an associated mid-level jet will move into the central Plains late this afternoon. This will coincide with strengthening low-level flow and maximized instability, which will make severe storms likely along parts of a convective line moving across the central High Plains. The greatest combination of instability, lift and deep-layer shear is forecast across western Nebraska and northeast Colorado, suggesting an enhanced threat for severe wind gusts. Gusts above 70 mph will be possible ahead of an organized line segment that is expected to move across the central High Plains during the early evening. The potential for severe wind gusts will extend southward and westward into the southern and central Rockies, but the threat will be more isolated in areas where instability remains weak. ...Northern High Plains... A mid-level low will move across the Intermoutain West. Ahead of the low, divergent south to south-southeasterly flow will be in place across the northern Rockies and northern Plains. During the afternoon, thunderstorms will develop in the north-central Rockies and move north to northeastward across the northern High Plains. An axis of moderate instability is forecast by afternoon from the Dakotas northwestward into northeast Montana. As large-scale ascent and moderate deep-layer shear overspread the northern High Plains late this afternoon and evening, organized storms will be possible. Severe wind gusts and isolated large hail will be the primary threats. ...Eastern Florida... A mid-level trough will move across the eastern Gulf of Mexico today, as an associated surface trough moves across the Florida Peninsula. Surface dewpoints in the lower to mid 70s F, along with surface heating will contribute to moderate instability by afternoon. As surface temperatures warm today, scattered thunderstorms are expected to develop along and ahead of the surface trough. RAP forecast soundings at 21Z in eastern Florida have MLCAPE in the 2000 to 3000 J/kg range, with 0-6 km shear around 20 knots. This, combined with steep low-level lapse rates could be enough for a marginal threat for severe wind gusts. ..Broyles/Weinman.. 09/17/2024 $$