Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
804 ACUS02 KWNS 191732 SWODY2 SPC AC 191730 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Thu Sep 19 2024 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE MIDWEST AND ALSO THE SOUTH-CENTRAL PLAINS... ...SUMMARY... Isolated strong to severe thunderstorms are possible in the late afternoon Friday in parts of Illinois, Indiana, and southwest Lower Michigan. Isolated strong to severe storms are also possible across parts of the south-central Plains. ...Midwest... A low-amplitude shortwave trough will pass across the Upper to central Great Lakes during the first half of the period. This will outpace a cold front that trails from a cyclone shifting northeast in MB, yielding a largely weakening to stalling front by Friday evening. Most guidance suggests at least isolated thunderstorms should form within a low-level warm conveyor ahead of the front, generally focused on a moderate buoyancy plume emanating northeast from parts of MO/AR. A fast westerly upper jet will further impinge on this portion of the front as well, favorably timed with peak boundary-layer heating. A few marginally severe storms may develop within this regime. Despite weak mid-level lapse rates, elongation of the mid to upper hodograph should support a threat for 1-1.5 inch hail, along with strong to marginally severe gusts from 45-60 mph. These threats should diminish quickly after sunset. ...Southern KS/northern OK vicinity... A mid/upper-level shortwave trough is forecast to move slowly eastward across the Southwest on Friday. Farther east, a surface boundary initially draped from the lower MO Valley into southern KS/northern OK is forecast to lift northward as a warm front. Large-scale ascent across much of the Plains may remain relatively limited, outside of low-level warm advection near/north of the front. However, relatively strong heating along the western/northern periphery of returning low-level moisture could support thunderstorm development during the afternoon somewhere in the vicinity of southwest KS/northwest OK. Effective shear of 30-40 kt will support potential for somewhat organized convection. Strong to localized severe gusts may be the most likely hazard, but hail cannot be ruled out if any more discrete storms can move into an environment of greater moisture/instability. ...New Mexico... Scattered thunderstorms will be possible across much of NM on Friday, in closer proximity to the approaching shortwave trough. While deep-layer shear will be rather strong, generally weak midlevel lapse rates and buoyancy may tend to limit the potential for more robust storms. If confidence increases regarding sufficient heating/destabilization, then severe probabilities may eventually be needed for parts of the region. ...Central Plains into the lower MO Valley... Guidance continues to vary regarding the potential for robust elevated convection Friday night into Saturday morning, within a low-level warm advection regime. Increasing elevated buoyancy and sufficient mid/upper-level flow could support a few stronger storms with hail potential, but confidence in sufficient coverage and a favored region for this potential is too low for probabilities at this time. ..Dean.. 09/19/2024 $$