


Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
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638 ACUS01 KWNS 100555 SWODY1 SPC AC 100553 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Thu Jul 10 2025 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS PARTS OF WESTERN AND CENTRAL KANSAS...CENTRAL AND EASTERN NEBRASKA...WESTERN IOWA AND PARTS OF SOUTHEASTERN SOUTH DAKOTA... ...SUMMARY... Strong thunderstorms posing a risk for severe hail, damaging wind gusts and perhaps a couple of tornadoes are possible late this afternoon into tonight across parts of the central Great Plains into mid Missouri Valley. ...Discussion... Stronger westerlies will remain confined to the higher latitudes through this period, with one significant short wave perturbation forecast to accelerate from eastern portions of the Canadian Northwest Territories through areas northeast of Hudson Bay, accompanied by a deepening surface cyclone. It appears that the leading edge of cooler, drier air in the wake of this cyclone will advance south of the international border into the northern Rockies and through adjacent portions of the northern U.S. Great Plains, trailed by another notable mid-level short wave impulse, which models indicate will dig near/east of the Canadian through northern U.S. Rockies. As this occurs, mid-level troughing within weaker flow in lower latitudes is forecast to slowly dig from the northern Great Basin toward the central Great Plains, suppressing stronger ridging in the subtropical to southern mid-latitudes, initially centered over the Southwest. This will be preceded by a couple of convectively generated or augmented perturbations migrating across the mid Missouri Valley and Upper Midwest, a modest mid-level trough slowly turning east-northeast of the lower Great Lakes vicinity, and several weak perturbations progressing through broad, weak cyclonic flow across the Southeast through southern Atlantic Seaboard. ...Great Plains into Midwest... Uncertainties remain concerning potential convective evolution through this period. Models suggest that surface boundaries may remain relatively diffuse, but residual seasonably moist boundary-layer air may become characterized by sizable CAPE with daytime heating, beneath steep lower/mid-tropospheric lapse rates, including warm elevated mixed layer air. There does appear at least a somewhat consistent signal within various convection allowing guidance that an MCV associated with ongoing convection across parts of the middle Missouri Valley could provide a focus for strong thunderstorm development later today across parts of the Upper Midwest. Otherwise, in advance of the digging upstream troughing, models indicate that a modest belt of southwesterly low-level flow (including 20-30+ kt in the 850-700 mb layer) will generally persist through the day east of the lee surface trough, from the Texas Panhandle/South Plains into the middle Missouri Valley. It appears that this will coincide with a corridor of stronger heating/deeper boundary-layer mixing across the higher plains, where thunderstorm activity initiating during the late afternoon may pose a risk for damaging wind gusts. Within the more moist low-level environment across eastern Nebraska into western Iowa, the wind fields, aided by veering with height, might become at least marginally conducive to a couple of supercells, in the presence of sizable CAPE, before forcing for ascent associated with the approaching mid-level trough tends to support upscale growing clusters this evening. ...Upper Ohio Valley into portions of New England... Near the southern periphery of the mid-level troughing shifting east or east-northeast of the lower Great Lakes region, models indicate that scattered thunderstorm development is probable during peak afternoon heating, in the presence of moderate CAPE (1000-2000+ J/kg) and shear enhanced at least somewhat by a belt of 20-30 kt westerly mid-level flow. This environment may become conducive to small hail and potentially damaging wind gusts, before activity weakens this evening. ...Southeast/Southern Atlantic Seaboard... Aided by forcing for ascent associated with the mid-level perturbations, in the presence of weak mid-level inhibition, one or two upscale growing clusters of storms may overspread the southern Atlantic Piedmont and coastal plain late this afternoon and evening. Forecast soundings indicate that a seasonably moist environment may become characterized by moderate CAPE, with perhaps a sufficient degree of sub-saturation to allow for evaporative cooling in downdrafts to contribute to modest surface cold pool development. In the presence of weak deep-layer southwesterly mean flow on the order of 10-15 kt, the potential for development of sufficiently strong rear inflow to support surface gusts in excess of 50 kt appears low, but even with peak gusts generally on the order of 35-50 kt, sporadic damage will still be possible. ..Kerr/Weinman.. 07/10/2025 $$