####018003356#### ACUS01 KWNS 170557 SWODY1 SPC AC 170556 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Wed Apr 17 2024 Valid 171200Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE OHIO VALLEY AND LOWER GREAT LAKES...AND IN PARTS OF NORTHEAST KANSAS AND WESTERN MISSOURI... ...SUMMARY... Scattered thunderstorms, capable of wind damage, isolated large hail and a tornado threat, are expected to develop across parts of the Ohio Valley and Lower Great Lakes this afternoon. Storms with large hail are expected tonight in parts of the central Plains and Ozarks. ...Ohio and Tennessee Valleys/Central Gulf Coast States... A negatively tilted upper-level trough, and an associated surface low, will move into the Great Lakes today. A corridor of maximized surface dewpoints will move eastward across the Ohio Valley today, as a cold front approaches from the west. Scattered thunderstorms will likely develop during the late morning, as low-level convergence and instability increases. These storms, in the form of clusters or short line segments, will move eastward across the Ohio Valley and Lower Great Lakes region during the afternoon. RAP forecast soundings across far eastern Indiana and western Ohio during the early afternoon show a favorable environment for severe storms, with MLCAPE near 1500 J/kg and 0-6 km shear around 50 knots. This should support an isolated large hail threat with the more discrete rotating storms. A wind-damage threat will also be possible, especially with the more organized line segments. Forecast soundings suggest that low-level shear will become more favorable in the late afternoon, with 0-3 km storm-relative helicity increasing into the 225 to 250 m2/s2 range. For this reason, the tornado threat is expected to be greater a bit further east from central and eastern Ohio into far western Pennsylvania. Further south into the Tennessee Valley and central Gulf Coast states, isolated thunderstorms are expected to develop ahead of a cold front, and near a moist axis with surface dewpoints in the 60s F. MLCAPE in the 750 to 1000 J/kg range, along with 0-6 km shear from 40 to 50 knots will be sufficient for an isolated severe threat. Marginally severe wind gusts and hail will be the primary threats. ...Central Plains/Ozarks... An upper-level trough will move through the north-central U.S. tonight, as a 70 to 80 knot mid-level jet passes through the trough. In response, a 40 to 50 knot low-level jet will develop further south across the central Plains. Thunderstorms are expected to initiate near the northern edge of the low-level jet late this evening from central Kansas into far southeast Nebraska. These storms are expected to move eastward across northeast Kansas and into western Missouri. Forecast soundings in northeast Kansas around 06Z have MUCAPE near 2500 J/kg, with effective shear around 45 knots. This, combined with 700-500 mb lapse rates around 7.5 C/km, should be favorable for elevated rotating storms with potential for very large hail. The large hail threat is expected to be greatest in the 04Z to 07Z time window, but may persist through late in the period. ..Broyles/Lyons.. 04/17/2024 $$ ####018003538#### ACUS02 KWNS 170559 SWODY2 SPC AC 170558 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Wed Apr 17 2024 Valid 181200Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE MID MISSISSIPPI VALLEY AND LOWER OHIO VALLEY...AND OVER A PORTION OF NORTHERN TEXAS... ...SUMMARY... Scattered strong to severe storms capable of damaging winds, large hail, and perhaps a couple tornadoes will be possible Thursday from parts of eastern Missouri into the lower Ohio Valley and vicinity. Locally damaging winds and hail are also expected over parts of northern Texas. ...Synopsis... On Thursday, an upper low will move east from Manitoba into western Ontario, with a broad area of cyclonic flow aloft from the northern Plains to the Upper Great Lakes. South of the primary midlevel temperature gradient, moderate winds to around 50 kt will extend southward from MO into the OH Valley, with 30 kt midlevel winds into northern TX. Southwest winds of 30-40 kt will exist around 850 mb, aiding theta-e advection into the Mid MS/OH Valleys. At the surface, a cold front will exist roughly from northern MO into northwest TX Thursday morning, with a weak low moving from MO into the OH Valley ahead off the front. A warm front will lift northward ahead of the low, allowing moistening to occur over much of southern IL, IN, and northern KY during the day, and spreading into western OH overnight. Ample moisture ahead of this front will result in an elongated area of strong to severe potential throughout the day. ...Mid MS Valley into the lower OH Valley... Severe probabilities have been shifted farther west given latest model trends, as strong to severe storms could begin rather early in the day. Ongoing areas of storms are expected on the nose of the low-level jet, possibly in the form of an MCS, roughly over northern MO. As the warm front lifts north ahead of any such system, this could prove favorable for a swath of damaging winds. Otherwise, activity is expected to form near the low and along the cold front, where instability and shear will also favor supercells with large hail and perhaps tornado risk. Given the potential for early storms, this lends uncertainty to the forecast, and precludes an upgrade of higher coverage probabilities as placement would be uncertain. Regardless of early day evolution, moderate westerlies atop the expanding moist sector should favor areas of damaging wind, hail, and perhaps a few tornadoes during the day and through early evening. The severe risk could potentially reach into western OH and northern KY late, depending on upstream evolution. ...Northern TX... A cold front will push quickly south across OK and MO during the day, and across the Red River during the late afternoon and early evening. Given the late frontal arrival, strong destabilization will occur with full heating and upper 60s to lower 70s F dewpoints. MLCAPE over 3000 J/kg is forecast, with steep lapse rates through a deep layer. Although shear will not be strong, hodographs will favor southeastward-moving cells developing near the front or within the narrow low-level lapse rate plume where it will become uncapped. Locally damaging downbursts along with hail will be possible with any storms that develop, warranting an upgrade in severe probabilities for this focused diurnal event. ..Jewell.. 04/17/2024 $$