Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
998 ACUS02 KWNS 171704 SWODY2 SPC AC 171703 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1203 PM CDT Tue Jun 17 2025 Valid 181200Z - 191200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN LOWER MICHIGAN INTO NORTHWEST OHIO...INDIANA...SOUTHERN ILLINOIS/MISSOURI...AND EXTREME WESTERN KENTUCKY... ...SUMMARY... Strong to severe storms are expected on Wednesday from parts of southern Missouri northeastward into southern lower Michigan. Damaging winds, isolated hail, and a few tornadoes will be possible. More isolated severe storms may develop across the southern Plains. ...Synopsis... A mid-level trough will traverse from MO/IA to the Southern Great Lakes on Wednesday. A surface low will accompany this mid-level trough and move from eastern Iowa to Michigan. A cold front will extend from this surface low to the southern Great Plains. Severe thunderstorms are expected along much of this frontal zone on Wednesday. ...Midwest into the Southern Great Lakes... Upper 60s to low 70s dewpoints will be present ahead of a cold front across the Midwest/Great Lakes on Wednesday morning. Some cloudcover is likely across the region, but only minimal heating (mid 70s) appears necessary for convective initiation. Therefore, expect relatively early storm development along and ahead of a cold front north of I-70 during the late morning to mid-day timeframe. Moderate instability and modest shear (35 to 40 knots) will promote storm organization. Very weak (~5.5 C/km) mid-level lapse rates amid a moist profile, should mostly limit hail production. Therefore, damaging wind gusts will likely be the primary threat. However, some tornado threat will also exist as forecast soundings show strong low-level curvature and significant streamwise vorticity in the lowest 1km. There is some uncertainty with storm mode, but a tornado threat would exist with either a broken line or a QLCS as it moves across northern Indiana into southern Michigan and northwest Ohio. ...Ozarks into the Mid-Mississippi Valley... There is uncertainty across southern Missouri and northern Arkansas regarding the strength of morning convection across the region. It is unclear whether this morning convection will reintensify and move east/northeast with a renewed threat, or if additional development will occur during the afternoon and be the primary threat. However, given the lack of strong low-level jet support, expect the overnight MCS to be weakening by morning with the additional afternoon development solution preferred. Moderate to potentially strong instability is forecast by mid-afternoon with modest (25-30 knots) of shear. This will support mostly multicell clusters with a threat for damaging wind gusts. ...Southern Plains... Strong heating is forecast south of the boundary across the southern Plains. This will result in moderate to potentially strong instability amid 25-30 knots of shear. Very warm 700mb temperatures (12C) will likely limit overall convective coverage. However, forecast soundings show a mostly uncapped environment where a surface boundary should be present. Therefore, at least isolated storms are possible. Modest shear and very steep lapse rates will support some hail/wind threat from any storms which can develop within this region. ...Northern Plains... Despite generally limited low-level moisture, relatively steep lapse rates and cool temperatures aloft may support a pocket of moderate destabilization across parts of far northeast MT and ND into northern MN Wednesday afternoon. Wind profiles will be relatively weak and unidirectional, but a couple stronger cells or clusters will be possible during the afternoon and evening, with localized potential for hail and strong to severe gusts. ...Mid Atlantic... Strong heating, combined with low 70s dewpoints will result in moderate to strong instability in the Mid-Atlantic on Wednesday. 12Z guidance has trended weaker with a belt of mid-level flow across the Mid-Atlantic Wednesday afternoon/evening. However, sufficient mid-level flow is still forecast for modest shear and some multicell clusters. Damaging wind gusts will be the primary threat from these scattered storms. ..Bentley.. 06/17/2025 $$