SPC Mar 13, 2025 0600 UTC Day 2 Convective Outlook
SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Thu Mar 13 2025 Valid 141200Z - 151200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN MISSOURI...FAR SOUTHEAST IOWA...CENTRAL AND SOUTHERN ILLINOIS...FAR WESTERN KENTUCKY...FAR NORTHWEST TENNESSEE...AND EXTREME NORTHEAST ARKANSAS... ...SUMMARY... A regional outbreak of severe storms is expected across much of the Mississippi Valley, eastward to the Lower Ohio and Tennessee Valleys late Friday afternoon into Saturday morning. Widespread damaging winds (some greater than 65 kt), several tornadoes (some strong), and large hail will all be possible. ...Synopsis... An intense cyclone will develop from the central Plains to the Upper Midwest on Friday. As this system rapidly deepens, an intense jet streak (100+ kt at 500 mb) will overspread the Ozarks and Mid-MS Valley. Meanwhile, a large area covering much of the MS Valley vicinity will see 850-700 mb southwesterly flow around 65-80 kt. Southerly low-level flow will transport mid 50s dewpoints as far north as IA/northern IL (decreasing with northward extent across the Upper Midwest). Richer boundary layer moisture (60s F dewpoints) will be confined to the Lower MS Valley and Deep South/TN Valley, though near-60 F dewpoints may reach the MS/OH River confluence. Rapidly developing convection is expected to develop by late afternoon from near a surface low over eastern NE and arcing east/southeast along a dryline into the Ozarks. Convection will develop northeast across the Mid-MS valley, with additional storms develop with southward extent into the Mid-South and TN Valley during the nighttime hours. ...Mid/Upper Mississippi Valley to the Lower OH/TN Valleys... Cold temperatures aloft near the main upper low will support steep midlevel lapse rates. While boundary moisture will be modest, MLCAPE up to 1000-1500 J/kg is possible. This will support rapid storm development amid intense deep-layer shear. Heating ahead of the dryline also will support some boundary layer mixing and steepening of low-level lapse rates. As a result, a rapidly developing QLCS is expected. Convection will shift east/northeast into the nighttime hours. Given fast storm motion and the intensity of deep-layer flow, swaths of significant wind gusts (greater than 65 kt) are anticipated over a large part of the Mid-MS Valley. A gradual weakening of convection is expected after midnight with north and east extent. With southward extent from parts of eastern MO/western IL into the Mid-South, some potential for a mix of linear convection and supercells appears possible. Vertical shear will support tornadoes within linear convection. The environment will especially be favorable for strong tornadoes with any supercells that develop. This activity may develop a little later than initial convection further north, with much of the threat being after dark from east-central MO/west-central IL southward to western TN. Given the intensity of maximum gusts expected, and widespread coverage of damaging gusts, a Moderate risk (level 4 of 5) has been included for portions of the Mid-MS Valley vicinity. ...MS/AL/TN Overnight... Persistent southerly low-level flow will bring mid to possibly upper 60s F dewpoints northward into the TN Valley overnight. Neutral to modest height falls are expected and a persistent, strong low-level jet will overspread the region. Forecast soundings indicate very favorable thermodynamic and kinematic profiles, which would support intense supercells. Forcing mechanisms will be somewhat modest over the region, which may limit convective coverage, and a somewhat more conditional risk. However, any storms that develop within this environment overnight will pose a risk for strong tornadoes, large hail and damaging gusts. ...Upper Midwest/Great Lakes vicinity... The severe risk will become more marginal into MN/WI/MI. Strong deep layer flow will overspread the region and any convection will pose a risk of strong gusts. An additional risk for hail also will exist, especially with any elevated convection near the warm front overnight. ..Leitman.. 03/13/2025
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