SPC AC 301245 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 AM CDT Sun Mar 30 2025 Valid 301300Z - 311200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE LOWER/MID MISSISSIPPI VALLEY INTO THE OHIO VALLEY AND SOUTHERN GREAT LAKES... ...SUMMARY... Numerous severe thunderstorms are expected today and tonight across a broad portion of the Southeast and lower/mid Mississippi Valley into the Ohio Valley and southern Great Lakes. Multiple swaths of widespread damaging winds appear likely. Large to very large hail and several tornadoes will also occur with supercells. A few of these tornadoes could be strong. ...Synopsis... A broad area of severe potential remains apparent today and tonight, with all severe hazards likely. The main mid-level shortwave trough of interest will move quickly northeastward from the Ozarks/mid MO Valley to the Upper Midwest and Great Lakes today, as larger-scale upper troughing gradually becomes more established over the MS Valley through the period. At the surface, the primary surface low over eastern IA this morning is expected to develop northeastward towards northern Lower MI by this evening, and eventually into southern Ontario/Quebec late tonight. An attendant cold front will sweep east-southeastward over much of the Midwest/OH Valley and mid/lower MS Valley through the period, while a warm front lifts northward in tandem with the surface low over portions of the Great Lakes. A dryline will mix eastward this afternoon across parts of north-central to south-central TX. ...Midwest/Ohio Valley to the Great Lakes... Mainly elevated thunderstorms are ongoing this morning across parts of northeast MO in associated with the northeastward-advancing shortwave trough. This activity should generally remain sub-severe, although isolated strong/gusty winds could occur with modest daytime heating this morning. Otherwise, a corridor of weak to moderate instability is expected to develop ahead of the cold front by early afternoon. Robust convection appears likely to initiate by 18-19Z, and it will spread quickly northeastward across much of the OH Valley and southern Great Lakes regions this afternoon and evening. A 50-70 kt southwesterly mid-level jet attendant to the shortwave trough will provide ample deep-layer shear for organized convection. Current expectations are for an initially more discrete mode, with supercells posing a threat for large to very large hail (around 1.5-2.5 inch diameter) given the presence of steep mid-level lapse rates and favorable deep-layer shear. A fairly quick transition (within a few hours of initiation) to a more linear/cluster mode is anticipated as the cold front surges eastward. Multiple swaths of numerous to potentially widespread severe/damaging winds appear likely as one or more clusters moves quickly east-northeastward over the OH Valley and southern Lower MI. With a 35-45 kt south-southwesterly low-level jet also present, strong low-level shear will likely support a threat for tornadoes, both with initial supercells and any lines/clusters that eventually form. Given the strength of the low-level flow, some of the tornadoes could be strong, especially with sustained supercells in the lower OH Valley vicinity. The threat for damaging winds and tornadoes should continue this evening into the overnight hours, until convection outpaces the low-level moisture return and eventually weakens over the upper OH Valley and central Appalachians. ...Central/East Texas into the Lower/Mid Mississippi Valley/Mid-South and Southeast... A band of mostly elevated convection developed earlier this morning over portions of north-central/east TX, likely in association with large-scale ascent preceding a westerly mid/upper-level jet nosing into central TX. While the overall environment remains quite favorable for organized severe convection, messy convective modes have tended to keep the severe hail threat isolated so far. Still, some risk for hail will continue through the morning. Strong destabilization is anticipated today ahead of this convection and a separate area of elevated thunderstorms over southern MO. Mid to upper 60s surface dewpoints will continue to stream northward across TX ahead of the dryline, and the lower/mid MS Valley and Southeast ahead of the cold front. This rich low-level moisture, combined with very steep (8-9 C/km) mid-level lapse rates and daytime heating, are expected to foster around 2000-3000 MLCAPE by early to mid afternoon. Rapid and intense thunderstorm initiation will likely occur by 18-21Z from parts of north-central/east TX to the Mid-South/mid MS Valley. Supercells are expected initially, with 40-50+ kt of deep-layer shear supporting robust updraft organization and rotation. A very favorable setup remains apparent for large to very large hail, as strong instability and deep-layer shear combine with steep mid-level lapse rates and low freezing levels. Some of this very large hail could reach up to 2-3 inches in diameter. With the primary shortwave trough ejecting to the northeast, low-level winds are forecast to remain fairly subdued through the afternoon and early evening, before gradually strengthening again tonight through early Monday morning. A risk for several tornadoes should be focused over parts of the Mid-South, a few of which could be strong given a favorable supercell mode. Similar to farther north in the OH Valley, a transition to more linear/cluster mode is expected this evening and overnight as the cold front continues advancing southeastward. A risk for line-embedded tornadoes should continue, and an increase in the severe/damaging wind threat is likely through the end of the period. Based on latest guidance trends, and to overlap with the Day 2 Convective Outlook, adjustments have been made to the southern/eastern extent of the risk areas across the lower MS Valley and Southeast. ...Florida Peninsula... A weak mid-level perturbation will move eastward over FL today. Modestly enhanced winds aloft, and a veering profile with height through mid levels, should support sufficient deep-layer shear for some thunderstorm organization. Any convection that develops in tandem with daytime heating this afternoon and early evening could pose an isolated threat for severe hail and damaging winds. Some adjustments have been made to the Marginal Risk across the FL Peninsula based on latest guidance trends. ..Gleason/Leitman.. 03/30/2025 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
Category: Watches, Warnings, Advisories, & Hazards