Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
495 ACUS02 KWNS 041728 SWODY2 SPC AC 041726 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1126 AM CST Mon Nov 04 2024 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SABINE TO LOWER MISSISSIPPI VALLEY...AND OVER PARTS OF WISCONSIN... ...SUMMARY... A tornado or two and locally damaging winds may occur on Tuesday across a portion of the Sabine to Lower Mississippi Valleys, and central to southern Wisconsin. ...Synopsis... A compact upper shortwave trough will shift northeast across the Middle and Upper MS Valley and upper Great Lakes vicinity on Tuesday. As the same time, another upper trough over the northern Rockies will dig south/southeast through the period, maintaining broad upper troughing over the West and into the Plains. Moderate to strong deep-layer southwesterly flow associated with the initial shortwave trough over the MS Valley will overspread east TX to the Great Lakes. At the surface, low pressure initially over northeast KS/northwest MO/southeast NE will lift northeast into southern Ontario by Wednesday morning. A cold front/composite outflow will extend from the Mid-MS Valley into east TX and the TX Gulf Coast vicinity. This boundary will slowly shift east through the period. Meanwhile, a warm front will be draped across the upper Great Lakes vicinity. Strong mid/upper level flow and these low-level boundaries and surface low will focus some potential for strong thunderstorms on Tuesday, mainly over WI and parts of southeast Texas to the Lower MS. ...East TX/Lower MS Valley... Convection will be ongoing Tuesday morning across east TX toward the TX coast as a cold front slowly progresses east. A corridor of modest instability will be in place ahead of the front from the TX coast/Sabine Valley into LA. Midlevel lapse rates are expected to remain poor. However, a moist boundary-layer (dewpoints in the low 70s F) and moderate low-level and deep-layer shear will support organized convection. Forecast soundings indicate enlarged, looping hodographs, becoming elongated above 3 km. This suggests rotation may accompany convection, and a tornado or two will be possible, particularly across parts of LA into southwest AR where low-level shear will be somewhat more favorable compared to points further south near the TX coast. Otherwise, line segments and cells may also produce locally strong gusts. The severe risk should move offshore the TX coast by around midday/early afternoon, while persisting through the afternoon to early evening further north across LA and the southeast AR vicinity. Overall, severe risk should be tempered by poor lapse rates and only modest destabilization, along with generally weak large-scale ascent further removed from the ejecting upper shortwave trough. ...WI... Warm advection ahead of the surface low/cold front moving from IA into WI will result in showers/thunderstorms and widespread cloud cover through the morning. This will limit diurnal heating, through forecast soundings suggest some areas could warm into the mid 50s to near 60 F by mid afternoon. This could allow for weak destabilization, though may be ill-timed as low-level winds begin to veer with time. While this lends to uncertainty in severe potential, at least a low-end/conditional risk for a tornado or two, or locally strong gusts appears possible. ..Leitman.. 11/04/2024 $$