SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook CORR 2 NWS Storm Prediction Center Norman OK 0142 AM CST Tue Nov 26 2024 Valid 271200Z - 281200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE ARKLAMISS REGION INTO CENTRAL/NORTHERN AL... CORRECTED FOR DAY REFERENCE IN SYNOPSIS ...SUMMARY... Isolated strong to severe storms are possible from the lower Mississippi Valley into parts of Alabama, primarily from late Wednesday night into early Thursday morning. ...Synopsis... A positively tilted mid/upper-level shortwave trough is expected to move quickly eastward from the central Rockies/Great Plains toward the lower/mid MS and TN Valleys from Wednesday into Wednesday night. Guidance still varies regarding the timing and amplitude of this shortwave, as well as with the strength of a surface low that is generally forecast to move eastward across parts of the TN/OH Valleys later in the period. ...Lower MS Valley into the TN Valley... Low-level moisture is expected to stream northeastward from the northwest Gulf of Mexico Wednesday afternoon into Wednesday night, with upper 60s F dewpoints reaching southern MS, and low/mid 60s F dewpoints extending into central/northern MS/AL. A warm layer between 850-700 mb will tend to suppress surface-based storm initiation through the day, though steep lapse rates above this layer will result in MLCAPE increasing above 1000 J/kg (with somewhat greater MUCAPE values) from LA into at least southern MS, while MLCAPE of near 500 J/kg may reach a larger portion of AL/MS. Notably, some guidance (such as the NAM) is much less aggressive with the northern extent of favorable instability. Low-level and deep-layer flow/shear are expected to become rather strong across much of the Southeast Wednesday evening/night, resulting in a conditionally favorable kinematic environment for organized storms. The primary uncertainty regarding severe potential is the coverage of deep convection within an initially capped environment. There is some signal for initially elevated development by late evening within a warm-advection regime, which may continue into the overnight hours as the boundary layer moistens and potentially better supports near-surface-based storms. Some development will also be possible along the cold front prior to 12Z. With strong deep-layer flow/shear and generally favorable midlevel lapse rates expected along/ahead of the front, isolated strong/damaging gusts and hail will be possible if deep convection can be sustained Wednesday night. The tornado threat is more uncertain, due to lingering MLCINH and the eventual undercutting nature of the front, but a tornado cannot be ruled out if convection can become near-surface-based with time. With the GFS/GEFS and ECMWF control/ensemble suggesting some potential for deep convection within a strongly sheared environment, a Marginal Risk has been included for primarily late in the forecast period. Some adjustments will likely be needed in subsequent outlooks, depending on trends regarding shortwave amplitude and frontal timing. ..Dean.. 11/26/2024