####018005102#### ACUS01 KWNS 081244 SWODY1 SPC AC 081243 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0743 AM CDT Mon Apr 08 2024 Valid 081300Z - 091200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF NORTHWEST AND NORTH-CENTRAL TEXAS... ...SUMMARY... Multiple rounds of severe thunderstorms should develop from mid afternoon through tonight across a large portion of the southern Plains into the Mississippi Delta region. Large to giant hail is the main threat, especially over northwest Texas, though a few tornadoes and severe gusts are also possible in an area extending east into northern Louisiana. ...Synopsis... Morning water-vapor imagery shows a positively-tilted mid-level trough over the Desert Southwest/northwest Mexico. This mid-level trough will amplify as it moves across the Southwest and northern Mexico. An associated belt of strong southwesterly flow will extend from the base of the trough across the southern Great Plains and into the lower MS Valley. A cyclone will develop in West Texas and deepen through the period as southerly low-level flow advects rich moisture into TX/LA [near the record high lowest 100-mb mean mixing ratio observed this early in the year at the Brownsville raob site (17.2 g/kg)]. A warm front will advance northward to the Red River by early evening. A cold front analyzed this morning moving south through the TX Panhandle/western OK will become stationary later today. ...Northwest Texas into north-central Texas... Strong heating on the northwest periphery of rich low-level moisture will weaken the cap across northwest TX by mid afternoon. Forecast soundings indicate a moderately unstable airmass (1000-2500 J/kg MLCAPE) will continue to destabilize into the evening as south-southeasterly flow strengthens and advects 50s (west) to mid 60s (near I-35) surface dewpoints into the region by early evening. Veering and strengthening flow with height (100+ kt at 250 mb) will favor supercells as the initial convective mode. Large to giant hail (3-4 inches in diameter) is possible in addition to some tornado risk towards evening. Some consolidation into a cluster/MCS may occur during the evening across north-central TX with some risk for all 3 hazards. ...East Texas into the ArkLaTex... Moderate to strong instability is expected to develop across east Texas and into western Louisiana this afternoon as upper 60s to near 70s dewpoints advect northward. Despite a solar eclipse across this region, its impact on the overall severe weather threat will likely remain minimal. Only moderate warming will be sufficient to erode inhibition across the region with a gradual strengthening of southerly 850-mb flow and isentropic ascent as the primary focus for storm development by mid to late afternoon. Strong instability and shear is expected and will support supercells capable of large to very large hail. However, there are some concerns about storm interference and updraft longevity. Initially, a warm nose around 700mb is evident on NAM/RAP forecast soundings which may limit more robust updraft development. This warm nose is forecast to erode by 23/00Z. However, by that time, widespread shower/thunderstorm development may be underway which could be a limiting factor to updraft longevity and a greater tornado/large hail threat. Some guidance suggests a MCS may develop out of the northwest/north-central Texas convection and move through northeast Texas during the overnight hours. This solution will greatly depend on the evolution of earlier convection and position of the convectively enhanced warm front by late evening. ...Texas Hill Country overnight... Increasing forcing for ascent via stronger mid-level height falls will overspread much of western/central Texas tonight. Continued moistening with mid-upper 60s deg F dewpoints beneath steep 700-500 lapse rates (8 deg C/km) will result in 2500 to 3000 J/kg MUCAPE. Elongated hodographs with 60-kt effective shear will promote supercells and mainly a risk for large to very large hail. Southerly 850-mb flow will increase overnight via a LLJ and act to augment initially limited hodographs. If a cluster organizes overnight (06-12z), a risk for severe gusts and perhaps a tornado could develop. Have extended Slight Risk equivalent wind/tornado probabilities southward for this potential scenario. ...West Texas early Tuesday... The dryline is expected to retreat into West Texas overnight with strong instability building back to near Midland early Tuesday morning. As strong upper forcing overspreads this region, at least isolated to scattered storms will probably develop on the western periphery of a strongly unstable/sheared environment. Have adjusted the some of the severe probabilities farther west where the progged western edge of moisture/buoyancy will be located. ..Smith/Mosier.. 04/08/2024 $$