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SPC Apr 28, 2024 0600 UTC Day 1 Convective Outlook

1 year 4 months ago

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sun Apr 28 2024 Valid 281200Z - 291200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PART OF EAST TEXAS...NORTHWEST LOUISIANA...FAR EASTERN OKLAHOMA...WESTERN-CENTRAL ARKANSAS AND SOUTHWEST TO SOUTH-CENTRAL MISSOURI... ...SUMMARY... Severe thunderstorms are likely today from parts of east Texas and northwest Louisiana north-northeastward into southwest Missouri. Damaging winds and a few tornadoes are expected along the stronger parts of the line. A couple of strong tornadoes could occur from southwest Arkansas into east Texas. A more isolated severe threat is expected today over parts of the lower to mid Missouri Valley. ...East Texas/Ark-La-Tex/Ozarks... A large linear MCS will move eastward across the Ozarks and Ark-La-Tex early in the period. The line is expected to become unorganized after daybreak and dissipate by late morning. A moist and unstable airmass is likely to remain mostly undisturbed across much of east Texas and Louisiana. This airmass is forecast to advect northward across the Ark-La-Tex during the afternoon. On the large-scale, a negatively tilted mid-level trough will move across the southern and central Plains today. As surface temperatures warm, thunderstorms will reform along the western edge of the warm sector by mid-afternoon. The convection is expected to organize into a line, producing wind damage and hail, moving eastward across the Ark-La-Tex and Ozarks during the late afternoon. The greatest severe threat will likely be along the southern half of the line, from southwest Arkansas and far southeast Oklahoma south-southwestward into east Texas. RAP forecast soundings at 00Z/Monday across far southwest Arkansas and in northeast Texas have MLCAPE ranging from 1500 to 3000 J/kg, with 0-6 km shear generally from 35 to 45 knots. Also, 0-3 km storm-relative helicity is forecast to increase into the 200 to 300 m2/s2 range during the late afternoon and early evening, as a 50 to 60 knot low-level jet strengthens. This environment will be favorable for tornadoes with embedded supercells, and with rotating elements near the leading edge of the line. A couple of strong tornadoes will be possible, mainly in the Ark-La-Tex and in east Texas, where instability is expected to be greatest. Hailstones greater than two inches in diameter could occur near the southern end of the line, if a couple supercells can remain semi-discrete. The more intense bowing segments will likely be accompanied by wind damage. Although a substantial severe threat is expected as far south as southeast Texas, there could be a gap in the line across part of east Texas where the severe threat is locally minimized. On the northern end of the line in the Ozarks, the magnitude of the severe threat will be conditional upon destabilization in the wake of the morning MCS. The severe threat associated with the line should persist into the late evening as the new MCS approaches the Mississippi River. ...Lower to Mid Missouri Valley/Mid to Upper Mississippi Valley... An upper-level trough will move eastward across the lower to mid Missouri Valley today. Ahead of the trough, a moist airmass will be in place across much of Missouri northward into southern Iowa. As surface heating takes place today, thunderstorms are forecast to develop along the western edge of the moist sector from east-central Kansas into southeast Nebraska. The storms will move eastward into Missouri and southern Iowa during the afternoon. RAP forecast soundings near Kansas City by 21Z have MLCAPE near 1200 J/kg, with 0-6 km shear around 60 knots. This, combined with steep low to mid-level lapse rates should support a severe threat during the afternoon. The primary hazards should be wind damage and hail. As convective coverage increases during the late afternoon and early evening, a line is expected to organize. Wind damage should become the primary threat as it approaches the Mississippi River during the evening. ..Broyles/Thornton.. 04/28/2024 Read more