ACUS01 KWNS 020556 SWODY1 SPC AC 020554 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1254 AM CDT Wed Apr 02 2025 Valid 021200Z - 031200Z ...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEAST ARKANSAS...FAR SOUTHEAST MISSOURI...FAR SOUTHERN ILLINOIS...WESTERN KENTUCKY...WESTERN TENNESSEE AND EXTREME NORTHWEST MISSISSIPPI... ...SUMMARY... A tornado outbreak is expected today and tonight from parts of the mid Mississippi and lower Ohio Valleys westward into the eastern Ozarks. Numerous tornadoes, along with multiple long-track EF3+ tornadoes appear likely. In addition, tornadoes, severe wind gusts, and large hail will be possible across a broad area from north Texas northeastward to the southern Great Lakes. ...Mid Mississippi and Lower Ohio Valleys/Eastern Ozarks... A potent mid-level trough will move northeastward across the central U.S. today, as a mid-level jet strengthens to over 120 knots, and ejects rapidly northeastward into the Upper Midwest. At the surface, a low will move into the upper Mississippi Valley, as a cold front advances eastward through the central states. Ahead of the front, a moist airmass will advect northward into the Ozarks and lower to mid Mississippi Valley, with surface dewpoints increasing into the mid to upper 60s F. While storms will likely be ongoing near the front during the day, the airmass further to the east is forecast to remain undisturbed and will significantly destabilize during the day. By early to mid afternoon, MLCAPE is forecast to increase into the 2500 to 3500 J/kg range across much of the moist airmass. The 500 mb jet is forecast to eject northeastward at nearly 55 knots into the upper Mississippi Valley. Large-scale ascent associated with the right entrance region of the jet will overspread the moist sector, becoming favorable for vigorous convective development. Model forecasts are in relatively good agreement, that scattered discrete convective initiation will take place well to the east of the front near the instability axis during the mid to late afternoon. Forecast soundings across the mid Mississippi Valley from 21Z to 00Z increase 0-3 km storm-relatively helicity to around 400 m2/s2, and have strong deep-layer shear near 60 knots. This will be favorable for supercells and tornadoes. The ECMWF and NAM are in good agreement, developing a 60 to 70 knot low-level jet max centered over far western Tennessee at 00Z. As supercells move eastward into the low-level jet, very strong low-level shear will be favorable for numerous tornadoes. The most intense tornadic supercells will be capable of producing long-track EF3+ tornadoes. Multiple EF3+ tornadoes are expected in the mid Mississippi Valley. The duration of the tornado threat should persist from afternoon into the evening. A potential for supercells and tornadoes will extend northward into the lower Ohio Valley and southwestward into the southern Ozarks. In those two locations, the more intense discrete supercells could produce strong tornadoes. In addition to the tornado threat, supercells associated with large hail and severe wind gusts are expected to form in the mid to late afternoon across a large area from the Ark-La-Tex northeastward to the southern Great Lakes. Large hail will also be possible with supercells that develop along and near the front, further west into the Ozarks. The more intense supercells should have potential to produce hailstones greater than 2 inches in diameter. During the mid to late evening and overnight period, several organized line segments are expected to organize and move eastward into the Tennessee Valley, lower Ohio Valley and southern Great Lakes. Gusts above 70 mph will be possible with the more intense bowing segments. The severe threat is expected to continue into the overnight period. ...North Texas... A mid-level trough will move northeastward across the central Plains this morning. At the surface, as a cold front will advance eastward through the southern Plains. Ahead of the front, a moist and unstable airmass will be in place over much of the eastern half of Texas. In spite of weak forcing, isolated thunderstorms may initiate along or ahead of the front as surface temperatures warm this morning. Forecast soundings ahead of the front in north Texas have 0-6 km shear around 50 knots with 700-500 mb lapse rates near 7.5 C/km. This environment will likely support a large hail threat with any supercells that can develop. Hailstones greater than 2 inches in diameter and severe wind gusts will be possible within the more vigorous supercell downdrafts. The severe threat is expected to gradually end during the day across parts of northwest and north-central Texas as the front moves eastward. However, isolated supercells with large hail could redevelop during the evening and overnight, as warm advection again brings low-level moisture northward into the Red River Valley. ..Broyles/Weinman.. 04/02/2025 $$