SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Thu Apr 03 2025 Valid 032000Z - 041200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM NORTHEAST TX TO MIDDLE TN... ...SUMMARY... Severe thunderstorms will continue to form and move along a stalled frontal zone from northeast Texas into middle Tennessee and southern Kentucky through late evening, with the possibility of very large hail and a couple of strong tornadoes. Very large hail will be possible after midnight from southwest Texas into cnetral Texas and southern Oklahoma. ...Northeast TX to middle TN/southern KY this afternoon/evening... Severe storms are developing along and to the immediate cool side of a rain-reinforced baroclinic zone from northeast TX across AR and middle TN/southern KY. Initial storm motions will tend to carry the convection to the cool side of the boundary (especially across AR), though there is some potential for surface-based supercells to form and move along the wind shift. The warm sector to the south is characterized by boundary-layer dewpoints ranging from mid 60s F across TN/KY to low 70s F from northeast TX into southern AR. The rich moisture and surface temperatures warming into the low-mid 80s beneath 7-8.5 C/km midlevel lapse rates maintain MLCAPE ranging from 1500 J/kg east to 3000+ in northeast TX/northern LA. Deep-layer vertical shear/hodograph length is more than sufficient for sustained supercells, while substantial low-level hodograph curvature (effective SRH of 200-300 m2/s2) and the moist boundary layer will support the potential for a couple of strong tornadoes with supercells moving along the boundary. Otherwise, large hail of 1.5-2.5 inches in diameter will be possible with both the surface-based and elevated supercells, as well as isolated wind damage as storms train along and just north of the boundary. ...SW into central TX and southern OK overnight... Within the large-scale trough over the Southwest, an embedded jet streak will move through the base of the trough from Baja to southwest TX by the end of the period. Mass response to the approaching jet streak will result in strengthening warm advection and the likelihood of elevated thunderstorm development over southwest TX after 06z. Storms will subsequently spread northeastward, with additional storm development expected by 12z from northwest TX into southern OK. Steep midlevel lapse rates, a rapid increase in moisture above the surface, and strong deep-layer shear will favor elevated supercells capable of producing very large hail (2-3 inches in diameter), as well as isolated damaging surface winds. ..Thompson.. 04/03/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Apr 03 2025/ ...Southern Plains/Mid-South/Tennessee Valley... With a prominent upper trough over the West, strong southwesterly winds aloft will overlie areas along/north of a frontal zone extending from the middle part of Texas into the ArkLaTex/Mid-South, east-northeastward to the central Appalachians and Mid-Atlantic States. With neutral to slightly rising mid-level heights, the convectively reinforced front is forecast to move little today across the ArkLaTex, Mid-South, and Tennessee Valley. Even though large-scale ascent will tend to remain somewhat nebulous near the front and southward into the warm sector, persistent low-level warm advection should aid in renewed thunderstorm development along/near the stalled front through the afternoon and evening. Any convection which can form on or just south of this boundary will have a rather favorably moist low-level airmass, steep lapse rates aloft, and strong deep-layer shear to support organized updrafts. A notable diurnal strengthening of the low-level jet /45-55 kt/ is expected today across the ArkLaTex to the Mid-South/Lower Mississippi Valley, where it will impinge on the west/southwest to east/northeast-oriented effective front. This is concerning regarding supercell tornado potential later today, some of which could be strong (EF2+) given the magnitudes of the deep-layer/low-level shear and moisture-rich environment with surface dewpoints in the upper 60s/near 70F. That said, some modal/mesoscale uncertainties still persist as to warm-sector development and the coverage and longevity of surface-based supercells, with convection potentially tending to be more prevalent/likely just north of the effective front. Otherwise, large to very large hail will be a threat with the expected supercellular development along/north of the front, with upscale-growing clusters posing a damaging wind threat as well. ...West-central/North Texas and southern Oklahoma late tonight... Elevated supercells are expected to again develop late tonight (after midnight CDT) and early Friday as forcing for ascent increases to the north of the surface front. These storms will pose a large hail threat, and possibly some severe-wind potential as well, particularly if elevated bow echo development occurs as storms spread northeastward within a highly sheared environment. ...Central Appalachians to Mid-Atlantic/Delmarva... Remnants of convection and related outflow boundaries will serve as a northern limit to any appreciable severe threat today. While some details remain uncertain, any storms that develop along/south of the front could pose risks for hail and damaging winds.