Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
543 ACUS02 KWNS 210602 SWODY2 SPC AC 210600 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Tue May 21 2024 Valid 221200Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS NORTH TEXAS...SOUTHEAST OKLAHOMA...AND MUCH OF ARKANSAS TO THE MISSOURI BOOTHEEL VICINITY... ...SUMMARY... Severe thunderstorms posing a risk for damaging gusts and hail will be possible from central Texas into the Ohio Valley and lower Great Lakes vicinity on Wednesday. The highest concentration of damaging gusts and large to very large hail is expected from north Texas to the Missouri Bootheel vicinity. ...Synopsis... An upper shortwave trough will move northeast across the Upper Midwest/Great Lakes vicinity on Wednesday. Meanwhile, convectively enhanced vorticity maxima from the Day 1/Tue period will develop east/northeast across parts of the Ohio Valley/Lower Great Lakes area in broad southwesterly deep-layer flow. Further south, broad, enhanced southwesterly flow will persist over the southern Plains to the Mid-South. One or more shortwave impulses are expected to float through this area ahead of a deepening large-scale western U.S. upper trough. At the surface, an occluding low near the MN/Ontario border will lift north through the period, with a weak surface trough extending into parts of the upper Ohio Valley and lower Great Lakes. The northern extent of a surface cold front will progress eastward across the Great Lakes vicinity. Meanwhile, the front will mainly stall from IN/southern IL into central OK and northwest TX. A dryline will move east into central TX. These boundaries will become the focus for thunderstorm development during the afternoon. ...Texas to Southern IL... A moisture-rich boundary layer will be present, with dewpoints in the upper 60s to low 70s F common. Atop this moist boundary layer, steep midlevel lapse rates around 8 C/km are forecast. This will result in strong to extreme instability (2500-4000 J/kg MLCAPE). Vertical shear will be favorable for supercells, with modestly enlarged low-level hodographs become elongated/straight above 3 km. Significant hail (greater than 2 inch diameter) will be possible with initial supercell development. How long semi-discrete supercells will be maintained is a bit uncertain. Upscale development into bowing segments will likely occur, resulting in an increasing damaging wind risk with time. A 35-45 kt southwesterly low-level jet is forecast to increase by early evening. This will support increasing 0-1 km SRH (to around 200 m2/s2) and a few tornadoes will be possible. A strong tornado cannot be ruled out, especially over parts of AR into north Texas. ...IN/KY to the Lower Great Lakes... Forcing for ascent across the region will mainly be provided by any MCVs from remnant Day 1/Tue convection floating through southwesterly flow, and the eastward-advancing cold front. A moist airmass with dewpoints in mid/upper 60s will be present over IN/OH/KY, with low/mid 60s extending northeast into NY/PA and vicinity. Strong heating and a plume of steep midlevel lapse rates will support moderate destabilization during the late morning/afternoon. Vertical shear will be sufficient for organized cells, though decreasing with northeast extent into eastern NY and the Mid-Atlantic vicinity. Isolated damaging gusts and marginal hail will be possible with thunderstorms into early evening. ..Leitman.. 05/21/2024 $$