Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
644 ACUS02 KWNS 070602 SWODY2 SPC AC 070600 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Tue May 07 2024 Valid 081200Z - 091200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST TEXAS INTO THE MID-SOUTH/MID MISSISSIPPI VALLEY AND LOWER OHIO VALLEY... ...SUMMARY... Scattered to numerous severe thunderstorms appear likely Wednesday across from parts of the southern Plains into the mid Mississippi, Ohio, and Tennessee Valleys. All severe hazards, including tornadoes, very large hail, and severe/damaging winds should occur. Some of the tornadoes may be strong. ...Synopsis... An upper cyclone initially over the northern Plains on Wednesday should gradually move towards the Upper Midwest through the period. A separate shortwave trough over the Great Lakes is forecast to advance eastward across NY and New England. A broad 50-70 kt mid-level west-southwesterly jet should remain over the southern/central Plains into the mid MS Valley, OH Valley/Midwest, and Northeast. This jet will aid in rather strong deep-layer shear across much of these regions. At the surface, a weak low over OK should develop northeastward to the mid MS Valley by Wednesday afternoon in tandem with a lobe of mid-level vorticity/ascent also spreading northeastward over this region. An attendant cold front should move east-southeastward across the southern/central Plains, with a dryline extending southward from central into south TX. A warm front should attempt to lift northward through the day across MO and southern IL/IN/OH. But, how far north the warm front will be able to lift northward remains rather uncertain. All of these boundaries should provide a focus for potential severe thunderstorm development Wednesday afternoon and evening. ...ArkLaTex into the Mid Mississippi Valley and Ohio Valley... A large area of significant severe potential remains evident across these regions on Wednesday. Across the broad warm sector, upper 60s to mid 70s surface dewpoints should generally prevail. Even modest daytime heating of this very moist low-level air, acting in concert with steepened mid-level lapse rates spreading eastward from the southern/central Plains, will foster around 2500-3500 J/kg of MLCAPE by Wednesday afternoon. Some locally higher/more extreme instability values will be possible. With enhanced flow associated with the previously mentioned mid-level jet, effective bulk shear of 40-50+ kt will easily support organized severe thunderstorms, including the potential for numerous supercells and intense bowing line segments. Based on latest guidance trends showing the warm front stalling/not making as much northward progress into the OH Valley, the northern extent of the higher severe probabilities has been trimmed some across this area. Otherwise, very large hail appears probable with initial development along the cold front and warm front, which may begin across MO as early as mid Wednesday morning. Additional supercell development may also occur along/near the warm front by early Wednesday afternoon across parts of the mid MS Valley into the lower OH Valley. In addition to the large/very large hail threat, a concern for tornadoes also exists with this warm-frontal activity given ample 0-1 km shear to support low-level updraft rotation. Some of these tornadoes could be strong given the forecast strength of the low-level shear. An increasing threat for severe/damaging winds is also apparent through the late afternoon, and likely continuing into at least the early evening, as convection should attempt to grow upscale into one or more intense bowing clusters. With that said, convective evolution is somewhat uncertain, and attempting to pinpoint areas of greater severe-wind potential remains difficult. ...Iowa and Vicinity... Isolated strong to severe thunderstorms appear possible in associated with a cold-core upper low across parts of IA and vicinity, mainly Wednesday afternoon. Although forecast instability and deep-layer shear appear fairly weak/marginal, a few instances of hail and strong/gusty winds appear possible. A brief tornado or two may also occur along/near the occluded front. ...Southern New England into NY and the Mid-Atlantic/Carolinas... Occasional hail and strong to locally damaging winds appear possible with isolated thunderstorms across parts of NY into southern New England as a surface low and attendant cold front move eastward through the day. Farther south into the Mid-Atlantic/Carolinas, greater instability is forecast. But, better forcing should generally remain displaced to the west. It remains unclear how many thunderstorms will form. Still, any that do could become strong to locally severe. ..Gleason.. 05/07/2024 $$