Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
481 ACUS02 KWNS 281723 SWODY2 SPC AC 281722 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1222 PM CDT Fri Jun 28 2024 Valid 291200Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM OHIO INTO PORTIONS WEST VIRGINIA...MARYLAND...PENNSYLVANIA AND NEW YORK... ...SUMMARY... Scattered damaging winds and a couple tornadoes are possible on Saturday from parts of Ohio into northern West Virginia/Maryland, central and western Pennsylvania, and western New York. ...Ohio Valley to the Northeast... Several vorticity maxima are forecast to migrate across the region within an area of enhanced southwesterly flow aloft ahead of the main upper shortwave trough progressing from the Upper Midwest to the lower Great Lakes. At the surface, low pressure will spread east/northeast from the upper Great Lakes into Ontario/Quebec. As this occurs, strong theta-e advection on southwesterly low-level flow will result in a very moist airmass spreading north/northeast from the Midwest into much of the Northeast. Early cloudiness and periods of showers may limit diurnal destabilization from eastern PA into NY. Pockets of stronger instability will overlap 30-40 kt westerly midlevel flow from parts of Ohio into western/central PA/NY. While midlevel lapse rates will remain quite poor, sufficient effective shear magnitudes amid rich boundary-layer moisture should support organized clusters and line segments capable of strong/damaging gusts. Vertically veering low-level winds will support somewhat enlarged and curved hodographs, with sufficient low-level instability and 0-1 km SRH. In addition to damaging gusts, a couple of tornadoes also will be possible. A more conditional risk may exist from late evening into the early overnight hours across parts of northern NY into VT as the surface front impinges on the area and the main upper shortwave trough ejects eastward. Strong vertical shear will be in place amid a very moist airmass. However, convection may remain elevated given poor timing with the diurnal cycle and impacts from daytime convection. If convection can become surface-based, damaging gusts will be possible. ...OK/KS to the Mid-MS Valley... Convection may be ongoing Saturday morning across parts of central MO. This activity may weaken during the morning, or slowly reintensify during the afternoon along outflow or the southward-advancing surface cold front. Additional convection is expected to develop along the sagging front across southern KS/northern OK during the late afternoon/evening. A couple of forward-propagating clusters are possible within this area of modest vertical shear, but rich boundary-layer moisture (dewpoints in the upper 60s/low 70s F) and moderate to strong instability. Isolated severe/damaging gusts and a few instances of hail will be possible with this activity. A corridor of higher probabilities may be needed in subsequent outlooks if confidence increases in location of better organized frontal convection. ...Central/Southern High Plains... Isolated convection is expected during the evening in a post-frontal upslope flow regime. Near 60 F surface dewpoints and steep midlevel lapse rates will support a corridor of moderate instability. While deep-layer flow will be light, vertically veering wind profiles will support 30-40 kt effective shear magnitudes amid a deeply mixed boundary-layer. Isolated strong to severe thunderstorms capable of strong gusts and hail will be possible. ...Northern IL into eastern WI and MI... Most forecast guidance is fairly sparse with convection across this area on Saturday. However, a very moist and unstable airmass will be in place ahead of the east/southeast-advancing cold front, along with favorable vertical shear for organized storms. Large-scale ascent will remain somewhat weak and ill-timed with the cold front progression, and low-level frontal convergence also will be poor. Severe probabilities have been adjusted some over the region based on low storm coverage and latest trends. However, a conditional severe threat will exist if storms develop. ..Leitman.. 06/28/2024 $$