2PM Day 3 Convective Outlook for Wednesday, June 25. THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN/CENTRAL HIGH PLAINS TO THE MIDWEST GREAT LAKES AND THE MID-ATLANTIC SOUTHWARD ACROSS THE SOUTHEAST AND INTO FLORIDA
SUMMARY
Strong to potentially severe storms are possible Wednesday in a corridor from the northern High Plains into the Midwest and Northeast, and also along and east of the Appalachians into the Southeast and much of Florida
Synopsis
Upper-level ridging across the eastern CONUS will start to weaken on Wednesday. A weak low will move west across the Florida Peninsula during the period. A strong mid-level jet streak will extend along the northeastern periphery of the ridge from northern Ontario to the Northeast. The trough across the western CONUS will deamplify through the period with a weak shortwave trough ejecting into the Plains.
Northern/Central High Plains and adjacent Plains
A deepening surface low will develop across northeast Colorado/northwest Kansas, and southwest Nebraska on Wednesday as a mid-level trough ejects over the Plains. Moderate instability is expected to develop south of the front which will extend east from this surface low across Nebraska and into Iowa. Isolated to scattered storms are expected along this front and near the intersection with the dryline/surface low. While mid-level flow is forecast to be somewhat weak, stronger upper-level flow may provide sufficient upper-level venting/deep-layer shear for some supercell organization.
Stronger flow will be present farther north across northeast Wyoming and southeast Montana. A few supercells are possible if low 60s dewpoints can advect into the region with moderate instability.
Midwest to the Mid Atlantic
Thunderstorms will likely be ongoing at the beginning of the period from the central Plains to the Great Lakes. These thunderstorms and their composite outflow will likely reinforce the boundary across the area. South of this boundary, a very moist airmass with moderate instability will be in place. Very weak shear will be the primary limiting factor to severe weather, but numerous thunderstorms in a moderately unstable and very moist environment should support some threat for wet microbursts and damaging wind gusts.
Mid-Atlantic to the Southeast and Florida
Steep mid-level lapse rates are expected across much of the eastern CONUS on Wednesday as the upper-level ridge weakens. Strong heating in a very moist environment should result in moderate to strong instability from Virginia southward into Florida. The highest confidence for storms will be along the sea breeze and the higher terrain. However, additional thunderstorms are also possible during the afternoon, particularly where any remnant outflow boundaries may remain from Tuesday night thunderstorm activity. Strengthening northeasterly flow across the region may provide enough shear for a few strong to severe multicell clusters capable of mostly damaging wind gusts.