SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Fri Jul 16 2021 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHEAST/MID-ATLANTIC AND THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Isolated strong to severe storms will be possible across portions of the Northeast/Mid-Atlantic and northern/central Plains on Saturday. ...Northeast/Mid-Atlantic... A belt of modestly enhanced mid-level southwesterly flow should be maintained Saturday across much of the Northeast and Mid-Atlantic ahead of a positively tilted upper trough. At the surface, a weak low is forecast to develop from the lower Great Lakes across NY and into southern New England by Saturday evening. A cold front should extend southwestward from this surface low across the Mid-Atlantic and into the central Appalachians, while a weak warm front extends across southern NY and southern New England. Current expectations are for multiple clusters of storms to develop along/ahead of the cold front and a pre-frontal trough through the day, and subsequently move eastward across the warm sector. Low/mid-level flow should not be overly strong, but generally 20-30 kt of deep-layer shear should be sufficient for modest updraft organization and mainly a multicell/cluster storm mode. Daytime heating of the moist low-level airmass ahead of these storms will likely foster steepened low-level lapse rates and moderate to strong instability, particularly across the Mid-Atlantic east of the Appalachian and Blue Ridge Mountains. Isolated damaging wind gusts should be the main threat. Both low-level and deep-layer shear may be slightly stronger across southern NY/New England, and marginal supercells posing both an damaging wind and brief tornado threat appear possible, particularly in the vicinity of the weak warm front. ...Northern/Central Plains... A large-scale upper ridge should build over the Rockies and adjacent High Plains on Saturday. Still, a swath of modestly enhanced mid-level northwesterlies will likely remain across parts of the northern/central Plains through the period. Initially high-based storms over the higher terrain of the central Rockies should develop eastward through Saturday afternoon and evening. Other storms may also develop across the northern High Plains along/east of a weak surface lee trough. Any storms that can persist should encounter greater low-level moisture and related boundary-layer instability east of the surface trough. Even though the mid-level northwesterly flow is expected to remain fairly modest, a strongly veering wind profile with height will support enough deep-layer shear for organized storms, including multicell clusters and supercells. Both isolated large hail and severe wind gusts may occur with this activity through Saturday evening. ..Gleason.. 07/16/2021 Read more LIVE: spc.noaa.gov
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