SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0153 PM CST Fri Nov 12 2021 Valid 122000Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHERN NEW ENGLAND... ...SUMMARY... Isolated damaging wind gusts and a brief tornado or two are possible through this afternoon across parts of southern New England. ...20Z Update... ...Southern New England... Area VAD profiles and radar imagery shows very strong veering low-level winds (i.e. 70 kt at 1 km and 0-1 km storm-relative helicity 550 to 600 m2/s2). Most of the convection within the warm sector ahead of the front has remained shallow and transient, likely as a result of the limited buoyancy. This trend is expected to continue, although the kinematics are strong enough to maintain low wind and tornado threat, especially with any more cellular/deeper convection within the warm sector. A few cells just off the southern MA/CT coast have recently shown a bit more structure and will likely pose the greatest threat in the near-term. ..Mosier.. 11/12/2021 .PREV DISCUSSION... /ISSUED 1020 AM CST Fri Nov 12 2021/ ...Southern New England... A narrow line of low-topped convection continues to track eastward across eastern NY into adjacent parts of VT/MA/CT. This activity has produced sporadic low-end wind damage this morning, and may continue to do so through the afternoon across southern and central New England. This convection has thus far been void of lightning activity, evidence of the very weak available buoyancy. Nevertheless, will expand the MRGL a little farther north to address this risk. Local VAD profiles at OKX/BOX and nearby TDWRs suggest intense low-level winds and shear across southern New England. The associated low-level warm advection and lift will promote the development of scattered pre-frontal showers and occasionally more intense convective cores this afternoon over eastern Long Island, RI, and eastern MA. One such cell is about 50 nm south of Long Island and has shown supercell tendencies despite being too shallow to produce lightning. The boundary layer air mass ahead of this activity is very weakly unstable, but might be sufficient to support an isolated tornado or damaging wind gust. Anticipated coverage and confidence of this scenario is low, so will maintain the ongoing MRGL risk but monitor mesoscale trends. Read more LIVE: spc.noaa.gov
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