SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1223 AM CDT Sat Oct 10 2020 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GULF STATES AND FROM NEW YORK TO NEW ENGLAND... ...SUMMARY... A few tornadoes are possible on Saturday across parts of the Gulf States. Severe gusts are also expected across parts of northern New York into western Maine. ...Tropical Cyclone Delta... Tropical Cyclone Delta continues its northeast movement across LA early this morning. As TC Delta lifts into northwest MS later by 18z, significant mid-level drying will surge east and the primary corridor of deepest convection should become focused from south-central AL into west-central GA. Latest model guidance does not allow appreciable buoyancy to develop immediately ahead of Beta over northern MS, and forecast soundings strongly suggest updrafts will struggle to attain heights necessary for lightning. Even so, strong low-level shear warrants at least low probabilities for locally strong winds or perhaps a brief tornado. Otherwise, the primary focus for more robust convection should focus downstream where partial breaks in cloud cover should allow for some boundary-layer heating and appreciably more instability, especially from southern AL into west-central GA. While this region will be along the eastern fringe of stronger low-level shear, forecast soundings exhibit adequate shear for supercells. Have extended wind/tornado probabilities downstream into the stronger region of instability where adequate shear will exist for sustained, robust updrafts. A few tornadoes and gusty winds are possible with this activity. ...NY to ME... Early-morning water-vapor imagery depicts at least two distinct short-wave troughs over ON. The lead feature will quickly shift into QC as the upstream short wave digs southeast toward the international border region later this afternoon. Focused mid-level height falls will spread across QC/northern New England with more appreciable falls expected after 11/00z over ME. A plume of higher-PW air will be drawn ahead of the front prior to this wind shift advancing south of the Canadian border. It appears warm-sector temperatures will warm quickly ahead of the front which will lead to convective development as minimal surface convergence will be needed for parcels to reach their LFC. Latest HREF supports this and scattered thunderstorms should evolve along the boundary across southeast ON/northern NY by 18z then spread southeast as the front surges toward New England. Increasingly westerly flow will favor the potential for gusty winds with this convection. With the mean flow expected to be parallel with this frontal convection, this could lessen more intense bow-type structures. For this reason, will maintain 15 percent severe wind probabilities. ..Darrow/Moore.. 10/10/2020
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