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 Forecast Discussion

000 ACUS03 KWNS 150731 SWODY3 SPC AC 150730 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Wed Aug 15 2018 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM A PART OF THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS AND FROM THE MID ATLANTIC TO NORTHEAST STATES... ...SUMMARY... A few storms with locally strong to damaging wind gusts will be possible from parts of Oklahoma through the lower Mississippi and Tennessee Valleys. Other strong storms might occur over a part of New England. ...Synopsis... A deamplifying lead shortwave trough will advance northeast through New England early Friday with an upstream trough immediately on the heels of this feature forecast to approach the Northeast States Friday night. Farther south a positive-tilt shortwave trough will move through the middle to lower MS and TN Valleys during the day. At the surface a weak surface low will evolve over the lower Great Lakes in association with the northern-stream upper trough. A cold front will stretch southwest from the low through the OH Valley and into MO and OK. Warm front extending eastward from the low should move slowly north through southern New England. A lee trough will become established east of the Appalachians. ...Southern Plains to lower Mississippi and Tennessee Valleys... Storms may be ongoing early Friday over a part of this region and especially the middle to lower MS Valley in vicinity of surface front and in association with vorticity maxima rotating through the positive-tilt upper trough. South of this activity, heating of the moist boundary layer will contribute to moderate instability with 1500-2000 J/kg MLCAPE, and storms are expected to redevelop along residual outflow boundaries during the afternoon. A belt of modest (20-35 kt) winds in the 850-500 mb layer should reside within base of the upper trough, and weak 0-6 km shear will promote multicell storm modes. Nevertheless, a few instances of locally strong to damaging wind gusts may accompany the some of the storms through early evening. ...Northeast States and Middle Atlantic regions... Storms will likely be ongoing within plume of subtropical moisture along warm conveyor belt from the Ohio Valley into a portion of the northeast states. Downstream from this activity and primarily east of the Appalachians, diabatic warming of the boundary layer may result in moderate instability with 1500-2000 J/kg MLCAPE possible. Storms may redevelop over the northeast U.S. along warm front, residual outflows from ongoing convection, as well as farther south over the higher terrain of the central Appalachians and spread east. Some augmentation of the vertical wind profiles will occur in association with the northern-stream shortwave trough and the migratory low-level jet, especially in the vicinity of the warm front. However, primary uncertainty in this region is extent of ongoing convection and clouds and the potential impact on destabilization. Therefore, will introduce a marginal risk category this outlook and continue to monitor for a possible slight risk in later updates. Otherwise, farther south across the Mid Atlantic, wind profiles will be weaker, but greater destabilization potential suggests multicell storms that move off the higher terrain or develop along lee trough may become capable of producing a few instances of downburst winds during the afternoon. ..Dial.. 08/15/2018 $$