SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0155 PM CST Sat Dec 12 2020 Valid 122000Z - 131200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms remain possible this afternoon over a small part of the Ohio Valley, and late tonight into early Sunday across a portion of Oklahoma and north Texas. ...20Z Update... Occasional lightning flashes may still occur with low-topped convection across parts of northern OH and far southeastern Lower MI for the next couple of hours. While strong low-level flow has been noted in the KCLE VWP, instability remains meager (MUCAPE 100-200 J/kg). Accordingly, the potential for strong/gusty winds with this convection is expected to remain very isolated at best. Otherwise, no changes have been made to the general thunderstorm area across parts of north TX and OK for late tonight. ..Gleason.. 12/12/2020 .PREV DISCUSSION... /ISSUED 1046 AM CST Sat Dec 12 2020/ ...Ohio Valley and Great Lakes region... Surface low situated over lower MI will accompany a low amplitude, but vigorous shortwave trough into the lower Great Lakes today. The Trailing cold front will advance east through the OH and TN Valleys. Due to limited low-level moisture and widespread clouds, the pre-frontal warm sector is only weakly unstable with a narrow corridor of 200-300 J/kg MUCAPE. As of late morning, a band of showers and thunderstorms persists within zone of deeper forcing along and just ahead of the front from IN into western OH. Activity is embedded within 40-60 kt flow in the 1-5 km layer. A strong wind gust or two cannot be ruled out, mainly from a portion of eastern IN into west central OH. However, severe threat should remain limited due to the very marginal thermodynamic environment and a tendency for deeper forcing to shift northeast into the Great Lakes with time. ...Oklahoma and North Texas... A shortwave trough now moving into the Great Basin will amplify as it reaches the southern High Plains late tonight. Steepening 700-500 mb lapse rates and a strengthening southerly low-level jet, within a zone of increasing forcing for ascent, might result in a convective layer deep enough for a few lightning flashes late in the period from a portion of northern TX into southern OK.
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