SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0801 PM CDT Thu Aug 12 2021 Valid 130100Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MID MISSISSIPPI VALLEY AND OHIO VALLEY... ...SUMMARY... Thunderstorms associated with damaging wind gusts and hail will be possible this evening across parts of the mid Mississippi Valley, and in parts of the Ohio Valley. Marginally severe storms with strong wind gusts and hail could also occur across parts of the central Plains. ...Ohio Valley/Central Appalachians... Water vapor imagery shows a broad cyclonic flow pattern in place across the north-central U.S. and Great Lakes. A very moist airmass exists from the mid Mississippi Valley east-northeastward across the Ohio Valley, where surface dewpoints are in lower to mid 70s F. The RAP is analyzing moderate to strong instability on the northern edge of the moist airmass where a couple distinct severe line segments are ongoing. The first is located to the east of the St. Louis Metro. This severe convective line will continue to move southeastward over the next few hours across southern Illinois, where steep low-level lapse rates will enhance downdraft speeds. This line may also impact parts of western Kentucky later this evening. Damaging wind gusts will be likely along the leading edge of this short line segment...see MCD 1506. The second convective line is ongoing from eastern Ohio into central Pennsylvania. The airmass ahead of this line is moderately unstable according to the RAP, with MLCAPE in the 2000 to 2500 J/kg range. A wind-damage threat should continue along the more organized parts of this line as it moves eastward across the southern and east-central Pennsylvania this evening. ...Central Plains... At the surface, a cold front is currently located across northern Kansas. The wind shift has been reinforced by convective outflow associated with scattered thunderstorms to the north of the front. Surface dewpoints near the front generally range from the mid 60s to the lower 70s F. This combined with surface temperatures in the upper 80s has resulted in an east-to-west corridor of strong instability. MLCAPE in northern Kansas is estimated in the 3500 to 4500 J/kg range according to the RAP. In addition, 0-3 km lapse rates are estimated to be in the 7.5 to 8.0 C/km range according to the RAP, which will be favorable for marginally severe wind gusts early this evening. The threat should gradually become more isolated as instability drops across the region after sunset. ..Broyles.. 08/13/2021 Read more LIVE: spc.noaa.gov
http://dlvr.it/S5Y85M
