SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0158 PM CST Sat Nov 14 2020 Valid 142000Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF MISSOURI AND ARKANSAS... ...SUMMARY... Thunderstorms may produce damaging winds and the threat of a few tornadoes this evening into tonight over parts of Missouri and Arkansas. ...20Z Update... The only appreciable change to the ongoing forecast has been to expand the Marginal/Slight risk areas a little westward in central/western MO based on latest observational and short-term guidance trends. It still appears likely that surface-based convective initiation along/ahead of a cold front across this area will occur after 00Z this evening. Both damaging wind gusts and a few tornadoes may occur with these initially semi-discrete storms, before transitioning to more of an isolated strong/gusty wind threat as storms congeal into one or more bowing line segments with eastward extent later in the evening/overnight. ..Gleason.. 11/14/2020 .PREV DISCUSSION... /ISSUED 1017 AM CST Sat Nov 14 2020/ ...MO/AR... Latest water vapor loop shows an amplifying upper trough over the central Rockies. This system will intensify and move into the Plains this evening - and into the mid MS Valley overnight. At the surface, a cold front will extend from central IA/MO into northeast OK by evening. This boundary will provide the focus for thunderstorm development. Present indications are that thunderstorms will begin to form - mainly after dark - from southeast IA into central MO and northwest AR. Moisture/instability will be very limited in the northern parts of the risk area, limiting a more robust severe event. However from central MO southward into northwest AR, forecast soundings suggest dewpoints approaching 60F and moderately steep mid-level lapse rates. This should yield sufficient CAPE for a few vigorous updrafts with supercells possible for a few hours. Very strong vertical shear would suggest a risk of all hazards in these fast-moving storms, including a few tornadoes. Storms will likely organize into bowing segments tonight and move into a progressively more stable air mass. Nevertheless, the potential for locally damaging wind gusts could be maintained as far east as southern IL and western KY/TN.
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