SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0240 PM CDT Thu Oct 22 2020 Valid 222000Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE UPPER MIDWEST... ...SUMMARY... Strong to severe thunderstorms are possible this afternoon and early evening over parts of eastern Iowa and small parts of adjoining Illinois and Wisconsin. ...Discussion... At this time, no appreciable changes appear necessary to the ongoing outlook, as prior reasoning continues to reflect the latest expectations regarding evolution of storms over the Iowa vicinity. Meanwhile, latest HRRR runs are less bullish with respect to any isolated severe risk over the Texas South Plains vicinity. However, will maintain low-probability/MRGL risk across this area for the time being. ..Goss.. 10/22/2020 .PREV DISCUSSION... /ISSUED 1114 AM CDT Thu Oct 22 2020/ ...MO/IA/IL/WI... Morning water vapor loop shows a deepening upper trough over the central Rockies that will emerge into the Plains this afternoon and tonight. Meanwhile at the surface, a cold front will begin surging southward across the Plains into IA/KS/OK by evening. This front will be the focus of lift and scattered precipitation later today. 12z CAM solutions are in strong agreement that thunderstorms will develop late this afternoon in vicinity of the cold front from central IA into central WI. A combination of a weak capping inversion and strong ana-frontal low-level winds are expected to relegate convective development to elevated storms behind the front. Stable near-surface conditions will limit the amount of convective augmentation of larger-scale wind gusts, suggesting that the risk of severe thunderstorm winds is marginal. Sufficient elevated CAPE, cool mid-level temperatures, and strong deep-layer shear may result in hail in the more robust updrafts through this evening. ...West TX... A small cluster of thunderstorms continues to be forecast for parts of west TX this afternoon and evening in vicinity of a diffuse surface dryline. Forecast soundings suggest some risk of hail and gusty winds in these storms through the early evening before nocturnal cooling decreases the threat.
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