SPC Sep 13, 2017 0600 UTC Day 2 Convective Outlook

By Newsroom America Feeds at 13 Sep 00:52

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1150 PM CDT Tue Sep 12 2017 Valid 141200Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS UPPER MIDWEST... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOUR CORNERS AREA... ...SUMMARY... On Thursday, isolated severe hail and wind storms are possible across parts of the Upper Midwest late afternoon and evening, and the Four Corners Area during the afternoon. ...Upper Midwest... A quasi-stationary front oriented from central/eastern SD into northern MN should be the focus for possible isolated severe storm development. Boundary-layer moisture will probably not be quite as robust as progged by NAM and NMM-B members of the SREF which have mean mixing ratios reaching 15-16 g/kg in central MN. The International Falls 13/00Z sounding sampled the richest boundary-layer moisture across the central states with a mean mixing ratio near 13 g/kg, as a dry continental air mass pervades south to the western Gulf, west of the remnants of Irma. This should result in a confined corridor of moderate MLCAPE near the front on Thursday, within the northeast extent of the Great Plains elevated mixed layer. This elevated mixed layer should effectively inhibit surface-based warm-sector storms. It is possible that convergence and diabatic heating along the front will be sufficient to overcome capping at or just after peak heating. On the fringe of moderate mid-level westerlies, effective shear may be adequate for a few multicell/transient supercell structures capable of isolated severe hail and locally damaging wind. ...Four Corners... Persistent upper low off the central CA coast will eject east as a compact shortwave trough. A belt of enhanced mid-level southwesterlies associated with this wave should overspread the region at peak heating. While buoyancy will be weak with MLCAPE around 500 J/kg, steep tropospheric lapse rates should favor a risk for isolated severe wind gusts and small hail. ..Grams.. 09/13/2017 Read more



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