SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Sun Oct 11 2020 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN MINNESOTA INTO NORTHERN KANSAS... ...SUMMARY... Isolated strong to severe thunderstorms are expected late this afternoon and evening across parts of the northern/central Plains into the Upper Midwest, with marginally severe thunderstorms also possible across parts of the Southeast and Mid-Atlantic. ...Northern/Central Plains... 00z models are in general agreement regarding the progression of a short-wave trough over the northwestern US. This feature is forecast to advance into the High Plains, extending from the western Dakotas into eastern CO by 12/00z, then shifting to near 97W longitude by the end of the period. Low-level moisture is currently a bit scant across the northern/central Plains where surface dew points are in the 30s/40s. However, strengthening LLJ across this region should allow moisture across KS to begin advancing north. Latest indications are this modified air mass will likely be drawn north across the mid-MO Valley into portions of southwestern MN prior to frontal passage. Latest guidance suggests a narrow corridor of strong boundary-layer heating will extend across the central Plains into southwestern MN by mid afternoon. While surface parcels may struggle to reach their convective temperatures, frontal convergence should easily assist parcels to their LFC, and scattered thunderstorms are expected to develop along the strongly forced high-latitude portions of the boundary by 21z. Forecast soundings suggest adequate deep-layer shear for potential supercells; however, strong forcing should result in a squall line quickly. Greatest threat with this initial activity will be hail/wind, evolving into more of a wind threat as the squall line matures. Have extended severe probabilities southwest along the front into portions of northern KS where forecast soundings suggest inhibition will be very weak with MUCAPE in excess of 2000 J/kg. Southern extent of large-scale forcing should extend into this region which should be adequate for scattered convection along the wind shift. ...Southeast/Mid-Atlantic... Remnants of TC Delta are quickly ejecting east-northeast across the TN Valley/northern Gulf States. Substantial mid-level drying is spreading across AL/GA early this morning and this drying should progress downstream into the western Carolinas early in the period. Overall, this system is gradually weakening with forecast soundings across the southeastern US/Carolinas exhibiting substantially weaker shear than the eastern Gulf States Saturday. Even so, adequate flow and moistening profiles suggest there is some risk for organized robust convection. The greatest risk is for locally damaging wind gusts, or perhaps a few brief/weak tornadoes. ..Darrow/Moore.. 10/11/2020
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