Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1143 AM CDT Thu Jun 22 2017 Valid 221630Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GULF COAST/LOWER MS VALLEY TO TN VALLEY... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL HIGH PLAINS AND CO/WY FRONT RANGE... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER MIDWEST/GREAT LAKES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE GULF COAST/LOWER MS VALLEY TO TN VALLEY... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE HIGH PLAINS TO THE GREAT LAKES/NORTHEAST STATES... ...SUMMARY... A few tornadoes and isolated damaging gusts are possible over a broad area across the Gulf Coast states, lower Mississippi Valley northward into the Tennessee Valley. Elsewhere, severe thunderstorms with damaging winds and large hail are possible from the central High Plains to portions of the Great Lakes. ...Gulf Coast States/lower MS Valley into TN Valley... Tropical Depression Cindy, centered over far west-central LA as of mid/late morning, is expected to continue to drift slowly north-northeastward through the afternoon into tonight. Even while the system may begin to fill with a tendency for a weakening surface low, strong low/mid-level southerly winds on the eastern periphery of the system will continue to yield the possibility of low-topped supercells and at least some tornado risk over a relatively broad area of the region. A few weakly rotating cells have been noted this morning across the western FL Panhandle as well as southeast LA into southern MS, and this same scenario/supportive environment should somewhat expand north-northwestward through the afternoon and evening. The overall tornado risk, which appears relatively modest overall across a broad region, should diurnally peak this afternoon into early/mid-evening, although some tornado risk could continue into the overnight and early morning hours of Friday. ...CO/WY Front Range and Central/southern High Plains... Isolated high-based storms are expected to develop by late afternoon along the south/southeastward-moving front spanning portions of KS into southeast NE. Where storms develop, moderate amounts of CAPE/vertical shear will allow for semi-organized clusters of storms capable of isolated large hail aside from a locally damaging wind risk with outflow dominant convection. Other storms are likely to develop this afternoon within an evolving post-frontal upslope flow regime, with initial development along and just east of the CO/southeast WY Front Range. As an increasingly moist environment develops into the region and the boundary layer destabilizes, relatively long/straight hodographs will support the possibility of splitting supercells capable of large hail. Severe-caliber wind gusts will also possible given relatively deep/well-mixed sub-cloud layers. ...Upper Midwest/Great Lakes... Ahead of a southeastward-moving cold front, a fast-moving cluster of storms will continue eastward from southeast MN into southern WI today to the north of an outflow boundary and weakening convection across eastern IA/far southern WI and far northern IL. Widespread cloudiness across WI to the north of the outflow boundary should largely curb surface-based severe potential, with storms otherwise likely to develop by mid/late afternoon along the southeastward-moving front across IA and possibly into far southeast MN/southwest WI. While the strongest winds aloft will tend to lag (to the west/northwest) the cold front, sufficient vertical shear (30-40 kt) in the presence of moderate buoyancy (generally 1500-2500 J/kg MLCAPE) will yield multicells and some supercells capable of large hail and damaging winds especially late this afternoon into evening. ..Guyer/Gleason.. 06/22/2017Read more
from SPC Forecast Products http://ift.tt/wWCv9s
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