SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1158 PM CST Tue Feb 16 2021 Valid 171200Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTHEAST LOUISIANA...FAR SOUTHERN MISSISSIPPI AND FAR SOUTHERN ALABAMA... ...SUMMARY... Isolated severe thunderstorms may occur from this evening into tonight across portions of the central Gulf Coast. A couple tornadoes, damaging wind gusts, and perhaps some hail will be possible. ...Central Gulf Coast... An upper-level trough will move across the Great Plains today as southwest mid-level flow remains in place from the southern Plains to the Eastern Seaboard. At low-levels, the northern edge of a moist airmass in the Gulf of Mexico will advect northward into the central Gulf Coast area as a jet near 850 mb moves eastward across the region. Isolated thunderstorms may develop early this evening near the axis of the low-level jet, in the vicinity of the mouth of the Mississippi River. The chance for thunderstorm development will increase during the evening as low-level moisture increases across the central Gulf Coast. The potential for thunderstorm development may become maximized during the late evening and early overnight period as instability finally develops across the central Gulf Coast. Forecast soundings across the central Gulf Coast this evening gradually increase surface dewpoints in the 50s and lower 60s F. The strongest instability is forecast to remain across far southeast Louisiana in the early evening, where isolated severe thunderstorm development will be possible. Further to the north in the vicinity of Biloxi, Mississippi and Mobile, Alabama, instability is forecast to increase by mid to late evening. At that time, forecast soundings near Mobile show strong speed shear in the lowest 3 Km above ground level with 60 to 70 kt of southwest flow in the mid-levels. This shear environment will be enough to overcome the weak instability across far southern Alabama and the western Florida Panhandle. Supercell development may occur on the northern edge of the stronger instability and to the west of the low-level jet, where shear will be maximized. Supercells may occur with a potential for wind damage and tornadoes. This severe threat is expected to gradually shift eastward across southern Alabama into the western Florida Panhandle during the overnight period. If a line of storms can organize, then a wind damage threat would be possible through late in the period. ..Broyles/Wendt.. 02/17/2021
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