SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0640 PM CST Tue Jan 12 2021 Valid 130100Z - 131200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few weak thunderstorms are possible overnight across parts of southeastern Louisiana into southern Mississippi and adjacent southwestern Alabama. ...01Z Outlook Update... Latest model output suggests that a relatively compact mid-level low will undergo some deepening while gradually accelerating toward the lower Mississippi Valley overnight. It appears that this will be accompanied by a strengthening jet on its southeastern periphery, including to 70-80 kt around 500 mb, across the northwestern Gulf of Mexico into Louisiana/Mississippi coastal areas by 12Z Wednesday. Recent runs of the Rapid Refresh have been similar to the NAM, indicating an area of strengthening mid-level upward vertical motion across south central Louisiana by 04-05Z (with the approach of the mid-level jet streak), before spreading northeastward through portions of southern Mississippi/adjacent southwestern Alabama overnight. Although this is well to the cool side of a stalled frontal zone over the southern Gulf of Mexico, evening RAOBS indicate the presence of relatively steep mid-level lapse rates across this region. This is generally based around the 700 mb level, where elevated moisture return is beginning to contribute to weak CAPE at Lake Charles LA. As large-scale ascent increases later this evening, this instability is expected to support increasing high-based convection. Although this will be mostly above the freezing level, the inflow layer may be close enough to allow for the development of a mixed-phase layer, and eventually charge separation and lightning within a possible small developing convective cluster. ..Kerr.. 01/13/2021
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