7/19 – Rob Knight’s “Elevated Heat Indices” Tuesday Morning Forecast
Today will bring a continuation of the past few days and a gradual warming trend as high pressure moves closer to the area. This will also bring low rain potential due to the compression of the atmosphere, especially west of I-59 corridor. The best potential for convection will be along the Mississippi Gulf Coast and extreme southeast Louisiana under the extension of a weakness well to the north. Low level southerly return flow will continue to draw rich low level moisture into the area. With temperatures gradually increasing and low level moisture maintenance taking place during max heating, heat index values will begin exceeding advisory criteria starting today and likely continuing on Wednesday as well. With high pressure continuing to spread closer to our vicinity only going with lower end rain chances at this time where a few showers and storms cannot be ruled out along the afternoon sea-breeze boundary.
By Thursday, the mid-level disturbance that is over us will to start to lift to the northeast, making way for the ridge that is situated over the western US. The models are in good agreement with the timing of the transition to high pressure around Friday evening. However, the models are struggling to come to a consensus on where the high pressure will set up. At the surface, models are in agreement that we will stay on the western fringe of the Bermuda high, causing southeast flow at the surface. Elevated heat concern as high temperatures consistently reach the mid-90s across the area starting Thursday with the more coastal areas in the low 90s. The high relative humidity values will make way for heat indices peaking in the 100s every day. As far as precipitation, this will be very typical for summertime in southeast LA and south MS. It will be mostly diurnally driven as rain chances peak around the afternoon and evening time-frame each day and decreasing in the late evening as the sun goes down.