12/20 – Rob’s “Below Seasonal Temperatures” Afternoon Forecast
A fast moving low-pressure system along the northern Gulf will continue to move NE. This trajectory will keep the area on the cooler and more stable side of the low through the entire short term period. As a result, southwest flow in the mid and upper levels in advance of the system will produce light precipitation and cloud cover persisting into early Tuesday. The highest rain potential and totals will occur along and south of the I-10 corridor. The extensive cloud cover will also keep temperatures well below average in the 50s today. Overall, a cool and gloomy stretch of weather is expected through Tuesday morning.
By Tuesday afternoon and evening, increasing subsidence in the wake of the departing system will bring clearing skies to the region. A thermal trough axis will continue to linger over the region, so temperatures will remain cooler than average in the 50s despite the increased solar insolation expected by the afternoon. Tuesday night will be the coldest night of the period as clear skies, lighter winds, and low dew-points promote strong radiational cooling. Lows should dip into the 30s for most locations with lower 40s south of the interstate.
High-pressure will begin building into the Gulf South on Wednesday and will become centered over the region by Friday and Saturday. Strong subsidence throughout the atmospheric column will keep skies clear and allow for a decent warming trend. Temperatures and Wednesday will be near average with highs in the lower to middle 60s and lows ranging from the upper 30s in coastal Mississippi. Further warming is expected as the high-pressure becomes centered over the area, and highs should be in the upper 70s and lower 80s by Christmas day.