Heavy rain threat easing, pattern switch tomorrow
The FLASH FLOOD WATCH has been canceled. However, one more round of showers and thunderstorms is ahead before a quieter, drier and slightly cooler stretch of weather ends the week.
While much of the area did receive rain on Monday, almost all of the 0.5 – 1.5 inch totals fell after dusk. Off and on activity was expected through the day and this did not occur. The heaviest amounts fell generally north of I-12 into the drainage basins for the Amite, Comite, Tangipahoa and Tickfaw Rivers. However, at this time, runoff is not expected to create any significant river flooding issues. Additionally, local rain will have no effect on the rising Mississippi River. Here is what to expect from of the “big muddy.”
Today and Tonight: Beneath mostly cloudy skies, high temperatures will extend to about 80 degrees. A significant change has been made to the forecast in that no more than an isolated shower is expected during the daylight hours. A cold front moving into the area tonight is expected to trigger scattered showers and thunderstorms. As has been the case since Saturday, downpours may occur in the heaviest storms dropping a quick inch or so of rain. Gusty wind is possible with the strongest storms as well. As the cold front pushes through, showers will wrap up close to dawn, winds will shift northwesterly and low temperatures will bottom out in the low 60s.
Up Next: By Wednesday, a cold front will be through with cooler and drier air filtering into the area. A lingering shower is possible early Wednesday, otherwise expect clearing skies and temperatures in the upper 70s. Wednesday night low temperatures could be almost 10 degrees below average in the upper 50s! Thursday and Friday will bring abundant sunshine and low humidity with afternoon thermometers in the mid 80s. Higher heat and humidity will return for the Memorial Day Weekend and so too will the chance for a “pop-up” afternoon shower by Sunday.
THE SCIENCE: An upper level trough is digging southward from the Upper Mississippi River Valley to the Southeastern U.S. As this occurs, a surface cold front will be driven through the area on Tuesday. Waves of energy in the mid-upper level flow will help the front initiate more showers and thunderstorms. The atmosphere remains nearly saturated at all levels which will continue the possibility of heavy rain coming out of the deepest storms. Upper level winds are slightly divergent and diffluent over S.E. La. and S.W. Ms. which should continue to support longer lasting storms as well which adds to the heavy rain threat. As has been the tricky part of the forecast since Sunday, timing of the most widespread activity will be the challenge on Tuesday. The latest model runs time out the most noticeable upper disturbance for the first half of Tuesday which should result in the most widespread and intense action at that time. The cold front will push through the region on Tuesday night. As the upper trough lags, a few showers could linger into early Wednesday. Northwesterly flow will then take hold, drying the atmosphere at all level and effectively shutting down precipitation. A brief run of cooler than average temperatures is expected with surface high pressure to the north on Wednesday. Mostly clear skies will end the week. By Thursday, the surface high will translate east of the area bringing return flow. Moderating temperatures can be expected through Sunday with humidity gradually increasing as well. Air mass thunderstorms could return to the forecast as early as Saturday.