Stormy start to the week, drier for Mardi Gras
While the week is beginning unsettled, timing of a cold front and thundershowers should work out just right for Mardi Gras.
Today and Tonight: For Lundi Gras, expect scattered showers and thunderstorms through mid-afternoon. It will not rain constantly and while organized severe weather is not anticipated, a storm or tow could briefly produce downpours, gusty wind and/or small hail. Late day breaks of sun will help high temperatures into the mid to upper 70s. Mostly cloudy skies continue tonight with a sticky low temperature in the upper 60s—higher than a normal high for the time of year. Winds will be south, southeast at 5-10mph.
Up Next: Mardi Gras day is looking drier with more sunshine, but we can’t completely rule out an isolated shower. It's certainly not looking to washout any plans. A cold front will push through on Wednesday, and that will usher in some cool, dry air leading into a fairly normal beginning to March. The chance of rain returns Sunday.
THE SCIENCE: As a warm front lifts through the area with a pocket of vorticity advection, prime period of strong lift will exist through the mid-afternoon. Forcing will diminish through the late afternoon and evening hours as the region comes under the influence of increasing subsidence and negative vorticity advection. No significant low level feature is noted to serve as a focus of convective initiation today, but the highest omega and greatest overall instability looks to be over the northern third of the forecast area. Fortunately, wind shear will be somewhat limited across the area. The strongest shear will be located over the same area with the highest. Given the shear and instability noted, some stronger storms could develop north of I-12 through afternoon. An isolated severe thunderstorm could develop, but the overall threat is limited at best. If severe storms develop, mid-level lapse rates would support some hail development while shear profiles support some strong wind gusts coming from any severe storm. Farther to the south and east, the threat of severe storms is basically nil due to a lack of decent shear and less overall instability. The increased subsidence and negative vorticity advection over the area will persist through tomorrow. The biggest result from this subsidence will be a drying and warming of the mid-level airmass resulting in the production of a fairly strong mid-level cap. This cap will effectively limit cloud development during the day tomorrow, and as a result most of the forecast area is expected to remain warm and dry tomorrow. Highs will easily climb into the lower to middle 80s which is near record territory. Only Southwest Mississippi may see enough weakness in the cap to allow isolated showers and thunderstorms. Any convection should dissipate by Tuesday evening as instability decreases with the loss of daytime heating. Wednesday will be a day of transition as a trough moving through the Plains and into the Midwest and Northeast will drive a fairly strong cold front through the forecast area. Strong low level forcing along the front combined with increased positive vorticity advection aloft will favor the development of showers and thunderstorms throughout the day on Wednesday as the front sweeps through the area. There will be a limited threat of severe thunderstorms on Wednesday mainly due to continued steep mid-level lapse rates and decent instability. Directional shear values will remain limited, but should support the development of a few strong to possibly severe thunderstorms Wednesday Afternoon. Temperatures will remain quite warm ahead of the front, and daytime highs are expected to climb back into the 80s. Conditions will gradually improve Wednesday Night in the wake of the front as a drier and more stable airmass moves in. However, some lingering low level cloud cover and showers could affect coastal portions of the forecast area through the overnight hours. Temperatures will also begin to cool dramatically behind the front with lows dipping back into the 40s and lower 50s Wednesday night. A cool and stable airmass will dominate the Gulf South for Thursday and Friday. Subsidence aloft and the dry airmass should keep skies mostly clear both days. These clear skies will allow lows to dip into the upper 30s and 40s both Thursday and Friday nights. Heading into the upcoming weekend, model guidance has become a bit less bullish on the strength of a low pressure system moving out of Texas and across the Gulf South. Both models now show a much weaker and more open shortwave feature sliding through the region. Given this, now expect to see only isolated showers by Saturday Evening mainly due to some lingering dry air in the mid-levels. There will be little to no instability to speak of, and winds will remain easterly through the day, so thunderstorms are not anticipated to develop on Saturday. Heading into Sunday, continued moisture advection into the area, and a stronger onshore flow in the mid-levels will result in higher precipitable water values and greater rain chances. Some weak forcing will remain over the area as a vorticity max slides through on the back of a largely zonal flow regime in the upper levels. This vort lobe should provide just enough lift to spark off some scattered convection as temperatures warm into the middle 70s.
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