Easter Weekend Severe Outbreak Possible
There is growing concern for a severe weather outbreak over Easter Weekend for a large part of the South & Southeast. A potent upper-level low will move out of the Desert Southwest into western Texas overnight Saturday, which will phase with an upper-level disturbance that will dive southeast out of the Pacific Northwest. The upper-level storm system will continue an eastward motion into the South & Southeast throughout the day Sunday. As the upper-level storm system moves into western Texas, it will help draw-in rich Gulf moisture into the South & Southeast. This warm, moist Gulf airmass will be the energy the storms need to become rather vigorous, which will be paired with the shear needed to allow storms to organize and sustain themselves via the upper-level storm system; there will be adequate speed and directional shear through the atmosphere to support all modes of severe weather.
Figure 1: Upper-level storm moving into western Texas
Figure 2: Warm air ahead of system
Figure 3: Gulf moisture pulled north
Figure 4: Strong shear via upper-level storm system
Figure 5: Potent low-level jet
The time-frame for severe storm is Friday through Monday; however, the most high-impact weather looks possible late-Saturday through Sunday. As the upper-level storm system approaches western Texas late-Saturday, the Gulf airmass will be pulled north into Texas and Louisiana. Lift will begin increasing across the region, which will lead to shower & thunderstorm development late-Saturday across much of Texas and Louisiana with the severe threat becoming enhanced overnight Saturday as the atmosphere grows increasingly unstable. Storms will have the capability to become severe along and south of a northward-moving warm front. The main hazards are large hail, damaging winds and tornadoes. North of the warm front, storms will develop with the main hazard being large hail. The Storm Prediction Center (SPC) has a slight risk (Level 2) of severe storms Saturday evening into the overnight hours for a large part of western, central & eastern Texas and western & southern Louisiana.
Figure 6: Saturday’s severe thunderstorm outlook
As the upper-level storm system advances east on Sunday, it will take a favorable tilt to enhance severe weather, and will continue to spread the warm, moist airmass north into the entire South and Southeast. This will increase severe thunderstorm chances for the region. The airmass will become extremely unstable as daytime heating occurs and as the storm system moves overhead. Tornadoes, damaging winds and large hail are possible. An enhanced tornado threat appears to setup along and south of I-20 across Louisiana, Mississippi, Alabama and western Georgia. A few strong, long-track tornadoes are possible on Sunday. The SPC has a slight risk (Level 2) of severe storms from eastern Texas, east into the Carolinas. Within the slight risk area, there is an enhanced risk (Level 3) between I-20 and I-10 from Louisiana east into western Georgia.
Figure 7: Sunday’s severe thunderstorm outlook
While the severe weather outbreak is a growing concern, there are still some gray areas that need to be ironed out. Numerical guidance is struggling with the timing of the upper-level system. This is not uncommon, weather models tend to struggle with handling vigorous upper-level lows across the Desert Southwest. The timing, however, it critical to determine if, when and where the enhanced-tornado threat will be realized. The current projected timing would help slightly decrease the severe chances Saturday for parts of Texas and Louisiana as the best parameters would come together overnight Saturday for severe weather. This would be a time in which the instability would be limited due to the overnight nature of the storms. Another issue to evaluate is how much convection occurs in the warm-sector ahead of the main lift associated with the upper-level storm system. If an abundance of convection occurs in the warm-sector, it could slightly reduce instability, which would act to slightly reduce the severe threat. These details will be ironed out over the next 24-36 hours. Regardless of the questions, a severe weather outbreak is likely. Go ahead and prepare now: have multiple sources for warning/watch information and have a severe weather shelter plan in place.