Texas Size Hail Tomorrow!

Wednesday Afternoon/Evening: A potent upper-level low will trek across New Mexico on the day Wednesday. As the upper-level low moves into Texas, convection should begin to develop across western Oklahoma and western Texas along the dryline by early Wednesday afternoon (not much convection should occur across the Southern Plains prior to noon on Wednesday because of a relatively strong CAP in place).

Due to the plentiful daytime heating, deep moisture, decent shear and very cold temps aloft, rapid development and intense convection is likely after 4:00PM Central (west of I-35). The main threats initially will be very large hail (larger than baseballs). The tornado threat may increase near the I-35 corridor around 7:00PM Central as the lower-levels of the atmosphere become slightly more favorable to support tornadoes; however, at the same time, it appears the storm-mode should transition to more of a linear nature (not isolated)–which could hinder tornado potential. The damaging wind threat will increase across eastern Texas during the nighttime hours tomorrow. Regardless, there is a tornado threat tomorrow afternoon across Texas and Oklahoma.

The aforementioned variables has led the Storm Prediction Center (SPC) to place a large part of Texas and Oklahoma in a risk for severe thunderstorms. An enhanced risk extends from southern Kansas, through central/eastern Oklahoma, down into northern and central Texas. Surrounding the enhanced risk is a slight and marginal risk (see Fig. 1 & 2). The enhanced risk is where the most widespread and damaging thunderstorms are likely but severe weather is possible in and around the slight and marginal areas.

Fig. 1: SPC Thunderstorm Outlook
Fig. 2: NWS Fort Worth Explainer

The severe threat will shift east on Thursday and Friday. Matthew will have a detailed article outlining the severe threat for the South and Southeast, later tomorrow.

Two-Day Severe Weather Event Including A Tornado Risk

Saturday-Early Sunday Morning: A strong shortwave system currently located over the Four Corners region has contributed to the development of a surface low pressure system over Mexico. As the shortwave advances eastward, the surface low will move northeastward across Texas tomorrow. By mid-afternoon, the low should be east of Dallas, TX, and by the evening, the system will begin moving across Louisiana/Arkansas. Widespread moderate rainfall will accompany this low across western Texas and across most of Oklahoma, but the primary concern for a potentially significant severe weather event is farther east into eastern Texas, northern Louisiana, southern Arkansas, and west-central Mississippi. Later into Saturday evening and early Sunday morning, the severe weather threat should continue across central-eastern Mississippi.

Aside from the light to moderate rainfall moving across northeast Louisiana and west-central Mississippi this evening, conditions across much of the Mid-South are quite pleasant. A frontal boundary associated with the previous storm system that dumped high snowfall amounts across the Plains and Upper Midwest is currently draped across the lower Mid-South. Since the frontal boundary never really had the opportunity to move well off the Gulf Coast, it won’t take much time for the low-level atmosphere to moisten as the surface low advances eastward over Texas. Dew points are only in the 40s and 50s across eastern Texas, northern Louisiana, and southern Arkansas this evening, but southerly/southeasterly winds will help bring dew points back into the upper 60s and 70s by tomorrow afternoon. Sufficient low-level moisture is a necessary ingredient for severe weather to occur.

Projected dew points on Saturday afternoon

Sometimes, morning thunderstorms and rainfall can help limit a severe weather risk if the atmosphere does not have adequate time to recover and become unstable. However, this should not be an issue tomorrow. Most of the widespread rainfall will remain mainly west of the Midsouth, and if morning activity develops across the region, it should remain scattered enough that plenty of daytime heating will still occur. Since the mid-level environmental temperatures will be quite cold (something that will actually contribute to more instability), temperatures around 70°F should be sufficient for moderate instability.

Projected radar for Saturday afternoon

Given sufficient instability and favorable wind shear profiles, a tornado risk exists across eastern Texas, northern Louisiana, southern Arkansas, and west-central Mississippi. Some tornadoes could be strong. Additionally, large hail and damaging winds will cause issues. The Storm Prediction Center has included a moderate and enhanced risk across those areas. If you are the risk zone, please plan accordingly, and ensure that you have a place to take shelter if a tornado hits your hometown.

Saturday severe weather outlook from the SPC

Sunday-Sunday Evening: The surface low will continue advancing northeastward on Sunday and eventually move across the Ohio Valley. Given this track, a broad and elongated severe weather risk will exist across a large part of the Southeast and extend into the lower Ohio Valley. The Storm Prediction Center has placed an enhanced severe weather risk from Alabama and Georgia northward into southern Ohio. A squall line will eventually develop and move eastward later Sunday or early Monday morning just ahead of an advancing cold front. Though the squall line will primarily pose a damaging wind risk with isolated tornadoes, the bigger tornado threat will exist ahead of the squall line during the day on Sunday, where thunderstorms could be more discrete. Comparatively, the tornado threat may not be as high as on Saturday; however, sufficient instability and wind shear should favor the development of tornadoes across parts of the slight and enhanced regions on Sunday. I will provide a follow-up update for the Southeast tomorrow evening. After monitoring how everything evolves tomorrow and tomorrow night, I expect I will have to make some modifications on the magnitude of the Sunday tornado risk. As suggested above, please have a plan in place.

Sunday severe weather outlook from the SPC
Tornado sheltering guidelines recommended by FEMA

-Meteorologist Matthew Holliday

Southeast Snow

The weather will get interesting for parts of the Southeast tomorrow as a coastal low develops and intensifies off the coast of the Carolinas (see Fig. 1). This surface low will lead to the potential of a brief period of snow for far northeast Georgia and parts of the Carolinas Tuesday morning.

Fig. 1: Coastal low Tuesday morning

Numerical guidance initially struggled with the placement of the surface low (some models showed the low near the coast of South Carolina and other models showed the low well off of the coast). Recently, however, guidance is indicating the low may hug the South Carolina coast, which would be far enough west to wrap in moisture to the Carolinas and possible far northeast Georgia.

As the precipitation develops and rotates into this region tomorrow morning (see Fig. 2), modeled soundings show a very dry surface and chilly temps aloft. This is the perfect setup for evaporational cooling, which will allow the rain to transition to snow after 5:00AM. Accumulations are questionable tomorrow but it does appear slushy accumulations may occur especially in the higher terrain of South Carolina and North Carolina (see Fig. 3).

Fig. 2: Future radar Tuesday morning
Fig. 3: FHW snowfall forecast

By lunchtime, the precipitation should begin to move towards the northeast and temperatures will warm, which will allow the snow to stop by the afternoon for this region.