Threat for Severe Weather Wednesday and Thursday

Figure 1. NAM-12km simulated radar loop from 4 AM CDT Thursday morning to 1 AM CDT Friday. Source: Tropical Tidbits

An anomalously strong upper-level trough is going to pivot from the Rockies into the Plains Wednesday, and into the eastern half of the country Thursday and Friday.

There will be a frontal system that will accompany the trough. It also looks like a surface low will develop and deepen Thursday/early Friday in the Tennessee Valley/Mid-Atlantic.

Unfortunately, a multi-day severe weather threat is looking likely. Some of the same areas impacted by severe weather this past weekend are at risk.

Wednesday

Based on the latest data, storms are expected to develop across eastern Texas during the afternoon/evening hours along a dry line and propagate east. They will likely be discrete at first. Bulk shear values will support supcercells.

Figure 2. Severe weather outlook for Wednesday. Image: NOAA SPC

However, the latest GFS and NAM suggest a squall line will form Wednesday night/early Thursday along the cold front (see figure 1).

Dew points surging into the 60s/70s, high CAPE (instability), and shear profiles will support the threat for organized severe storms. Large hail is expected to be the primary threat. Although, damaging winds & tornadoes will be possible too.

The Storm Prediction Center (SPC) has already highlighted a level 3 (out of 5) enhanced risk area (see figure 2).

Thursday

Current indications are a squall line will sweep across Louisiana and Mississippi during the day, and advance into Alabama and Florida Panhandle overnight, continuing the threat for severe weather.

Figure 3. Severe weather outlook for Thursday, depicting the broad 15% risk area defined by the SPC. Image: NOAA SPC

There is some uncertainty, though. Model guidance is projecting a highly sheared warm sector. But in the same respect, models are indicating that instability could become somewhat limited by the evening/nighttime hours.

Regardless, all modes of severe weather look to be on the table.

The SPC has maintained a relatively broad 15% (slight) risk area (see figure 3). Note that adjustments are likely.