Calm before the storm

We are on the eve of what will most likely be the most significant/widespread severe weather event in the state so far this year. Without wasting any time, let’s dive in to the setup.

At the surface, the models are in general agreement on a deepening surface low tracking through northern Indiana. Ahead of this low, strong southerly flow will transport rich low level moisture northward. Aloft, an 850 mb jet of 50-70 knots will develop through the Ohio Valley, placing Indiana in the favorable left front quadrant. Given the aforementioned moisture transport, good heating and steep lapse rates aloft, MLCAPE should range from AOB 750 J/kg in the extreme northern part of the state to 2000-3000 J/kg in the central and southern portions.

Thunderstorms may be ongoing for much of the day in scattered fashion, but it is unclear how much of this activity will be surface based. A more widespread severe threat will develop to our west sometime Tuesday afternoon before spreading east into Indiana during the evening. As forcing increases and wind profiles become more unidirectional with time, upscale growth into a linear system/QLCS is anticipated with risks for damaging winds, hail and tornadoes well into the night.

The tornado threat will be somewhat dependent on storm mode, but shear profiles suggest we can’t discount the threat entirely even after a transition toward a more linear mode. The 09z run of the SREF shows a high probability of several key ingredients coming together tomorrow evening.

At this time, given the anticipated track of the surface low (best low level shear), I expect the greatest tornado threat to lie roughly between US 24 and I-70, including areas such Lafayette, Kokomo, Marion, Terre Haute, Indianapolis, Anderson and Muncie. If the surface low tracks a little farther north, then the greater tornado threat could shift up toward Route 6. Areas outside this zone certainly aren’t at zero risk and everyone should be paying close attention to the weather tomorrow into Wednesday.

The SWAT Chasers will be active Tuesday and we’ll be providing updates throughout the day.


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