December 23, 2015 Severe Weather Potential

Contrary to other potential severe high-shear, low-CAPE (HSLC) setups so far this autumn and winter, tomorrow’s setup appears to have the majority of pieces in place. The main story may be the high-CAPE setup during the afternoon and early evening across the Mississippi and Tennessee Valleys, areas encompassed by the Storm Prediction Center’s Day 2 enhanced risk. However, many signs point to a continued threat overnight extending into the Ohio Valley. While this will again occur west of several of our collaborating WFOs, it will likely be an event worth studying.


Figure 1. Images from 1200 UTC 22 Dec. 2015 GFS, valid 0000 UTC 24 Dec. 2015: (top left) 500 hPa absolute vorticity and geopotential heights, (top right) 850 hPa isotachs (kt), wind barbs, and geopotential heights, (bottom left) 2-m theta-E and 10-m wind barbs, and (bottom right) 0-3 km energy helicity index.

Figure 1, valid at 0000 UTC December 24th, shows a strong, negatively tilted trough across the Midwest with an attendant 850 hPa closed low and intense low-level jet. A baroclinic zone is evident in the 2-m theta-E field across the Midwest and Ozarks, with a warm sector extending into Great Lakes region. The EHI shows a “reservoir” of favorable values extending from the Ohio River southward into the Deep South. Additionally, SREF mean SHERBS3 (Fig. 2, left) and SHERBE (Fig. 2, right) values remain enhanced across the Tennessee and Ohio Valleys from 00z through 06z, suggesting a continued threat of severe weather during the overnight hours.


Figure 2. SREF ensemble mean SHERBS3 (left) and SHERBE (right) values valid for 0000 UTC 24 Dec. 2015 (top) and 0600 UTC 24 Dec. 2015 (bottom).

Finally, despite fairly modest lapse rates overnight in the Ohio Valley (Fig. 3) compared to those farther south (Fig. 4), hodographs appear favorable for the development of embedded rotation within an evolving QLCS in both locations.


Figure 3. 1200 UTC 22 Dec. 2015 NAM forecast sounding valid for 0300 UTC 24 Dec. 2015 in central Ohio.


Figure 4. As in Fig. 3, but for eastern Tennessee.

Though this may not get a lot of comments due to the holidays around the corner, I wanted to post a brief overview due to the heightened threat. This should be quite an event to watch!


This entry was posted in CIMMSE, Convection, CSTAR, High Shear Low Cape Severe Wx, Uncategorized. Bookmark the permalink.

3 Responses to December 23, 2015 Severe Weather Potential

  1. Grant Wise says:

    Hey, I know this is a real simple question, but since I am not a geography wiz: at what location would the Tennessee valley transition into the Ohio valley? Is central Kentucky in the Ohio or Tennessee valleys? Thanks!

  2. Jonathan Blaes @ WFO RAH says:

    Nice post Keith. I’ll leave it to the Ohio Valley folks to chime in on the details with this event but there were numerous severe weather reports in the Ohio Valley, north of the attention grabbing killer tornadoes in the Deep South (

    Grant, this image may clarify things a bit…

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