Midday Update: Severe Weather Threat Increasing

As I mentioned this morning in the forecast post, a severe weather threat looked to be in the works this evening as a powerful cold front moves into the region. Well, with the help of southwesterly flow (aka warm air advection), this is looking more likely right now. As a matter of fact, the SPC just outlined southern KY and the WxOrNotBG region in a Slight risk for severe weather this evening.

As we speak, there is a surface low to our north in central Indiana, with a cold front extending to its southwest, and a warm front to its northeast. Expect the northeasterly propagation to continue this afternoon, and for the warm air to continue to build. The warm sector has already entrenched well into western Kentucky, with 70 degree temperatures out there. The key to this is the moisture being drawn up here, though.

Dewpoints are already in the mid 60s in western Kentucky, much earlier and a bit further north than expected. This has expended the area that can see sufficient instability develop, and has allowed for southern Kentucky’s chances at severe weather to increase this morning. Already we are seeing instability develop to our west that will likely develop eastward into the southern Kentucky region as well.

This is providing energy for the thunderstorms to develop into, and be sustained later. This instability will allow for the thunderstorms to intensify, as well as grow taller, a key part in tapping into the intense winds that will likely be present later on this evening in the lower levels of the atmosphere.  Wind shear will be plentiful this evening, so thunderstorms will only be more organized with the help of instability.

The development of this instability really has me concerned about our severe threats this evening. There is plenty of forcing along the cold front, but with sufficient to good instability present, this is a set up that presents threats with the storms. Additionally, some breaks in the clouds have developed to our southwest, and if those work there way in here for any amount of time, we’ll likely see even more warming; and thus, more instability developing.

So, what’s this mean?

Well, first of all, models are struggling with initialization of temperatures and dewpoints. Additionally, the models are not initializing convection well at all right now. Take a look at the HRRR, a hi-res model, and the real radar right now.

Not so good. Many of the showers the HRRR is showing right now are not present in real life. This doesn’t lend confidence to the forecast from the HRRR, at least on the convection side.

However, I can tell you what I anticipate based on trends and current surface conditions. I would expect BG and areas around BG to warm up to near 70 within the next 1 to 2 hours. Butler County is already sitting at 65°F, with Logan County at 67°F. Expect an increase in moisture as southwesterly flow in the atmosphere continues to advect warm, moist air into the region. Dewpoints should reach the 60s soon than we reach the 70s. Additionally, anticipate winds to remain gusty across the region.

As the cold front and large scale atmospheric dynamics approach this evening, anticipate thunderstorms to begin to breakout along the front currently over Arkansas. These will likely grow upscale into a line of convection, or a broken line of convection, with precipitation falling behind the initial line. The line will either be along the front, or just ahead of it, so anticipate the cool down to begin immediately, or pretty dang close to it, after the passage of the line of storm.

Our main threat this evening will be straight line winds, with an isolated tornado being possible. There will be a lot of shear in the atmosphere, so these will likely be the major threats.

The winter weather threat is still the same as it was this morning. The details on that can be found in the forecast post this morning, or in Landon’s Vlog. As always, be sure to follow @WxOrNotBG on Twitter, and Landon Hampton on Facebook for the latest information.