Risk for Sunday severe weather upgraded to “moderate”

Probability of of severe weather within 25 miles of a point. Hatched Area: 10% or greater probability of significant severe weather within 25 miles of a point. (More Info)

Indiana, Ohio and the southern half of lower Michigan are in a bulls eye for severe weather tomorrow. There’s a moderate risk of severe weather as well as an enhanced risk of significant severe weather between 8 a.m. EST Sunday, Nov. 17 and 8 a.m. EST Monday, according to the Day 2 Convective Outlook that the National Weather Service (NWS) Storm Prediction Center (SPC) issued at 12:32 p.m. EST today.

As you can see on the map at left, the outlook indicates a 45 percent probability of severe weather and a 10 percent probability of significant severe weather. The SPC defines significant severe weather as F2 or greater tornadoes, damaging winds with speeds greater than 65 knots (74.8 mph), or large hail 2 inches or greater in diameter. To better understand probability figures, see this excellent explanation on the SPC website.

Here’s the basic setup: A surface low pressure system is forecast to undergo significant deepening as it moves from the upper Mississippi Valley into the Great Lakes region by tomorrow afternoon. A cold front trailing from the low will sweep through the mid-Mississippi, Ohio and Tennessee Valleys, while a warm front lifts northward through the Great Lakes region.

The potential exists for a widespread damaging wind event and a few tornadoes tomorrow afternoon and tomorrow night, especially in and near the moderate (45 percent) risk area across parts of the Ohio Valley and Great Lakes. Depending on how the situations develops, discrete supercell thunderstorms are possible, as well as an organized, bowing line of storms capable of producing widespread damaging straight-line wind. Isolated tornadoes associated with embedded meso-vortices will also be possible with that line of storms.

This morning, the northern Indiana NWS forecast office, put the infographic and statement below on its Facebook page:

NWS infographic indicating risk for tornadoes and damaing winds tomorrow.

PLEASE SHARE…A Severe Weather Outbreak is likely for Sunday. The risk for severe weather will start early in the morning and last all day. The greatest risk is for damaging winds and tornadoes. There is a slight chance for an isolated strong tornado, especially if any discrete storms can form ahead of the cold front. The severe weather threat will diminish in the evening as the cold front moves across the forecast area. Fall severe weather outbreaks are not uncommon for our forecast area and should not be taken lightly. Notify friends and family so they are not caught off guard by this severe weather outbreak.”

In addition, the northern Indiana office sent out a tweet at midday today that reads, “Before potentially serious weather events we have conference calls with Emergency Management and Media. Today is one of those days.”

In the Hazardous Weather Outlook that the northern Indiana office put out at 4:29 a.m. EST, we find the following notification for SKYWARN storm spotters: “Spotter activation will likely be needed Sunday in to early Sunday evening.”

Watch the northern Indiana office’s Facebook page and Twitter feed for updates on this situation throughout the day today. The next outlook for tomorrow from the SPC isn’t due until they issue a Day 1 Convective Outlook early tomorrow morning.