The severe weather season has been rather quiet so far this yearIt’s been a rather quiet. Tornado, hail, and wind reports have all been below the average year-to-date totals, and states like Oklahoma and Kansas are waiting for their first tornado of 2018, which is record-breaking. However, that will likely change next week as multiple days of severe weather will likely emerge.
The driving factor of this severe weather event will be a trough of low pressure moving into the West. The set up will not be perfect to produce severe storms but it will be conducive enough for strong storms to develop. This trough will take on a positive tilt opposed to a negative tilt. In this set up, the trough’s axis will be orientated from the southwest to northeast in comparison to an orientation from the southeast to the northwest, in a negative tilt. The positive tilt to the trough will keep the strongest of upper-level winds back to the west of where the storms will develop.
The threat for severe weather will begin Tuesday. The Storm Prediction Center has already outlooked portions of the Central Plains and Midwest, regions that have high risks for these types of storms. They have also done this on Wednesday for parts of the Southern Plains. All threats will be present with these storms: large hail, damaging winds, and tornadoes. Could there be an outbreak of tornadoes? Yes, but it’s too early to discuss all of the details at this time.
Based on the model data, most of the ingredients will be present. Temperatures will be mild as high pressure to the east allows for a strong flow of warmer temperatures coming in from the south. Maximum temperatures are expected to be in the 70s and 80s. This southward flow will also open up the Gulf of Mexico, allowing for increasing humidity or dew points values into the Central US. Typically, dew points of at least 60 degrees are needed for strong storms. By Tuesday, dew points in the 60s will surge to the north, and those values will increase on Wednesday and Thursday. These storms will also form along a dry line, which is a tight dew point gradient, providing higher dew points to the east and lower dew points to the west. Instability is also needed. Instability (CAPE) allows for storms to grow and tower. It also allows for larger hail to form as it will be suspended in the atmosphere for a longer time. The highest of CAPE values will be found on Wednesday and Thursday in the Southern Plains. This is when values will reach the 2000-4000+ range. These numbers are on the higher end of the scale.
Lastly, you need strong winds in all levels of the atmosphere. If the winds change in direction by height, that creates a favorable setup for tornadoes. In this particular severe weather event next week, winds at 850 millibars, or at about 5000 feet in altitude, will reach up to 70 mph while coming out of the south. The strongest of these winds are also expected to overlap where the storms form. Higher up toward the jet stream level at 300 millibars, winds will be coming out from the west, and then southwest, reaching speeds of up to 140 mph, but these stronger winds will be found to the west of where the storms will be located. In the storm zone, winds may reach 80-90 mph at the jet stream level, which is still favorable for severe weather.
This is still an evolving situation, but the threat for multiple days of severe weather is increasing, especially for the Southern Plains from Tuesday through at least Thursday. All of the favorable ingredients that are responsible for producing severe weather will be present, but the question is whether they will all come together create some very dangerous storms. This potential remains up in the air.
Here’s an overview of the general, large-scale setup:
Stay with WeatherOptics for new information of this severe weather threat next week.