The last soaking rain to fall in Alabama occurred on April 25th. Since then, it has been mainly dry despite a little rainfall on April 28th and 29th. The only city to get measurable rain in May is Anniston receiving .68" on the 12th. The mostly hot and dry pattern is about to turn into a wetter one, something we might typically see during the summer months.
The jet stream will shift enough to the east to allow a return flow to set up across The South. Increased Gulf moisture combined with daytime heating will mean unstable conditions developing each afternoon starting on Thursday. Scattered showers and storms will fire daily, but the storms that form will most likely be disorganized multicells especially on Thursday and then more pulse-like in nature through the weekend.
How do I know? Well you need wind shear aloft for storms to live a long period of time. Imagine winds increasing with height and a storm developing in that environment. The storm will tilt with height and that allows the updraft region to separate from the downdraft region. When the wind shear is low, these regions don't separate and storms don't last long. The threat for severe weather is low but not zero. On occasion, the storms can unleash their moisture at once and cause downdraft winds to exceed 50 mph especially with the pulse like storms if enough heating can occur. Model data shows shear values as high as 25kts on Thursday and as low as 10kts on Friday.
Vertical Wind Shear and Storm Mode:
- 0-6 km bulk shear > 40 kts – supercells
- 0-6 km bulk shear 20-35 kts – organized multicells
- 0-6 km bulk shear < 10-20 kts – disorganized multicells
Rainfall amounts through the 20th are expected to be above normal according to the Climate Prediction Center. Model data suggests widespread amounts ranging from 2" to 4" though locally higher amounts are likely. The outlook through the rest of the month looks persistent once this warmer and wetter pattern takes over. The only change might come during the last week in May when model data shows stronger wind shear moving in and that could mean a better chance for severe storms. We'll keep you posted as we monitor trends.
Finally, Mother Nature will work her magic and provide water for our lawn and garden and knock down the pollen count! It may be challenging at times squeezing in outdoor activities over the next couple of weeks, especially during the afternoon and evening hours due to the daily threat for storms. Remember, if you hear thunder to go indoors. It's not safe to return outside until 30 minutes after the last clap of thunder.
Thanks and be safe,
Jill Gilardi Fox 6 Meteorologist