James Spann: Dangerous severe weather threat for Alabama tomorrow

CALM BEFORE THE STORM: As expected, this has been a beautiful spring day across Alabama. With ample sunshine, temperatures are in the low 80s. Nothing on radar. Clouds will move in tonight, and showers and storms will likely arrive in the 4 a.m. to 6 a.m. time frame tomorrow.

The Storm Prediction Center has a “slight risk” of severe storms up for much of Central and South Alabama early tomorrow morning; the main issue for places like Birmingham, Tuscaloosa, Anniston and Gadsden will involve hail and strong, gusty winds. The primary tornado threat before 7 a.m. will be over far Southwest Alabama, where there will be some surface-based instability.

TOMORROW’S SEVERE WEATHER THREAT: The large-scale features certainly will support a severe weather day in Alabama. A surface low will be southeast of St. Louis, supported by a deep upper trough with strong wind fields. Forecast surface-based CAPE values (instability) are expected to soar into the 3,000-4,000 j/kg range, making for a “powder keg” situation by afternoon.

The SPC has much of the state now in a “moderate” or “enhanced” severe weather risk.

Don’t get too caught up in looking at these risk maps and the associated lines, colors and verbiage. This is simply a guideline; storms don’t read these maps and certainly don’t know where the lines are. Just understand all of Alabama will have a significant severe weather risk tomorrow.

TIMING/THREATS: There will be multiple waves of storms from 4 a.m. until 7 p.m. The primary threat with the morning storms, as discussed above, will come from hail and strong, gusty winds. Storms during the midday, afternoon and evening will be capable of producing large hail, damaging straight-line winds and tornadoes. A few strong, violent, long-track tornadoes are possible, especially over the central and eastern counties of Alabama.

For Birmingham and Tuscaloosa, the risk of severe storms should be over by 5 p.m., and the storms should be out of the northern half of the state by 7. Storms could linger across Southeast Alabama through 9 p.m.

RAIN: Amounts around 1 inch are likely; no flooding issues are expected.

CALL TO ACTION: Be sure you have a way of getting warnings; a NOAA Weather Radio is the baseline, and a good smartphone app is the other tier. Identify the safe place in your home, and be sure everyone knows where it is. In that safe place have helmets for everyone, along with hard-sole shoes and preferably a portable airhorn in case you need help.

Be sure you have the ABC 33/40 app on your phone so you can watch our live severe weather coverage, if needed:

WILL THIS BE LIKE APRIL 27, 2011? I don’t like the question. April 27, 2011 was a generational event; they tend to happen once every 40 years or so. Just understand if there is only one tornado in the entire state, and if comes down your street, then it’s your April 27.

TAKE A DEEP BREATH: This is the core of the spring tornado season in Alabama, and these kind of threats are fairly common. We have had a very quiet five-year period, and we all knew it couldn’t stay quiet forever. Just have a way of hearing warnings, have an action plan and have a good readiness kit in that safe place, and we will be just fine. And there is always the chance this could be a “bust” — a situation with storms not as severe as expected. It takes many things coming together at a single place and time for severe storms to form.

COLDER AIR: Thursday will be breezy and much cooler with gradual clearing; some lingering light rain or drizzle is possible Thursday morning over the northeast corner of the state. Temperatures Thursday will hold in the cool 50s much of the day. We drop into the 37- to 40-degree range by daybreak Friday. Then, Friday will be sunny and cool with a high in the low 60s.

The coldest morning will come early Saturday, when mid 30s are likely with lots of frost. Colder spots have a good chance of going below freezing.

THE WEEKEND: Expect a bright, sunny sky Saturday and Sunday with a warming trend; the high Saturday will be in the upper 60s, followed by mid 70s Sunday.

NEXT WEEK: Medium-range model data suggests we might see some rain back in here Tuesday or Wednesday of next week, but for now it doesn’t look like a setup for severe thunderstorms as the “wave train” takes a break for a while.

SPOTTER TRAINING IS TONIGHT IN TUSCALOOSA: It begins at 6:30 at Shelton State Community College. We need more trained spotters; please come help us make the warning process better. No need to register; just show up!

Click here to see the Beach Forecast Center page.

WEATHER BRAINS: You can listen to our weekly 90-minute netcast anytime on the web, or on iTunes. This is the show all about weather featuring many familiar voices, including meteorologists at ABC 33/40.

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