James Spann: Showers, storms for Alabama Thursday; severe storms Friday night, Saturday

BLUE SKY: We have a cloudless sky across Alabama this afternoon with temperatures in the 70s. Tonight will be clear and cool, with a low between 46 and 54 degrees.

Wednesday will be another mostly sunny, mild day with a high in the 70s. Clouds increase Wednesday night.

THURSDAY: A fast-moving disturbance will bring showers and a few thunderstorms into the state Thursday. The Storm Prediction Center (SPC) has defined a marginal risk (level 1 out of 5) of severe thunderstorms for a good part of the state.

A few storms Thursday could produce gusty winds and some small hail, but the overall threat is low with weak dynamic support. The high will be between 70 and 76 degrees.

On Friday, the weather will be dry with a mix of sun and clouds. A few spots over the southern half of the state could reach 80 degrees.

SEVERE WEATHER THREAT FRIDAY NIGHT THROUGH EARLY SUNDAY MORNING: The SPC has much of Alabama in an enhanced risk of severe thunderstorms Saturday and Saturday night.

Here are the updated key messages:

• Severe storms could move into northwest Alabama as early as Friday night, generally after 9 p.m. We expect multiple rounds of strong to severe storms from 9 p.m. Friday through 6 a.m. Sunday. Of course, we won’t have continuous rain during this 33-hour window; the sun might even pop out at times. But a strong to severe thunderstorm is possible at any hour during this time frame.
• I know there are many outdoor events Saturday; there is no way of knowing exactly when a severe storm will move through a specific city or town at this point. Just be very weather aware Friday night through Sunday morning during the defined window.
• All modes of severe weather will be possible with the heavier storms, including large hail, damaging winds and a few tornadoes. A strong tornado will be possible, if not likely, under these conditions (EF-2 or higher by definition).
• Gradient winds (not related to thunderstorms) will gust to 30-40 mph, not as extreme as the gradient winds we experienced one week ago. The main concern will be severe storms this time.
• Rain amounts of 2-3 inches are possible, and some flooding could develop. The heaviest rain will be across north Alabama.
• Is this another April 27, 2011? No. That event was generational. But every severe weather threat needs to be taken seriously; all it takes is one tornado coming down your street to make it your April 27. This does look like a higher-end severe weather threat for Alabama.
• Have a reliable way of hearing warnings — never an outdoor siren. A NOAA Weather Radio is the baseline. Be sure Wireless Emergency Alerts are enabled on your phone and have the ABC 33/40 weather app installed.
• Know the safe place in your home, and in that place have helmets for everyone. If you live in a mobile home, know the location of the nearest shelter or business that is open 24/7. Have transportation arranged.

Once we get within 60 hours of the event, we will be able to see output from high-resolution, convection-allowing models that will give us a much better idea of the small-scale features that usually determine the magnitude of a severe weather event.

The sky begins to clear Sunday as dry air returns to the Deep South.

NEXT WEEK: The weather looks dry for the first half of the week; global models suggest a disturbance could bring showers and possibly a thunderstorm to Alabama late Wednesday and Wednesday night.

ON THIS DATE IN 1953: An F4 tornado cut an 18-mile path through Haskell and Knox counties in Texas. Seventeen people were killed, and an eight-block area of Knox City was leveled.

ON THIS DATE IN 1963: A tornado moved through southern and eastern Cullman County, killing two and injuring six others. The hardest-hit communities included Berlin and Fairview.

For more weather news and information from James Spann and his team, visit AlabamaWx.