More showers, storms through Friday and Saturday

Weather

We say it often: summer storms can be some of the worst weather you deal with all year.

Wednesday night, it was a storm strong enough to do some wind damage around the Athens area. The National Weather Service in Huntsville investigated that damage following a Tornado Warning, but has not yet found evidence of pure tornado damage.

Thursday afternoon, it was flooding. Phil Campbell got as much rain in one afternoon as it would usually rain in all of August and September combined (8.30 inches): between 6 and 9 inches based on radar estimates. The rain gauge at Dime (southeast of Phil Campbell) registered 4.73″ Thursday afternoon, and the Russellville Airport measured 2.73″ in the same batch of storms.

Radar estimated rainfall from southeastern Franklin County on Thursday, August 19, 2021

How does one single storm drop so much rain?

We can measure water content in the air with an upper air sounding (weather balloon). The nearest one – Birmingham – showed 2.07″ of ‘precipitable water’ at 7 PM Thursday. That means if all of the water vapor in the atmosphere rained down in a column, it would add up to 2.07 inches. That doesn’t limit a single storm, because it is drawing in moisture from surrounding areas. A stalled storm like the one that hit Phil Campbell can keep dropping rain because it’s borrowing from the rest of the nearby atmosphere; it’s not just stuck with the water within the storm.

Friday starts with more rain and more scattered storms: not severe, just locally-heavy again. Rain/storms become most numerous from late morning to early afternoon; that keeps temperatures below average again: highs in the mid-80s (‘normal’ or ‘average’ would be 91°F). Individual thunderstorms can drop more than 1-2″ of rain in less than an hour, so be ready for some big-time heavy rainfall for a third-straight day.

Sample snapshots of the Futurecast (Baron 3K model) shows how storm coverage changes throughout the day: peaking from lunchtime through early afternoon, fading through the evening. Storms will keep rumbling across Central Alabama through the evening.

Good news for Football Friday: it will not rain every game out Friday night. The majority of Friday’s rain/storms happen relatively early in the day, most ending between 4 PM and 8 PM. Generally, game-time temperatures will be in the upper 70s to lower 80s: no real heat danger, but some fields probably soaked!

Bad news: a few scattered thunderstorms in the area may still cause lightning delays or postponements. The storms that happen Friday evening bring very heavy rainfall, a lot of lightning, and they will be somewhat slow moving. They’re also concentrated farther south on Friday evening: a greater chance of storms from Marion, Winston, Cullman, Blount, Etowah and Cherokee Counties southward through Central Alabama.

Saturday: Scattered storms develop again on Saturday: literally at almost any hour of the day from sunrise to sunset. That does not mean all-day rain; it means a chance that storms will be nearby (or overhead) throughout the day. It does appear that the best chance of rain and storms occurs fairly early Saturday (8 AM to 1 PM) with fewer isolated downpours in the afternoon and evening. Rain and clouds in the area keep temperatures below average again: highs in the middle to upper 80s (average is around 91°F).

Sunday: It’s not clear that we’ll be totally storm-free on Sunday, but the odds are much lower. Only a few isolated showers or storms develop: smaller, less intense and covering less territory in the afternoon and evening. Less rain and more sunshine add up to higher temperatures, too. Expect high temperatures around 88°F to 92°F with a heat index near 100°F between noon and 5 PM.

Looking for the rest of the forecast? It’s always online at WHNT.com/Weather and in the “Daily Forecast” section on Live Alert 19!

-Jason
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