textproduct: NWS Birmingham

KEY MESSAGES

Issued at 128 PM CDT THU AUG 20 2026

- Heat: Major HeatRisk is expected to persist through the end of the workweek, with heat indices are forecast between 105 to 109 degrees. Heat Advisory remains in effect.

- Thunderstorms: Severe storms are possible this evening and overnight, with damaging wind gusts and locally heavy rainfall as the primary threats. Additional storm development is expected Friday afternoon across southern portions of central Alabama, with damaging winds and heavy rain remaining the main concerns.

DISCUSSION

(This afternoon through Wednesday) Issued at 128 PM CDT THU AUG 20 2026

Water vapor imagery early this afternoon reveals a stout upper trough cutting across the Great Lakes region as an upper level ridge builds out to our west. Between these two features, a shortwave can be seen sliding across the Midwest into the Tennessee Valley. This will help guide a cold front our way over the coming days. Closer to home, a stalled boundary lingering across the state will help promote isolated showers and storms across our southern areas this afternoon as low level convergence is maximized. As we head into the evening hours, the aforementioned shortwave slides closer to the region, aiding the generation of additional showers and storms along a leftover boundary from this morning's convection across Tennessee. Latest CAMs hint at this activity congealing into a somewhat broken line and moving through Central Alabama from roughly 03-10Z Friday. Increased instability, dry mid-level air and high DCAPE support the threat of occasional downbursts with these storms. Additionally, PWATs over 2" (per the 12Z KBMX sounding and GOES TPW imagery) would lead to locally heavy rainfall. As a result, SPC has upgraded much of northern Alabama to a Slight Risk (Level 2 out of 5) for severe storms. WPC maintains a Marginal Risk (Level 1 out of 4) for excessive rainfall through the overnight hours.

Another round of storms appears likely on Friday. Another ripple in the H5 flow will move through the southeast Friday afternoon, likely generating scattered showers and storms to the south of the slow moving boundary. Greatest chances for precipitation on Friday will be across our southern areas. Threats remain the same on Friday - damaging winds and locally heavy rainfall.

Upper level ridging attempts to build in over the weekend. Increased subsidence and drier air will help to lower rain chances as we head through the weekend. Rain chances look to return early next week as a series of shortwaves prepare to rotate through the NW flow aloft.

Now for the Heat - High temperatures over the coming days will continue to run from the low to mid 90s. Persistent humid conditions will promote daily heat indices in the 105-109 degree range both today and tomorrow. This will promote a moderate to major heat risk over most of the region. The current Heat Advisory will be extended through Friday evening to cover our southern counties as they are most likely to see reading in the 105-109 range tomorrow. Drier air over the weekend will help keep heat indices in check, generally in the 100-104 range.

95/Castillo

AVIATION

(18Z TAFS) Issued at 128 PM CDT THU AUG 20 2026

VFR conditions are currently in place across all terminals. Timing for convection later today has been pushed back by a few hours. Latest CAMs do not bring any activity in until after 00Z. While we could see some isolated activity before 00Z, confidence is low. A broken line of storms will push through the area late this evening into the overnight hours. Have included PROB30s for TSRA to account for this activity. There are some signs of a secondary batch of showers and storms but confidence is low here so did not include any mention. Convection trends will need to be monitored and amendments will likely be needed. Winds will be generally light out of the west outside of any storms.

Note: AMD NOT SKED for AUO due to a weather observation outage.

95/Castillo

FIRE WEATHER

MinRH values will generally be above 45% as we close out the work week. Low to moderate rain chances will persist today and Friday before we dry out over the weekend. Drier air moving in on Saturday will drop RHs in to the 35-45% range for most locations. However, winds look to remain light enough at this time to negate fire weather concerns.

PRELIMINARY POINT TEMPS/POPS

Gadsden 73 94 70 94 / 50 20 0 0 Anniston 72 92 70 92 / 40 30 10 0 Birmingham 74 93 72 93 / 40 20 10 0 Tuscaloosa 75 96 72 97 / 40 20 10 0 Calera 74 93 72 94 / 30 30 20 0 Auburn 75 91 72 90 / 20 50 30 0 Montgomery 74 96 73 96 / 20 40 30 0 Troy 73 95 71 94 / 20 50 40 10

BMX WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 9 PM CDT this evening for the following counties: Barbour-Bullock-Coosa-Fayette-Jefferson-Lamar-Macon- Marion-Pike-Shelby-Walker.

Heat Advisory until 9 PM CDT Friday for the following counties: Autauga-Bibb-Chilton-Dallas-Elmore-Greene-Hale-Lowndes-Marengo- Montgomery-Perry-Pickens-Sumter-Tuscaloosa.