Area Forecast Discussion

KEY MESSAGES

- Tropical Storm Bertha is expected to move west near the coast of the northern Gulf through the end of the week. This system is expected to be asymmetrical with a majority of the impacts south of the center.

- A Heat Advisory is in effect for the remainder of this afternoon. The combination of sinking air aloft as an upper level ridge from the Rockies builds in and the outflow from Tropical Storm Bertha will develop oppressive heat into Wednesday. An Extreme Heat Warning has been issued areawide Wednesday. Max afternoon heat index is expected to range from 113 to 117 degrees.

- Over the weekend into early next week, the upper level ridge will remain control with limited rain chances and hot conditions.

DISCUSSION

(This evening through next Monday) Issued at 144 PM CDT Tue Jul 21 2026

The short term pattern is relatively active with Tropical Storm Bertha tracking northwest below the Florida Panhandle and a strong subtropical ridge resting over over the Southern Plains. 1:00PM CDT satellite analysis illustrates convection over Bertha is asymmetrical with the wind field. The system has two strong southern quadrants with deep convection, however, the northern hemisphere of the storm remains open and continues to pull in dry air. This effect is an important and helpful inhibiting factor keeping the system from rapidly intensifying. That said, Tropical Storm Watches have been posted along and below the Atchafalaya Basin.

Combination of compressional warming from the subtropical ridge to the northwest and the approaching tropical storm Bertha will result in hot temperatures Wednesday. That in addition to high dewpoints, have warranted an Extreme Heat Warning across the forecast area. Heat indices are forecast to climb up to 113-117F. Extra care should be taken for people, plants, and pets during these dangerously hot conditions.

Basis the latest analysis from our colleagues at the National Hurricane Center, Bertha is expected to take a due west track along or just south of the Louisiana coast line. As the system approaches the Mississippi Delta, land interaction will begin to disrupt the low level flow. Any further northward deviation in track would further increase this effect. Additionally, the system will pull more dry air into the center of circulation decreasing convection in this region.

Bertha still requires close monitoring regardless of strength. The system will have close proximity to the coast. Even decaying tropical systems can develop short term hazards such as excessive rainfall as they expand and interact with the local environment. While the flooding rainfall threat is favored toward the coast, squalls of rain bands could develop inland Thursday. At this time, there are no severe wind, hail, or tornado probs. However, please continue to monitor forecasts going forward through dissipation. Bertha is expected to weaken into a tropical depression quickly passing offshore Cameron Parish Thursday afternoon. Forecast confidence remains high that high wind shear and dry air will impede the systems ability to maintain and significant weakening is expected as it approaches the Southeast Texas coast.

Once Bertha, or her remnants, have cleared the area Friday afternoon, temperatures will range in the mid 90s with drier weather expected through next Monday.

Kowalski / 30

AVIATION

(00Z TAFS) Issued at 626 PM CDT Tue Jul 21 2026

Thunderstorms will remain in vicinity of KAEX for the next 2-3 hours. A brief period of lower vis and ceilings may occur. Additional convection may occur near KLFT or KARA late tonight. The remainder of the region will remain VFR through mid day Wednesday, however convection will move in late in the period around the circulation of Bertha. NW winds will become more northerly during Wednesday.

AVIATION

(18Z TAFS) Issued at 144 PM CDT Tue Jul 21 2026

VFR conditions are expected to prevail through the evening hours across all terminals with exception of LFT and ARA. A region of VCTS may allow TS through mid afternoon and reduce conditions across Acadiana. Tonight convection is expected to be mostly null with increasing west winds into Wednesday. Hot conditions are expected which result in stronger thermals near the boundary layer / LCL.

14

MARINE

Issued at 144 PM CDT Tue Jul 21 2026

High pressure over the northwest Gulf and the circulation around Tropical Storm Bertha will bring modest west northwest winds into Wednesday. At this time Tropical Storm watches have been posted for Vermilion Bay and offshore waters to the south, as far west as Vermilion / Cameron Parish line. Marine conditions for Wednesday night through Friday will depend on the eventual track and strength of Tropical Storm Bertha as it moves just inland or over the northwest Gulf. All marine interests should continue to monitor updates on Tropical Storm Bertha.

FIRE WEATHER

Issued at 144 PM CDT Tue Jul 21 2026

Hot and humid conditions are expected across the region through midweek. Afternoon minimum RH values will be in the 45 to 60 percent range. With temperatures nearing 100, an Extreme Heat Warning is in place over the entire forecast area. Please consider these conditions for the safety of those out in the field. Tropical Storm Bertha will approach the area on Thursday. At the moment this system is expected to be asymmetrical with a majority of the higher winds and rain amounts to the south of the track of the center.

LCH WATCHES / WARNINGS / ADVISORIES

LA...Tropical Storm Watch for LAZ074-252>254.

Heat Advisory until 7 PM CDT this evening for LAZ027>033-044-045- 055-073-074-141>143-152>154-241>243-252>254.

Extreme Heat Warning from 10 AM to 8 PM CDT Wednesday for LAZ027>033-044-045-055-073-074-141>143-152>154-241>243- 252>254.

TX...Heat Advisory until 7 PM CDT this evening for TXZ180-201-259>262- 515-516-615-616.

Extreme Heat Warning from 10 AM to 8 PM CDT Wednesday for TXZ180- 201-259>262-515-516-615-616.

GM...Tropical Storm Watch for GMZ435-436-452-455-472-475.