textproduct: Huntsville

KEY MESSAGES

Updated at 242 AM CDT Sat Sep 19 2026

- Conditions will be favorable for strong-severe thunderstorms each afternoon from Today-Tuesday, with the greatest spatial coverage of storms expected to occur on Monday and Tuesday. Locally damaging downburst winds, frequent lightning and heavy rainfall will be the main storm impacts.

- Hot temperatures will continue from Today-Monday, with highs in the mid-upper 90s in the valley. A Heat Advisory remains in effect through 8 PM CDT today.

- A slightly cooler and drier airmass will arrive late in the forecast period, with highs dropping back into the 80s on Thursday/Friday.

NEAR TERM

(Today) Issued at 242 AM CDT Sat Sep 19 2026

Another hot day expected across the TN Valley. We will run about 10 degrees above seasonable daytime highs of the mid 80s. Heat Advisory remains in effect until 8pm this evening. The TN Valley is stationed between an upper level ridge centered across the Southern Plains, an upper low meandering across FL and a disturbance sliding through the Midwest. The sfc cold front sinking southward from the OH Valley, sadly, will not make it to us.

The front developed convection off to our northeast last night and outflow boundaries from that should help ignite storms for us around lunchtime in NE AL and Southern Middle TN. The outflow from those storms will travel westward and create additional development. In SPC's latest Day 1, they pulled back on the Marginal Outlook for the forecast area, leaving a sliver in Jackson and DeKalb counties, however thermodynamics still support downbursts occurring within and outside of the outlook area this afternoon and evening. Forecast soundings suggest MLCAPE can be as high as 1500-2000 J/kg, with PWATs in the 1.6-1.8" and steep low- level lapse rates, which could support a risk for locally damaging downbursts and frequent lightning with this activity. Outside of any convection, daytime highs will reach the lower 90s in the elevated terrain and the mid to upper 90s elsewhere. Heat index values will reach up to 105 degrees.

SHORT TERM

(Saturday night through Monday night) Issued at 1057 PM CDT Fri Sep 18 2026

Short range model consensus suggests that a weakening mid-level ridge will extend from the northwestern Gulf Coast into the TN Valley from Saturday night-Sunday night. In the low-levels, a light S-SE flow will return to the region on Saturday night as an area of low pressure shifts eastward from northern IL into the southeastern Great Lakes, and subtle convergence at the onset of this regime could result in showers and thunderstorms continuing a bit later into the evening hours tomorrow (particularly across our southeastern counties). Otherwise, we expect another hot day on Sunday, with temperatures warming quickly after sunrise and peaking in the m-u 90s in lower elevations Sunday afternoon. Although afternoon thunderstorm coverage may be a lit lower (compared to Saturday) due to lack of a discernible convergence axis at the surface, at least isolated storm are expected to develop during the afternoon hours (particularly in regions of terrain-induced lift), and thermodynamic profiles will once again support a risk for locally damaging downburst winds and frequent lightning with the most intense cells.

For the latter portion of the short term period, a low-amplitude mid-level wave in the southern stream (progressing eastward over the Red River Valley on Sunday and Sunday night) is expected to gradually decay across the northern part of the TN Valley on Monday and Monday night. As this occurs (and a slightly more amplified northern stream trough digs east-southeastward into the Mid-MS Valley), W-SW flow aloft will increase into the 10-15 knot range. In the low-levels, weak cyclogenesis (in response to the lower-latitude disturbance) is predicted in the vicinity of the eastern Ozark Plateau on Sunday/Sunday night, with the low expected to shift slowly eastward into Middle TN on Monday before opening into a trough Monday night. Lift provided by the shortwave (coupled with stronger low-level confluence in the vicinity of the low) will support a higher coverage of showers and thunderstorms region-wide Monday afternoon (and continuing well into Monday night). Due to the increase in deep-layer flow, storms will be moving at higher speeds (from WSW to ENE) and may be strong-locally severe (especially during the afternoon-early evening hours).

LONG TERM

(Tuesday through Friday) Issued at 1057 PM CDT Fri Sep 18 2026

Latest extended range forecast data suggest that a weak northern stream trough will advance slowly eastward from the Mid-MS Valley into the northern Mid-Atlantic states next week, as it will likely be blocked by ridging to its north. At the surface, a trough (initially extending from central parts of MS/AL north- northeastward into the Upper OH Valley) is predicted to remain nearly stationary on Tuesday, and will likely focus development of additional showers and thunderstorms across our region both during the day and at night. In similar fashion to Monday, a few strong-severe thunderstorms may occur during the afternoon and evening hours, aided by high CAPE and increasing W-NW flow aloft.

Although there is some uncertainty regarding precisely when this will occur, the surface trough is expected to shift slowly southeastward at some point Wednesday/Thursday, allowing a cooler/drier airmass (originating from an anticyclone across southern QC) to spread southeastward into the region. This coupled with 20-30 knot W-NW flow aloft and dry advection through the depth of the tropospheric column will allow rain chances to decrease considerably on Thursday/Friday. Afternoon highs will fall back into the l-m 80s by the end of the work week, with overnight lows Thursday night/Friday morning in the u50s-l60s.

AVIATION

(06Z TAFS) Issued at 1242 AM CDT Sat Sep 19 2026

VFR conditions are expected to exist at the terminals early this morning, featuring a few high-based Cu (beneath higher-lvl convective debris clouds) and calm winds. Although sufficiently clear skies may support development of patchy BR/FG in a few locations btwn 10-13Z, we will not include vsby reductions in the forecast at this point. Diurnal Cu will develop once again by 16Z, with weakening influence from an upper-lvl ridge perhaps resulting in a slightly greater coverage of terrain/outflow- induced convection during the mid/late aftn hours (compared to today). Thus, a PROB30 group has been included at both terminals from 19-1Z to indicate the most likely timeframe for impacts from TSRA (including potential issuance of AWWs for lightning and strong wind gusts).

HUN WATCHES/WARNINGS/ADVISORIES

AL...Heat Advisory until 8 PM CDT this evening for ALZ001>010-016.

TN...Heat Advisory until 8 PM CDT this evening for TNZ076-096-097.