textproduct: Huntsville

KEY MESSAGES

Updated at 853 AM CDT Mon Sep 21 2026

- The coverage of showers and thunderstorms will remain fairly high through Tuesday. Conditions will be favorable for strong- severe thunderstorms, particularly this afternoon/evening and again on Tuesday afternoon. Locally damaging downburst winds, frequent lightning, and heavy rainfall will be the main hazards.

- A slightly cooler and drier airmass will begin to arrive on Wednesday. Highs will fall back into the lower-mid 80s from

NEAR TERM

(Rest of Today and Tonight) Issued at 853 AM CDT Mon Sep 21 2026

As an upper level trough and subsequent sfc low pressure system shift southeastward toward the Tennessee Valley, our environment remains favorable for thunderstorm development this afternoon into the evening hours. MLCAPE values are forecast to comfortably reach 1200+ J/kg along and east of I-65, accompanied by DCAPE near 800-900 J/kg as well as steep low level lapse rates. Dew points will reach the upper 60s to low 70s with subsequent PWATs in the 1.6-1.8" range (near 90th percentile per BMX climatology). Therefore, our primary concern will be downburst gusty to damaging winds (40-60 mph) in addition to frequent lightning and heavy rainfall. Storm speed should be slow (similar to the past several days, remaining around 5-10 mph) which will cause ponding of water in areas of poor drainage in areas where storms form. CAMs are initializing very poorly, however, this will likely fall in the timeline of diurnally fueled convection with the main window for storms being 2 PM - 8 PM CT. There is a low chance a few thunderstorms persist past 8 PM into the late night hours, but these should be below severe limits with the loss of daytime heating. Despite parameters being more favorable along and east of I-65, a low chance for severe weather remains in place for all of northern AL and southern middle TN. SPC has outlooked the area in a Marginal risk (level 1 of 5) for severe weather, with damaging winds being the primary hazard. Be sure to have multiple ways to get warnings this afternoon into the evening hours.

Heat, on the other hand, should be slightly less of a threat today with more widespread thunderstorm formation/cloud cover. Highs are forecast to reach the upper 80s to mid 90s with heat indices remaining 100 degrees or less. A Moderate HeatRisk (level 2 of 4) still exists, so be sure to remain hydrated and seek shade when outdoors.

SHORT TERM

(Tuesday through Wednesday night) Issued at 853 AM CDT Mon Sep 21 2026

As the aforementioned low pressure system continues into the Tennessee Valley, continued forcing for thunderstorms will exist with the primary concern being damaging winds yet again. As of now, SPC has outlooked the southeastern portions of our CWA in a Marginal risk (level 1 of 5) for severe weather due to the potential for damaging winds. Similarly to Monday, MLCAPE values of 1000-1200 J/kg with DCAPE around 600-800 J/kg and steep low level lapse rates will support a risk of gusty to damaging winds (40-60 mph). Parameters look slightly less favorable Tuesday than they will be today (Monday) so slightly less confident in the overall severe threat. Additionally, as the sfc low pushes southeast through the area, coverage should also be more limited with the bulk of activity remaining where the current SPC outlook resides (primarily in NE AL). Timing for this should line up with diurnal support once again with the peak storm potential being between 2 PM - 8 PM. Low chances for thunderstorms will continue to linger overnight, however, support of daytime heating will be lost and storms should remain sub severe.

The frontal boundary will likely briefly stall to our southeast, which will allow low chances for rain to continue in our eastern areas through Wednesday. We are not outlooked for severe weather at this time and confidence remains low in strong storm formation behind the boundary. Dry weather should fully return to the forecast Thursday.

Temperatures during the short term are forecast to gradually decrease with highs being capped in the low to mid 80s by Thursday and overnight lows dropping into the lower 60s by Thursday morning. Don't get too excited about the cooler temperatures, as the CPC continues to outlook us for above normal temperatures in the extended range.

LONG TERM

(Thursday through Sunday) Issued at 1101 PM CDT Sun Sep 20 2026

Global models suggest that a weak mid/upper-level low (initially across the central Appalachians) will phase with a smaller disturbance to its east later this week to form a deep low that will sit off the northern Mid-Atlantic Coast this weekend. This will ensure a continuation of dry NNW flow aloft across the TN Valley for much of the period, before this regime weakens Saturday and Sunday. With indications that low-level confluence across will progressively diminish on Thursday/Friday, the risk for showers in the east will continue to fall as light N-NE flow advects a drier airmass into the region from a high across southeastern Canada. Highs will be in the l-m 80s, with overnight lows dropping into the m-u 50s this weekend (when dewpoints could drop into the 40s).

AVIATION

(18Z TAFS) Issued at 1214 PM CDT Mon Sep 21 2026

VFR to MVFR conditions should occur intermittently through the TAF period as scattered, low-medium chances for thunderstorms begin to occur this afternoon through late this evening. A low chance exists for these thunderstorms to persist overnight. Confidence is low on spatial coverage, so have included these thunderstorms as a PROB30 group at both sites. Amendments may be needed and AWWs are likely this afternoon.

HUN WATCHES/WARNINGS/ADVISORIES

AL...None. TN...None.