textproduct: Huntsville

KEY MESSAGES

Updated at 157 AM CDT Wed Aug 12 2026

- A Heat Advisory is in effect for the entire forecast area Today through Friday, with extensions and upgrades likely through the weekend.

- A low conditional threat for strong to severe storms will exist once again this afternoon.

NEAR TERM

(Today) Issued at 157 AM CDT Wed Aug 12 2026

The MCS that originated up in the Lower Great Lakes yesterday has finally pushed into NE AL and sinking southward. Thankfully it is moving at a faster pace that earlier tonight, reducing flooding concerns for us. The outflow boundary it has produced is creating additional development ahead of it as well. The main hazards with this line and the other convection it creates is frequent lightning, heavy rainfall and gusty to strong winds. In recent satellite and radar scans though, lightning intensity and radar reflectivity is weakening, cloud tops are warming and it's becoming more outflow dominate. Will keep an eye on any pockets to reintensify though before it's able to push completely out of the forecast area in the next few hours.

Otherwise, no major changes to the rest of today's forecast. For more about the rest of today, see previous discussion below.

Previous Discussion: After a brief break in shower/thunderstorm activity late tomorrow morning, convection is predicted to redevelop by mid-day in the vicinity of a remnant outflow boundary extending from western Middle TN into northeast AL/northwest GA. This confluence axis may reinforced by outflow from another MCS that should evolve from the Upper Midwest southeastward into the central Appalachians later tonight, and will serve as a focus for additional convective initiation as it shifts slowly southward through our region tomorrow afternoon. With forecast soundings once again exhibiting very steep low-level lapse rates and MLCAPE in the 2500-3000 J/kg range (as temps peak in the l-m 90s), locally damaging downburst winds will once again be a concern, along with frequent lightning and heavy rainfall (which could result in flash flooding). Prior to the onset of convective impacts, the combination of temperature and dewpoint will yield heat indices in the 103-107F range for much of the valley (if not perhaps a bit higher), and a Heat Advisory remains in effect beginning at 1 PM CDT.

SHORT TERM

(Wednesday night through Friday night) Issued at 1045 PM CDT Tue Aug 11 2026

The general synoptic pattern across our region is expected to remain unchanged on Wednesday night, and with most members of the 12Z HREF suggesting that another large MCS will be crossing the OH Valley late tomorrow afternoon/early tomorrow evening, chances for nocturnal showers and thunderstorms (initiated by convective outflow) will remain elevated across our region. However, beginning on Thursday, solutions from the global models suggest that the subtropical high to our south will begin to intensify and expand northward in response to gradual amplification of an upstream longwave trough over the eastern North Pacific. As this occurs, strengthening subsidence and weakening steering currents aloft will both contribute to a progressively lower coverage of afternoon/early evening convection on both Thursday and Friday. That said, very steep lapse rates will exist both days (along with high CAPE and DCAPE), and for this reason damaging downburst winds will remain a concern regardless of storm coverage.

Due to less convective impacts, afternoon temperatures will rise by a few degrees each day, reaching the m-u 90s on Friday. Although deep mixing may eventually scour some of the low-level moisture from parts of the region by Friday, dewpoints for the majority of the CWFA will remain in the u60s-m70s, resulting in apparent temps solidly reaching the 105-110F range by Friday afternoon. Thus, a Heat Advisory will remain in effect until 7 PM CDT Friday.

LONG TERM

(Saturday through Tuesday) Issued at 1045 PM CDT Tue Aug 11 2026

Extended range data from the latest suite of global models is in general agreement that a subtropical high (centered from the Lower MS Valley to the southeastern Atlantic Coast) will continue to strengthen this weekend, with geopotential heights perhaps reaching 600 dam. Thus, excessive heat will continue to be a concern across the TN Valley, with highs remaining in the m-u 90s from Saturday-Monday (and perhaps exceeding 100F in several locations on both Sunday and Monday afternoons). Although a few afternoon storms may occur on both Saturday and Sunday (primarily in the higher terrain of northeast AL), rain chances will remain low and there is a very high chance that the pre-existing Heat Advisory will need to be extended through Monday, perhaps with an upgrade to an Extreme Heat Warning due to Heat Index readings surpassing 110F. By late in the forecast period, there are indications that the subtropical high may begin to retrograde into the southern High Plains, perhaps allowing NW flow aloft to become reestablished across our region by Monday/Tuesday. Should this occur, a weak cold front may bring a broken line of showers and thunderstorms to the region Monday evening, followed by a slight drop in temperatures/dewpoints on Tuesday.

AVIATION

(06Z TAFS) Issued at 1248 AM CDT Wed Aug 12 2026

There have been no significant changes to previous aviation forecast reasoning, as current radar/satellite imagery and sfc obs suggest that convective outflow (currently entering the region from the northeast) will initiate additional SHRA/TSRA in our region early this morning. However, due to the time of day, the number of additional convective cells is expected to be rather low and for this reason we have only included a PROB30 group from 7-11Z. Although VFR conditions and lgt SW winds will continue for the second half of the TAF period, redevelopment of at least sct TSRA appears likely to occur tomorrow aftn in the vicinity of another outflow boundary dropping south-southwestward into the region. Thus, we have introduced a second PROB30 group to account for this activity from 18-22Z. Lightning, brief strong wind gusts and mod-heavy rain are expected to be the greatest impacts from the storms.

CLIMATE

Issued at 301 AM CDT Tue Aug 11 2026

The Climate Prediction Center has included the whole area in a Moderate to a High Risk for Much Above Normal Temperatures for August 18th through August 22nd. The High Risk includes locations south of a line from Lexington, to Athens, New Hope and Fort Payne. The Moderate Risk include locations north of that line. Therefore, there is a 40-60% chance in the Moderate Risk locations and a 60-80% chance for those in the High Risk areas for temperatures above 95-97 degrees F during this period.

More information on the CPC U.S. Hazards Outlook can be found at:

https://www.cpc.ncep.noaa.gov/products/predictions/threats/threats.php

HUN WATCHES/WARNINGS/ADVISORIES

AL...Heat Advisory from 1 PM this afternoon to 7 PM CDT Friday for ALZ001>010-016.

TN...Heat Advisory from 1 PM this afternoon to 7 PM CDT Friday for TNZ076-096-097.