textproduct: Huntsville

KEY MESSAGES

Updated at 1045 PM CDT Tue Aug 11 2026

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

- A low conditional threat for strong to severe storms will exist once again tomorrow afternoon. Please check back for updates.

NEAR TERM

(This Evening through Wednesday) Issued at 1045 PM CDT Tue Aug 11 2026

Through the duration of the near term period, our forecast area will remain beneath the northeastern flank of a subtropical ridge extending from the southern High Plains into the southeastern Gulf/southern FL Peninsula. Although the ridge is predicted to gradually weaken with time, the height gradient aloft will remain sufficiently contracted to result in NW flow aloft of 10-20 knots. In the low-levels, light SW flow will persist between an area of low pressure across NE/KS and a zonally-oriented ridge extending from the southwestern North Atlantic into the north-central Gulf.

At the present time, a long-lived MCS (which originated earlier today in the vicinity of a warm front across the Lower Great Lakes) extends from south-central KY into the Smoky Mountains of eastern TN/western NC. Although this feature should continue to weaken through 6Z due to both nocturnal stabilization and weaker deep-layer shear (and an increasing propensity for the MCS to become outflow dominant) with southward extent, clusters of thunderstorms have recently developed in a region of enhanced low- level warm advection to the southwest of the primary MCS (from middle into southeastern TN). Current thinking is that this regime will slowly expand southwestward into our CWFA in conjunction with the lengthy outflow boundary (perhaps as early as 4-6Z in the northeast, but moreso in the 6-10Z timeframe). Although storm coverage and intensity will both be much lower in our region compared to points to our north/east, MUCAPE will only slowly fall into the 1000-1500 J/kg range by 12Z, and this could support frequent lightning and SPS-caliber winds (up to 40-45 MPH) with stronger cores. Otherwise, it will be another warm/muggy night, with lows in the l-m 70s.

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

(00Z TAFS) Issued at 742 PM CDT Tue Aug 11 2026

Lingering afternoon convection (oriented along a narrow axis from north-central into east-central AL) will continue to dissipate early in the TAF period. Thus, we expect VFR conditions to prevail at the terminals this evening, beneath sct-bkn layers of Ac and Ci. During the early morning hours, there is some concern that outflow (originating from a large MCS currently extending from the central OH Valley into southwestern VA/northeastern TN) may enter the region from the northeast and initiate additional SHRA/TSRA. However, due to the time of day, the number of additional convective cells is expected to be rather low across our region and for this reason we have only included a PROB30 group from 4-8Z/HSV and 6-10Z/MSL. 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. However, we will refrain from introducing another PROB30 group in the forecast until timing becomes more certain.

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 Wednesday to 7 PM CDT Friday for ALZ001>010-016.

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