Thunderstorms repeatedly trained Southwestward across Morgan County, producing large swaths of rainfall amounts between 3 to 6 inches over 2-3 hours on the evening of the 25th.
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The episode as NWS HUN wrote it up.
Thunderstorms repeatedly trained Southwestward across Morgan County, producing large swaths of rainfall amounts between 3 to 6 inches over 2-3 hours on the evening of the 25th.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Huntsville, AL wrote its last area forecast discussion before the first event at Jul 25, 5:46 PM CST, 19 minutes earlier.
Area Forecast Discussion National Weather Service Huntsville AL 646 PM CDT Sun Jul 25 2021 .UPDATE... For 00Z TAFS. && .NEAR TERM...(This afternoon and Tonight) Issued at 230 PM CDT Sun Jul 25 2021 Earlier this morning, initial cu and eventual shower development occurred as a weak short wave moved southward into the area. Activity in assoc/w this feature has continued into this afternoon along a general W-E axis stretching from SE TN westward across NW GA and into Dekalb, Marshall and Cullman Counties. SHRA have been most vigorous recently along the AL/GA border, with some recent increase in convective strength in some of the cells in DeKalb County, which will have to be watched in the very near term. Otherwise, isold/sctd showers have developed elsewhere in the area due to generally mesoscale diff heating and outflow boundaries. Most cells are relatively small and short-lived owing to the weak environmental shear in place. A few cells in the region have displayed weak MARC signatures recently. MLCAPEs in excess of 2000 J/kg, 0-3 km ~8 C/km, and PWs near 2 inches will still be supportive of strong cells and wind gusts from a thermodynamic standpoint, however the lack of wind shear will still tend to limit convective organization. Cells may also present a local heavy rain and flash flooding risk, but this will be limited to isolated locations. Importantly, heat index values have neared 105 F in NW portions of Alabama, thus a Heat Advisory was issued at ~18Z. Based on expected trends for air and dew point temperatures, the Advisory is set to expire at 23Z. Shower and thunderstorm activity will decrease this evening, but a stronger upr short wave will be moving SEWRD into the TN Valley late tonight. Convective activity in assoc/w this feature may push into northern portions of our area by daybreak. .SHORT TERM...(Monday through Tuesday) Issued at 230 PM CDT Sun Jul 25 2021 The upr wave and an associated low-lvl convergence boundary will move gradually southward into the area on Monday. These features will enhance both dynamic and thermodynamic forcing for showers and thunderstorms and we will continue to carry likely POPs for late Monday morning into the afternoon. Thermodynamic parameters will tend to be somewhat similar to values today, but PW values may approach 2.2 inches (or higher), while lapse rates may be a little lower. While a strong wind gust threat may still exist, the greater risk may be for locally heavy rainfall leading to flash flooding. Deep layer shear will still be very limited and storm organization/longevity will likewise be limited, but cell movement will be fairly slow. Increased amplification of the west CONUS ridge and east CONUS trough will occur on Tuesday, providing confidence that the upr wave and low-lvl convergence will progress southward through the area. However, its presence especially in the morning and early afternoon on Tuesday will continue shower/thunderstorm chances. Chances for strong wind gusts and locally heavy rainfall will be present, especially in southern portions of the area on Tuesday afternoon as the convergent axis and upr-lvl wave move southward across that portion of the area. .LONG TERM...(Tuesday night through Saturday) Issued at 230 PM CDT Sun Jul 25 2021 Will be in a transition of airmasses by Wednesday as the bulk of the deep moisture is pushed south of the area. Northerly flow will reside aloft as the upper high pushes over the central Plains and a broad upper trough pushes off the northern Atlantic coast. Despite this, near sfc conditions will remain relatively unchanged as sfc dewpoints stay in the low to mid 70s. Little in the way of change of sensible temperatures will occur, as daily afternoon heat indices near or top 100 degrees. High temperatures will range from the low to mid 90s each afternoon, with widespread mid 90s expected on Thursday. Overnight lows will be in the low to mid 70s each night. Mostly dry weather is expected through mid-week, then a more active pattern returns for the weekend as an upper trough digs over the eastern US. At this point in time, confidence is too low to warrant likely PoPs, but will keep daily chances in through the weekend, peaking in the afternoon and evening each day. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 646 PM CDT Sun Jul 25 2021 Ongoing scattered showers and thunderstorms will continue through the evening and AWWs may be required. Otherwise, VFR conditions prevail overnight until patchy fog develops in the early morning hours. It is possible this fog becomes dense and intensify below airport minimums at times, but this does not appear likely at this time. After a mostly clear morning, scattered to numerous showers and storms develop again tomorrow afternoon. MVFR to IFR ceilings and visibility will be present in the stronger storms, and AWWs may be required. Persistent heavy rainfall may lead to ponding of water on runways. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && NEAR TERM...KDW SHORT TERM...KDW LONG TERM...25 AVIATION...30 For more information please visit our website at weather.gov/huntsville.
Hazardous Weather Outlook National Weather Service Huntsville AL 313 PM CDT Sun Jul 25 2021 ALZ001>010-016-TNZ076-096-097-261115- Lauderdale-Colbert-Franklin AL-Lawrence-Limestone-Madison-Morgan- Marshall-Jackson-DeKalb-Cullman-Moore-Lincoln-Franklin TN- 313 PM CDT Sun Jul 25 2021 This Hazardous Weather Outlook is for north Alabama and portions of southern middle Tennessee. .DAY ONE...Tonight... Isolated to scattered thunderstorms will continue into the evening hours. Wind gusts of 40 to 50 MPH, frequent lightning, and locally heavy rainfall will be possible with the strongest storms. A Heat Advisory is in effect for Lauderdale and Colbert Counties through 6 PM, as heat indices will be around 105 degrees. .DAYS TWO THROUGH SEVEN...Monday through Saturday... Scattered to numerous thunderstorms are expected on Monday and Tuesday, with only isolated activity anticipated south of the TN River on Wednesday. After a break in precipitation on Thursday, scattered thunderstorms will return to the region over the weekend. Dangerously high heat indices in the 100 to 105 degree range will be possible during the later half of the work week. .SPOTTER CALL TO ACTION STATEMENT... Activation of storm spotters and emergency management personnel is not anticipated at this time.
The Northeast Alabama radar (KHTX), 99 km away, was scanning. The volume nearest the first event began at 00:07 UTC.
1 flash flood. Local standard time, as filed.
Trained spotter reported 6 to 8 inches of moving water across the intersection of Highway 31 and Lacon Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alabama in 2021Every state in 2021This day in weather historyWarnings in Alabama, July 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 969291.