Strong to severe thunderstorms moving through Saginaw Bay produced at least 2 waterspouts.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS DTX wrote it up.
Strong to severe thunderstorms moving through Saginaw Bay produced at least 2 waterspouts.
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 Detroit, MI wrote its last area forecast discussion before the first event at Jul 24, 12:21 PM EST, 2 hours 9 minutes earlier.
Area Forecast Discussion National Weather Service Detroit/Pontiac MI 121 PM EDT Sat Jul 24 2021 .AVIATION... The warm front has cleared the terminal corridor late this morning with lingering areas of haze mixing out as daytime heating begins in earnest. Some hi-res guidance tries to develop isolated showers mid- afternoon in the warm sector however will keep mention out of TAFs due to limited areal coverage and generally lower confidence in these showers initiating. Better chances for precip still expected late afternoon through the evening as a cold front sweeps in from the upper Great Lakes. A line of scattered to numerous thunderstorms develop ahead of the front tracking from NW to SE giving the northern TAF sites an earlier timing window (~22-02Z). Best window for the southern terminals will be ~00-04Z. Strong to severe storms will be possible in the line. Torrential rainfall is likely so any storm will be able to quickly drop vsbys in IFR territory. Rain chances end by midnight. For DTW... VFR conditions take hold this afternoon before a line of storms advance into the area between 01-03Z. Some of these storms will have the potential to be strong to severe with heavy rainfall likely dropping vsbys down into IFR. .DTW THRESHOLD PROBABILITIES... * High for ceilings 5000 ft or less through tonight. * Moderate for thunderstorms late evening/early tonight. && .PREV DISCUSSION... Issued at 1059 AM EDT Sat Jul 24 2021 UPDATE... Regional surface observations this morning show that the surface warm front has advanced to the eastern CWA, stretching roughly from Caro to Mount Clemens. It will continue to slowly advance east through the rest of the morning and early afternoon. The warm sector behind it is characterized by dew points mainly in the lower 70s but a few sites just upstream have reached 74 to 75. This muggy air mass will be more than sufficient to fuel scattered to numerous storms later today. Plenty of low and midlevel clouds linger over the region this morning but some clearing is already developing across the central Lower Peninsula. This will help contribute to a quick ramp-up in instability as mentioned in the early morning forecast package. Monitoring ongoing convection over northern Lower that is kicking out an outflow boundary to the south. This may provide the trigger for some storms over the Tri-Cities and Thumb over the next 1 to 3 hours. Instability remains meager in this region due to the thick blanket of clouds, so threat of strong to severe storms with this activity will be low. The main forcing associated with the inbound shortwave will ramp up during the 2 to 5pm time frame, beginning the main severe threat window. Overall timing of convection outlined in the previous discussion stands with the Tri-Cities and Thumb seeing the most storms during the afternoon and early evening. The threat then spreads south through the evening, exiting to Ohio and Ontario by around midnight. The main hazards remain damaging wind gusts, torrential downpours leading to localized flooding, and large hail. Question remains regarding where the warm front settles by this afternoon which could provide a local backing to surface wind and localized threat for an isolated supercell and/or tornado this afternoon or evening. The chance of this occurring appears to be maximized in the Thumb region with some potential for a localized wind influence along the lakeshore. However, latest runs of hi-res guidance do take the warm front out over Lake Huron so the threat appears to remain low at this time. PREV DISCUSSION... Issued at 402 AM EDT Sat Jul 24 2021 DISCUSSION... Main focus with this forecast package will be the threat for severe weather, mainly during the afternoon and evening. Damaging winds and locally heavy rainfall will be the primary threats with large hail up to 1 inch also possible. While probability is low, an isolated tornado or two cannot be ruled out with activity today. A warm front currently lifting through Michigan will advect a very warm and humid airmass bringing more than enough moisture to fuel strong to severe thunderstorms. Dewpoints in the wake of this warm front will rise into the 70s while PWAT values are progged to climb to between 1.75" to 2.00". This past evening's 00Z RAOB already showed high moisture in place with a PWAT of 1.66". Several forcing mechanisms at play today will result in a few windows for showers and thunderstorms to develop. Some scattered activity will be possible through this morning associated with isentropic ascent along the warm frontal boundary, but the first main window for strong to severe thunderstorms will be related to ongoing nocturnal convection driving through northern lower Michigan. This convection may layout an outflow boundary across the Saginaw Valley and northern Thumb as bulk of activity looks to stay just north. This will coincide with the better synoptic forcing along the progressing warm front and shortwave trough. There should be enough instability to support thunderstorms, but lack of shear early in the day leads to mainly a wind and locally heavy rainfall threat as convection may struggle to become better organized. The main window for severe weather will start in the early/mid afternoon and carry through the evening forced by a prefrontal and the mid level shortwave digging into Lake Michigan by late this afternoon. Severe potential will be dependent on how early day convection and cloud cover may inhibit max destabilization, as is the case in these types of situations. However, the conditional threat remains good as the better shear will arrive at this time with increased flow around the base of the shortwave trough leading to better organized convection. The rich low level moisture under diurnal heating should still lead to moderate to locally strong buoyancy/destabilization yielding MLCAPE values of 1000-2000 J/kg. The mid level lapse rates will be mostly below 6 C/km, though much steeper low level lapse rates develop in the afternoon leading to a greater threat for damaging winds. Hail still remains possible if any updrafts can become organized. Cannot rule out an isolated tornado threat early in the convective evolution ahead of the shortwave as forecast soundings suggest some discrete supercell potential while low level shear increases with backing of surface winds near the warm front into this evening. Locally heavy rainfall can be expected with any activity throughout the day given the expected high degree of moisture. Early isolated to scattered convection posing a severe threat early in the afternoon should evolve into the evening hours as more of a scattered to broken line segments with clusters of storms advancing along the frontal zone/prefrontal trough. Storm motion will be from northwest to southeast at around 30 mph. The main time frame for severe weather will be from 3 pm to about midnight tonight with northern portions of the CWA being impacted in the earlier portion of this time frame and southern portions towards the later. Once the main prefrontal trough pushes east of southeast Michigan, some lingering activity may remain as the lagging frontal boundary eventually arrives. No strong cold air intrusion is expected in the wake of this frontal passage, but it will help lower the humidity across the area. As clouds begin to clear out for Sunday, temperatures are expected to climb into the upper 80s to 90 degrees. Dry conditions carry into Monday with surface high pressure in place. Ridging builds across the Rockies putting southeast Michigan on the northeast end of the heat dome and under persistent northwest flow aloft. Various shortwaves passing within this flow will bring the next chance for precipitation on Tuesday as well some cooler temperatures by mid to late next week. MARINE... Upper-level trough to bring widespread showers and elevated thunderstorms across northern Lake Huron this morning, with activity driving through into Central Lake Huron/Saginaw Bay into the late morning and early afternoon. Sustained southerly flow will ramp up across northern and central Lake Huron through the mid and late morning hours, increasing to or slightly above 20 knots. Outflow and low-level convergence to then produce scattered to numerous showers and storms mainly for the Saginaw Bay, southern Lake Huron, and locations south this afternoon and evening. Instability will build through the afternoon which in turn will produce some localized strong to severe storms. Wind gusts to or in excess of 34 knots will be possible with the stronger storms. General storm activity and severe threat will wane late Saturday night, with a cold front swinging through on Sunday morning. Passage of the front will veer wind direction from southerly to westerly throughout the day on Sunday. A weak pressure gradient to then hold over the Great Lakes through the midweek period, which will bring lighter winds to the area. HYDROLOGY... A storm system will move through the Great Lakes today with scattered to numerous showers and thunderstorms expected during the afternoon and evening. High degree of moisture will arrive lift into southeast Michigan with PWAT values increasing to or near 2.00". Heavy downpours will thus be possible in any thunderstorms with rainfall rates in excess of a half inch per hour possible in the strongest storms. Basin-average amounts of a quarter to half inch are forecast for most of SE Michigan but areas that see multiple rounds of storms may see totals up to or exceeding 1 inch. The potential for this to occur is highest in the Thumb region including the Port Huron vicinity. This may lead to localized flooding of low- lying and flood prone areas. The bulk of showers and thunderstorms are expected to move out late tonight. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && AVIATION.....KDK UPDATE.......TF DISCUSSION...AA MARINE.......AM HYDROLOGY....AA You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.
Hazardous Weather Outlook National Weather Service Detroit/Pontiac MI 421 AM EDT Sat Jul 24 2021 MIZ047>049-053>055-060>063-068>070-075-076-082-083-250830- Midland-Bay-Huron-Saginaw-Tuscola-Sanilac-Shiawassee-Genesee-Lapeer- St. Clair-Livingston-Oakland-Macomb-Washtenaw-Wayne-Lenawee-Monroe- 421 AM EDT Sat Jul 24 2021 This hazardous weather outlook is for portions of southeast Michigan. .DAY ONE...Today and Tonight Scattered strong to severe storms are possible this afternoon and evening, mainly from 3 pm to about midnight. Any isolated to scattered cells early in the convective evolution will transition primarily to scattered to broken line segments. Storm motion will be from northwest to southeast at around 30 mph. Damaging wind gusts, torrential downpours, and isolated large hail are the primary threats. with a low probability for an isolated tornado or two. .DAYS TWO THROUGH SEVEN...Sunday through Friday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed this afternoon and evening. LCZ460-LEZ444-LHZ361>363-421-422-441>443-462>464-250830- Lake St Clair- Michigan Waters of Lake Erie from Detroit River to North Cape MI- Lake Huron from 5NM east of Mackinac Bridge to Presque Isle Lt beyond 5 NM off shore- Lake Huron from Presque Isle Light to Sturgeon Point MI beyond 5NM off shore- Lake Huron from Sturgeon Point to Alabaster MI beyond 5NM off shore- Outer Saginaw Bay SW of Alabaster to Port Austin MI to Inner Saginaw Bay-Inner Saginaw Bay SW of Point Au Gres to Bay Port MI- Port Austin to Harbor Beach MI-Harbor Beach to Port Sanilac MI- Port Sanilac to Port Huron MI- Lake Huron from Port Austin to Harbor Beach beyond 5NM Off Shore- Lake Huron from Harbor Beach to Port Sanilac beyond 5NM Off Shore- Lake Huron from Port Sanilac to Port Huron beyond 5NM Off Shore- 421 AM EDT Sat Jul 24 2021 This hazardous weather outlook is for portions of Lake Erie, Lake Huron and Lake St Clair. .DAY ONE...Today and Tonight Scattered strong to severe storms are possible this afternoon and evening, mainly from 3 pm to about midnight. Any isolated to scattered cells early in the convective evolution will transition primarily to scattered to broken line segments. Storm motion will be from northwest to southeast at around 25 kts. Damaging wind gusts, torrential downpours, and isolated large hail are the primary threats. with a low probability for an isolated tornado or two. .DAYS TWO THROUGH SEVEN...Sunday through Friday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed this afternoon and evening. You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit. AA
The NCL Michigan radar (KAPX), 130 km away, was scanning. The volume nearest the first event began at 19:28 UTC.
2 waterspout, 2 marine thunderstorm wind. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Lake Huron in 2021Every state in 2021This day in weather history
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: 975947, 975948, 975949, 975950.