Isolated to scattered thunderstorms developed in the late afternoon hours within a warm and humid airmass out ahead of a cold front well to the west. One cluster of thunderstorms impacted the Savannah area and produce very heavy rainfall, damaging wind gusts, and large hail.
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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 CHS wrote it up.
Isolated to scattered thunderstorms developed in the late afternoon hours within a warm and humid airmass out ahead of a cold front well to the west. One cluster of thunderstorms impacted the Savannah area and produce very heavy rainfall, damaging wind gusts, and large hail.
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 Charleston, SC wrote its last area forecast discussion before the first event at May 21, 11:25 PM EST, 35 minutes earlier.
Area Forecast Discussion National Weather Service Charleston SC 1225 AM EDT Mon May 22 2017 .SYNOPSIS... A series of disturbances will track across the Southeast through midweek. A cold front will push offshore Wednesday night into Thursday. High pressure will then prevail through next weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Best rain chances will occur along/east of I-95 in Southeast South Carolina through daybreak. 30-40% pops look reasonable there with 20% pops elsewhere. && .SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY/... Unsettled conditions will continue through this period. Due to convection, lead time for precise forecast details will remain limited. Monday: Weak shortwave troughs aloft will interact with an environment featuring PWATS close to 2 inches and various mesoscale boundaries including the sea breeze to produce scattered/numerous showers/thunderstorms. Greatest coverage should occur during the afternoon/evening hours. A brief/isolated severe weather episode and localized excessive rainfall cannot be ruled out but remains unlikely. Monday night: Convection should undergo some degree of diurnal weakening during the evening. Then, a shortwave approaching from the west should promote increasing precipitation coverage overnight, especially inland and over coastal waters. Tuesday through Tuesday night: Shortwaves ejecting east/northeast from an amplifying/upstream longwave trough and an associated 40-50 knot 850 mb jet will provide forcing for ascent within a persistent plume of PWATs approaching 2 inches. This regime should support numerous/widespread showers/thunderstorms. Occasional breaks in convective precipitation, rather than steady rainfall appears most likely, although extended rain-free periods could remain limited, especially north of I-16. Locally excessive rainfall could occur, but the severe threat should remain low. Wednesday, the longwave trough will continue to amplify upstream, drive a strong cold front toward the region. This regime should again support numerous/widespread showers/thunderstorms. If a break develops between the Tuesday night precipitation and pre-frontal convection, the combination of deep-layered forcing for ascent, 0-6 km bulk shear increasing to 40-50 knots and destabilization could support severe weather especially Wednesday afternoon/evening. However, the prospects for destabilization remain highly uncertain. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Showers/thunderstorms will be pushed offshore with a trough and surface cold front Wednesday night. Some remnant showers may remain along the coast into Thursday morning. High pressure will build in from the west and prevail into the weekend. Temperatures will gradually rise during the long term. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... Isolated showers will meander near KCHS through sunrise, but any direct impacts would be brief. Main concern for today is possible thunderstorm impacts at both KCHS and KSAV. Latest data support decent chances for impacts at KCHS late morning into the early afternoon as the sea breeze moves inland. Will carry TEMPO MVFR vsbys 17-20z to cover for now. Lower conditions will be possible, but will need to see a bit more run-to-run consistency in the various CAMS before going any lower. At KSAV, current data suggest the better rain probabilities will remain west of the terminal this afternoon. Will therefore hold off on any mention of SHRA or TSRA. This will be reevaluated for the 12z TAF cycle. Extended Aviation Outlook: An unsettled weather pattern will bring periods of flight restrictions through Wednesday night. Then, VFR expected through late week. && .MARINE... Overnight: The waters will be situated between a developing warm front to the north, sub-tropical ridging to the east and an upstream cold front that approaches the Appalachians late. There is very subtle low level jetting overnight, allowing for SE to S winds mostly in the 10-15 kt range. Seas will average 2 ft within 15 nm, 3 ft further out. Monday through Tuesday: Outside any thunderstorms Monday, south/southwest winds should average 10-15 knots, accompanied by seas 2-3 ft. Monday night, expect southwest winds around 15 knots with gusts to 20 knots, and seas will build to 2-4 ft, highest at 20 nm and beyond. Outside thunderstorms, which could produce locally gusty winds, lightning and very heavy rain, these conditions should prevail through Tuesday. Tuesday night through Wednesday night: Between offshore high pressure and inland low pressure/an approaching cold front, Small Craft Advisories will likely be required for areas outside Charleston Harbor as southwest winds increase to gust 25-30 knots and and seas build to 4-6 feet nearshore and to 5-8 feet beyond 20 nm. Thursday through Friday: A strong cold front will cross the waters Thursday, and elevated offshore winds could remain at SCA strength. Then, winds/seas should relax significantly by Friday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. &&
Hazardous Weather Outlook National Weather Service Charleston SC 404 PM EDT Sun May 21 2017 AMZ330-350-352-354-374-GAZ087-088-099>101-114>119-137>141-SCZ040- 042>045-047>052-222015- Charleston Harbor- Waters from South Santee River to Edisto Beach SC out 20 nm- Waters from Edisto Beach SC to Savannah GA out 20 nm- Waters from Savannah GA to Altamaha Sound GA out 20 nm...including Grays Reef National Marine Sanctuary- Waters from Savannah GA to Altamaha Sound GA extending from 20 to 60 nm-Jenkins-Screven-Candler-Bulloch-Effingham-Tattnall-Evans- Inland Bryan-Coastal Bryan-Inland Chatham-Coastal Chatham-Long- Inland Liberty-Coastal Liberty-Inland McIntosh-Coastal McIntosh- Allendale-Hampton-Inland Colleton-Dorchester-Inland Berkeley- Inland Jasper-Beaufort-Coastal Colleton-Charleston-Coastal Jasper- Tidal Berkeley- 404 PM EDT Sun May 21 2017 This Hazardous Weather Outlook is for Atlantic coastal waters, southeast Georgia and southeast South Carolina. .DAY ONE...Tonight. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Monday through Saturday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter assistance is not anticipated at this time.
The Charleston,SC radar (KCLX), 60 km away, was scanning. The volume nearest the first event began at 05:01 UTC.
3 hail, 2 thunderstorm wind, 1 heavy rain. Local standard time, as filed.
The ASOS at the Savannah/Hilton Head International Airport (KSAV) measured 6.61 inches of rain for the day. This broke the daily rainfall record and ranks as the 15th wettest day on record at KSAV.
A report of nickel sized hail in Port Wentworth was received via social media.
Hail up to the size of quarters on the Houlihan bridge was reported via social media. The hail reportedly fell for about 10 minutes.
Multiple trees were reported down near the Houlihand bridge, causing the bridge to be closed to traffic.
Chatham County Emergency Management reported a tree down on a house on Bonnybridge Road in Port Wentworth.
Penny sized hail reported in Port Wentworth. Wind gusts of approximately 55 mph were also reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Georgia in 2017Every state in 2017This day in weather historyWarnings in Georgia, May 2017
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: 698963, 698952, 698962, 698964, 698965, 698966.