The National Weather Service has put Chelsea under a High Wind Warning and a Coastal Flood Warning for this weekend’s nor’easter. The flood alert was upgraded overnight: the city’s own notice earlier in the week described a Coastal Flood Watch, and at 2 a.m. Saturday the weather service’s Boston office raised it to a warning for all of Suffolk County.
What the warnings say
- High Wind Warning, until 8 a.m. Sunday. Northeast winds of 20 to 30 mph with gusts up to 60 mph. The weather service warns that damaging winds “will blow down trees and power lines,” that power outages are expected, and that travel will be difficult, especially for high-profile vehicles.
- Coastal Flood Warning, until 8 p.m. Sunday. Up to one foot of water above ground in low-lying areas near shorelines and tidal waterways, with minor flooding and pockets of moderate flooding over several high tides starting late Saturday. The weather service adds that the water “may struggle to vacate the area after the high tides” because the northeast wind will not let up. The worst flooding is expected south of Boston and on the Cape and Islands.
- Rain. The forecast for Chelsea calls for rain and thunderstorms through Monday: a half to three quarters of an inch Saturday, up to an inch Saturday night, and up to another inch each of Sunday and Sunday night.
High tides to watch
Flooding risk peaks around high tide. NOAA’s predicted high tides at its Boston Harbor gauge, the closest to Chelsea, are:
- Saturday, September 26: 11:34 a.m. and 11:54 p.m.
- Sunday, September 27: 12:12 p.m.
- Monday, September 28: 12:36 a.m. and 12:51 p.m.
Those are astronomical predictions. A storm surge driven by the northeast wind would push water above them, which is what the warning is about.
What to do
The weather service’s instruction is short: protect flood-prone property, and if you have to travel, “do not drive around barricades or through water of unknown depth.” The city has asked residents to secure anything outdoors that can blow away, charge phones, stay away from flood-prone areas, and have enough supplies on hand. Treat any downed wire as live and report it to the utility and to 911.
The city sends emergency alerts by text, phone and email during severe weather, flooding and snow emergencies. Sign-up is through the City of Chelsea’s emergency alerts page on chelseama.gov.
We will update this post if the warnings change.