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Washington region sees worst coastal flooding in years amid heavy rain and strong winds

Highest water levels along Tidal Potomac and Chesapeake Bay anticipated late Friday night into early Saturday morning

By
October 29, 2021 at 6:04 p.m. EDT

* Coastal flood warning through Saturday morning for Tidal Potomac River and Chesapeake Bay | Forecast through the weekend *


Radar courtesy MyRadar | © OpenStreetMap contributors

Key points

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  • Coastal flooding has resulted in 2 to 4 feet of inundation along the shores of the tidal Potomac River and Chesapeake Bay. In some areas, the highest water levels and most severe coastal flooding are anticipated late Friday night into the predawn hours Saturday at the next high tide. Water levels should gradually fall over the weekend.
  • On Friday afternoon, Old Town Alexandria recorded its third highest tide on record, and highest since 2003.
  • One to two inches of rain fell across the region, with some flooding of small streams. A little more rain is possible this evening before tapering to scattered showers overnight.
  • Winds gusted to 30 to 40 mph in the immediate area and to around 50 mph near the Bay Friday morning but have since waned. The gusty winds and rain resulted in dozens of downed trees in the region.
  • The hazardous weather closed Calvert and Anne Arundel County schools while St. Mary’s and Prince George’s counties dismissed early.

East Coast storm bringing worst coastal flooding since 2003 to parts of Mid-Atlantic

Updates

6 p.m. — Coastal flooding is key concern overnight as storm’s wind and rain fade (final update)

Through this evening the rain will taper to showers (as noted in 5 p.m. update below) and, as winds have died down, the most turbulent weather has moved off. However, for the shores of the Tidal Potomac and Chesapeake Bay, which have been flooded all day, waters levels will rise even more in some areas.

The Weather Service predicts the water level in Annapolis to reach 5.2 feet at midnight, its third highest tide on record and highest since Isabel.

The water level at Old Town’s next high tide, at 3:42 a.m. Saturday, is forecast to be slightly lower than its Friday afternoon level (also its third highest on record, as noted below).

Over the weekend, tidal levels should gradually fall across the region.

This is our last update in this story.

Below find some more images of the flooding in the region:

5:30 p.m. — Old Town Alexandria records third highest tide level on record, largest since Hurricane Isabel

At 3:24 p.m. Friday, around high tide, the water level in Old Town Alexandria reached 5.99 feet, the third highest on record. It only trails the high tides in Hurricane Isabel in 2003 (8.66 feet) and a storm in March 1936 (7.40 feet).

5 p.m. (updated at 6 p.m.) — Rainfall totals range from 1 to 2 inches, with a little more possible

Through 6 p.m., storm rain amounts range from 1 to 2 inches across the region although we’ve seen a few totals of 2 to 3 inches in narrow corridors to the west and east of Washington. Here are totals from the airports:

  • Reagan National: 1.15 inches
  • Dulles: 1.31 inches
  • BWI Marshall: 2.73 inches

We could conceivably add a couple more tenths of an inch to these totals with lingering rain and showers this evening, but the bulk of the heavy rain has fallen in areas south of Baltimore.

4:15 p.m. — Winds have eased but downpours to persist another couple of hours

We can cross one hazard off the list now, as winds, which peaked late this morning, have relaxed some. But moderate rain and occasional bursts of heavy rain continue over the Washington region and will persist another couple of hours. Around Baltimore, the rain may linger until around 7 p.m.

Continue to watch out for high water, especially near streams and poor drainage areas.

2:40 p.m. — Some more visuals of the coastal flooding

The high water is not only inundating Annapolis and Old Town Alexandria, but also the shorelines along the rest of the Chesapeake Bay and Tidal Potomac through Southern Maryland and Virginia’s Northern Neck. In some places the water is entering homes.

Here are some more images of the coastal flooding in the region — with high tide occurring around now in many spots:

2:10 p.m. — A few more hours of heavy rain for immediate D.C. area and points north

South of Fairfax County, the rain has eased or stop, but there is more heavy rain to come especially for areas near the Beltway and north. Some of the rain will be heavy.

Radar shows downpours in eastern and southeast Virginia streaming to the north and northwest and short-term models show it pivoting into the immediate area and points north over the next few hours. This will prolong rainfall and push totals well over an inch in many spots.

Totals are beginning to mount with 0.74 inches at Reagan National, 0.81 inches at BWI Marshall and 1.21 inches at Dulles through 2 p.m.

Winds have started to ease from the District south, but are still very gusty to the northeast. BWI just gusted to 38 mph.

1:15 p.m. — Scenes of coastal flooding around the region

High tide has occurred or is approaching along much of the Chesapeake Bay and Tidal Potomac and, on social media, we’re seeing some dramatic images of the inundation. Here is a sample:

12:40 p.m. — Flood warning issued for District and surrounding area

Due to the heavy rain pointed at the immediate D.C. area and points west, the National Weather Service has issued a flood warning through the afternoon. Around 0.5 to 1 inches has fallen in the warned area and another inch or so could fall.

“A period of heavy rain is expected this afternoon through 3 p.m. with rainfall rates around one inch per hour,” the Weather Service wrote. “This will cause creeks and streams to rise through late this afternoon.”

12:20 p.m. — Heavy, wind-swept rain pointed at D.C. area; Peak wind gusts over 50 mph reported along Bay

The intensity of rain is generally increasing across the region which may culminate in a brief period of very heavy rain during the early-to-mid afternoon. Radar shows a band of downpours near Fredericksburg headed due north; this may focus in the western half of the region, along and west of Interstate 95. These downpours may help mix down some strong gusts which could cause some more trees to come down. They could also cause some localized flooding.

Rainfall totals so far are mostly around 0.5 inches in the immediate area but the rain coming over the next several hours should push most locations over an inch. More substantial rains have fallen to our southwest with around 2 inches in Charlottesville.

Meanwhile, winds continue to howl, gusting between 30 and 40 mph. The strongest winds, as expected, have focused right along the Bay with gusts to 50 and 55 mph at Shade Side and Sandy Point in Anne Arundel County and 46 mph at Point Lookout and Patuxent River in St. Mary’s County.

11:20 a.m. — More scenes of escalating coastal flooding along the Chesapeake Bay and Potomac river

High tide is at noon in Annapolis and the water is rising, as shown in the image above. The flooding is not confined to Annapolis. As apparent in the image below, water is rapidly rising along the Tidal Potomac in St. Mary’s County, where the river resembles an ocean:

The winds, gusting to 30 to 40 mph over soaked soils, continue to cause downed trees in the region:

Winds, thus far, have caused more problems than rain. Rainfall amounts generally around 0.25 to 0.5 inches, although the heaviest rain is still expected to come this afternoon.

10:15 a.m. — Coastal flooding in Old Town and Annapolis and mounting reports of downed trees

Moderate coastal flooding is ongoing along the tidal Potomac River and Chesapeake Bay and, as the tide builds into this afternoon (high tides midday to midafternoon), major flooding is possible. Both Old Town and Annapolis are reporting flooded streets, according to the National Weather Service.

In Old Town, King Street and Strand Street are closed.

In Annapolis, Main Street (at Compromise Street) Dock Street and surrounding park lots and sidewalks are closed due to standing water.

Meanwhile, the combination of rain and winds gusting up to 30 to 40 mph are causing more trees to fall (Dulles clocked a gust of 40 mph at 10 a.m.). The Weather Service received a report of a tree blown down on the inner loop of the Beltways near exit 31A in Silver Spring (MD-97 Georgia Avenue).

Here are some more pictures of the coastal flooding from earlier:

9:15 a.m. — Turbulent weather developing: downpours with 35 mph gusts moving in, with reports of downed trees

Radar shows a large area of moderate rain with some heavier embedded downpours moving into the immediate metro area from the south. Winds are already quite gusty with Reagan National and Dulles Airports reporting gusts of around 35 mph, with winds sustained around 20 mph.

Expect wind-swept rain to continue and some treefalls are probable; the National Weather Service has received more than a dozen reports of downed trees and wires throughout the region.

Our next update will be in about an hour.

Original article

A powerful storm system, which originated from the record-setting rain event in California and spawned tornadoes in the South, will bring multiple types of hazardous weather to the Washington region into Saturday.

Waves of rain, some heavy, will pass through the entire region Friday, which could cause pockets of flooding near streams and areas of poor drainage. Generally, 1 to 2 inches of rain should fall, with a few areas seeing up to twice that amount.

Winds, meanwhile, will gust to at least 30 mph in most areas — being strongest from midmorning into the afternoon. Along the western shores of the Chesapeake Bay, the gusts could top 50 mph, prompting wind advisories and high-wind warnings. The combination of the heavy rain and high winds is likely to cause scattered power outages.

But perhaps the most notable hazard will be the high water along the shores of the Chesapeake Bay and in the Tidal Potomac River, which could be 2 to 3 feet above normal, flooding unprotected areas.

“One of the biggest tidal flood events of the past 10-20 years (possibly since Hurricane Isabel at some locales), is expected Friday & Saturday,” the National Weather Service tweeted.

Powerful storm system to sock eastern U.S. with gusty downpours, coastal flooding

The rain

Scattered showers will become steadier and heavier as Friday morning wears on. The heaviest rain is likely between midday and late afternoon.

Although much of October was dry, 1 to 3 inches of rain fell Monday night, somewhat increasing the potential for flooding Friday. The Weather Service has issued a flood watch for the immediate D.C. metro area, forecasting 1 to 2 inches of rain with isolated amounts of 2 to 4 inches.

“Heavy amounts of rain will cause creeks and streams to slowly rise, possibly out of their banks as well as the potential for flooding in urban areas,” the Weather Service cautioned.

This is not a high-end flood threat, but those creeks and streams and areas of poor drainage that often flood during heavy rain may flood yet again. Allow for extra time commuting Friday afternoon, and avoid routes near areas that are prone to flooding.

If you encounter a flooded road, do not try to drive through the water. Turn around, don’t drown.

Although significant rainfall should exit by early Friday evening, intermittent showers could continue into Friday night. From the predawn hours Saturday through the day, any lingering showers should be rather spotty.

The wind

In the immediate D.C. area, the predicted peak gusts of between 30 and 40 mph, should not cause too many problems on their own. However, as rain loosens the soil, stronger gusts could trigger some isolated tree-falls and power outages.

The winds could be more hazardous in the counties adjacent to the Chesapeake Bay, i.e., Anne Arundel, Calvert and St. Mary’s. In those areas, gusts topping 50 mph could cause scattered downed trees and utility lines leading to power outages.

Computer models indicate that winds will be strongest between around sunrise and late afternoon Friday before easing. The late-morning and early-afternoon hours, in particular, are times to watch.

Coastal flooding

Water levels began rising along the Tidal Potomac and Chesapeake Bay Thursday, causing mostly moderate coastal flooding. But the high-tide periods between Friday and Saturday morning are of greatest concern, when water levels may rise to historic levels, resulting in 2 to 3 feet of shoreline inundation.

The Weather Service listed potential impacts as “impassable roads, water into low shoreline homes/buildings; flooding docks and marinas.”

Particular points of concern are along the Tidal Potomac, the District’s Southwest Waterfront and Old Town Alexandria, Va.

“The unprotected area on the Southwest Waterfront at the DC Seafood Market is expected to flood,” the Weather Service wrote. “Water is expected to approach parts of the Hains Point Loop Road, but it will likely be closed. Water is expected to approach buildings near King Street and Union Street” in Old Town Alexandria.

Water rises of 2 to 3 feet above normally dry land are anticipated in Annapolis at high tide. The Weather Service wrote that Annapolis City Dock will be engulfed and that floodwaters will affect “numerous roads in Annapolis and on the Naval Academy Campus, along with structures throughout the neighboring area.”

The tide on the Severn River in Annapolis is expected to reach 5 feet around just after midnight Saturday, which would be the third-highest on record there, trailing only the high tides seen during Hurricane Isabel in 2003 and the Chesapeake Bay-Potomac hurricane of 1933.

Similarly, in Old Town Alexandria, the predicted peak height of 5.41 feet around 2 a.m. Saturday would be the third-highest on record, trailing Isabel and a storm in 1936.

As persistent winds from the east and southeast push water against the coast, these coastal zones face a prolonged period of abnormally high tides.

“Surge models continue to indicate a moderate to high impact coastal flood event lasting several tide cycles (more than 48 hrs),” the Weather Service wrote in a technical discussion.

Occurrences of unusually high water levels have been increasing in the Mid-Atlantic region because of sea-level rise associated with climate change. Between 2000 and 2015, the incidence of high-tide flooding doubled from an average of three days per year to six, according to a 2018 NOAA report. Such days are projected to proliferate in the coming decades as the climate continues to warm.

Federal report: High-tide flooding could happen ‘every other day’ by late this century

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