The District dodged the bullet with Hurricane Florence on Friday, as the storm made landfall about 350 miles to the south in the Carolinas. The outer periphery of its circulation has sent moderate breezes and very spotty showers through the area.
But the storm may not be done with us: delayed but not denied. There is some chance it brings a period of rain and wind Monday into Tuesday, although the worst may pass to our west and north, which is the somewhat more likely scenario.
If we see significant rainfall, which is possible but not probable, there will be a risk of flooding because we’ve had so much rain over the past several months. Should gusty winds materialize as well, trees may fall, since they are not well rooted in the saturated ground.
The evolution of two areas of high pressure, which will hand off control in steering the storm, will determine how much rain we see.
Through Saturday, Florence will be gently nudged by an area of high pressure toward the southwest, over South Carolina. But Sunday, as that high pressure cell scoots off to the east, the former hurricane will turn north, passing through western North Carolina.
On Monday or Tuesday, as the storm moves north through West Virginia, a new high pressure cell building in from the west will try to push the storm to the east. That eastward turn will play the deciding role in how significantly Florence’s remnants will affect us.
Here are the two most likely scenarios:
Scenario 1: The former hurricane passes us to our west and north. Some showers/storms. (55 percent)
In this scenario, the storm center would track through West Virginia or even the Ohio Valley and not turn back to the east until Pennsylvania or New York. It would draw plenty of moisture north through our region, resulting in showers and storms Monday and Tuesday, which could be locally heavy. But we would miss the solid slug of heavy rain and wind associated with Florence’s remnant circulation.
Because of the added spin in the atmosphere, we would have to monitor the potential for brief tornadoes embedded within any thunderstorms.
Rainfall potential: Generally less than an inch, but locally higher amounts possible.
The old and new versions of the American model, the Britain UK Met model, the Canadian model and several hurricane forecasting models support this scenario.
Scenario 2: The former hurricane passes close to us. Substantial rain, gusty winds. (45 percent)
In this scenario, the storm center would track through West Virginia and then turn east between Northern Virginia and southern Pennsylvania. We would have a period of heavy rain and storms Monday into Tuesday, which could result in areas of flooding.
As in Scenario 1, we’d need to monitor the potential for tornadoes.
Because of the likelihood of heavy rainfall (3 to 6 inches or so) in the mountains to our west, we would have to monitor the possibility of Potomac River flooding as that water flows downstream.
In addition, we could see winds gust over 30 mph, which, given the wet ground, could lead to downed trees and some power outages.
Rainfall potential: 2 to 4 inches, highest amounts likely north and west of Washington.
The European model supports this scenario.
The forecast will evolve over the weekend, so stay tuned for updates.