Moisture from tropics to feed D.C. rainmaker
A general 1-4" of rain likely for metro region
By the time tropical storm Nicole nears the mid-Atlantic coast, it will have transitioned into an entirely different kind of weather-maker more closely resembling a 'Noreaster than a tropical storm. Though the track of Nicole itself is now forecast to pass mainly east of Washington, its deep plume of moisture will be feeding a new low pressure system riding up a front draped across the mid-Atlantic. The end result will be generous rainfall amounts with localized flooding.
RAINFALL MAP AND TIMELINE
When will conditions be the worst? The heaviest rain is anticipated late tonight and early tomorrow morning. Allow plenty of extra time for the a.m. commute.
When will it end? Per the timeline above, rain will start winding down in the early afternoon in the southwest suburbs (Prince William and Fauquier counties) and probably mid-to-late afternoon in the northeast suburbs (PG and Anne Arundel counties)
Will this be as bad as Isabel with downed trees and power lines? No way. No how. Though winds may be quite gusty at the Md./De./Va. beaches, winds in the immediate metro region will probably only be on the order of 10-20 mph (with some higher gusts possible during heavy rain bands). Widespread power outages are not anticipated locally. Some of the eastern suburbs, however, adjacent to the Chesapeake Bay could see gusts of 30-50 mph - perhaps enough to cause some isolated outages.
Keep reading for more FAQs
Does the drought mean less chance of flooding? Not entirely. The answer is yes for areas that only see around 1 to 2 inches. The ground is dry enough that it can probably handle that much unless it falls within a very short period of time like 1 to 3 hours. But if the potential for higher storm totals (around 3-4" or more) verifies, then flooding is a legitimate concern.
When there's enough rain over a short enough period of time, flooding can occur no matter how dry the ground is. Computer models indicate (through what's called Flash Flood Guidance) that given the current soil moisture conditions, flash flooding would be possible for areas that receive around 3-4 inches over a 6-12 hour period.
I have a flight tomorrow. Will there be delays? Yes...there will likely be flight delays, particularly in the morning due to the potential for heavy rain and low visibilities. Also, this storm will impact much of the East Coast, so delays at other airports will have ripple effects.
Will there be flooding along the tidal Potomac? There is a coastal flood watch for the potential for minor flooding from tides two to three feet above average late Thursday and Thursday night. Flooding along the lines of what was seen during Isabel or anything close to that is not expected.
What will impacts at the Va./Md./De. beaches be like? Heavy rain and gusty winds are likely, starting tonight in Va., and extending northward towards Md. and De. into tomorrow. Sustained winds of 25-35 mph are possible (higher gusts) and around 2-4" of rain. A high surf advisory has been issued with seas of eight to 13 feet possible. Minor to moderate coastal flooding is possible, as described by the National Weather Service in Wakefield, Va.:
[FOR TIDAL FLOODING] WE WILL BE KEYING IN ON THE EARLY AFTERNOON HIGH TIDE CYCLE ON THURSDAY. WITH GALE FORCE ONSHORE WINDS A DISTINCT POSSIBILITY, THE GREATEST TIDAL DEPARTURES COULD OCCUR AT THAT TIME. THIS COULD PRODUCE TIDAL FLOODING. MINOR LOOKS ALMOST A LOCK. MODERATE A POSSIBILITY.
How confident are you in your forecast? Except for a few isolated locations, the storm that came through earlier this week failed to produce the predicted amounts of precipitation, which ranged from 1-3" here at CWG to higher amounts (such as the National Weather Service's 2-4") from other outlets. As we explained in a post-mortem assessment, the tracking of that storm's low-pressure center too far west of the region subjected the metro area to the mercy of showery, hit-or-miss type precipitation, which for most locales turned out to be more miss than hit.
The chances of this latest storm fizzling appear to be lower as its low-pressure center is expected to track closer to the area, giving us a better chance at seeing a solid area of rain over the area for an extended stretch of time. But, while we're fairly confident we'll see significant rains near or over 1 inch, confidence is lower as to whether and where we'll see higher totals on the order of 2-4" or more.
(CWG's Dan Stillman contributed to this post)
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