The Sully Square plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
Partly cloudy
Mostly cloudy
Mostly sunny
Partly cloudy
Sunny
Mostly sunny
Mostly sunny
81° on Nov. 15, 1993, the hottest reading for this week of the year since 1960. Next is 80° in 1985.
Sully Square’s center stands about 340 ft above sea level. Within three miles the land runs from 260 ft to 460 ft, a difference of 200 ft: rolling country. The highest named summit within 15 miles is Gantt Hill, about 510 ft, 10 miles east.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 47×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Shale, siltstone. Age: Triassic, 202 to 252 million years old. About 6 mi of the line.
Schist. Age: Neoproterozoic to Cambrian, 487 to 1,000 million years old. About 6 mi of the line.
Sandstone. Age: Triassic, 202 to 252 million years old. About 4 mi of the line.
Shale, sandstone, siltstone. Age: Triassic, 202 to 252 million years old. About 2 mi of the line.
Conglomerate. Age: Triassic, 202 to 252 million years old. About 2 mi of the line.
Metagraywacke. Age: Neoproterozoic to Cambrian, 487 to 1,000 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 2 smaller units along the line are not listed.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Sully Square reaches Chesapeake Bay and the Atlantic Ocean by way of Cub Run, Bull Run, the Occoquan and the Potomac: about 130 river miles.
85 miles of the trip are on the Potomac.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Sully Square; river miles along the main stem, rounded.
Sully Square has a humid subtropical climate. Summer afternoons average 88° in July; winter nights fall to about 25° in January. A normal year brings about 21 inches of snow; with the rain, that comes to about 43 inches of water.
On November 14 Sully Square normally reaches 57° and falls to 36°. The record high is 80°, in 1985; the record low 13°, in 1986. The most rain on this date, 1.90 in, fell in 1972.
Normals 1991–2020 and records since 1960 from the Sterling-Dulles Airport Area threaded record (Washington Dulles International Airport, here). NOAA, through RCC-ACIS.
