Widely scattered locations across the upper basin received trace amounts of rain (up to 0.1 inches) over the past 24 hours. Precipitation totaling 0.01 to 0.25 inches is expected in the upper basin over the next three days. Higher amounts of half an inch are also possible in scattered locations in Pennsylvania and along the Virginia-West Virginia border. Flow at Point of Rocks is holding steady above 1500 cfs.
The Potomac basin upstream of Little Falls dam received no significant precipitation over the past 24 hours. The forecast for the next 3 days is 0.01 to 0.10 inches throughout much of the basin, though up to 0.50 inches is expected in the southeastern portion of the basin, including in the Washington, DC, metropolitan area.
Less than a quarter inch of rain fell in portions of the upper basin over the past 24 hours. Scattered locations with higher precipitation amounts of up to one inch also occurred. Trace amounts, up to 0.1 inches, of rain are expected over the next three days. Flows remain steady above 1,500 cfs.
River flow continues to slowly decline. There was no appreciable precipitation in the Potomac basin over the past 24 hours. An average basin-wide accumulation of less than 1/10 of an inch is expected over the next three days.
No appreciable rain fell in the basin over the past 24 hours. A trace amount, up to 0.1 inches, is expected over the next three days.
Daily flows:
Little Falls gage flow 2021-08-03: 1286 MGD (2390 cfs)
Little Falls gage flow 2021-08-04: 1195 MGD (est., based on recently available real time data) (2220 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2021-08-03: 904 MGD (1680 cfs)
Point of Rocks flow 2021-08-04: 893 MGD (est., based on recently available real time data) (1660 cfs)
According to MARFC, no precipitation fell in the basin over the last 24 hours. A trace amount, up to 0.1 inches, is expected over the next three days.
Note a correction to Washington Aqueduct's reported 7/31 withdrawal. The reported number was 121 MGD while the correct number was 132 MGD.
About 0.1 inches of rain fell in the basin over the past 24 hours; a trace to 0.25 inches is expected over the next three days.
No appreciable rain fell in the basin over the past 24 hours; a trace to 0.25 inches is expected over the next three days.
Recent basin-wide average precipitation (above Little Falls):
(based on CO-OP's Low Flow Forecast System analysis of Middle Atlantic River Forecast Center (MARFC) gridded multi-sensor precipitation estimates)
Yesterday's area-weighted average basin precipitation: 0 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.31 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.45 (inches)
Flow in the river has held fairly steady over the past several days, at around 1800 cfs at Point of Rocks, and according to National Weather Service forecasts this will continue to be the case for the upcoming week. No appreciable precipitation fell over the basin during the past 24 hours. The Washington metropolitan area may receive up to an inch of rain over the next 3 days, but much less rain is expected west of the metro area.
The basin received almost a ¼ inch of rain over the last 24 hours. Little rain is expected in the portion of the watershed above Little Falls over the next three days. According to Middle Atlantic River Forecast Center ensemble flow forecasts, flow at Point of Rocks is expected to remain above 1800 cfs over the weekend.
Though flow conditions are not yet of great concern, we intend to continue daily monitoring reports over the weekend, and would appreciate it if you can continue sending withdrawal and reservoir storage data.