Trace amounts of rain fell upstream of the metro area yesterday. Otherwise, the basin received no precipitation over the last 24 hours. The 48-hour forecast indicates a chance of up to 1 inch of rain in the southern Shenandoah area and between 1/2 and 3/4 of an inch across the rest of the basin. The 5-day forecast predicts accumulations of 1/2 an inch across the basin.
Point of Rocks flow has fallen below 2,000 cfs again. Over the last 24 hours, approximately 0.1 to 0.25 inches of rain fell over portions of the basin. The 48-hour forecast predicts up to a 0.25 inch of rain over the basin. The 5-day forecast predicts total accumulations of 0.25 to 0.9 inches of rain over the basin.
As you may have noticed, for several days the flow at Point of Rocks dropped below the threshold of 2,000 cfs (1293 MGD). When this occurs, daily monitoring and reporting of Potomac River flows and withdrawals are conducted by CO-OP per the Drought Operations Manual of the Water Supply Coordination Agreement. Last Friday we asked that CO-OP utilities begin sending us reports of yesterday's demand, and we will be sending out a daily summary of demands and flows.
Daily monitoring is discontinued because Point of Rocks flow has well exceeded the low flow monitoring threshold. Also, the observed precipitation over the past 48-hours has equaled 1 to 6 inches across most locations in the basin, and the forecast includes additional precipitation in the near future. Thank you all for your contributions to the monitoring effort.
The October Water Supply Outlook, which reports on water conditions in the basin, will be published sometime next week when the available data reflects the recent precipitation in the basin.
Over the past 24 hours between 0.5 and 4.0 inches of rain has accumulated across the basin, with the heavier rainfall occurring in the downstream area. The 48-hour forecast indicates a chance of another 2.0 to 8.0 inches of rain. Flow at the Point of Rocks gage remains below the 2,000 cfs threshold for now, but we expect it to continue to rise throughout the day. If the anticipated rain arrives in the upstream portions of the basin we expect to discontinue daily monitoring tomorrow.
The 24-hour observed precipitation shows that a 1/10 to a 1/4 inch of rain fell on some locations in the basin. The weather forecasts gives a chance of showers for this afternoon and a higher chance of rain for Thursday. The 48-hour and 5-day quantitative precipitation forecasts show 1/2 to 3.8 inches of rain possible across the basin.
The weather forecast and operational recommendations remain the same
as this morning.
Daily Flows:
Little Falls gage flow 09/26: 500 MGD (770 cfs)
Little Falls gage flow 09/27: 860 MGD (est., based on most
recently available real time data) (1330 cfs)
Note: Gage flow at Little Falls is measured after water
supply withdrawals.
Point of Rocks flow 09/26: 710 MGD (1100 cfs)
Point of Rocks flow 09/27: 690 MGD (est., based on recently
available real time data) (1070 cfs)
The weather forecast and operational recommendations are unchanged from this morning.
Daily Flows:
Little Falls gage flow 09/25: 500 MGD (770 cfs)
Little Falls gage flow 09/26: 440 MGD (est., based on most recently available real time data) (686 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 09/25: 770 MGD (1190 cfs)
Point of Rocks flow 09/26: 720 MGD (est., based on recently available real time data) (1120 cfs)
There have been no changes to the weather forecast and operational recommendations remain the same.
Daily Flows:
Little Falls gage flow 09/24: 600 MGD (930 cfs)
Little Falls gage flow 09/25: 490 MGD (est., based on most recently available real time data) (759 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 09/24: 790 MGD (1220 cfs)
Point of Rocks flow 09/25: 790 MGD (est., based on recently available real time data) (1220 cfs)
There have been no changes to the weather forecast and operational recommendations remain the same.
Daily Flows:
Little Falls gage flow 09/23: 650 MGD (1010 cfs)
Little Falls gage flow 09/24: 580 MGD (est., based on most recently available real time data) (892 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 09/23: 820 MGD (1270 cfs)
Point of Rocks flow 09/24: 800 MGD (est., based on recently available real time data) (1230 cfs)