Below are several items summarizing recent precipitation and stream flow:
- Images showing precipitation in Virginia and other areas of the United States, and stream flow in Virginia, over the seven-day period ending September 11, 2017 (information available as of September 12).
- Flooding overview maps for Virginia and nationwide, as of September 12.
The Virginia Water Resources Research Center thanks the agencies mentioned below for providing precipitation and stream-flow information and images. For the current month’s other weekly reports on stream flow and precipitation, please see the News Grouper posts available at this link: https://vawatercentralnewsgrouper.wordpress.com/?s=Virginia+Precipitation.
For monthly reviews of precipitation, stream flow, and drought, please see the posts available at this link: https://vawatercentralnewsgrouper.wordpress.com/?s=Monthly+Water+Status.
For more information on current and historical surface-water and groundwater conditions in Virginia, please see the U.S. Geological Survey (USGS) Virginia Science Center’s Web site, http://va.water.usgs.gov/.
The following two color-coded maps show southeastern U.S. precipitation amounts (top map) and the percent of normal precipitation compared to normal for this period of the year (bottom map) over the seven-day period ending September 12, 2017. As of that date, these data were provisional (needing to be verified for accuracy and subject to possible revision). The maps were accessed from the National Oceanic and Atmospheric Administration’s (NOAA) Southeast Regional Climate Center, located at the University of North Carolina in Chapel Hill; online at http://www.sercc.com/climateinfo/precip_maps.
Another source of precipitation data is the National Weather Service’s Advanced Hydrologic Prediction Service, online at http://water.weather.gov/precip/. The site provides maps showing precipitation nationwide or by state for specific days, months, or years. The site also has the capability to show county boundaries, and other map layers available include river flood forecasts and current flood/severe weather warnings. Shown below is the continental U.S. 7-day precipitation map as of 8 a.m. EDT on 9/12/17. The impact of Hurricane Irma on the southeastern United States is clear from this graph. Please note that UTC, the time shown on the maps at the site, is four hours ahead of Eastern Daylight Time and five hours ahead of Eastern Standard Time.
Seven-day-average Virginia stream flows at gaging stations as of September 11, 2017 are indicated in the map below, from the U.S. Geological Survey (USGS) WaterWatch for Virginia, accessed online at http://waterwatch.usgs.gov/index.php?m=pa07d&r=va&w=map. The map’s color-coded dots compare the previous week’s average stream flows to the normal flow levels for that week over the historical record for each gaging station. The color codes/percentile classes used by USGS are as shown in the chart following the map. Note: Additional gaging stations (such as for reservoirs or for inactive sites) are shown on maps available at the USGS’ National Water Information System Mapper, online at https://maps.waterdata.usgs.gov/mapper/index.html.
As of about 2:15 p.m. EDT on September 12, 2017, 9 stream-gaging stations in or near Virginia were either experiencing flooding or near flood stage, according to the National Weather Service’s Advanced Hydrologic Prediction Service’s (AHPS) map of stream and river levels relative to flood stage (color-coded) for Virginia and nearby areas. The AHPS map for Virginia is shown below, along with the nationwide map as of the same time. The maps are available online at http://water.weather.gov/ahps/forecasts.php; at that site, one can select Virginia or any other state of interest.