Precipitation Hazards Web Service from the Weather Prediction Center(WPC) depicts forecasted Precipitation Hazards where there is a probable threat of Excessive Rainfall Outlook (ERO) for the next five days will exceed flash flood guidance(FFG) within 40 kilometers (25 miles) of a location. The web service’s ERO locations are displayed as polygons. These Hazards are provided by the twelve NWS River Forecast Centers (RFCs) whose service areas cover the lower 48 states. WPC uses national Flash Flood Guidance (FFG), whose 1, 3, and 6-hour values represent the amount of rainfall over those short durations which it is estimated would bring rivers and streams up to bankfull conditions. The primary Precipitation hazard is Flash Flooding and WPC provides guidance with the warnings’ use estimates to build these polygons that contain the likelihood that FFG will be exceeded by assessing environmental conditions (e.g. moisture content and steering winds), recognizing weather patterns commonly associated with heavy rainfall, and using a variety of deterministic and ensemble-based numerical model tools that get at both the meteorological and hydrologic factors associated with flash flooding. These Hazard ERO polygons are produced by a highly collaborative product and benefits from the input of meteorologists and hydrologists among the Weather Forecasted Offices, RFCs, and National Water Center. The EROs polygon are rendered based on Excessive Rainfall Risk Categories.

Update Frequency:Every 3 hours

ERO Categories are as follows:

No Area /Label [Probability Less than 5% Chance of Flash Flood] - Flash floods are generally not expected

Marginal (MRGL) – [At least 5% Chance of Flash Flooding]-Possible Isolated flash flood -Localized and primarily affecting places that can experience rapid runoff with heavy rainfall.

Slight (SLGT) [At least 15% Chance of Flash Flooding]- Possible Scattered flash floods that are mainly localized. The most vulnerable are people in urban areas, roads small streams, and washes. Isolates significant flash floods are possible.

Moderate (MDT) [At least 40% Chance of Flash Flooding]- Numerous flash floods are likely- Numerous flash flooding events with significant events are possible. Many streams may flood potentially affecting large rivers.

High (High) [At least 70% Chance of Flash Flooding] - Widespread flash floods are expected Conditions include severe widespread flash flooding. Areas that do not normally experience flash flooding have conditions where lives and property are in greater danger.

Link to graphical web page: https://www.wpc.ncep.noaa.gov/qpf/excessive_rainfall_outlook_ero.php

Link to data download (shp): https://www.wpc.ncep.noaa.gov/qpf/excessive_rainfall_outlook_ero.php

Link to metadata

Questions/Concerns about the service, please contact the DISS GIS team

Time Information:

This service is not time enabled.