I apologize for my incorrect response previously. Not only does the NOAA have this data, but it is free, readily available AND goes up to the 1,000-year event! This is news to me.
According to page 9-535 of the Pennsylvania Stormwater
Best Management Practices
Manual
DRAFT - JANUARY 2005
9.5 Precipitation Data for Stormwater Calculations
In 2004 the National Weather Service’s Hydrometeorological Design Studies Center published updated
precipitation estimates for much of the United States, including Pennsylvania. NOAA Atlas 14
supercedes previous precipitation estimates such as Technical Memorandum NWS Hydro 35 and
Technical Papers 40 and 49 (TP-40 and TP-49) because the updates are based on more recent and
expanded data, current statistical techniques, and enhanced spatial interpolation and mapping
procedures. (Bonnin et al., 2003 and NWS, 2004) The “Precipitation-Frequency Atlas of the United
States,” NOAA Atlas 14, provides estimates of 2-year through 1000-year storm events for durations
ranging from 5 minutes to 60 days as shown for Harrisburg in Table 9-2 (available online at http://
hdsc.nws.noaa.gov/hdsc/pfds/). Users can select precipitation estimates for Pennsylvania from over
300 observation sites, by entering latitude/longitude coordinates, or by clicking on an interactive map
on the Precipitation Frequency Data Server. These new rainfall estimates should be utilized for all
applicable stormwater calculations.
Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve