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000 NOUS41 KBOX 311426 PNSBOX CTZ002-MAZ011-311830- Public Information Statement National Weather Service Taunton MA 1026 AM EDT WED AUG 31 2016 Service Change Notice To: Subscribers: -Family of Services -NOAA Weather Wire Service -Emergency Managers Weather Information Network -Other NWS Partners...users and employees From: Robert M Thompson, Meteorologist-In-Charge Weather Forecast Office Taunton MA Subject: Changes in gage reporting and Flood Categories for stream gage at Thompsonville on the Connecticut River Effective at 1600 Coordinated Universal Time on Wednesday October 5 2016, the National Weather Service in Taunton MA announces an update to gage reporting and flood categories for the Advanced Hydrologic Prediction Service (AHPS) site Connecticut River at Thompsonville, CT. Starting on Wednesday October 5 part of a datum conversion...river stage observations displayed by the NWS for the Thompsonville gage will read exactly 10.00 feet higher they would have been under the old datum. This change is being made to allow NWS Taunton to display river stage data consistent with those values displayed by the river gage owner and operator, the United States Geological Survey (USGS). Past river stage data for the Connecticut River at Thompsonville were displayed by the NWS using the gage zero elevation (datum) of 38.48 feet NGVD29. However, for the Thompsonville gage the USGS utilizes a datum of 27.75 feet NAVD88, which corresponds to 28.48 feet NGVD29. This discrepancy resulted in NWS displaying river stage data with a numerical value exactly 10 feet lower than data displayed by the United States Geological Survey (USGS). Beginning at 1600 Coordinated Universal Time (12 Noon EDT) Wednesday October 5th, River Stage Data displayed by the NWS for the Connecticut River at Thompsonville will utilize the same gage zero elevation (datum) as that used by the USGS. For NWS web pages and other resources, this will result in a numerical change in river stage data by +10.00 feet. With this change, NWS Taunton plans to update Flood Stage, Flood Categories and Impact Statements for the Thompsonville Forecast Point to also reflect the USGS datum. While the new Flood Categories have higher numerical values, they are not a consequence of higher flood levels. The updated Flood Categories are as follows: 1. New Flood Stage is 15 feet. Previous Flood Stage was 5 feet. 2. New Moderate Flood Stage is 17 feet. Previous Moderate Flood Stage was 7 feet. 3. New Major Flood Stage is 19 feet. Previous Major Flood Stage was 9 feet. Daily River Stage forecasts will continue to be available for the Connecticut River at Thompsonville via the web site When issued, River Flood Warnings and Flood Statements for this location will continue to be available via various means, including NOAA All-Hazards Radio and on the web via and Observations and forecasts for Connecticut River at Thompsonville serve the north central Connecticut communities of Suffield, Enfield, East Windsor, Windsor, Windsor Locks, and South Windsor. Please direct any questions or comments on this change to: Nicole M. Belk Senior Service Hydrologist National Weather Service Forecast Office 445 Myles Standish Blvd. Taunton MA 02780 E-mail: $$ For the latest updates...please visit our webpage at You can follow us on Facebook at You can follow us on Twitter at @NWSBoston is the U.S. government's official web portal to all federal, state and local government web resources and services.