Public Information Statement
Issued by NWS Boston, MA

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NOUS41 KBOX 311426

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


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