NOUS41 KWBC 011345
PNSWSH

Service Change Notice 26-36
National Weather Service Headquarters Silver Spring MD
945 AM EDT Wed Apr 1 2026

To:	 Subscribers:
	 -NOAA Weather Wire Service
	 -Emergency Managers Weather Information Network
	 -NOAAPort
	 Other NWS Partners and Employees

From:	 Nicole Kinsman
	 Deputy Director, Alaska Region

Subject: Change to Water Level Datum Displayed on the National
Water Prediction Service (NWPS) Webpage at Select Alaska Region
Sites on May 1, 2026

National Weather Service (NWS) Alaska Region Weather Forecast
Offices (WFOs) in Anchorage and Fairbanks, in coordination with
the Alaska–Pacific River Forecast Center (APRFC), will change
the coastal water level and flood stage reference datum
displayed on the National Water Prediction Service (NWPS)
webpage (https://water.noaa.gov/) for fourteen sites in western
and northern Alaska from Mean Lower Low Water (MLLW) to Mean
Higher High Water (MHHW) on or about May 1, 2026.

The fourteen sites changing from MLLW to MHHW are listed below:

Naknek River Tide Gauge (NNKA2)
Dillingham Bay Tide Gauge (DBHA2)
Kwigillingok Tide Gauge (KWGA2)
Kipnuk Tide Gauge (KIPA2)
Tununak Tide Gauge (TNUA2)
St Michael Bay Tide Gauge (SMBA2)
Norton Sound Tide Gauge at Unalakleet (ULRA2)
Bering Sea at Shaktoolik (SHTA2)
Norton Sound Tide Gauge at Nome (NMTA2)
Deering Tide Gauge (DRTA2)
Kotzebue Sound Tide Gauge at Kotzebue (KZTA2)
Red Dog Dock Tide Gauge at Red Dog Mine (RDDA2)
Kivalina Tide Gauge (KVTA2)
Prudhoe Bay Tide Gauge (PRDA2)

Any new gages in western or northern Alaska north of Naknek will
be posted in MHHW datum.

This change will not require action by partners or customers.
The most noticeable change will be new flood stage level
references as these values are converted from MLLW to MHHW.

These sites have been selected to change datums to communicate
impacts from coastal flooding.	Providing the water level data
relative to MHHW supports the NWS Alaska Region goal to provide
consistent use of the MHHW datum reference in coastal flooding
products and decision support services to partners and the
public.  For mariner support, coastal data in MLLW can still be
found at NOAA Ocean Service’s page:
https://tidesandcurrents.noaa.gov/

If you have questions or comments please contact:

Rebecca Heim
Marine Program Manager
NWS Alaska Region Headquarters
Anchorage, AK
Rebecca.Heim@noaa.gov

National Service Change Notices are online at:

https://www.weather.gov/notification/