I was able to reproduce the error with the current version of xarray and then have it work with the new version. Here is what I did:

Make new environment conda create -n test_xarray xarray netcdf4 dask

Check version ``` (test_xarray) kthyng@adams ~ % conda list xarray

packages in environment at /Users/kthyng/miniconda3/envs/test_xarray:

Name Version Build Channel

xarray 2023.3.0 pyhd8ed1ab_0 conda-forge ```

In python: import xarray as xr urls = ["https://opendap.co-ops.nos.noaa.gov/thredds/dodsC/NOAA/WCOFS/MODELS/2023/03/31/nos.wcofs.2ds.n001.20230331.t03z.nc", "https://opendap.co-ops.nos.noaa.gov/thredds/dodsC/NOAA/WCOFS/MODELS/2023/03/31/nos.wcofs.2ds.n002.20230331.t03z.nc"] xr.open_mfdataset(urls) returns the following the first time xr.open_mfdataset(urls) is run but the second time it runs fine. OSError: [Errno -70] NetCDF: DAP server error: 'https://opendap.co-ops.nos.noaa.gov/thredds/dodsC/NOAA/WCOFS/MODELS/2023/03/31/nos.wcofs.2ds.n002.20230331.t03z.nc'

Next I used the PR version of xarray and reran the code above and then it was able to read in ok on the first try.

Note: after a week or so those files won't work and will have to be updated with something more current but the pattern to use is clear from the file names.