Extract NWM flow series
extract_nwm(file, comids, variable = "streamflow")
a NetCDF file produced with create_nomads_nc, or create_nomads_ts
a vector of NHD comids to extract
a channel file variable to extract (should be same as the one used to create the file)
a data.frame of comid,dateTime,value
if (FALSE) {
outfile = create_nwm_nc(type = "short_range", dstfile = tempfile(ext = ".nc"))
flows = extract_nwm(outfile, comids = c(101,1001,102900))
}