The excellent (free for Mac and PC) navigation app qtVlm has just added a new optional feature that is free for testing until May 15, 2026—after which it becomes a subscription option. Namely they have added an internal GRIB server that now includes the Operational Forecast System (OFC) model for tide and current forecasts, as well as other models.
This means we are no longer limited to the NOAA harmonic predictions of the currents at spot locations, at just a few specific times, but now we have currents at all locations at all times. Plus the OFS model takes into account local wind and pressure as well as river run off, which makes the forecasts more accurate than the harmonic predictions, which do not account for local environmental conditions. (We still need to use the harmonics for specific data at narrow passes where NOAA has metered stations.)
The OFS updated four times a day, with forecasts every hour out to 2 days in most cases, but 3 days in the Pacific NW, which is covered by Salish Sea and Columbia River region (SSC-OFS). This region takes us to the north end of Vancouver Island, where we would switch to the West Coast region (WC-OFS) — but the Canadian harmonic data would still be valuable along the Canadian waters of the Inside Passage.
Likewise, Randy Washburne's book Southeast Alaska Current Atlas remains a leading reference for those waters.
For all of Swiftsure and for any racing in Puget Sound or the San Juans, the OFS SSC data are certainly the most important source, which now can be loaded with a button click into qtVlm, which also has state of the art presentation of NOAA charts.
We can now, for example, add the OFS currents to the HRRR winds and do realistic optimum sailboat routing on inland waters. The new qtVlm GRIB server lets you load both of these at once into one of three Grib slots.
OFS currents are described in detail in Modern Marine Weather, 4th ed.
To learn how we use qtVlm in our online training courses, see this note on Getting Started with qtVlm. The Training Mode discussed there expedites learning qtVlm that has so many features, plus it adds charts, harmonics, and other resources. qtVlm is among the top of the line in weather analysis and routing, and it is in fact the top of the line in electronic navigational chart (ENC) presentation.
Here is a short video showing how to access these OFS current data, which starts with downloading and installing the latest version: https://www.meltemus.com/index.php/en/download (which you can do from the Getting Started page, with video examples.)
Once the free intro period is over (May 15, 2026), the main app remains free, but the convenient GRIB service will be come a subscription add-on.
