To whom it may concern,

At OTX, we've observed a consistent wet bias in the URMA observation grid, particularly with minimum relative humidity (minRH) values often appearing 5% to 15% too high when copied into the forecast grid.

This inaccuracy significantly impacts our fire weather forecasts (FWF) and spot forecasts, as trends are populated from these observations. We frequently have to make manual edits to correct errors in the trends, some of which show a trend in the opposite direction than reality. These trends are read over the radio during fire season and significantly affect our fire partners.

According to our iMETs, referencing S290/S390 courses, RAWS/ASOS sites being off by 5% or more is considered unacceptable. We are hoping for a resolution to this issue or guidance on any adjustments we might be missing locally.

We have compiled examples from April 27th through May 10th, including tables and images, which detail these discrepancies. Please refer to the attached Google Slides for more information. We are also happy to provide further examples upon request.

https://docs.google.com/presentation/d/10U7RblAe3VPOIcuyEvwhuv9__-hgkASaztSSollPNCs/edit?slide=id.g33d6df8f36c_0_61#slide=id.g33d6df8f36c_0_61

Thanks for any help you can provide!