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John Forsythe of CIRA presented a virtual talk at the spring training seminar for the National Weather Service (NWS) Juneau, Alaska Weather Forecast Office (WFO) titled ”Experimental Layer Precipitable Water Transport and Percentile Products”. WFO Juneau’s area of responsibility is over 150,000 square miles, including the Panhandle and the eastern Gulf of Alaska. Juneau is responsible for monitoring and forecasting a wide variety of hazards, including for ships at sea, commercial and civil aviation including complex mountainous terrain, and inland flood and landslide threats. CIRA developed and transitioned to NOAA operations in 2024 a satellite-derived product called Advected Layer Precipitable Water (ALPW), which allows forecasters to see the flow of moisture at different layers globally, including the data sparse oceans. This lets forecasters see the “plumbing” of the atmosphere – how much and where pipelines of water vapor are flowing. Two new experimental products are being evaluated by CIRA’s NWS partners, including the Juneau WFO. These are Layer Vapor Transport and a Percentile Ranking of ALPW. Both provide forecasters a measure of the extremity of a flood event, in advance of when the rain starts falling. Forecasters provided positive comments and feedback on both products, which CIRA produces hourly around the clock. An example of the Layer Vapor Transport for the lowest layer of the atmosphere for an atmospheric river approaching SE Alaska is shown in the Figure below. (POC: J. Forsythe, CIRA, John.Forsythe@colostate.edu) Funding: JPSS PGRR and NOAA CPO.