The Hydrometeorological Prediction Center's (HPC) experimental Alaska Medium Range forecasts are part of a National Centers for Environmental Prediction (NCEP) commitment to providing meteorological support for areas outside of the contiguous U.S. (OCONUS).  The experimental Alaska Medium Range product suite is being developed to mimic that which is currently available for the CONUS.   Differences between the product suites are primarily the result of addressing problems specific to the National Weather Service Alaska Region (e.g., highly varied terrain).

Currently, the experimental Alaska Medium Range product suite consists of:

• Day 4-8 Surface Fronts and Pressures graphics
• Day 4-8 500 hPa Height graphics
• Alaska Medium Range Forecast Discussion
• Day 4-8 Maximum/Minimum Temperature grids
• Day 4-8 12-hour Probability of Precipitation grids
• Day 4-8 derived Dewpoint Temperature, Cloud Cover, Precipitation Type, and Wind Speed/Direction grids

The surface fronts and pressures graphics and 500mb hPa heights are valid at 1200 UTC on forecast days 4-8. Each of the grids will be available downscaled to 5-km horizontal resolution.   Since these products are not yet operational, they may not always update in a timely fashion.

One meteorologist is intended to be dedicated to Alaska Medium Range forecasting each day, and the shift is scheduled from 1300 UTC to 2200 UTC.  The Alaska forecaster utilizes data from recent deterministic and ensemble model output and collaborates with the CONUS Medium Range forecaster before beginning graphical composition.  This collaboration is important because the Alaska Medium Range Fronts and Pressures graphics must be merged with the final CONUS Medium Range Fronts and Pressures graphics for consistency.   Deterministic and ensemble model output available to forecasters at NCEP/HPC include the GFS, Global Ensemble Forecast System (GEFS), Canadian GEM Global, Canadian GEM Ensembles, ECMWF, ECMWF Ensembles, Navy NOGAPS, UKMET, and the North American Ensemble Forecast System (NAEFS).

Graphical forecasts for 500 hPa heights and surface fronts and pressures are generated using blending tools available to HPC forecasters.  Gridded forecasts for maximum/minimum temperature, probability of precipitation, and dewpoints, etc...are also created using blending tools available to HPC meteorologists.  These tools allow the forecaster to blend preferred solutions from any of the aforementioned deterministic and ensemble forecasts.  Generally, the same blends will be used to generate graphics and grids for consistency, but the blend tools do allow forecasters to add a climatology bias to forecasts, which should limit inconsistencies in forecasts with less predictable features.  Consequently, the amount of climatology added is generally a function of forecast confidence and predictability.

The experimental Alaska Medium Range Discussion is intended to complement the graphical products by outlining the model forecast preference, communicating forecast confidence, conveying areas of uncertainty and providing a catalyst for collaboration between HPC and NWS Alaska Region Weather Forecast Offices (WFOs).

The 10th and 90th percentile Maximum/Minimum Temperature and Wind Speed forecast tools are still being developed, but they are expected to use output from the NAEFS to generate a range of meteorologically possible values.  The Alaska forecaster will choose the most likely scenario, while the spread of the NAEFS ensemble will determine the range of possible values for the forecast.   This process will provide users both a sense of confidence from the ensemble members and a range of forecast possibilities, assuming favorable verification during testing.