About the Alaska Medium Range Forecast
About These Products
|Day 4-8 500 hPa Height Graphics
|Day 4-8 Fronts and Pressure Graphics
|Day 4-8 Max/Min Temps and Probability of Precipitation Grids
|Alaska Medium Range Discussion
The Weather Prediction Center's (WPC) 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 Alaska Medium Range product suite has
been 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).
The 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 are available downscaled to 5-km horizontal resolution.
One meteorologist is dedicated to Alaska Medium Range forecasting each day, and the shift
is scheduled from 1130 UTC to 2030 UTC. The first part of the shift is dedicated to producing
the CONUS medium range grids (min/max temperatures, PoPs, etc.). 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/WPC include the GFS,
Global Ensemble Forecast System (GEFS), Canadian GEM Global, Canadian GEM Ensembles, ECMWF,
ECMWF Ensembles, Navy NAVGEM, 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 WPC forecasters. Gridded forecasts for maximum/minimum temperature,
probability of precipitation, and dewpoints, etc. are also created using blending tools available
to WPC 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 Alaska Medium Range Discussion complements the graphical products by
outlining the model forecast preference, communicating forecast confidence, conveying areas of
uncertainty and providing a catalyst for collaboration between WPC and NWS Alaska Region Weather
Forecast Offices (WFOs).