Friday, April 8, 2022

Anchorage Ski Outlook - How to Forecast

1 Minute
5 Minutes
Use Meteoblue Multimodel to see differences in magnitude and timing between models for sun, precip, and temp. For wind, different models have different resolution - think number of pixels in a picture - resolution affects wind forecast, so just look for relative windiness over a week. Confidence in your forecast will be higher if the different models agree. Check back on Meteoblue every day to see if the models are consistently forecasting the same weather - if the forecast is different each time you check then the confidence in your forecast will decrease.
Use the Southcentral Alaska Mountain Forecast and the NWS Point Forecast for the Rain/Snow line - they are imperfect products, but so is rain line forecasting.
15 Minutes
  • Short Term Forecast Southcentral AK - most useful, provides specific weather.
  • Model Discussion - usually useful, informs confidence in your forecast.
  • Long Term Forecast - sometimes useful, provides possible trends.
  • Analysis and Upper Levels, Marine Gulf of AK - details and learning opportunities.
  • New Snow -  Use to figure out what area is favored. Hatcher Pass, Anchorage Front Range, and Turnagain Arm storms are better captured by high resolution models (NAM & ECMWF). Note, Windy uses a 10X conversion from precip to snow, with cold storms, the Snow/Water ratio will be 15X or higher.
  • Winds @ 3000 ft - Surface winds. These require high res, so NAM/HRRR are best, then ICON and ECMWF, with GFS the worst.
  • Winds @ 250 hPa - Jet stream elevation - the weather conveyor belt. When it overruns us from the SE it brings precip to western Prince William Sound mountains and the Tordillos/Neacolas. As it rotates and overruns to the SW it favors precip for Hatcher, Anchorage Front Range, Thompson Pass, and the Central Alaska Range. Look to see if the jet stream is coming from as far south as Hawaii for warm Pineapple Express storms. From the N it brings cold and often outflow winds.
Long Term - Should I do a Fly-In Trip???
  • Windy's 10 Day ECMWF and GFS Forecasts - Do the two models agree? Is the forecast changing each time you pull it up? For higher confidence in your forecast look for agreement between the two models and between runs of each model.
  • NWS Forecast Discussion (referenced above) - This product is produced twice daily. Read the long term forecast. Does each new forecast discussion say generally the same thing or it changing? Look for the terms "confidence", "agreement" and "differences" throughout the forecast discussion - this will let you how much the Weather Service is trusting the models.
  • Meteoblue GFS Ensemble and ECMWF Meteogram - Farther into the future the model spread will generally grow. The bigger spreads there are for temp, precip, and wind, the less confidence you have in your forecast and the more prepared you need to be to shovel and hunker down!
And as always - beware of falling snow!!!

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