Weather forecast uncertainty lies in the chaotic nature of the atmosphere and in the imperfect representation of the atmosphere in numerical weather forecast models. Instead of making a single prediction of the most likely future weather, a set or ensemble of forecasts are produced to give an indication of the range of possible future states of the atmosphere. Ideally, the verified future atmospheric state should fall within the predicted ensemble spread, and the amount of spread should be related to the uncertainty (error) of the forecast.

Additionally, data are downscaled in order to increase the detail or resolution of the forecast. In this case, downscaling is the process of establishing statistical relationships between the large-scale model-predicted variables and small-scale local variables.

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

The Utah Snow Ensemble is an 82-member ensemble for predicting snow over the contiguous western United States based on the ECMWF ensemble (ENS) and the US National Centers for Environmental Prediction Global Ensemble Forecast System (GEFS), with 51 members coming from the ENS and 31 from the GEFS. The forecasts are provided in 6-h intervals out to 240 hours (10 days). A summary of the data and methods and graphics is provided below.

Shown is the forecast snow for the next 10 days (240 hours) for most of the state of Colorado. The color scales are printed to the left of each panel.

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

The Utah Snow Ensemble is an 82-member ensemble for predicting snow over the contiguous western United States based on the ECMWF ensemble (ENS) and the US National Centers for Environmental Prediction Global Ensemble Forecast System (GEFS), with 51 members coming from the ENS and 31 from the GEFS. The forecasts are provided in 6-h intervals out to 240 hours (10 days). A summary of the data and methods and graphics is provided below.

Shown is the forecast liquid water for the next 10days (240 hours) for most of the state of Colorado. The color scales are printed to the left of each panel.

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

The Utah Snow Ensemble is an 82-member ensemble for predicting snow over the contiguous western United States based on the ECMWF ensemble (ENS) and the US National Centers for Environmental Prediction Global Ensemble Forecast System (GEFS), with 51 members coming from the ENS and 31 from the GEFS. The forecasts are provided in 6-h intervals out to 240 hours (10 days). A summary of the data and methods and graphics is provided below.

Shown is the forecast snow for the next 10 days (240 hours) for most of the state of Colorado. The color scales are printed to the left of each panel.

Plumes refer to a time series of each model run at a specific loaction, in this case the precipitation forecast for the Storm Peak Lab near the top of Mt. Werner. Generally, mid-mountain snowfall at the Steamboat Ski Area is about 3/4 of the summit snowfall.

Times on the bottom axis are in UTC, or Coordinated Universal Time, which is the time at 0 degrees longitude. It used to be referred to as Zulu time, hence the Z designation in the charts, and does not adhere to daylight savings time, so it is 7 hours ahead of MST (0Z refers to 5pm MST the day before and 12Z refers to 5am) and 6 hours ahead of MDT.

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

The Rapid Refresh Forecast System Ensemble is a 6-member ensemble that is under development for future operational use by the National Weather Service. Based on the FV3 dynamical core (i.e., the software that solves the atmospheric equations of motion), it is run at 3-km grid spacing and provides forecasts out to 60 hours. The RRFS Ensemble is projected to go operational in 2024, although there have been a number of issues and challenges identified during testing that may affect that, in particular related to the forecasting of convective storms in the midwest. The RRFS Ensemble has not been carefully evaluated over the western US, so one of the reasons we are producing this product is to evaluate its fidelity for orographic precipitation.

Shown is the average and maximum forecast snow for the next 2.5 days (60 hours) for most of the state of Colorado. The color scales are printed at the bottom of each panel. Snow amounts can be roughly estimated by multiplying the liquid water by 10 or so during warm storms and 20 or so during very cold storms.

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

Short Range Ensemble Forecast: A total of 26 members of the two main short range modeling systems used operationally in the U.S. are used to construct the ensemble.

Shown is the average and maximum forecast liquid water for the next 2.5 days (60 hours) for most of the state of Colorado. The color scales are printed at the bottom of each panel. Snow amounts can be roughly estimated by multiplying the liquid water by 10 or so during warm storms and 20 or so during very cold storms.

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

The Rapid Refresh Forecast System Ensemble is a 6-member ensemble that is under development for future operational use by the National Weather Service. Based on the FV3 dynamical core (i.e., the software that solves the atmospheric equations of motion), it is run at 3-km grid spacing and provides forecasts out to 60 hours. The RRFS Ensemble is projected to go operational in 2024, although there have been a number of issues and challenges identified during testing that may affect that, in particular related to the forecasting of convective storms in the midwest. The RRFS Ensemble has not been carefully evaluated over the western US, so one of the reasons we are producing this product is to evaluate its fidelity for orographic precipitation.

Plumes refer to a time series of each model run at a specific loaction, in this case the precipitation forecast for the Storm Peak Lab near the top of the Steabmoat Ski Resort. Generally, mid-mountain snowfall at the Steamboat Ski Area is about 3/4 of the Storm Peak Lab snowfall, which is often well-represented by the Rabbit Ears SNOTEL.

Times on the bottom axis are in UTC, or Coordinated Universal Time, which is the time at 0 degrees longitude. It used to be referred to as Zulu time, hence the Z designation in the charts, and does not adhere to daylight savings time, so it is 7 hours ahead of MST (0Z refers to 5pm MST the day before and 12Z refers to 5am) and 6 hours ahead of MDT.

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

The Rapid Refresh Forecast System Ensemble is a 6-member ensemble that is under development for future operational use by the National Weather Service. Based on the FV3 dynamical core (i.e., the software that solves the atmospheric equations of motion), it is run at 3-km grid spacing and provides forecasts out to 60 hours. The RRFS Ensemble is projected to go operational in 2024, although there have been a number of issues and challenges identified during testing that may affect that, in particular related to the forecasting of convective storms in the midwest. The RRFS Ensemble has not been carefully evaluated over the western US, so one of the reasons we are producing this product is to evaluate its fidelity for orographic precipitation.

Plumes refer to a time series of each model run at a specific loaction, in this case the precipitation forecast for Steamboat Springs Bob Adams Airport.

Times on the bottom axis are in UTC, or Coordinated Universal Time, which is the time at 0 degrees longitude. It used to be referred to as Zulu time, hence the Z designation in the charts, and does not adhere to daylight savings time, so it is 7 hours ahead of MST (0Z refers to 5pm MST the day before and 12Z refers to 5am) and 6 hours ahead of MDT.

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

Point forecast for the top of the Steamboat Ski Area on Mt Werner from the National Centers for Environmental Prediction (NCEP) North American Mesoscale Forecast System (NAM). Model output available every third hour.

All times local

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.

Point forecast for the top of the Steamboat Ski Area on Mt. Werner from the Colorado Avalanche Information Center

All times local

Meteorologists love to see how the forecast changes between successive model runs, so take advantage of my unique Previous forecast / Next forecast navigation at the bottom of the image. Careful - scales may change between forecasts.