Note:  While we are transitioning our web pages, products marked with an (*) link to product pages on the old system. Products on those pages are up-to-date, but links on those pages may go to old information or may be broken. Thank you for your patience!

About SWinG

Attention: MDL's SREF Winter Guidance (SWinG) is a prototype! Data on these pages may not always be current.

SREF Winter Guidance (SWinG) uses output from the Short Range Ensemble Forecast system (SREF) to produce reliable and accurate probability distributions of weather elements at a set of stations. Unlike traditional Model Output Statistics (MOS), SWinG uses statistical postprocessing methods that work with short samples. The most important of these techniques is a modified form of Bayesian Model Averaging (BMA).

SWinG Station list

Brief guide to SWinG products [PPT file with audio] 

View a more complete description of the BMA Technique [PDF]  *works best with IE or Firefox

The weather elements chosen for SWinG must be readily observed or analyzed daily. This emphasizes upper air parameters (e.g., 850 mb temperature, 1000-850 mb thickness) over sensible weather elements (e.g., chance of snow, chance of freezing rain).


Here is our current list of weather elements:

Weather Element Time Projections
2m Temperature Every 3 hours to 87 hours
850 mb Temperature Every 3 hours to 87 hours
850 mb Height Every 3 hours to 87 hours
1000-500 mb Thickness Every 3 hours to 87 hours
1000-700 mb Thickness Every 3 hours to 87 hours
1000-850 mb Thickness Every 3 hours to 87 hours
850-700 mb Thickness Every 3 hours to 87 hours
Czys Ptype [PDF] Every 3 hours to 87 hours
Energy Ptype [PDF] Every 3 hours to 87 hours
Snow Liquid Ratio [PDF] Every 3 hours to 87 hours


We will continue to expand the list of weather elements in 2013.

Note: The SWinG project is actively using the NWS V-lab (NWS Portal), where users can leave feedback and view additional documentation and case studies

join link

View SWinG Forecast Images and Text

SWinG images are meteograms or "plume diagrams". They show the time evolution of the probability distributions of a number of weather elements for a single station. The black line shows the median of the distribution, and shaded areas show the 10th, 30th, 70th, and 90th percentiles.

View SWinG Images

SWinG text forecasts are whitespace-delimited files that contain forecasts for a single weather element. Each line represents a forecast probability distribution for one station at one time projection. Here is an explanation of the columns:

Column Heading Explanation
1 VALIDTIME The forecast date and time as yyymmddhh
2 STN Station Identifier (stations with # in their identifiers are substitutions.
See our Station List
3-13 CDF05-CDF95 The labeled percentile of the forecast distribution. E.g., if CDF30=1.5 degrees Celsius, then there is a 30 percent chance the temperature will be 1.5 degrees Celcius or less.
14 MEAN The weighted mean of the bias corrected SREF member forecasts
15 SD The standard deviation of the forecast distribution