The NOAA winter forecast is available on their website at NOAA.gov. On the site, you can find the complete nontechnical forecast within the current U.S. Winter Outlook.
The NOAA winter forecast is issued once each month, around the middle of the month at 8:30am EST. The forecast is based on the analysis of numerous factors of the land, ocean and atmosphere.
One of the most influential factors on the winter forecast is the presence or absence of an El Nino effect. The presence of El Nino produces winters that are warmer and drier than usual, translating into lower snowfall totals for the Northern U.S.