Precipitation Onset Most likely onset time of winter precipitation (snow, sleet, freezing rain). Rain is not included here. This information is provided when a Winter Storm Warning or Winter Weather Advisory is issued for expected snow or ice accumulation; typically 6 to 24 hours in advance. Because this is an experimental product, it may not update in a timely fashion. Winter Storm Severity Index (WSSI) The purpose of this experimental Winter Storm Severity Index (WSSI) is to provide NWS partners and the general public with an indication of the level of winter precipitation (snow and ice) severity and its potential related societal impacts. The WSSI does not depict official warnings, and should always be used in context with official NWS forecasts and warnings. Because this is an experimental product, it may not update in a timely fashion. Always check the creation and valid times. The purpose of this experimental Winter Storm Severity Index (WSSI) is to provide NWS partners and the general public with an indication of the level of winter precipitation (snow and ice) severity and its potential related societal impacts. The WSSI does not depict official warnings, and should always be used in context with official NWS forecasts and warnings. Because this is an experimental product, it may not update in a timely fashion. Always check the creation and valid times. For more information, please refer to the following links: Product/Service Description Document and WSSI Users Guide. Please provide us your feedback here. NDFD Graphic Forecast Displays The NWS NDFD graphic products are derived from a prescribed set of data contained within the NDFD. These graphics are representations of the official NWS digital forecast. The graphics are created on national and regional scales and will follow a standardized format prescribed by the NWS to best meet the needs of its users Low Tracks Graphic The graphic depicts the forecast location of significant surface lows impacting the 48 contiguous United States in 12 hour increments out to 72 hours into the future. The low position and track forecast by NCEP WPC meteorologist is in white. Each low position is accompanied by a lead time (Eastern Time). The circles around each low represents a 75% probability the observed low will be located with the circle. Note: The probability is derived using previous season's verification data. For reference, existing surface lows are depicted with a red marker without yellow circles. Reported The graphic contains a plot of the latest snowfall reports from the current or most recent past event. As snow and/or ice reports come into the NWS (you can email reports to The graphic contains a plot of the latest snowfall reports from the current or most recent past event. As snow and/or ice reports come into the NWS (you can email reports to phi.skywarn@noaa.gov or Tweet to @NWS_MountHolly), we will pass them on here. With the map linked here, and the supporting reports below it, you can keep tabs on how much has fallen.