Graphical Forecasts
Flash Flood Potential Forecast
These graphics are designed to provide guidance information on the potential for, and areal coverage of, significant flash
flooding during the next three days over the area for which NWS Las Vegas has forecast responsibility. The index ratings are based on forecasts of precipitable water and mean winds in the 700-400 mb layer, conditional upon the development of thunderstorms. There is no explicit probabilistic information, although any threat area occurring within a zone where the probability of precipitation is forecast to be less than 30% is constrained to a low risk rating. Information on interpreting index ratings can be found at the bottom of this page.
Dry Lightning Potential Index
These graphics are designed to provide guidance information on the potential for, and areal coverage of, Red Flag Fire Weather conditions associated with "dry lightning", i.e., convective events in which the humidity of the lower boundary layer is dry enough so as to preclude the development of significant precipitation, resulting in a heightened potential for lightning generated fires. Graphics for the "Day 1" through "Day 3" forecast periods are generated twice daily over the area for which NWS Las Vegas has forecast responsibility. The index ratings are based on forecasts of afternoon boundary layer relative humidity and static stability as implied by the Lifted Index. Qualifying factors such as fuel type, fuel moisture content, integrated CAPE, large scale convective triggering mechanisms, boundary interactions and other mesoscale circulations are not considered in the creation of the Dry Lightning Potential Index (DLPI) product. It simply provides a quick visual reference to information regarding synoptic scale meteorological conditions which "might" signal the development of dry lightning conditions, along with an implied probabilistic factor.
Red Flag Potential Index
These graphics are products designed to provide guidance information on the potential for, and areal coverage of, Red Flag Fire Weather conditions developing during the "Day 2" through "Day 4" forecast periods (i.e., tomorrow and the next two days) over the area for which NWS Las Vegas has forecast responsibility. The index ratings are based on forecasts of afternoon boundary layer relative humidity and mean 20-foot, 10-minute average winds. It is important to understand that the three states for which WFO Las Vegas provides Fire Weather support each define the threshold criteria for triggering a Fire Weather Watch or Red Flag Warning differently. Qualifying factors such as fuel moisture content, minimum duration requirements of the mean wind threshold, or the potential for "dry lightning" are not considered in the creation of the Red Flag Potential Index (RFPI) product. It simply provides a source of quick reference, visual information regarding the basic meteorological conditions which "might" signal the development of local Red Flag conditions.
24-hr Probability of 0.10 inch of rainfall
These graphics are designed to provide guidance information on the potential for, and areal coverage of, significant rainfall over the area for which NWS Las Vegas has forecast responsibility. The probabilities are based on the Short-Range Ensemble Forecasts (SREF)
24-hr Probability of 0.25 inch of rainfall
These graphics are designed to provide guidance information on the potential for, and areal coverage of, significant rainfall over the area for which NWS Las Vegas has forecast responsibility. The probabilities are based on the Short-Range Ensemble Forecasts (SREF)
|
www.weather.gov 
