Accurate prediction of Cloud-to-Ground (CG) lightning is vital to the protection of life and property. Unfortunately, the first, and sometimes only, lightning strike of a thunderstorm can result in personal injury or death. Intense to severe lightning storms (i.e., those producing extremely large numbers of cloud-to-ground lightning flashes) pose a threat to electric utilities and forested areas, as well as many other public and private concerns. Predicting storms with high numbers of flashes is also important because these storms are often producing severe weather in the form of hail, wind, tornadoes and flash floods. Although lightning usually starts far less than one-quarter of all wildfires, lightning started wildfires from dry thunderstorms (i.e., those that produce lightning but little rainfall) account for more than 50 percent of the acres burned each year.

The Storm Prediction Center (SPC), located in Norman, Oklahoma, issues national thunderstorm outlooks as well as fire weather outlooks for dry thunderstorms in the western U.S. as part of the overall SPC mission. In an effort to better forecast thunderstorms and lightning, an automated method to predict the probability of lightning was developed at the SPC that employs a set of climatological as well as meteorological lightning predictors in a perfect prog(nosis) approach (Bothwell, 2002). Both the lightning climatologies and perfect prog forecasts have been available to the meteorologists at the SPC since 2003. The scheme produces 3 hour lightning forecasts on a 40 km grid out to 87 hours. The perfect prog forecasts are run using input data from the operational NAM-WRF NWP model. These forecasts are updated every 6 hours with the latest NAM model run. The approach used herein, is to derive equations for one or more CG lightning flashes as well as forecast equations for events with significant numbers of lightning flashes (e.g., 100 or more CG flashes per three hour period). Using the perfect prog approach, the methodology is in place to calculate probabilities for areas of intense to severe lightning. These predictions provide a three to four day forecast of one or more CG flashes as well as a forecast of more significant lightning.

Since the summer of 2006, these experimental forecasts of CG lightning flashes from the perfect prog scheme have been made available over an Internet Web page to Western Region (WR) National Weather Service (NWS) meteorologists along with forecasters from various Federal wildland fire agencies in the western United States. During the summer of 2007, these experimental forecasts were also produced for the Raleigh, North Carolina Weather Forecast Office (WFO) for use in their early morning hazardous weather updates. The goal for the Raleigh WFO is to highlight days where high number of CG flashes would likely be more of a threat across their forecast area.

The perfect prog scheme used at the SPC to forecast lightning for the lower 48 states is being expanded to include Alaska. A new multi-year collaborative project between the SPC and the Forest Service that is funded by the Joint Fire Science Program (JFSP) will lead to the production of both a detailed lightning climatology for Alaska and automated perfect prog lightning prediction equations by the summer of 2009. Finally, this paper will discuss how the forecasts have verified during the summers of 2006 and 2007.