Cool-season nighttime tornadoes pose a particular challenge to forecasters, and are also a substantial threat to the public. In the wake of the Super Tuesday Outbreak of February 2008, it was found that many people did not expect tornadoes, especially in February, and especially at night. Late night tornado events also pose a significant challenge to public safety officials when alerting the public to the impending threat can be extremely difficult after people have gone to bed. While it is recognized that the bulk of these events will remain difficult to forecast and highly uncertain, the SPC is in the best position to offer guidance and meteorological support ahead of these "high impact, low probability" events. To that end, this is a initial attempt to improve our commitment to saving lives and protecting property.
Beginning December 1, 2009 and lasting through March 31, 2010, the Storm Prediction Center will issue Public Severe Weather Outlooks (PWO) following the issuance of a 2000 UTC and/or 0100 UTC Day 1 Outlook (SWODY1) when a 10 percent probability of significant tornadoes (hatched area) is forecast after dark anywhere in the CONUS. These PWOs will be specifically worded to address the threat of nighttime tornadoes and issued even if an earlier PWO was issued for significant severe weather during daylight hours.
Here is an example of what this product would look like:
PUBLIC SEVERE WEATHER OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0600 PM CST WED JAN 06 2010 ...SEVERE THUNDERSTORMS EXPECTED OVER PARTS OF XXXX OVERNIGHT... THE NWS STORM PREDICTION CENTER IN NORMAN OK IS FORECASTING THE POSSIBLE DEVELOPMENT OF TORNADOES OVER PARTS OF XXXX OVERNIGHT. CONDITIONS ARE EXPECTED TO SUPPORT THE POTENTIAL FOR A FEW STRONG AND POSSIBLY LONG-LIVED TORNADOES. WHILE OVERALL SEVERE THUNDERSTORM COVERAGE IS NOT EXPECTED TO BE WIDESPREAD...THE POTENTIAL FOR A SIGNIFICANT TORNADO AFTER DARK WARRANTS HEIGHTENED SAFETY PRECAUTIONS. TORNADOES DURING THE OVERNIGHT HOURS AT THIS TIME OF YEAR CAN BE PARTICULARLY DANGEROUS BECAUSE THEY ARE USUALLY FAST-MOVING AND OBSCURED BY RAIN AND DARKNESS. THE AREAS MOST LIKELY TO EXPERIENCE THIS ACTIVITY INCLUDE XXXX AND XXXX STATE AND LOCAL EMERGENCY MANAGERS ARE MONITORING THIS DEVELOPING SITUATION. THOSE IN THE THREATENED AREA ARE URGED TO REVIEW SEVERE WEATHER SAFETY RULES AND TO LISTEN TO RADIO...TELEVISION...AND NOAA WEATHER RADIO FOR POSSIBLE WATCHES...WARNINGS...AND STATEMENTS TONIGHT. ..CARBIN.. 01/06/2009 $$