NOUS41 KWBC 231822



Service Change Notice 12-29

National Weather Service Headquarters Washington DC

120 PM EDT Thu Aug 23 2012


To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS partners and employees


From:      Eli Jacks

           Chief, Fire and Public Weather Services Branch


Subject:   Transition of NWS Storm Prediction Center (SPC)

           Thunderstorm Outlook (CONUS Only) from Experimental to

           Operational Status Effective September 26, 2012


Effective Wednesday, September 26, 2012, at 1700 Coordinated Universal Time (UTC), the SPC Thunderstorm Outlook becomes operational.  This product is issued only for the CONUS.


The SPC Thunderstorm Outlook depicts the expected geographic areas of thunderstorms including 10, 40 and 70 percent probabilities in 4 or 8 hour time periods. A 40 percent probability means that given similar environmental conditions, a thunderstorm would be observed at any one location (in either a county or city) within the 40 percent thunder probability area four times out of ten, or 40 percent of the time.


Forecasts of thunderstorms are critical for the protection of life and property since every thunderstorm contains lightning that is a potential killer. The high temporal and spatial resolution of the SPC Thunderstorm Outlook will aid both NWS forecasters and NWS partners in time-sensitive decisions related to thunderstorms and ultimately provide greater safety for the U.S. public. 


SPC Thunderstorm Outlook issuance and valid times are:


Issue Time (UTC)     Valid Periods (UTC)

----------           -------------------

  0600Z              1200-1600, 1600-2000, 2000-0000

  1300Z              1600-2000, 2000-0000, 0000-0400

  1700Z              2000-0000, 0000-0400, 0400-1200

  2030Z              0000-0400, 0400-1200

  0130Z              0400-1200


The SPC Thunderstorm Outlooks web-based graphic is online at:


If you have any questions, please contact:
   John Ferree
   NWS Severe Storms Services
   Norman, OK  73072
National Service Change Notices are online at: