NAM AIR QUALITY DIAGNOSTIC DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 1009 AM EDT THU AUG 04 2011 *** The following information pertains to initialization errors noted on the 12Z NAM that may negatively impact the performance of the 12Z CMAQ output as used for air quality forecasting. Specifically, errors that apply to temperature, winds, relative humidity and precipitation are included. This discussion only applies to geographical regions of the CONUS where air quality is currently forecast to be degraded (i.e. CODES: YELLOW/ORANGE/RED/PURPLE/MAROON). *** ...OKLAHOMA... A COMPLEX OF THUNDERSTORMS OVER MISSOURI IS MORE WIDESPREAD THAN INITIALIZED WHICH MAY HELP TO REINFORCE THE FRONTAL BOUNDARY LYING ACROSS SOUTHERN OKLAHOMA AND REDUCE HEATING OVER NORTHEAST OKLAHOMA. ...ALABAMA... PRECIPITATION AND CLOUD COVER OVER NORTHERN ALABAMA ARE MORE WIDESPREAD THAN INITIALIZED AND TEMPERATURES ACROSS NORTHEAST ALABAMA ARE 5 TO 8 DEGREES COOLER THAN INITIALIZED. JAMES