040 FXUS64 KBMX 101559 AFDBMX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BIRMINGHAM AL 1059 AM CDT WED APR 10 2013 .UPDATE...TODAYS WEATHER. && .DISCUSSION...VERY FEW CLOUDS ACROSS CENTRAL ALABAMA THIS MORNING DUE TO SUBSIDENCE UNDER THE UPPER RIDGE. SURFACE TEMPERATURES ARE RUNNING SEVERAL DEGREES WARMER ACROSS THE NORTH THIS MORNING COMPARED TO 24 HOURS AGO...WHILE READINGS ARE SIMILAR ACROSS THE SOUTH. RAISED HIGHS TODAY ONE OR TWO DEGREES MOST AREAS... ESPECIALLY ACROSS THE NORTH. THE MODELS ARE COMING IN SLOWER WITH THE ARRIVAL OF THE SQUALL LINE TOMORROW...AND WE WILL BE DELAYING THE ONSET OF SEVERE WEATHER BY SEVERAL HOURS. THE MULTI-MEDIA BRIEFING AND SEVERE WEATHER GRAPHICS WILL BE UPDATED ON OUR WEB SITE BETWEEN 12 NOON AND 1 PM CDT. 58/ROSE && .AVIATION... 12Z TAF DISCUSSION. VFR CONDITIONS ARE FORECAST THROUGH THE NEXT 18 HOURS. LIGHT WINDS WILL INCREASE THIS MORNING OUT OF THE SOUTHEAST TO SOUTH...WITH GUSTS UP TO 18-22KTS THROUGH THE AFTERNOON. AS THE FRONTAL BOUNDARY CONTINUES TO SLIDE CLOSER TO THE AREA OVERNIGHT...CEILINGS WILL BEGIN TO DROP. LOOKS LIKE THE FRONT AND ASSOCIATED STORMS WILL REMAIN WEST OF THE AREA THROUGH THIS TAF PERIOD. THIS WILL NEED TO BE ADDED IN THE NEXT SET OF TAFS. && .PREV DISCUSSION... /ISSUED 620 AM CDT WED APR 10 2013/ TEMPERATURES EARLY THIS MORNING ARE STILL IN THE 60S ACROSS MUCH OF ALABAMA WITH THE BIRMINGHAM AIRPORT REPORTING 68 DEGREES AT 3 AM AND DEWPOINTS IN THE MID TO UPPER 50S. WARM AND MOIST AIR WILL CONTINUE TO ADVECT IN AHEAD OF THE COLD FRONT THAT WILL MOVE INTO THE STATE EARLY THURSDAY MORNING. IT DOES NOT TAKE TOO MUCH METEOROLOGICAL KNOWLEDGE TO FIND THE FRONT THIS MORNING. THE FRONT CURRENTLY STRETCHES FROM WESTERN ILLINOIS SOUTHWARD DOWN INTO SOUTHERN TEXAS. THE TEMPERATURE CHANGE BEHIND THE FRONT IS AROUND 40 DEGREES ACROSS CENTRAL AND EASTERN OKLAHOMA. THE BULK OF THE THUNDERSTORM ACTIVITY BACK TO THE WEST IS BEHIND THE FRONT WITH THE MAJORITY OF THE FORCING JUST BEHIND THE FRONT. CURRENT WATER VAPOR IMAGERY INDICATES A CLOSED UPPER LEVEL LOW OVER THE ROCKY MOUNTAINS. THIS UPPER LEVEL LOW WILL SLOWLY LIFT TO THE NORTHEAST. A SECOND SHORTWAVE TROUGH CAN BE NOTED ROTATING AROUND THE BASE OFF THE TROUGH ACROSS THE DESERT SOUTHWEST. THIS SHORTWAVE WILL BE THE FEATURE THAT WILL BRING CENTRAL ALABAMA THE THREAT FOR SEVERE WEATHER ON THURSDAY. TODAY...EXPECT HIGH CLOUDS WILL INCREASE ACROSS THE AREA AHEAD OF THE APPROACHING UPPER LEVEL TROUGH. WITH MOSTLY SUNNY TO PARTLY CLOUDY SKIES AND UPPER LEVEL HEIGHTS NEAR THOSE FROM YESTERDAY...EXPECT HIGH TEMPERATURES WILL BE SIMILAR TO YESTERDAY WITH HIGHS IN THE LOW TO MID 80S ACROSS CENTRAL ALABAMA. HEIGHT FALLS WILL EVENTUALLY OCCUR BY THE END OF THE DAY AS THE SHORTWAVE TROUGH PIVOTS ACROSS THE SOUTHERN PLAINS. MODELS CONTINUE TO SLOW DOWN THE TIMING OF THE SYSTEM. IT APPEARS THAT FRONT WILL ENTER THE FORECAST AREA JUST BEFORE 18Z THURSDAY. WITH THE OVERALL SLOWER PROGRESSION OF THE SYSTEM...HAVE REMOVED THE MENTION OF ANY SEVERE WEATHER FROM THE HWO ON WEDNESDAY. THE CAPPING WEDNESDAY AFTERNOON SHOULD BE SUFFICIENT TO PREVENT ANY CONVECTION. ADDITIONALLY...THE FORCING AHEAD OF THE FRONT IS VERY WEAK AND IF ANY UPDRAFTS DO FORM THEY WOULD BE POORLY ORGANIZED AND SHORT-LIVED. MODELS INDICATE THAT THE SQUALL LINE WILL BE WEAKENING AS IT ENTERS WESTERN PORTIONS OF THE AREA. DUE TO THE WEAKER INSTABILITY AND DECREASE IN THE LOW LEVEL JET. HOWEVER...SOME OF THE STORMS COULD STILL BE STRONG TO SEVERE WITH DAMAGING WINDS AND HEAVY RAINFALL BEING THE MAIN THREATS. PW VALUES WILL INCREASE TO NEAR 1.8 INCHES AND THE STORMS SHOULD RATHER PROFICIENT RAIN PRODUCERS. NOT WORRIED MUCH WITH ANY CELLS AHEAD OF THE LINE ACROSS WESTERN ALABAMA WITH THE OVERALL WEAKENING TREND AND CAPPING IN PLACE. BY LATE MORNING AND INTO THE AFTERNOON...INSTABILITY VALUES WILL INCREASE TO 750 TO 1500 J/KG. CONVECTIVE TEMPERATURES WILL BE IN THE LOW 70S AND IT WILL NOT TAKE MUCH HEATING TO HAVE THESE INSTABILITY VALUES REALIZED. ADDITIONALLY...THE LOW LEVEL JET WILL INCREASE AS THE UPPER LEVEL TROUGH TAKES ON A SLIGHT NEGATIVE TILT AS IT ROTATES THROUGH THE SOUTHEAST. 850 MB WINDS WILL INCREASE TO AROUND 40-50 KT WITH 0-1 KM HELICITY VALUES OF 200-250 M2/S2. SOME OF THE MODELS INDICATE A SECONDARY LOW DEVELOPING ALONG THE FRONT ACROSS THE FORECAST AREA AND THIS WOULD ACT TO FURTHER ENHANCE THE LOW LEVEL SHEAR. THE SREF NOW INDICATES AROUND A 70 PERCENT CHANCE FOR HELICITY VALUES OVER 150 M2/S2. HOWEVER...HODOGRAPHS ARE NOT OVERLY CURVED WITH LITTLE CHANGE IN HEIGHT IN THE LOW LEVEL WIND FIELDS. THE MAIN THREATS AGAIN WILL BE DAMAGING WINDS AND HEAVY RAINFALL AS THE QLCS/SQUALL LINE MOVES THROUGH THE STATE. HOWEVER...STILL CAN NOT RULE OUT THE POSSIBILITY FOR A COUPLE OF ISOLATED TORNADOES. AT THIS TIME...THE HIGHEST THREAT FOR AN ISOLATED TORNADO WILL BE OVER THE EASTERN HALF OFF THE FORECAST AREA AS THE SQUALL LINE RE-INTENSIFIES LATE IN THE MORNING INTO THE EARLY AFTERNOON HOURS. THE MAIN CONVECTIVE MODE WILL BE THE QLCS/SQUALL LINE WITH THE LINEAR NATURE OF THE FORCING. STILL CAN NOT RULE OUT A FEW ISOLATED CELLS AHEAD OF THE LINE...ESPECIALLY THURSDAY AFTERNOON AS THE CAP ERODES ACROSS EASTERN ALABAMA. THE FRONT SHOULD PUSH THROUGH THE AREA BY 06Z AND END ANY THREAT FOR SEVERE WEATHER BY MIDNIGHT. COOLER AND DRIER AIR WILL MOVE IN FOR THE WEEKEND WITH SURFACE HIGH PRESSURE MOVING INTO PLACE AND ZONAL FLOW ALOFT. THE WEEKEND WILL BE RATHER NICE WITH HIGH TEMPERATURES IN THE MID TO UPPER 70S AND LOWS IN THE UPPER 40S TO LOW 50S. THE NEXT CHANCE FOR RAIN WILL OCCUR EARLY NEXT WEEK AS AN UPPER LEVEL TROUGH MOVES ACROSS NORTHERN MEXICO INTO THE NORTHERN GULF. SEVERE WEATHER DOES NOT APPEAR LIKELY EARLY NEXT WEEK WITH THE MAIN UPPER LEVEL JET WELL TO THE NORTH. WENT HIGHER THEN GUIDANCE WITH TEMPERATURES LATE IN THE FORECAST PERIOD AS HEIGHT RISES OCCUR EARLY NEXT WEEK AS A TROUGH AMPLIFIES OVER THE DESERT SOUTHWEST. 05/MA .PRELIMINARY POINT TEMPS/POPS... GADSDEN 87 61 75 48 72 / 0 10 100 50 0 ANNISTON 85 63 77 50 73 / 0 10 100 70 0 BIRMINGHAM 86 65 74 47 71 / 10 10 100 40 0 TUSCALOOSA 87 66 74 48 73 / 10 20 100 20 0 CALERA 85 64 74 49 71 / 10 10 100 50 0 AUBURN 85 63 78 53 73 / 0 10 70 100 0 MONTGOMERY 88 62 79 52 74 / 0 10 100 90 0 TROY 86 62 78 52 74 / 0 10 80 100 0 && .BMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$