995 FXUS64 KBMX 202159 AFDBMX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BIRMINGHAM AL 359 PM CST FRI JAN 20 2012 .SYNOPSIS... STALLED FRONTAL BOUNDARY STILL REMAINS OFF TO OUR NORTH ACROSS THE TENNESSEE VALLEY REGION...AND WILL SLOWLY MOVE NORTHWARD AS A WARM FRONT THROUGHOUT THE NIGHT TONIGHT. A SECONDARY WARM FRONT WAS ALSO MOVING NORTHWARD ACROSS THE STATE THIS AFTERNOON WITH A REINFORCING PUSH OF WARM MOIST AIR. 1003MB SURFACE LOW ACROSS EASTERN OKLAHOMA WILL CONTINUE TO MOVE ACROSS ARKANSAS AND INTO WESTERN TENNESSEE BY MIDNIGHT TONIGHT. THE TRAILING COLD FRONT WILL THEN SLOWLY MOVE SOUTHWARD INTO NORTHWEST ALABAMA DURING THE EARLY MORNING HOURS ON SATURDAY PRODUCING A CHANCE OF STRONG TO SEVERE STORMS FOR THOSE AREAS. THE THREAT FOR SEVERE WEATHER WILL LAST INTO THE AFTERNOON HOURS FOR THE CENTRAL PORTION OF THE STATE...AND THE THREAT WILL GRADUALLY END BY THE LATE EVENING HOURS ON SATURDAY AS THE FRONT WEAKENS AND STALLS OUT ACROSS SOUTHERN ALABAMA. LARGE HAIL AND DAMAGING STRAIGHT-LINE WINDS REMAIN THE MAIN THREATS. YET ANOTHER FRONT LOOKS TO MOVE THROUGH OVERNIGHT SUNDAY AND INTO THE EARLY MORNING HOURS ON MONDAY THAT COULD PRODUCE A MORE SIGNIFICANT CHANCE OF SEVERE THUNDERSTORMS...BUT THERE ARE SEVERAL DETAILS TO BE IRONED OUT WITH THE STRENGTH OF THE SYSTEM. 56/GDG && .SHORT TERM... TONIGHT THROUGH MONDAY MORNING. SCATTERED TO NUMEROUS SHOWERS CONTINUE THIS AFTERNOON ACROSS EASTERN AND NORTHERN PORTIONS OF THE CWA OUT AHEAD OF THE SECONDARY WARM FRONT STRETCHING FROM TUPELO MS SOUTHEASTWARD TO TROY. THE FRONT IS SEPARATING DEWPOINTS IN THE MID 50S ACROSS NORTHERN ALABAMA FROM LOW TO MID 60S ACROSS THE REST OF THE STATE. GOING AHEAD AND LOOKING AT TONIGHT'S IMPACTS FROM THE COLD FRONT MOVING IN...THE BEST DYNAMICS IN TERMS OF A LOW LEVEL JET AND 0-6KM BULK SHEAR ARE GOING TO BE ACROSS OUR NORTHWEST COUNTIES AS THE FRONT MAKES ITS WAY SOUTHWARD. 45-50 KNOTS OF BULK SHEAR STILL LOOK LIKELY. THE CHALLENGE WILL BE THE AMOUNT OF INSTABILITY PRESENT. BASED ON CURRENT RUC ANALYSIS...SB CAPES OF 1000-1500J/KG ARE ALREADY MOVING INTO THE SOUTHWESTERN PORTIONS OF THE CWA. THIS WOULD LEAVE ME TO BELIEVE THAT PLENTY OF INSTABILITY WOULD BE ABLE TO MOVE NORTHWARD THROUGH THE NIGHT...AND FORECAST SOUNDINGS ARE ACTUALLY INDICATING AROUND 800-1000J/KG OF SB CAPE ACROSS MARION COUNTY AFTER 06Z TONIGHT AND DRY AIR ALOFT. THEREFORE...THERE IS INCREASING CONFIDENCE IN THE POSSIBILITY OF SEVERE STORMS WITH DAMAGING STRAIGHT LINE WINDS AND LARGE HAIL THE MAIN THREATS. AN ISOLATED TORNADO WILL ALSO BE POSSIBLE ACROSS THE NORTHWESTERN COUNTIES AS WELL...WHERE THE MOST SHEAR WILL BE PRESENT. AS THE FRONT MOVES SOUTHWARD THROUGH THE MORNING AND INTO THE AFTERNOON HOURS...THE POSSIBILITY OF DAMAGING WINDS AND LARGE HAIL WILL CONTINUE THROUGH CENTRAL ALABAMA ALONG THE FRONT WITH GOOD INSTABILITY TO WORK WITH...BUT UPPER LEVEL DYNAMICS WILL WEAKEN THROUGHOUT THE AFTERNOON HOURS AND REDUCE THE SEVERE THREAT FOR SOUTHERN ALABAMA INTO THE EVENING HOURS AS THE FRONT BEGINS TO STALL ALONG THE I-85 CORRIDOR. THE STALLED FRONT THEN MOVES NORTHWARD AS A WARM FRONT SUNDAY AFTERNOON PLACING ALL OF ALABAMA BACK INTO THE WARM SECTOR OUT AHEAD OF THE NEXT AMPLIFIED NEGATIVELY-TILTED SHORTWAVE TROUGH MOVING ACROSS THE PANHANDLE OF TEXAS. THE SURFACE LOW GENERATED BY THE SHORTWAVE THEN QUICKLY MOVES NORTHEASTWARD INTO ILLINOIS WITH A TRAILING COLD FRONT. DYNAMICS LOOK FAIRLY IMPRESSIVE WITH THIS SYSTEM WITH 50-60 KNOTS OF LOW-LEVEL SHEAR. MODELS ARE ALSO INDICATING 0-6KM BULK SHEAR VALUES OF 60-65 KNOTS. THERE ARE STILL SOME QUESTIONS AS TO HOW MUCH INSTABILITY WILL BE PRESENT BY THE TIME THE FRONT MAKES ITS WAY THROUGH WESTERN ALABAMA...BUT WE WILL DEFINITELY HAVE TO WATCH THIS SYSTEM CLOSELY. HAVE GONE AHEAD AND PLACED A LOW CONFIDENCE SEVERE WORDING IN THE HWO FOR MONDAY MORNING. 56/GDG .LONG TERM... MONDAY AFTERNOON THROUGH THURSDAY. LOOKING OUT INTO THE EXTENDED...THE COLD FRONT ON MONDAY LOOKS TO MOVE OUT OF THE AREA BY THE AFTERNOON. HIGH PRESSURE AND NORTHERLY WINDS AT THE SURFACE WILL ALLOW TEMPERATURES TO DROP INTO THE UPPER 30S ON TUESDAY MORNING...AND LEAVE THE AREA WITH AT LEAST ONE DRY DAY ON TUESDAY. A TROUGH OVER THE WEST IS PROGGED TO PUSH SOUTHEASTWARD ON TUESDAY. MODELS ARE BEGINNING TO COME TOGETHER SLIGHTLY WITH THEIR SOLUTIONS FOR THIS SYSTEM. BOTH THE GFS AND ECMWF HAVE THE TROUGH TRANSITIONING INTO AN UPPER LEVEL CLOSED LOWS OVER SOUTHERN NEW MEXICO BY TUESDAY EVENING...HOWEVER FROM THERE BOTH MODELS BEGIN TO DIVERGE. THE ECMWF HAS THE CLOSED LOW MOVING SOUTHEASTWARD DURING THE DAY ON WEDNESDAY...AND TAKING IT OVER THE NORTHERN GULF OF MEXICO BY THURSDAY. MEANWHILE...A SURFACE LOW PRESSURE SYSTEM BEGINS TO FORM ALONG A COLD FRONT AND MOVES NORTHEASTWARD ACROSS CENTRAL ALABAMA ON THURSDAY AFTERNOON. THE COLD FRONT EXITS CENTRAL ALABAMA BY EARLY FRIDAY MORNING...WITH ALL OF THE PRECIPITATION EXITING THE AREA AS WELL. THE GFS...HOWEVER...HAS THE CLOSED LOW MOVING MORE INLAND OVER TEXAS AND LOUISIANA WITH THE COLD FRONT MOVING ACROSS THE AREA SEVERAL HOURS LATER THAN THE ECMWF SOLUTION. WITH BOTH SOLUTIONS...SOUTHEASTERLY WINDS OUT AHEAD OF THE COLD FRONT FILTER IN PLENTY OF GULF MOISTURE...WITH DEWPOINTS REACHING INTO THE UPPER 50S IN SOME LOCATIONS. DID NOT MAKE ANY CHANGES TO THE POP OR WEATHER GRIDS...SINCE UNCERTAINTIES WITH TIMING REMAINS HIGH. WITH THE SYSTEM...WE COULD HAVE ANOTHER ROUND OF STRONG TO SEVERE THUNDERSTORMS...HOWEVER THE TIMING AND LOCATION OF THE SURFACE LOW WILL PLAY ROLE INTO WHETHER THIS OCCURS. 73 && .AVIATION... 18Z TAF DISCUSSION. IFR TO MVFR CEILINGS PREVAILING EARLY AFTERNOON THUS FAR. IT LOOKS AS THOUGH A WARM FRONT IS LIFTING NORTHWARD THROUGH THE SOUTHERN THIRD OF THE STATE WITH SHOWERS JUST AHEAD OF THE BOUNDARY. CEILINGS SHOULD LIFT BEHIND THE FRONT TO MVFR AS CURRENT OBS TRENDS SUGGESTS. LATER TONIGHT...CEILINGS SHOULD FLUCTUATE BETWEEN IFR AND MVFR WITH A COLD FRONT BEGINNING TO SLOWLY PUSH INTO THE STATE. SHOWERS AND THUNDERSTORMS SHOULD DEVELOP ALONG THE FRONT AND PUSH NEAR TCL/BHM/AND BY LATE MORNING. WINDS SOUTHERLY TONIGHT BECOMING WESTERLY AS THE FRONT APPROACHES LATE TOMORROW MORNING. && .PRELIMINARY POINT TEMPS/POPS... GADSDEN 60 62 48 67 50 / 90 100 10 20 70 ANNISTON 60 65 51 69 51 / 60 100 10 20 70 BIRMINGHAM 62 64 51 69 51 / 70 100 10 20 70 TUSCALOOSA 62 65 51 72 50 / 60 90 10 20 70 CALERA 61 65 53 70 52 / 60 100 10 20 70 AUBURN 60 68 57 70 56 / 40 100 20 20 60 MONTGOMERY 61 71 58 73 55 / 30 90 20 20 60 TROY 61 71 60 74 57 / 20 80 20 20 50 && .BMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 56/88