FXUS64 KBMX 021005
AFDBMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
405 AM CST WED DEC 2 2009
.MESOSCALE DISCUSSION...
RATHER COMPLEX WEATHER SITUATION SETTING UP FOR CENTRAL ALABAMA FOR
THE REMAINDER OF THE OVERNIGHT INTO TOMORROW EARLY AFTERNOON. AT
THE TIME OF WRITING...MODELS ARE STILL A LITTLE INCONSISTENT AS
LITERALLY 20 TO 50 MILES MAKES A BIG DIFFERENCE IN THE TYPE AND MODE
OF CONVECTION FOR THE PERIOD. BASED ON THE LATEST SURFACE OBS...THE
SURFACE LOW CENTER HAS MOVED ON SHORE NEAR THE SOUTHEAST LA
COASTLINE WITH AN ASOS STATION IN THE AREA REPORTING 995 MB. THIS
IS ALREADY 3 OR SO MB LOWER THAN THE OPERATIONAL MODELS ARE
PREDICTING...INCLUDING THE LATEST AND GREATEST RUC13. THE
ASSOCIATED WARM FRONT HAS ALSO MOVED INLAND AS WINDS ALONG THE FL/AL
COAST HAVE TURNED NEARLY SOUTH AND DEWPOINTS AND TEMP ARE BEGINNING
TO SURGE. THE COLD FRONT AND WARM SECTOR OUT AHEAD ARE STILL
PROGGED TO MOVE INLAND THROUGH THE REMAINDER OF THE PERIOD. HAVE
STRUGGLED SOMEWHAT WITH HOW FAR NORTHWARD INTO CENTRAL ALABAMA THE
WARM SECTOR WILL SURGE AHEAD OF THE COLD FRONT. THAT REALLY IS
WHERE THE PRIME SPOT WILL REMAIN. IT IS ALSO TRICKY IN THAT THE
SURFACE LOW IS DEEPENING SO RAPIDLY THAT A CLEARLY DEFINED COLD
FRONT MAY BE RATHER HARD TO DISTINGUISH FROM THE WINDS ALONE...SO
BEST ADVICE WILL BE TO WATCH HOW FAR EASTWARD THE ORGANIZED LINE OF
CONVECTION WILL PUSH. IN FACT...THERE MAY BE SEVERAL WAVES OF
INITIAL SUPERCELL ACTIVITY IN THE WARM SECTOR FOLLOWED BY A MORE
ORGANIZED SQUALL-TYPE LINE WITH THE FRONTAL FORCING. STARTING TO
NOTICE THIS TAKING SHAPE JUST SOUTH OF NEW ORLEANS WITH A SECOND
WEAKER LINE FORMING JUST ACROSS THE TX STATE LINE INTO SOUTHWESTERN
LA.
BEST FORECAST FOR NOW...IS TO EXPECT THE WARM SECTOR WITH A FEW
SUPERCELLS POSSIBLE INTO OUR SOUTHEAST CLOSER TO DAYBREAK...WITH THE
WARM FRONT SURGING NORTHEASTWARD CLOSER TO LUNCHTIME. THIS WILL PUT
AREAS SOUTH OF INTERSTATE 85 UNDER THE GUN THROUGH THE EARLY MORNING
HOURS AND AREAS SOUTH OF INTERSTATE 20 IN A FAVORABLE AREA LATER IN
THE MORNING. IT IS POSSIBLE THAT TALLADEGA COUNTY MAY BE THE CUTOFF
COUNTY TO THE NORTH AND WEST...SO FOLKS EAST AND SOUTH SHOULD BE ON
THE LOOKOUT FOR POTENTIAL DEVELOPMENT. AS LOW CONTINUES NORTHWARD
THE REMAINDER COUNTIES GENERALLY INTERSTATE 65...WEST MAY EXPERIENCE
SOME ELEVATED CONVECTION LATER TODAY. THE MAIN THREAT WOULD BE
ISOLATED SEVERE HAIL...WITHOUT DAMAGING SURFACE WINDS AND/OR
TORNADOES...BEING THAT THOSE COUNTIES WILL LIKELY REMAIN IN THE COLD
SECTOR. ELEVATED CONVECTION IS ALREADY BEING SEEN AT THIS HOUR
NORTH OF THE SURFACE LOW ACROSS INTERIOR LA WITH THE DECREASING
LAPSE RATES ALOFT.
ONE MORE NOTE OF CONCERN IS THE ABSENCE OF A STEADY RAIN POCKET
ACROSS MUCH OF THE AREA THAT I HAVE PROGGED TO BE IN THE WARM
SECTOR. THIS WILL REALLY INCREASE THE CHANCE TO GET SOME SURFACE
HEATING AFTER SUNRISE...IF THE TREND CONTINUES. NOT EXPECTING AT
THE MOMENT TO SEE ANY BREAKS IN THE CLOUDS...BUT IF SO...IT COULD
BECOME A MORE DANGEROUS SITUATION FOR THE WARM SECTOR.
NONETHELESS...TEMPERATURES RISING INTO THE UPPER 60S AND MAYBE EVEN
LOWER 70S...WITH DEWPOINTS FOLLOWING...ACROSS THE SOUTHEAST AND EAST
ARE STILL IN THE CARDS.
17/KLAWS
.SHORT TERM...TONIGHT THRU FRIDAY.
SURFACE LOW WILL MOVE INTO MIDDLE TENNESSEE BY SUNSET TODAY WITH
LOW LEVEL CONVERGENCE SHIFTING INTO GEORGIA. COMBINATION OF APPROACHING
UPPER LEVEL SHORT WAVE TROF AND WRAP AROUND MOISTURE WILL TRIGGER
SCATTERED SHOWERS ACROSS NORTHERN COUNTIES DURING THE EVENING HOURS.
STRONG PRESSURE GRADIENT ON BOTTOM SIDE OF DEEP SURFACE LOW WILL
KEEP WINDS IN THE RANGE IN THE EVENING DIMINISHING TO 5-10 MPH
AFTER MIDNIGHT.
COLD AIR STRATUS WILL LIKELY LINGER INTO THE MORNING HOURS ON
THURSDAY BUT SHOULD GRADUALLY DISSIPATE DURING THE DAY. MOSTLY
CLEAR AND COLD THUR DAY NIGHT WITH LOW SIN THE LOWER TO MIDDLE 30S.
HIGH CLOUDS WILL BE ON THE INCREASE DURING THE DAY FRIDAY AS NEXT
GULF SYSTEM BEGINS TO GET ORGANIZED.
.LONG TERM...FRIDAY NIGHT THRU TUESDAY.
MAJORITY OF MODELS ARE SHOWING SOME FORM OF PRECIPITATION MOVING
ACROSS CENTRAL ALABAMA FRIDAY NIGHT AND SATURDAY MORNING. DEEPER
MOISTURE WILL BECOME AVAILABLE ACROSS CENTRAL ALABAMA AS ANOTHER
SURFACE LOW MOVES ACROSS NORTH GULF OF MEXICO. THE UNCERTAINTY IS
IN THE AMOUNT OF LIFT AND STRENGTH OF COLD AIR ADVECTION. LIGHT
RAIN SHOULD MOVE INTO SOUTHERN ALABAMA FRIDAY NIGHT WITH
PRECIPITATION OVER NORTH ALABAMA MORE DEPENDENT ON SHORT WAVE
TROF. LATEST MODEL RUNS ARE SHOWING COLD AIR ADVECTION MIGHT NOT
BE AS STRONG AS PREVIOUS MODEL RUNS...AND ONCE AGAIN MODELS ARE
HAVING A DIFFICULT TIME WITH EVOLUTION AND TRACK OF SURFACE LOW.
LIGHT RAIN SHOULD MOVE INTO SOUTH ALABAMA FRIDAY EVENING WITH
LIGHT PRECIPITATION BREAKING OUT OVER NORTH ALABAMA AFTER
MIDNIGHT. THICKNESS VALUES SHOW TEMPERATURE PROFILES WILL COOL
DOWN ENOUGH AFTER MIDNIGHT FRIDAY NIGHT FOR PRECIPITATION TO BE
BECOME ALL SNOW ALONG AND NORTH OF I-20...WITH A MIXTURE AS FAR
SOUTH AS MONTGOMERY AND AUBURN BY SUNRISE SATURDAY. THE SNOW AND
RAIN/SNOW MIXTURE WILL LIKELY LINGER INTO SATURDAY MORNING.
SURFACE TEMPERATURES WILL NOT LIKELY FALL MUCH BELOW 32
DEGREES...SO ANY ACCUMULATIONS WILL LIKELY BE LESS THAN ONE-
INCH...MAINLY ON GRASSY AREAS IN THE HIGHER ELEVATIONS OF EAST
ALABAMA. THIS SYSTEM WILL PULL OUT RAPIDLY ON SATURDAY WITH
CLEARING SKIES DURING THE AFTERNOON.
SOUTHERN STREAM WILL CONTINUE IN AN ACTIVE PHASE WITH ANOTHER
SYSTEM MOVING ACROSS THE GULF COAST STATES EARLY NEXT WEEK. MODELS
HAVE BEEN SHOWING A SOMEWHAT SLOWER MOVEMENT AND ITS ARRIVAL...
WITH RAIN MOVING IN ON TUESDAY OR EVEN TUESDAY NIGHT. SHORT WAVE
TROF ASSOCIATED WITH THIS SYSTEM WILL BE WEAKER THAN PREVIOUS ONES
AND ONLY EXPECT SHOWERS AT THIS TIME.
58/ROSE
&&
.AVIATION...06Z TAF DISCUSSION.
MAIN AVIATION CONCERN IS RAIN/WIND ASSOCIATED WITH APPROACH OF SFC
LOW TONIGHT INTO WED FROM THE SW INTO CENTRAL AL. PRECIP IS MAINLY
EXPECTED TO BE STRATIFORM RAIN...CONFIDENCE IS NOT HIGH ENOUGH TO
PUT TS IN TAFS. HOWEVER...MGM/TOI WILL BE UNDER A STRONG LOW LEVEL
JET WITH MAXIMA GOING RIGHT OVER THESE TERMINALS...HAVE INSERTED LLWS
FOR 11Z THRU 15Z. WINDS OVERALL WILL INCREASE DURING THE OVERNIGHT
HRS AS THIS SYSTEM GETS CLOSER. EXPECT IFR CONDS THROUGH MOST OF
THE PERIOD DUE TO LOW CLOUDS AND RAIN. LOCALLY HEAVY RAINFALL
POSSIBLE ACROSS THE SOUTHEAST SECTIONS. WIND DIRECTION WILL
BE VEERING FROM ERLY BECOMING SE/SSE THROUGH 12Z...THEN MAINLY
SOUTHWEST AFTER 18Z. OVERALL SURFACE WINDS AROUND 15 TO 25 MPH WITH
GUSTS 25 TO 35 MPH POSSIBLE.
KSL
&&
.PRELIMINARY POINT TEMPS/POPS...
GADSDEN 61 39 49 31 50 / 90 30 10 0 10
ANNISTON 63 40 51 33 51 / 90 20 10 0 10
BIRMINGHAM 60 41 51 33 50 / 90 30 10 0 10
TUSCALOOSA 59 40 52 33 50 / 70 20 10 0 10
CALERA 62 41 53 35 50 / 90 20 10 0 10
AUBURN 68 44 54 36 53 / 90 10 10 0 10
MONTGOMERY 68 43 57 36 53 / 90 10 10 0 10
TROY 70 42 57 35 54 / 90 10 10 0 10
&&
.BMX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH IS IN EFFECT TONIGHT UNTIL 6 PM TODAY
FOR TALLAPOOSA-CHAMBERS-LOWNDES-ELMORE-MONTGOMERY- MACON-
BULLOCK-LEE-RUSSELL-PIKE-BARBOUR-DALLAS-AUTAUGA.
WIND ADVISORY IS IN EFFECT TONIGHT UNTIL 6 PM TODAY FOR ALL OF
CENTRAL ALABAMA.
&&
$$
