284
FXUS64 KLIX 241301
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
701 AM CST TUE NOV 24 2009
UPDATE
SOUNDING DISCUSSION
A BIT OF MOISTURE IS PRESENT FROM THE SURFACE UP TO 950 MB AND
NEAR 400 MB WITH A LARGE AREA OF DRY AIR IN BETWEEN...PRECIPITABLE
WATER VALUE OF 0.57 INCHES. DENSE FOG HAS DROPPED VISIBILITIES IN
AREAS ACROSS THE CWA...THE FOG IS EXPECTED TO BURN OFF BY 9 AM. AN
INVERSION IS PRESENT NEAR 700 FEET AND 3300 FEET. WINDS ARE LIGHT
AND VARIABLE AT THE SURFACE AND WESTERLY ALOFT.
PREV DISCUSSION
/ISSUED 341 AM CST TUE NOV 24 2009/
SYNOPSIS...
A SURFACE LOW IS CENTERED OVER NORTHEASTERN KANSAS WITH A COLD
FRONT EXTENDING SOUTHWARD THROUGH EASTERN OKLAHOMA AND CENTRAL
TEXAS. HIGH PRESSURE IS CENTERED BEHIND THE FRONT OVER
NORTHWESTERN COLORADO.
LOCALLY...AMPLE LOW LEVEL MOISTURE HAS ALLOWED LOW CLOUDS AND FOG
TO DEVELOP IN SOME AREAS...ESPECIALLY ACROSS SOUTHERN MISSISSIPPI
AND AREAS OF SOUTHEAST LOUISIANA NORTH OF THE TIDAL LAKES. A
DENSE FOG ADVISORY HAS BEEN ISSUED FOR AREAS ALONG AND NORTH OF
THE INTERSTATE 10/12 CORRIDOR UNTIL 9 AM CST.
SHORT TERM...
FOG AND LOW CLOUDS SHOULD GRADUALLY LIFT THROUGH THE MORNING WITH
A RETURN TO PARTLY CLOUDY SKIES BY EARLY AFTERNOON. IT STILL
LOOKS LIKE THE UPPER LOW AND SURFACE COLD FRONT WILL MOVE THROUGH
THE AREA TONIGHT. THE MAIN CHANGE IS THAT I HAVE REMOVED ANY
MENTION OF PRECIP OVER LAND AREAS. WITH NO REAL RETURN FLOW AHEAD
OF THE FRONT...MOISTURE WILL REMAIN LIMITED TO THE LOW
LEVELS...GENERALLY BELOW 800 MB OR ABOUT 6 KFT. ADDITIONALLY...
THERE IS ABSOLUTELY NO PRECIPITATION CURRENTLY ASSOCIATED WITH THE
FRONT. SO WHILE AN ISOLATED SHOWER OR TWO CANNOT BE COMPLETELY
RULED OUT...THE CHANCE IS LOW ENOUGH THAT I DIDN/T FEEL IT
NECESSARY TO BE MENTIONED IN THE FORECAST. WE SHOULD JUST SEE AN
INCREASE IN CLOUDS AS THE FRONT MOVES THROUGH THE AREA.
ONCE THE FRONT PASSES THROUGH THE REGION...CLOUDS WILL CLEAR
QUICKLY AS DRY HIGH PRESSURE BUILDS INTO THE AREA BEHIND IT. THIS
INITIAL SURGE OF COOL DRY AIR WILL KEEP TEMPERATURES NEAR OR JUST
BELOW NORMAL FOR THIS TIME OF YEAR. HOWEVER...EXPECT A MORE
SIGNIFICANT COOL DOWN LATER IN THE WEEK.
LONG TERM...
BY THURSDAY...A SECOND UPPER LEVEL LOW WILL MOVE SOUTHWARD OUT OF
CANADA....BRINGING A STRONGER SURGE OF COLD AND DRY AIR INTO THE
AREA. STRONG COLD AIR ADVECTION WILL KEEP TEMPERATURES BELOW
NORMAL ON THURSDAY...WITH HIGHS TOPPING OUT IN THE LOW 60S. AS
COLD AIR ADVECTION CONTINUES INTO THE NIGHT...WE SHOULD SEE THE
COLDEST TEMPERATURES OF THE SEASON THUS FAR THURSDAY NIGHT/FRIDAY
MORNING. A FEW HOURS OF NEAR FREEZING TEMPERATURES ARE EXPECTED
ACROSS THE FAR NORTHERN ZONES. THIS REPRESENTS A TIMING CHANGE
FROM PREVIOUS FORECASTS WHICH INCLUDED THE COLDEST TEMPERATURES
FOR FRIDAY NIGHT/SATURDAY MORNING.
LATEST MODEL GUIDANCE IS IN AGREEMENT THAT THE UPPER TROUGH WILL
LIFT OUT OF THE AREA A LITTLE FASTER THAN PREVIOUSLY FORECAST.
THIS IN TURN ALSO RESULTS IN THE SURFACE HIGH SHIFTING EASTWARD A
LITTLE FASTER AND ALLOWING WINDS TO SHIFT TO A MORE EASTERLY
DIRECTION OVERNIGHT FRIDAY NIGHT. WHILE RADIATIVE COOLING WILL
STILL RESULT IN BELOW NORMAL TEMPERATURES FRIDAY NIGHT...THE
SLIGHT INCREASE IN LOW LEVEL MOISTURE WILL KEEP TEMPERATURES
A FEW DEGREES WARMER THAN INDICATED IN EARLIER FORECASTS.
HIGH PRESSURE WILL CONTINUE TO SHIFT EASTWARD THROUGH THE END OF
THE WEEK AS AN UPPER TROUGH DIGS INTO THE ROCKY MOUNTAINS REGION
AND A SURFACE LOW TAKES SHAPE OVER NORTHERN TEXAS. THERE IS
CONSIDERABLE SPREAD IN THE MODEL FORECASTS CONCERNING THIS SYSTEM.
THE GFS REPRESENTS THE STRONGER AND MORE PROGRESSIVE OF THE
SOLUTIONS WITH A COLD FRONTAL PASSAGE LATE SUNDAY NIGHT/EARLY
MONDAY MORNING. THE ECMWF IS CONSIDERABLY WEAKER AND SLOWER WITH A
COLD FRONTAL PASSAGE HOLDING OFF UNTIL THE TUESDAY EVENING TIME
FRAME. WHILE THE REAL SOLUTION PROBABLY LIES IN BETWEEN...HAVE
GENERALLY HEDGED TOWARD THE GFS AS IT IS MORE IN LINE WITH
GUIDANCE FROM HPC.
AVIATION...BIGGEST ISSUE WILL BE IN THE FIRST 4-6HRS. BOTH
REDUCED VISBIES AND LOWERED CIGS WILL OCCUR AT MOST OF THE
TERMINALS. FG AND BR HAVE ALREADY DEVELOPED AT MOST SITES WITH
CIGS QUICKLY STARTING TO FOLLOW SUIT. MSY...NEW...AND GPT MAY
ACTUALLY STAY MORE IN MVFR AND EVEN VFR STATUS THANKS TO CIRRUS
INVADING EXTREME SE LA FROM THE GULF. BTR/MCB/HDC AND EVEN ASD
TEMPORARILY WILL LIKELY DEAL WITH LIFR AND IFR CONDITIONS THROUGH
THE MORNING BUT SHOULD QUICKLY IMPROVE AFTER SUNRISE. ONCE
EVERYONE MOVES INTO VFR STATUS LOOK FOR THESE CONDITIONS TO
CONTINUE THROUGH TODAY. A COLD FRONT IS EXPECTED LATE THIS
AFTN/EVN AND THIS FRONT SHOULD BE MOSTLY DRY BUT THERE IS A VERY
SLIM CHANCE OF AN ISOLATED SHRA OR TWO. THE ONLY OTHER
METEOROLOGICAL ISSUE OF SIGNIFICANCE WILL BE WINDS VEERING AROUND
TO THE NW AFTER PASSAGE OF THE FRONT B/T 21Z AND 03Z.
MARINE...HIGH PRESSURE EARLY TODAY WILL GIVE WAY TO A MOSTLY DRY
COLD FRONT THIS EVN. AT THE SAME TIME A WEAK SFC LOW WILL DEVELOP
AND MOVE THROUGH THE CNTRL GULF TODAY. THESE TWO FEATURES WILL
CAUSE WINDS TO SLOWLY PICK UP TODAY BUT THEN AS THE FRONT MOVES
THROUGH LOOK FOR BREEZY NW WINDS POSSIBLY LEADING TO EXERCISE
CAUTION HEADLINES TONIGHT AND TOMORROW. WINDS WILL BE A BIGGER
ISSUE LATE IN THE DAY ON THANKSGIVING AND OVERNIGHT HEADING INTO
FRI. A SECOND...STRONGER SURGE OF COLD AIR WILL TAKE PLACE THEN
AND WITH STRONG CAA THIS SHOULD HELP TRANSPORT STRONGER WINDS JUST
ABV THE SFC. SMALL CRAFT ADVISORIES WILL PROBABLY BE NEEDED SOME
TIME LATE THU AFTN THROUGH THE OVERNIGHT HRS. HIGH PRESSURE WILL
QUICKLY MOVE OVER THE AREA FRI BRINGING WINDS AND SEAS BACK DOWN.
BY SUN THE CENTER OF THE SFC HIGH WILL PUSH EAST AND THIS WILL
ALLOW ONSHORE TO REDEVELOP. NEXT SYSTEM APPEARS TO BE EARLY NEXT
WORK WEEK AND THIS COULD BE A STRONG ONE.
PRELIMINARY POINT TEMPS/POPS
MCB 69 45 64 39 / 10 10 0 0
BTR 72 47 66 41 / 10 10 0 0
MSY 71 53 66 47 / 10 10 0 0
GPT 69 50 68 44 / 10 10 0 0
LIX WATCHES/WARNINGS/ADVISORIES
LA...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR LAZ034>040-
046>050.
GM...NONE.
MS...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR MSZ068>071-
077-080>082.
GM...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page