FXUS64 KLIX 230538
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1138 PM CST TUE DEC 22 2009
.AVIATION...
VFR CONDITIONS WILL PREVAIL FOR MUCH OF TONIGHT AND DURING THE DAY
WEDNESDAY FOR THE TAF SITES. MAINLY MID AND HIGH LEVEL CLOUDS ARE
EXPECTED EARLY IN THE PERIOD WITH CEILINGS AROUND 5K FEET MOVING
INTO AREA DURING THE EARLY MORNING HOURS. MVFR CEILINGS WILL BE
POSSIBLE AT TIMES DURING THE EARLY MORNING TIME FAME AT BOTH KMCB
AND KBTR. A FEW SHOWERS WILL BE POSSIBLE AT KMCB AND KBTR DURING
THE LATE MORNING AND AFTERNOON...BUT SHOULD HOLD OFF AT KMSY AND
KGPT UNTIL WEDNESDAY EVENING/NIGHT. PREVAILING MVFR CEILINGS ARE
FORECAST FOR BOTH KMCB AND KBTR WEDNESDAY EVENING ALONG WITH
INCREASING RAIN CHANCES. 11
&&
.PREV DISCUSSION... /ISSUED 826 PM CST TUE DEC 22 2009/
UPDATE...
UPDATED TO BEEF UP CLOUD COVER AND TO ADAPT TEMPERATURE AND DEW
POINT GRIDS TO REALITY...AS MOST OF THE DROP OFF IN BOTH VALUES
HAS ALREADY OCCURRED. CIRRUS DECK SHOULD BE PREVALENT THE REST OF
THE NIGHT. 35
SOUNDING DISCUSSION...
EVENING SOUNDING STILL RATHER DRY WITH PRECIPITABLE WATER VALUES
AROUND 2/3 OF AN INCH. BOUNDARY LAYER INVERSION AT 900 FT...A
STRONGER ONE AROUND 4000 FEET. SOUTHEAST WINDS AT THE SURFACE
BECOME SOUTHWEST AROUND 850 MB. ANY SIGNIFICANT MOISTURE IS
LIMITED TO THAT PORTION OF THE SOUNDING ABOVE 500 MB...THUS THE
CIRRUS DECK. 35
PREV DISCUSSION... /ISSUED 356 PM CST TUE DEC 22 2009/
SHORT TERM...
SYNOPTIC FLOW BEGINNING TO RESPOND TO THE STRENGTHENING PRESSURE
GRADIENT OUT WEST. WIND SPEEDS SHOULD CONTINUE TO BE ELEVATED
THROUGH THE NIGHT KEEPING ANY CHANCE OF FOG AT BAY. WINDS WILL
CONTINUE TO ALSO BRING AN ABUNDANCE OF MOISTURE BACK TO THE AREA
FROM THE DEEP GULF. MOISTURE LOADING IS ALREADY OCCURRING OVER
EAST TX WHERE SH/TS ARE BREAKING OUT. ONLY LIGHT SHOWERS EXPECTED
FOR THE NORTHERN MOST TIER OF OUR AREA TONIGHT AND A GOOD PORTION
OF WED. THE MAIN TS AREAS WILL WAIT UNTIL THERE IS ENOUGH SUPPORT
UPSTAIRS TO GET STARTED. NICE 30H DIVERGENT SLOT MOVES ACROSS A
WARM FRONT THAT MANAGES TO MOVE TO NEAR THE MISS/LA EAST WEST
BORDER BY EARLY THU MORNING. THE WARM FRONT WILL BECOME A FOCUS
FOR TS ACTIVITY BUT MORESO HELPING THESE TS GET CONNECTED WITH
THIS SPLIT FLOW ALOFT FROM LFT TO BTR TO MCB. THE SLOWER MOVEMENT OF
THE WARM FRONT COULD CAUSE SOME HEAVIER PRECIP AMOUNTS AS WELL.
THIS ALL STARTS OUT AROUND MIDNIGHT WED NIGHT ALONG THE WARM FRONT
THAT WILL BE LOCATED FROM LFT TO SLIDELL TO NEAR MOBILE THEN OUT
INTO THE GULF. SHOWERS SHOULD BE THE MAIN FEATURE ALONG THE WARM
FRONT EAST OF THE LFT TO BTR AREA. BUT WHERE THE CONVECTION IS
ABLE TO TAP THE BETTER DYNAMICS ALOFT...THERE WILL BE A FEW THAT
COULD BECOME SEVERE. AS THE WARM FRONT MOVES NORTH WE SHOULD SEE
THE TS BECOME STRONGER AS IT APPROACHES THE MISS STATE LINE. NOW
FOR THE COLD FRONT AND ASSOCIATED SQUALL LINE.
A STRONG 50-55KT JET JUST ABOVE THE BOUNDARY LAYER WILL EXIST AND
THIS WILL GET CAUGHT UP IN SEVERAL TS DOWNBURSTS. DRY AIR WILL
QUICKLY MOVE IN BEHIND THIS SQUALL LINE FORCING IT EAST QUICKLY.
THE SPEED OF THE LINE...NEG BUOYANCY DUE TO DRY AIR INTRUSION AND RAIN
SHAFTS CAUSING THE 50KT JET TO DIVE TO THE SFC WILL CAUSE SEVERAL
IF NOT MANY TS TO BOW ALONG THE MAIN LINE. QUITE SIMPLY...THERE
SHOULD BE A VERY GOOD POTENTIAL TO SEE MANY SEVERE TS WITH STRAIGHT
LINE WIND DAMAGE. TORNADIC POTENTIAL WILL ALSO BE PRESENT. AS
STRONG SE WINDS FALL INTO THE VERY WEAK WIND SPEEDS OF THE TROUGH
AXIS...IT WILL CAUSE NUMEROUS MICROSCALE VORTICIES. THESE SMALL
SPINUPS WILL GET ADVECTED NORTHWARD ALONG THE SQUALL LINE WITH THE
MAIN SYNOPTIC FLOW(SOLENOIDAL ADVECTION). WHEN THESE AREAS FALL
INTO A LARGER BOWING SEGMENT...THEY CAN ADD TO THE STRENGTH OF THE
VORT CENTER LOCATED ON EITHER END OF THE BOW AND MAY CAUSE A
TEMPORARY SPINUP CREATING A TORNADO. ALL THAT SAID TO SIMPLY SAY THERE
WILL BE THE POSSIBILITY OF TORNADOES AHEAD AND ALONG THE MAIN LINE
OF TS.
LONG TERM...
ONCE THE COLD FRONT MOVES THROUGH...SOME VERY COLD AIR WILL BEGIN
TO MOVE INTO THE AREA. TEMPS SHOULD STRUGGLE TO REACH 50 IN MANY
AREAS FRI AND SAT. ANOTHER IN A LINE OF SEVERAL GULF LOWS WILL
BEGIN TO AFFECT THE AREA BY NEXT WEEKEND. WITH TWO MORE SYSTEMS
SLATED FOR THE AREA BEFORE THE END OF THE YEAR...WE SHOULD EASILY
BEAT THE ALL TIME WETTEST MONTH ON RECORD AT MSY SINCE WE ONLY
NEED ABOUT .18" OF RAIN FOR THE SITE.
MARINE...
WINDS WILL START TO INCREASE THIS EVENING AS THE PRESSURE GRADIENT
TIGHTENS ACROSS THE REGION. THE COMBINATION OF STRONG HIGH
PRESSURE PUSHING TOWARDS THE ATLANTIC AND CYCLOGENESIS OCCURRING
IN THE SRN PLAINS - OK/TX PANHANDLES WILL CREATE MODERATE TO
STRONG SERLY FLOW. WINDS WILL APPROACH SCS CRITERIA THIS EVENING
ACROSS THE COASTAL WATERS AND SHOULD ENCOMPASS ALL OF THE COASTAL
WATERS AND TIDAL LAKE TOMORROW. BY TOMORROW NIGHT WINDS WILL
INCREASE TO NEAR SCY CONDITIONS AS THE SFC LOW CONTINUES TO DEEPEN
AND APPROACH THE RED RIVER VALLEY. A SCY HAS ALREADY BEEN ISSUED
FOR ALL OF THE COASTAL WATERS BEGINNING LATE TOMORROW EVENING AND
THEN THE TIDAL LAKES AFTER 12Z THU. A COLD FRONT WILL PUSH THROUGH
THE ALL OF THE MARINE ZONES BY LATE TOMORROW AFTN/EVN. WINDS WILL
QUICKLY VEER AROUND TO THE NORTH BUT SHOULD REMAIN QUITE STRONG. A
SCY WILL LIKELY NEED TO BE EXTENDED INTO THE OVERNIGHT HOURS THU.
THE OTHER ISSUE WITH THE FRONT WILL BE STRONG TO SVR STORMS AS A
SQUALL LINE WILL DEVELOP ALONG IT. THESE STORMS WILL EASILY BE
CAPABLE OF PRODUCING WINDS OF 40-50KTS AND IF ANY STORMS CAN
DEVELOP AHEAD OF THE SQUALLINE THEN WATERSPOUTS WILL BE A PROBLEM
AS WELL. ALL STORMS WILL COME TO AN END AFTER THE COLD FRONT MOVES
THROUGH. /CAB/
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 53 66 58 67 / 30 30 90 100
BTR 56 72 59 66 / 30 30 90 100
MSY 56 73 61 72 / 10 20 80 100
GPT 53 68 59 67 / 10 30 70 100
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY FROM MIDNIGHT THURSDAY TO 6 AM FRIDAY FOR
THE FOLLOWING ZONES: COASTAL WATERS FROM PASCAGOULA MS TO
THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60
NM...COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST
PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS
FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO LOWER
ATCHAFALAYA RIVER LA FROM 20 TO 60 NM...AND COASTAL WATERS
FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO LOWER
ATCHAFALAYA RIVER LA OUT 20 NM.
SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 6 AM FRIDAY FOR THE
FOLLOWING ZONES: AND LAKE PONTCHARTRAIN AND LAKE MAUREPAS.
MS...NONE.
GM...SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 6 AM FRIDAY FOR THE
FOLLOWING ZONES: AND LAKE PONTCHARTRAIN AND LAKE MAUREPAS.
SMALL CRAFT ADVISORY FROM MIDNIGHT THURSDAY TO 6 AM FRIDAY FOR
THE FOLLOWING ZONES: COASTAL WATERS FROM PASCAGOULA MS TO
THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60
NM...COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST
PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS
FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO LOWER
ATCHAFALAYA RIVER LA FROM 20 TO 60 NM...AND COASTAL WATERS
FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO LOWER
ATCHAFALAYA RIVER LA OUT 20 NM.
&&
$$
