FXUS64 KLIX 291325
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
725 AM CST SUN NOV 29 2009
.UPDATE...
.SOUNDING DISCUSSION...
NO PROBLEMS WITH THE FLIGHT THIS MORNING. MOISTURE ON THE INCREASE
AS A GRADUAL RETURN FLOW FROM THE GULF BEGINS TO TAKE PLACE WITH
THE PW UP TO 1.15 INCHES. STILL PLENTY OF DRY AIR ABOVE 600
MILLIBARS. A STRONG INVERSION IN PLACE FROM THE SURFACE UP TO 1000
FEET ABOVE SEA LEVEL THIS MORNING. LIGHT SOUTHERLY WINDS AT THE
SURFACE AND A FAIRLY STRONG WESTERLY FLOW ALOFT. PATCHES OF
RADIATION FOG FORMED BELOW AND ALONG THE INVERSION WHERE THE
SOUNDING SHOWS DEW POINT DEPRESSIONS AROUND ZERO DEGREES.
&&
.PREV DISCUSSION... /ISSUED 426 AM CST SUN NOV 29 2009/
SHORT TERM...
SURFACE HIGH PRESSURE IS NOW LOCATED WEST OF THE AREA. THIS WILL
MEAN MORE SUBSTANTIAL CHANGES TO ATMO MOISTURE ACROSS THE AREA. LAST
SOUNDING INDICATED AN EXTREMELY DRY LAYER BETWEEN THE SFC AND AROUND
800MB. THIS SHOULD BE MUCH MORE ERODED BY THIS SOUNDING AND
COMPLETELY GONE BY THIS AFTERNOON. WATER VAPOR IMAGERY SHOWS
SUBTROPICAL MOISTURE MOVING ACROSS MEXICO THROUGH TX AND INTO THE
REGION. THE MAIN FEATURES ACROSS THE COUNTRY INCLUDE UPPER RIDGE
OVER THE SOUTHEAST...UPPER LOW CUTTING OFF NEAR THE AZ/CA
BORDER...AND UPPER TROUGH MOVING THROUGH THE EXTREME NORTHERN
PLAINS. SFC ANALYSIS SHOWS WESTERN EDGE OF THE COLD FRONT THAT WILL
IMPACT THE AREA RACING ACROSS WESTERN OK AND THE TEXAS PANHANDLE.
THIS BOUNDARY SHOULD BE REACHING THE NWRN PORTION OF LA AROUND
SUNSET. MEANWHILE...HIGH LEVEL CLOUDS WILL MOVE IN FROM THE WEST IN
ASSOCIATION WITH MID LEVEL SWRN MOISTURE PLUME. HIGH TEMPS WILL
MODIFY A LITTLE MORE TODAY WITH HIGHS IN THE UPPER 60S TO LOWER 70S.
DID UNDERCUT GUIDANCE A FEW DEGREES AGAIN TODAY DUE TO SLIGHTLY WARM
BIAS AS OF MOST RECENT FCSTS. OTHER THAN BEING MOSTLY CLOUDY...RAIN
WILL NOT IMPACT THE CWA DURING THE DAY. DEWPOINTS SHOULD INCREASE
SUBSTANTIALLY OVERNIGHT WHICH WILL RESULT IN MUCH WARMER LOWS
TONIGHT.
LONG TERM...
MODELS ARE IN GOOD AGREEMENT ON THE TIMING OF THE FRONT. THE INITIAL
WIND SHIFT FOR THE CWA SHOULD BE AROUND SUNRISE MONDAY. A BAND OF
POST FRONTAL SHOWERS BRING THE FIRST ROUND OF RAIN TO THE AREA. THE
BOUNDARY WILL STALL ACROSS THE NORTHERN GULF MONDAY NIGHT. A SFC LOW
WILL THEN DEVELOP IN THE WESTERN GULF. AT THE SAME TIME...UPPER LOW
MENTIONED EARLIER WILL BE TRACKING EASTWARD ACROSS NORTHERN MEXICO.
FROM THIS POINT...THERE IS SOME DISAGREEMENT OF THE TRACK OF THE
SFC LOW. GFS HAS THE MOST SOUTHERLY TRACK WITH THE LOW MAINLY
STAYING ALONG THE COASTAL PARISHES. NAM IS THE MOST NORTHERLY WHILE
ECMWF IS IN THE MIDDLE OF THOSE TWO SO HAVE GONE WITH THIS
COMPROMISE MOVEMENT. THE MAIN CONCERN WITH THIS SYSTEM IS HEAVY
RAINFALL ACROSS THE SOUTHERN HALF OF THE AREA TUESDAY AFTERNOON
THROUGH WEDNESDAY MORNING. COULD SEE A 3-5 INCH SWATH ALONG COASTAL
PARISH OF LA AND MS.
SHOULD BE IN THE CLEAR BY THURSDAY AS THE UPPER LOW QUICKLY EJECTS
NORTHEASTWARD AND BECOMES ABSORBED BY A TROUGH DIGGING ACROSS THE
COUNTRY. STRONG COLD AIR ADVECTION WILL BRING TEMPERATURES DOWN TO
CONDITIONS EXPERIENCED LAST WEEK WITH THE PREVIOUS STRONG COLD FRONT
THAT MOVED THROUGH. FRIDAY MORNING SHOULD BE THE COLDEST WITH
FREEZING TEMPS FOR OVERNIGHT LOWS IN ALL SOUTHERN MS COUNTIES AND
POSSIBLY A FEW PARISHES ALONG THE LA/MS BORDER. GRADUAL WARMING WILL
ENSUE THIS WEEKEND.
MEFFER
AVIATION...
VFR SKIES WITH SPOTTY MVFR VSBY NOTED CURRENTLY ACROSS SE LA AND S
MS. KMCB STARTING TO LOWER TO 2SM BR. MVFR CEILINGS NOTED IN W LA
AND E TX. CEILINGS ARE EXPECTED TO DEVELOP AND LOWER TO THE LOWER
END OF VFR NEXT 12 TO 24 HOURS. COLD FRONTAL PASSAGE APPEARS TO BE
BETWEEN 15Z-18Z MONDAY AT KBTR AND KMCB...BETWEEN 18Z AND 21Z AT
KMSY AND KGPT. MVFR AND OCCASIONAL IFR CONDITIONS ARE LIKELY AFTER
15Z MONDAY. 24/RR
MARINE...
VERY LIGHT WINDS AND FLAT SEAS TODAY WILL SLOWLY BUILD TONIGHT AND
MONDAY IN ADVANCE OF APPROACHING STRONG COLD FRONT. THE FRONT LIKELY
TO ARRIVE NEAR ATCHAFALAYA BAY BY NOON CST MONDAY AND EAST OF
PASCAGOULA BY 6 PM CST MONDAY. MODELS SHOW CONSENSUS AND CONSISTENCY
IN DEVELOPING A LOW PRESSURE SYSTEM IN THE WEST GULF TUESDAY MORNING
THAT MOVES NORTHEAST INTO OR ALONG THE LOUISIANA COAST WEDNESDAY
MORNING. GIVEN THE DEGREE OF BAROCLINICITY WITH THE
SYSTEM...FREQUENT GALE FORCE GUSTS ARE LIKELY AND A BRIEF PERIOD OF
SUSTAINED GALE CONDITIONS ARE POSSIBLE LATE TUESDAY NIGHT OR
WEDNESDAY MORNING. EXTRA-TROPICAL STORM SURGE MODELS INDICATE A
MODEST STORM SURGE DURING THE HIGH TIDE PORTION OF CYCLE WEDNESDAY
MORNING. COASTAL FLOODING SHOULD BE MINIMAL DUE TO SHORT DURATION
RUN-UP AND PRECONDITIONED OFFSHORE FLOW MONDAY INTO EARLY TUESDAY.
24/RR
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 68 54 58 43 / 10 30 70 20
BTR 71 57 63 46 / 10 30 70 30
MSY 72 60 70 50 / 10 10 50 30
GPT 73 57 71 49 / 10 10 50 20
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&
$$
