Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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000
FXUS64 KLIX 250934
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
334 AM CST THU DEC 25 2014

.SYNOPSIS...

HIGH PRESSURE CENTERED OVER THE AREA EARLY THIS CHRISTMAS MORNING.
LITTLE IN THE WAY OF CLOUD COVER OVER LAND...BUT THERE ARE COLD
AIR STRATOCUMULUS CLOUDS OFFSHORE. NORTH SHORE LOCATIONS ARE
CURRENTLY IN THE MIDDLE AND UPPER 30S. SOUTH OF LAKE PONTCHARTRAIN
AND NEAR MARINE INFLUENCES...TEMPERATURES WERE GENERALLY IN THE
40S.

&&

.SHORT TERM...

HIGH PRESSURE WILL GRADUALLY SHIFT EASTWARD TO THE ATLANTIC COAST
BY FRIDAY AFTERNOON. THIS WILL RESTART ONSHORE FLOW AND INCREASE
MOISTURE. IT WILL TAKE A WHILE FOR MOISTURE TO RETURN FULLY AS
YESTERDAYS COLD FRONT HAS REACHED THE SOUTHERN GULF OF MEXICO.
EXPECT DRY WEATHER TODAY AND TONIGHT. AS ISENTROPIC ASCENT
BEGINS OVER THE COOL AIR TOMORROW AFTERNOON...THERE COULD BE A FEW
SHOWERS BY LATE AFTERNOON...BUT SHOULD NOT AMOUNT TO MUCH.

RAIN CHANCES INCREASE FRIDAY NIGHT INTO SATURDAY AS AN UPPER TROF
MOVES OUT OF THE SOUTHWEST STATES TOWARD THE AREA. INSTABILITY IS
NOT AS GOOD AS WHAT WE SAW TUESDAY...WITH CAPES 500-1000 AND
LIFTED INDICES -2 TO -4 ON SATURDAY...AS WELL AS MARGINAL LAPSE
RATES. MARINE LAYER COULD AGAIN BE A LIMITING FACTOR. BEST
HELICITY VALUES OCCUR WHILE FORECAST SOUNDINGS INDICATE ANY
CONVECTION IS ELEVATED. BY THE TIME ANY STORMS BECOME SURFACE
BASED...HELICITY VALUES DROP SIGNIFICANTLY. THIS MORNINGS SWODY3
CARRYING A MARGINAL RISK FOR SEVERE WEATHER SATURDAY ACROSS
WESTERN TWO THIRDS OF THE AREA.

NOT A LOT OF VARIANCE IN GUIDANCE TEMPERATURES THROUGH FRIDAY
NIGHT AND HAVE ACCEPTED BLENDED VALUES. PRECIPITATION ON SATURDAY
SHOULD HOLD TEMPERATURES TOWARD THE COOL END OF GUIDANCE. 35

&&

.LONG TERM...

FRONT WILL HAVE A DIFFICULT TIME GETTING EAST OF THE AREA ON
SUNDAY AS TROF LAGS ACROSS TEXAS. THIS WILL HOLD RAIN CHANCES IN
THE LIKELY CATEGORY INTO SUNDAY NIGHT BEFORE THE WEAKENING TROF
FINALLY PASSES EAST OF THE AREA. MULTIPLE IMPULSES MOVING THROUGH
THE TROF...THERE WILL BE SEVERAL PERIODS OF PRECIPITATION WITH
RAIN TOTALS OF TWO TO THREE INCHES CERTAINLY REASONABLE FOR THE
WEEKEND. WE WILL NEED TO MONITOR THIS AS THE TUESDAY EVENT HAS
PRIMED THINGS SOMEWHAT. CANNOT RULE OUT A FEW STRONG STORMS ON
SUNDAY EITHER...DEPENDING ON EXACT LOCATION OF THE FRONT. SPC
DISCUSSED POTENTIAL FOR SUNDAY...BUT CONFIDENCE NOT HIGH ENOUGH TO
OUTLOOK.

MEDIUM RANGE GUIDANCE A LITTLE MORE IN LINE NOW...AT LEAST THROUGH
MID WEEK NEXT WEEK. GUIDANCE IS TRENDING DRIER FOR MONDAY AND
TUESDAY. WILL HOLD SLIGHT POPS FOR ONE MORE RUN FOR THOSE DAYS PER
GFS GUIDANCE BUT WILL NOTE THAT ECMWF GUIDANCE HAS US DRY THOSE
TWO DAYS. ANOTHER SOUTHWESTERN TROF WILL APPROACH TOWARD THE END
OF NEXT WEEK...BUT SOME DIVERGENCE IN SOLUTIONS...AND WILL JUST
BLEND FOR NOW.

QUITE A BIT OF SPREAD IN TEMPERATURES BEGINNING SUNDAY IN THE
MEDIUM RANGE TEMPERATURE GUIDANCE. THIS HAS A LOT TO DO WITH EXACT
LOCATION OF THE COLD FRONT. ECMWF HAS THE FRONT SOMEWHAT FURTHER
EAST THAN THE OPERATIONAL GFS...WHICH GIVES AS MUCH AS A 15 DEGREE
TEMPERATURE DIFFERENCE OVER THE WESTERN PORTION OF THE CWA FOR
SUNDAY AND SUNDAY NIGHT. THIS ALSO OCCURS IN THE GFS ENSEMBLE
NUMBERS WITH THE OPERATIONAL GFS ONE OF THE WARMEST...IF NOT THE
WARMEST MEMBERS...SUNDAY THROUGH THE END OF THE FORECAST. WILL USE
A MODEL BLEND IN RECOGNITION OF THE COOLER MEMBERS AND ECMWF.

&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL THROUGH FRIDAY MORNING. 22/TD

&&

.MARINE...

THE CENTER OF A HIGH PRESSURE RIDGE HAS BEEN MOVING INTO THE
CENTRAL GULF COAST REGION OVERNIGHT...AND THE RESULTANT SLACKENING
PRESSURE GRADIENT OFFSHORE HAS BEEN ALLOWING WINDS TO DIMINISH BELOW
SMALL CRAFT ADVISORY CRITERIA. CHAOTIC SEAS UP TO AROUND 6 FEET OVER
THE OFFSHORE WATERS ARE STILL VERY UNPLEASANT FOR SMALL CRAFT TO
NAVIGATE THROUGH...AND A /SMALL CRAFT EXERCISE CAUTION/ HEADLINE
WILL REMAIN IN EFFECT UNTIL 6 AM THIS MORNING. WINDS SHOULD CONTINUE
TO DIMINISH TO 10 KNOTS OR LESS OVER MOST INNER WATERS NEAR TO
SHORTLY AFTER SUNRISE...AND TO 10 TO 15 KNOT OVER THE OFFSHORE
WATERS. THE CENTER OF THE HIGH WILL MOVE SLOWLY EAST ACROSS THE
LOCAL AREA THROUGH ABOUT MIDDAY TODAY THEN SHIFT EAST THIS AFTERNOON
THROUGH THE WEEKEND. FAIRLY LIGHT EAST WINDS OF 10 KNOTS OR LESS
THIS AFTERNOON ARE EXPECTED TO TURN EAST TO SOUTHEAST 10 TO 15 KNOTS
TONIGHT AND FRIDAY.

THE PRESSURE GRADIENT WILL LIKELY UNDERGO ADDITIONAL TIGHTENING
FRIDAY NIGHT INTO SATURDAY MORNING AS THE HIGH PRESSURE RIDGE
REMAINS ANCHORED TO THE EAST AND THE NEXT FRONTAL SYSTEM APPROACHES
THE WESTERN GULF COAST AND LOWER MISSISSIPPI VALLEY. EAST/SOUTHEAST
WINDS ARE EXPECTED TO RISE INTO THE 15 TO 20 KNOTS RANGE DURING THIS
TIME...THEN THE WINDS SHOULD WEAKEN SATURDAY AFTERNOON THROUGH
SUNDAY AS A COLD FRONT MOVES INTO THE CENTRAL GULF COAST REGION.
CONFIDENCE IN THE TIMING OF THIS FRONT IS LOW AT THIS TIME...HOWEVER
SOME STRONGER NORTHEAST WINDS NEAR 15 KNOTS ARE EXPECTED TO DEVELOP
ON TUESDAY AS FRONT SHOULD BE WELL OFFSHORE INTO THE NORTHERN OR
CENTRAL GULF OF MEXICO BY THAT TIME. 22/TD

&&

.DECISION SUPPORT...

DSS CODE...GREEN
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT

DECISION SUPPORT SERVICES (DSS) CODE LEGEND
GREEN  = NO WEATHER IMPACTS THAT REQUIRE ACTION
BLUE   = LONG FUSED WATCH/WARNING/ADVISORY IN EFFECT OR HIGH
         VISIBILITY EVENT
YELLOW = HEIGHTENED IMPACTS WITH SHORT FUSED
         WATCH/WARNING/ADVISORY ISSUANCES; RADAR SUPPORT
ORANGE = HIGH IMPACTS - SLIGHT TO MODERATE RISK SEVERE; NEARBY
         TROPICAL EVENTS; HAZMAT OR OTHER LARGE EPISODES
RED    = FULL ENGAGEMENT FOR MODERATE TO HIGH RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  56  40  63  55 /   0  10  20  50
BTR  58  43  66  58 /   0  10  20  60
ASD  56  42  65  58 /   0  10  20  70
MSY  55  48  67  60 /   0  10  20  70
GPT  56  45  64  58 /   0   0  20  70
PQL  57  41  65  55 /   0  10  20  60

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&

$$







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