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

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000
FXUS64 KLIX 131256
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
656 AM CST SAT FEB 13 2016

...SOUNDING DISCUSSION...

A COLD FRONT MOVED ACROSS THE AREA AND OFFSHORE OVERNIGHT
DELIVERING DRIER AND COOLER AIR TO OUR AREA. THIS HAS RESULTED IN
OUR PRECIPITABLE WATER VALUE BEING CUT IN HALF FROM LAST EVENING
AND IS MEASURED AT 0.42 INCHES THIS MORNING. THE ATMOSPHERE IS
STABLE WITH A TEMPERATURE INVERSION FROM 1100 TO 3100 FEET. WINDS
AT THE SURFACE WERE FROM THE NORTHEAST AND THEN BACK AND BLOW FROM
THE NORTHWEST FROM 6000 FEET TO THE TROPOPAUSE. A PEAK WIND SPEED
OF 119 KNOTS WAS SAMPLED AT 42000 FEET.

12Z BALLOON INFO: A ROUTINE FLIGHT THAT LASTED 105 MINUTES AND
ATTAINED A HEIGHT OF 20.8 MILES ABOVE THE GROUND BEFORE BURSTING
NEAR BRETON NATIONAL WILDLIFE REFUGE 75 MILES DOWNRANGE FROM THE
OFFICE.

ANSORGE

&&

.PREV DISCUSSION... /ISSUED 346 AM CST SAT FEB 13 2016/

SHORT TERM...

A BACKDOOR COLD FRONT HAS MOVED THROUGH THE AREA
TONIGHT...RESULTING IN A RETURN TO NORTHEAST FLOW AND A SURGE OF
DRIER AND COLDER AIR INTO THE AREA. THE DRY AIR HAS BEEN ADVECTING
IN AT A MUCH QUICKER RATE THAN THE COLD AIR...BUT TEMPERATURES
HAVE FINALLY BEGUN TO FALL ACROSS THE AREA OVER THE LAST COUPLE OF
HOURS. CONTINUED COOLING THROUGH THE REMAINDER OF THE OVERNIGHT
HOURS CAN BE EXPECTED...AND FORECAST LOWS FOR THIS MORNING LOOK TO
BE ON TRACK.

THE COLD AIR ADVECTION SHOULD PERSIST THROUGH THE DAY...WITH
925MB TEMPERATURES COOLING FROM THE LOWER 50S THIS MORNING TO THE
MIDDLE 40S BY THIS AFTERNOON. AS A RESULT...SURFACE HIGHS SHOULD
ONLY CLIMB INTO THE UPPER 50S AND LOWER 60S TODAY. THESE READINGS
ARE A GOOD 15 DEGREES COOLER THAN SEEN YESTERDAY AFTERNOON. THE
MUCH DRIER AIRMASS OVER THE AREA WILL KEEP CLEAR SKIES IN PLACE AS
WELL. THESE CLEAR SKIES COMBINED WITH THE DRY AIRMASS IN PLACE
SHOULD ALLOW OVERNIGHT LOWS TO COOL INTO THE 30S AND LOWER 40S
OVER THE AREA. THE WARMEST READINGS WILL BE ALONG THE LOUISIANA
COAST AND SOUTH OF LAKE PONTCHARTRAIN.

HEADING INTO TOMORROW...WINDS SHOULD QUICKLY VEER BACK TO THE
SOUTHEAST DURING THE MORNING HOURS...AS A SURFACE HIGH OVER THE
AREA SHIFTS TO THE EAST. TEMPERATURES SHOULD MODERATE SLIGHTLY
BACK INTO THE LOWER TO MIDDLE 60S...WHICH IS THE SEASONAL NORM FOR
MID-FEBRUARY. THIS ONSHORE FLOW COMPONENT WILL ALSO ALLOW FOR
MOISTURE ADVECTION TO OCCUR THROUGH THE DAY...AND EXPECT DEWPOINTS
TO CLIMB FROM THE UPPER 20S AND 30S IN THE MORNING INTO THE UPPER
40S AND LOWER 50S BY THE EVENING HOURS. AS THIS
OCCURS...INCREASING OMEGA WILL BE DEVELOPING OVER THE AREA REGION
IN RESPONSE TO A 100+ KNOT JET STREAK MOVING ACROSS TEXAS AND INTO
THE GULF SOUTH. THIS JET STREAK WILL ALSO TRANSPORT SOME MID AND
HIGH LEVEL MOISTURE INTO THE AREA...AND EXPECT TO SEE CLOUD COVER
BE ON THE INCREASE THROUGH THE AFTERNOON AND EVENING HOURS
TOMORROW. THERE COULD EVEN BE AN ISOLATED SHOWER DEVELOPING NEAR
THE ATCHAFALAYA BASIN BY LATE AFTERNOON.

CONDITIONS WILL BEGIN TO DETERIORATE SUNDAY NIGHT AS THE JET
STREAK SLIDES ACROSS THE AREA...AND A POTENT UPPER LEVEL TROUGH
BEGINS TO DIG INTO THE ARKLATEX. IN THE LOW LEVELS...A SURFACE LOW
SHOULD DEVELOP OVER TEXAS AND QUICKLY MOVE INTO THE ARKLATEX
REGION BY MONDAY MORNING. AS THIS LOW DEEPENS...A DRY LINE SHOULD
FORM TO THE SOUTH ACROSS CENTRAL TEXAS. THIS DRY LINE WILL SWEEP
EASTWARD ON THE BACK OF THE PARENT UPPER LEVEL TROUGH...AND SHOULD
BE LOCATED OVER WESTERN LOUISIANA BY MONDAY MORNING. THE
COMBINATION OF UPPER LEVEL FORCING ALOFT AND A STRONG BAROCLINIC
LOW IN THE LOW LEVELS WILL SUPPORT THE FORMATION OF SHOWERS AND A
FEW THUNDERSTORMS ACROSS MOST OF THE FORECAST AREA BY LATE SUNDAY
NIGHT. GIVEN THESE PARAMETERS...HAVE WENT WITH HIGH END CHANCE
POPS FOR MUCH OF THE AREA SUNDAY NIGHT.

THE DRY LINE AT THE SURFACE AND THE UPPER LEVEL TROUGH AXIS WILL
BOTH SLIDE THROUGH THE FORECAST AREA MONDAY AFTERNOON. THE LATEST
MODEL SOUNDINGS SUGGEST THERE WILL BE SOME THERMODYNAMIC SUPPORT
FOR DEEPER CONVECTION AND THUNDERSTORMS TO DEVELOP. MUCAPE VALUES
WILL BE AROUND 1500 J/KG AND LIFTED INDICES ARE EXPECTED TO ON THE
ORDER OF -5C. A FAIRLY LOW LCL WILL ALSO BE IN PLACE AT AROUND
2000 FEET. THERE SHOULD ALSO BE AMPLE MOISTURE TO WORK WITH...AS
PW VALUES RISE TO AROUND 1.10 INCHES AND MIXING RATIOS INCREASE TO
AROUND 10 G/KG. ADDITIONALLY...WET BULB ZERO HEIGHTS SHOULD BE
AROUND 9000 FEET...WHICH WOULD SUPPORT SOME HAIL FORMATION IN THE
DEEPEST CONVECTION. LOOKING AT KINEMATIC SUPPORT...SOME MARGINAL
SHEAR IS IN PLACE WITH 0-3KM HELICITY VALUES OF AROUND 150 M2/S2
AND TOTAL SHEAR OF 40 KNOTS. THESE VALUES WOULD SUPPORT SOME WEAK
MESOCYCLONIC DEVELOPMENT IN THE MOST PERSISTENT UPDRAFTS...AND
SOME TILTING OF THE UPDRAFT WHICH WOULD ALLOW FOR LONGER LASTING
CONVECTION. GIVEN ALL OF THESE PARAMETERS...A FEW STRONG TO
POSSIBLE THUNDERSTORMS CANNOT BE RULED OUT ON MONDAY. OUTSIDE OF
THE THUNDERSTORM THREAT...NUMEROUS TO WIDESPREAD SHOWERS CAN BE
EXPECTED THROUGHOUT THE DAY UNDER A MOSTLY CLOUDY SKY. THE STRONG
FLOW OFF THE GULF SHOULD ALLOW TEMPERATURES TO CLIMB BACK INTO THE
LOWER 70S MONDAY AFTERNOON...FURTHER FUELING OVERALL INSTABILITY
ACROSS THE AREA.

AT THIS TIME...IT LOOKS LIKE THE BEST CHANCES FOR RAIN OVER
WESTERN ZONES WILL BE IN THE LATE MORNING AND EARLY AFTERNOON AS
THE DRY LINE MOVES IN. THIS DRY LINE WILL RACE EASTWARD ACROSS THE
REMAINDER OF THE FORECAST AREA THROUGH THE AFTERNOON HOURS...AND
SHOULD BE OVER THE MISSISSIPPI COASTAL COUNTIES BY THE EVENING.
THE DRY LINE SHOULD THEN PUSH EAST OF THE AREA BY LATE EVENING
MONDAY...WITH CLEARING SKIES AND DIMINISHING RAIN CHANCES THROUGH
THE EVENING HOURS. ONLY A FEW SHOWERS MAY BE LINGERING IN THE
FAR EASTERN OUTER WATERS BY TUESDAY MORNING. THERE SHOULD BE
LITTLE IN THE WAY OF COLD AIR ADVECTION ASSOCIATED WITH THE DRY
LINE PASSAGE MONDAY NIGHT...WITH OVERNIGHT LOWS ONLY EXPECTED TO
COOL INTO THE MIDDLE TO UPPER 40S.

LONG TERM...

ONCE THE SYSTEM ON MONDAY PASSES TO THE EAST...A MUCH QUIETER
WEATHER REGIME IS EXPECTED TO SETTLE IN FOR THE REMAINDER OF NEXT
WEEK. THE AREA WILL REMAIN BENEATH A DEEP LAYER NORTHWEST FLOW
REGIME FOR TUESDAY AND WEDNESDAY. STRONG SUBSIDENCE AND CONTINUE
DRY AIR ADVECTION INTO THE AREA WILL KEEP SKIES CLEAR AND
HUMIDITIES LOW. GIVEN THE LACK OF ANY COLD POOL WITH THE BUILDING
AREA OF HIGH PRESSURE...TEMPERATURES SHOULD GENERALLY BE NEAR
SEASONAL NORMS IN THE MIDDLE TO UPPER 60S DURING THE AFTERNOON
HOURS AND THE 40S AND LOWER 50S AT NIGHT.

HEADING INTO THURSDAY...A SHORTWAVE RIDGE AXIS WILL MOVE ACROSS
THE GULF SOUTH. STRONG SUBSIDENCE THROUGHOUT THE ATMOSPHERE WILL
BRING CLEAR SKIES AND WARMER DAYTIME HIGHS TO THE REGION.
AFTERNOON HIGHS SHOULD EASILY CLIMB INTO THE LOWER 70S ON
THURSDAY...AND MAY EVEN RISE INTO THE MIDDLE 7OS. OVERNIGHT LOWS
WILL BE LITTLE CHANGED IN THE 40S AND LOWER 50S AS A FAIRLY LARGE
DIURNAL RANGE IS EXPECTED GIVEN THE CLEAR SKIES AND DRY AIR OVER
THE REGION. A REPEAT OF THE SAME CONDITIONS CAN BE EXPECTED FOR
FRIDAY...WITH EVEN WARMER TEMPERATURES POSSIBLE AS COMPRESSIONAL
HEATING INCREASES. A WEAK FRONT MAY SLIP THROUGH THE AREA FRIDAY
NIGHT AND SATURDAY...BUT THIS FRONT WILL BE MOISTURE STARVED. AT
MOST...A WIND SHIFT TO THE NORTH COULD OCCUR...BUT TEMPERATURES
SHOULD BE LITTLE CHANGED.  32

AVIATION...

VFR CONDITIONS ARE EXPECTED AT ALL TERMINALS TODAY WITH GUSTY NORTH
WINDS DURING THE DAYLIGHT HOURS SETTLING TO LIGHTER LEVELS AFTER
SUNSET. 24/RR

MARINE...

FRONT HAS MOVED OFF THE COAST BUT COLD AIR ADVECTION IS A
BIT IN LAG FROM WINDSHIFT. DRY AIR DRAINAGE DOWN THE MOBILE
RIVER/BAY BASIN IS PRODUCING SOME GUSTY WINDS AND HIGHER SEA STATE
IN THE EASTERN WATERS THAT WILL EVENTUALLY SPREAD WESTWARD AS THE
COLD AIR ADVECTION FILTERS INTO THE NORTH GULF LATER THIS MORNING.
THE FRONTAL PASSAGE FOR MONDAY DOES NOT APPEAR TO BE AS STRONG AS
EARLIER INDICATED IN MODELS BUT SHOULD STILL BE ABLE TO PRODUCE
MARGINAL SMALL CRAFT ADVISORY CONDITIONS FOR SOME DURATION MONDAY
NIGHT. 24/RR

DECISION SUPPORT...

DSS CODE....BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...RIVER FLOODING CONTINUES ON THE PEARL RIVER AND
MISSISSIPPI RIVER AT RED RIVER LANDING.

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 RISK SVR AND/OR DIRECT
         TROPICAL THREATS; EVENTS OF NATIONAL SIGNIFICANCE

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  58  33  62  52 /   0   0  10  40
BTR  61  39  64  53 /   0   0  10  40
ASD  59  35  63  53 /   0   0   0  40
MSY  59  45  64  52 /   0   0   0  40
GPT  58  36  61  51 /   0   0   0  40
PQL  58  32  60  50 /   0   0   0  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 9 AM CST THIS MORNING FOR GMZ555-557-
     572-575-577.

MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 9 AM CST THIS MORNING FOR GMZ557-572-
     575-577.

&&

$$


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