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

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FXUS64 KLIX 150354
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
954 PM CST FRI NOV 14 2014

.UPDATE...

TAKING A LOOK AT HOURLY TEMPERATURES TRENDS THIS EVENING...THE
ONLY AREAS FALLING IN LINE WITH THE EARLIER FORECAST ARE ALONG THE
PEARL RIVER VALLEY AT BOGALUSA AND SLIDELL...AND ALONG THE
PASCAGOULA BASIN NEAR PASCAGOULA WHERE COLD AIR DRAINAGE WAS
COMING INTO PLAY. ELSEWHERE...TEMPERATURES WERE RUNNING ABOUT 2 TO
4 DEGREES ABOVE EARLIER FORECASTS. SKIES SHOULD REMAIN CLEAR WITH
THE ONLY EXCEPTION BEING IN THE FAR NORTHWEST AND SOUTHWEST WHERE
TWO AREAS OF WARM ADVECTION LOWER CLOUDS WITH BASES AROUND 5000
FEET WERE ADVANCING SLOWLY EAST. IT IS ANTICIPATED THE WEDGE OF
DRY AIR OVER THE REGION WILL HOLD AND KEEP THESE CLOUDS MOSTLY ON
THE FRINGE OF THE WESTERN FORECAST AREA MOST OF TONIGHT BEFORE
TRYING TO MAKE SOME BETTER PROGRESS INTO WESTERN AREAS ON
SATURDAY. THE 3 TO 5 KNOTS OF NORTHERLY WINDS WERE JUST ENOUGH TO
ALSO HELP SLOW THE TEMPERATURE DROP...AND THESE WIND SPEEDS MAY
CONTINUE THROUGH THE NIGHT GIVEN THE AXIS OF THE SURFACE RIDGE AND
PRESSURE GRADIENT ARE NOT EXPECTED TO CHANGE MUCH. GIVEN THESE
FACTORS...THERE IS STILL PLENTY OF NIGHTTIME HOURS LEFT FOR
TEMPERATURES TO FALL IN LINE WITH FORECAST...SO HAVE ONLY MADE
SOME ADJUSTMENTS TO THE HOURLY VALUES...BUT HAVE KEPT THE FORECAST
LOWS THE SAME. THIS MEANS IT IS VERY UNLIKELY THE CITY OF NEW
ORLEANS AND THE MORE POPULATED SUBURBS SOUTH OF THE LAKE WILL
EXPERIENCE A FREEZE...HOWEVER...THE MORE RURAL PORTIONS OF ALL THE
PARISHES OF METRO NEW ORLEANS WILL LIKELY BE NEAR TO JUST BELOW
FREEZING FOR AN HOUR OR TWO. GIVEN THIS SCENARIO...IT IS PRUDENT
TO KEEP THE FREEZE WARNINGS INTACT. THE COLDER NORTHERN LOCATIONS
COULD GET CLOSE TO A HARD FREEZE...BUT THE LOCAL CRITERIA OF
SEEING MID 20S FOR A FEW HOURS IS UNLIKELY FOR MOST. FORECAST
UPDATES HAVE BEEN SENT. 22/TD

&&

.MARINE...

NORTHERLY WINDS HAVE INCREASED BACK TO 15 TO 20 KNOTS OVER THE
EASTERN MISSISSIPPI SOUND...AND A FEW AREAS NEAR THE BORDER WITH
THE ALABAMA WATERS MAY BE NEAR 20 KNOTS FOR A FEW HOURS OVERNIGHT.
GIVEN THE PERSISTENT PRESSURE GRADIENT...POSSIBLY TIGHTENING
SLIGHTLY WITH THE INCREASING THERMAL GRADIENT WITH LAND...HAVE
EXTENDED THE /SMALL CRAFT EXERCISE CAUTION/ HEADLINE OVERNIGHT FOR
THE MISSISSIPPI SOUND...AND KEPT THE HEADLINE IN EFFECT FOR THE
COASTAL WATERS AND SOUNDS EAST OF SOUTHWEST PASS. 22/TD

&&

.PREV DISCUSSION... /ISSUED 705 PM CST FRI NOV 14 2014/

SOUNDING DISCUSSION...

ROUTINE SOUNDING TERMINATED JUST NORTH OF THE WEST END OF DAUPHIN
ISLAND ALABAMA AT AN ALTITUDE OF 108K FEET OR ABOUT 20.5 MILES UP.
AIRMASS REMAINS RATHER DRY WITH A PRECIPITABLE WATER VALUE OF 0.48
INCHES. BASE OF THE MAIN INVERSION IS NEAR 3500 FEET THIS
EVENING...FAIRLY CLOSE TO WHERE IT WAS THIS MORNING. SOUNDING HAD
NORTHERLY WINDS IN THE LOWEST 5000 FEET AND MAINLY WESTERLY FOR
THE REMAINDER OF THE SOUNDING THROUGH 100 MB. PEAK WIND OF 85
KNOTS AT 38K FEET. WHILE SURFACE DEW POINTS ARE CURRENTLY NEAR 30
LOCALLY...MOST AREAS ARE RETAINING DEW POINTS IN THE 20S. ABOUT
500 FEET UP...DEW POINTS WERE IN THE LOWER AND MIDDLE TEENS
FAHRENHEIT. 35

PREV DISCUSSION... /ISSUED 357 PM CST FRI NOV 14 2014/

SHORT TERM...

DECREASING GRADIENT FLOW...A VERY DRY AIRMASS...AND CLEAR SKIES
COMBINED WITH A COLD AIRMASS WILL ALLOW FOR ANOTHER FREEZE TO
IMPACT A LARGE PORTION OF THE FORECAST AREA TONIGHT. A FREEZE
WARNING REMAINS IN EFFECT FOR ALL OF THE FORECAST AREA...EXCEPT
ALONG THE IMMEDIATE LOUISIANA COAST WHERE READINGS WILL REMAIN
ABOVE FREEZING. ALTHOUGH THE FREEZE WARNING IS IN EFFECT FOR METRO
NEW ORLEANS...FREEZING CONDITIONS ARE NOT EXPECTED IN THE
IMMEDIATE VICINITY OF LAKE PONTCHARTRAIN. THE WESTBANK WILL BE
MORE LIKELY TO SEE A FREEZE TONIGHT.

THE HIGH THAT HAS DOMINATED THE AREA THE LAST FEW DAYS WILL BEGIN
TO RETREAT TO THE EAST TOMORROW AND AN ONSHORE FLOW COMPONENT WILL
DEVELOP. THIS ONSHORE FLOW WILL BRING INCREASING MOISTURE INTO THE
AREA THROUGH THE DAY...AND EXPECT TO SEE SOME SCATTERED CLOUD
COVER DEVELOP BY THE AFTERNOON HOURS. TEMPERATURES WILL REMAIN
BELOW NORMAL...BUT WILL BE A GOOD 10 DEGREES WARMER THAN HIGH
TEMPERATURES SEEN TODAY.

A POTENT SHORT WAVE TROUGH WILL DIG DOWN FROM THE NORTHERN ROCKIES
AND INTO THE SOUTHERN PLAINS SUNDAY NIGHT. AS THIS OCCURS...THE
GULF SOUTH WILL BE PLACED INTO THE RIGHT ENTRANCE REGION OF A
STRONG UPPER LEVEL JET. THIS INCREASED OMEGA ALOFT WILL INTERACT
WITH AN AREA OF ENHANCED BAROCLINICITY OVER TEXAS. AS THIS
INTERACTION CONTINUES THROUGH THE NIGHT...CYCLOGENESIS WILL TAKE
PLACE OVER SOUTHERN TEXAS. THIS LOW WILL QUICKLY RACE TO THE
NORTHEAST AND PASS DIRECTLY OVER THE FORECAST AREA SUNDAY
AFTERNOON INTO SUNDAY EVENING ON THE BACK OF ANOTHER JET STREAK
ROUNDING THE BASE OF THE DEEPENING TROUGH IN THE PLAINS STATES. AT
THIS TIME...THE THREAT FOR SEVERE WEATHER REMAINS LOW. IF ANY
STRONGER STORMS ATTEMPT TO DEVELOP THEY WOULD LIKELY BE CONFINED
TO THE COASTAL WATERS AND POSSIBLY EXTREME COASTAL LOUISIANA WHERE
THE WARM SECTOR IS DEEPEST AND THE AIRMASS MOST UNSTABLE.

THE HEAVIEST RAINFALL WILL BE ASSOCIATED WITH THE DEFORMATION
ZONE ON THE NORTHWEST SIDE OF THE SURFACE LOW. EXPECT TO SEE A
BAND OF HEAVIER RAIN WITH ELEVATED THUNDERSTORMS EMBEDDED IN
STRETCHING ACROSS THE NORTHERN HALF OF THE FORECAST AREA. A
GENERAL 1 TO 2 INCHES OF RAINFALL WILL BE POSSIBLE...BUT SOME
LOCALIZED RAINFALL AMOUNTS OF UP TO 4 INCHES COULD OCCUR. THE
RAINS WILL FALL OVER A 6 TO 12 HOUR PERIOD...AND THE GROUND IS
FAIRLY DRY SO FLOODING SHOULD NOT BE A CONCERN.

LONG TERM...

MONDAY MORNING WILL SEE A SURGE OF COLDER AIR WRAP AROUND THE
PARENT HUDSON LOW IN EASTERN CANADA. THIS SECONDARY SHORT WAVE AND
COLDER AIRMASS WILL MERGE WITH THE SOUTHERN STREAM ENERGY TO
CREATE A DEEP LONGWAVE TROUGH OVER THE EASTERN CONUS. AS THE
POTENT 1030MB SURFACE HIGH MOVES INTO THE AREA...VERY COLD AIR
WILL ALSO SETTLE OVER THE REGION THROUGH THE DAY ON MONDAY AND
INTO MONDAY NIGHT. 925MB TEMPERATURES WILL PLUNGE FROM AN AVERAGE
OF AROUND 8C MONDAY MORNING TO -2C BY MONDAY EVENING. THIS
TRANSLATES INTO A NEARLY 20F DROP IN SURFACE TEMPERATURES. AS A
RESULT...EXPECT TO SEE FALLING TEMPERATURES THROUGH THE AFTERNOON
HOURS ON MONDAY.

FORTUNATELY...AS THIS COLDER AIR SURGES INTO THE AREA...DRIER AIR
WILL ALSO ADVECT IN. RAIN CHANCES WILL DECREASE THROUGH THE
MORNING HOURS AND SKIES WILL ALSO BEGIN TO CLEAR RAPIDLY BY MONDAY
EVENING. THUS...NO WINTRY WEATHER IS EXPECTED WITH THIS NEXT SURGE
OF COLDER AIR. OVERNIGHT LOWS MONDAY NIGHT WILL ONCE AGAIN FALL
BELOW FREEZING ACROSS MOST OF THE FORECAST AREA AND STRONG
GRADIENT FLOW WILL BRING BREEZY CONDITIONS TO THE AREA. DAYTIME
HIGHS ON TUESDAY WILL STRUGGLE TO REACH THE UPPER 40S EVEN UNDER
FULL SUN...AND A HARD FREEZE MAY IMPACT THE NORTHERN HALF OF THE
FORECAST AREA TUESDAY NIGHT AS THE HEART OF THE 1030MB HIGH
SETTLES DIRECTLY OVER THE FORECAST AREA.

THE HIGH WILL BEGIN TO RETREAT ON WEDNESDAY AND EXPECT TO SEE
WINDS TURN BACK TO THE SOUTHEAST BY THE AFTERNOON HOURS. THIS
ONSHORE FLOW WILL CONTINUE ON THURSDAY AS THE RIDGE AXIS BECOMES
CENTERED OVER THE EASTERN SEABOARD. A WARMER AND MORE MOIST
AIRMASS WILL GRADUALLY ADVECT INTO THE AREA...AND EXPECT READINGS
TO RISE BACK INTO THE LOWER TO MIDDLE 60S BY THURSDAY AFTERNOON.

AVIATION...

NO SIGNIFICANT AVIATION IMPACTS ARE EXPECTED THROUGH THE FORECAST
PERIOD AS A DRY AND STABLE AIRMASS DOMINATES THE AREA.

MARINE...

GRADIENT FLOW WILL CONTINUE TO WEAKEN TONIGHT AND TOMORROW AS A
SURFACE HIGH RETREATS TO THE EAST OF THE AREA. WINDS WILL SHIFT
FROM THE NORTHEAST TO THE EAST AND THEN SOUTHEAST DURING THIS
PERIOD. HEADING INTO SUNDAY...A LOW PRESSURE SYSTEM WILL MOVE
THROUGH THE AREA. INCREASED ONSHORE FLOW WILL DEVELOP IN ADVANCE
OF THIS LOW...AND EXPECT TO SEE EXERCISE CAUTION CONDITIONS
DEVELOP IN THE GULF WATERS FOR SUNDAY AND SUNDAY NIGHT. A STRONG
FRONTAL BOUNDARY WILL THEN SWITCH WINDS TO THE NORTHWEST AND NORTH
DURING THE DAY ON MONDAY. AS COLDER AND DRIER AIR SURGES OVER THE
WATERS...STRONG GRADIENT FLOW ALOFT WILL EASILY MIX DOWN TO THE
SURFACE. EXPECT TO SEE ANOTHER ROUND OF SMALL CRAFT ADVISORY
CONDITIONS TAKE HOLD DURING THE DAY ON MONDAY AND PERSIST INTO
TUESDAY.

DECISION SUPPORT...

DSS CODE...BLUE.
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  26  56  44  65 /   0   0  10  90
BTR  26  57  46  69 /   0   0  10  90
ASD  26  57  45  70 /   0   0  10  60
MSY  35  56  51  70 /   0   0  10  60
GPT  30  56  48  69 /   0   0  10  50
PQL  26  56  42  69 /   0   0  10  40

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FREEZE WARNING UNTIL 9 AM SATURDAY FOR THE FOLLOWING ZONES:
     ASCENSION...ASSUMPTION...EAST BATON ROUGE...EAST
     FELICIANA...IBERVILLE...LIVINGSTON...NORTHERN
     TANGIPAHOA...ORLEANS...POINTE COUPEE...SOUTHERN
     TANGIPAHOA...ST. CHARLES...ST. HELENA...ST. JAMES...ST.
     JOHN THE BAPTIST...ST. TAMMANY...UPPER JEFFERSON...UPPER
     LAFOURCHE...UPPER PLAQUEMINES...UPPER ST. BERNARD...UPPER
     TERREBONNE...WASHINGTON...WEST BATON ROUGE...AND WEST
     FELICIANA.

GM...NONE.
MS...FREEZE WARNING UNTIL 9 AM SATURDAY FOR THE FOLLOWING ZONES:
     AMITE...HANCOCK...HARRISON...JACKSON...PEARL
     RIVER...PIKE...WALTHALL...AND WILKINSON.

GM...NONE.
&&

$$







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