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

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

590
FXUS64 KLIX 121302
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
802 AM CDT SAT APR 12 2014

.SOUNDING DISCUSSION...
NO PROBLEMS WITH FLIGHT THIS MORNING. PROFILE STILL RELATIVELY DRY
ABOVE 885 MB BUT FEATURES A SATURATED INVERSION AT THE SURFACE AND
A NEARLY SATURATED MARINE LAYER COLUMN BELOW 885 SUBSIDENCE
INVERSION. THE SUBSIDENCE INVERSION EXTENDS TO 770 MB THEN
ADIABATIC THROUGH TROPOPAUSE AT 210 MB. TROP TEMP -71C.
PRECIPITABLE WATER 0.80 INCHES IS THE SAME AS 00Z SOUNDING. WINDS
WERE SOUTHEAST 5-20 KT SURFACE TO 4800FT...A CALM LEVEL AT
6700FT...EAST 5-10 KT UP TO ANOTHER CALM LEVEL AT 15.6KFT...THEN
WESTERLY 25-70 KT ABOVE. PEAK WIND 260/69 KT AT 51.1KFT. LIFTED
INDEX IS -4.9 BUT LARGE CAP SHOULD LIMIT CONVECTION TO JUST MARINE
LAYER AFFECTS WITH SUPPRESSION ABOVE 6500 FT. BALLOON BURST AT 7.9
MB OR 31500M/19.6 MILES UP ABOUT 36 MILES DOWNRANGE...2 MILES
SOUTH OF PASS CHRISTIAN IN THE MISSISSIPPI SOUND.  24/RR

&&

.PREV DISCUSSION... /ISSUED 426 AM CDT SAT APR 12 2014/

SYNOPSIS...

HIGH PRESSURE CENTERED OFF THE ATLANTIC COAST WITH AXIS OF HIGH
EXTENDING WESTWARD ACROSS CENTRAL MISSISSIPPI AND NORTHERN
LOUISIANA. ONSHORE FLOW RETURNING MOISTURE TO THE AREA. LOW CLOUDS
AND/OR FOG HAVE DEVELOPED AT MOST LOCATIONS IN THE AREA. WHILE
MOST AREAS ARE SEEING TEMPERATURES IN THE MID 60S AT 3 AM...A FEW
LOCATIONS HAVE FALLEN INTO THE MIDDLE AND UPPER 50S.

SHORT TERM...

A DIFFLUENT WEST TO WEST-SOUTHWEST MID/UPPER LEVEL FLOW WILL
DOMINATE OVER THE CENTRAL GULF COAST REGION THROUGH SUNDAY. WINDS
WILL BE GRADUALLY RISING AT ALL LEVELS AS A BROAD TROUGH DEVELOPS
OVER THE WESTERN/CENTRAL STATES AND CAUSES THE SOUTHERN STREAM TO
GET MORE ACTIVE GOING INTO LATE SUNDAY. SURFACE HIGH PRESSURE WILL
REMAIN IN CONTROL AND KEEP THE FORECAST AREA DRY THROUGH THE DAYTIME
HOURS ON SUNDAY BEFORE THE NEXT FRONTAL SYSTEM APPROACHES. NEAR CALM
TO LIGHT SOUTHEAST WINDS HAVE ALLOWED FOR LOW LEVEL RADIATIONAL
COOLING AND MOISTURE ADVECTION WHICH HAS RESULTED IN AREAS OF LOW
STRATUS AND FOG EARLY THIS MORNING. WILL CONTINUE TO MONITOR
VISIBILITY TRENDS WHICH SHOW LOCALLY 1/4 MILE IN A FEW OBSERVATIONS.
IF DENSE FOG BECOMES MORE PERSISTENT OR WIDESPREAD WITH BELOW 1/4
MILE VISIBILITY THEN A DENSE FOG ADVISORY MAY BE REQUIRED FOR A FEW
HOURS. THE FOG SHOULD BURN OFF BY AROUND 9 AM...THEN IT SHOULD BE
PARTLY CLOUDY...WARM...AND MORE HUMID. A TIGHTENING PRESSURE
GRADIENT TONIGHT WILL KEEP WINDS UP...SO ANY FOG SHOULD REMAIN LIGHT
AND ASSOCIATED WITH MORE OF A LOW OVERCAST CLOUD DECK. SUNDAY WILL
BE SIMILAR TO TODAY...EXCEPT IT WILL BE MORE BREEZY WITH SOUTH WINDS
15 TO 25 MPH WITH HIGHER GUSTS. 22/TD

LONG TERM...

SUNDAY NIGHT THROUGH THE END OF THE FORECAST.

SHORTWAVE MOVING OUT OF TEXAS INTO THE MIDDLE AND LOWER
MISSISSIPPI RIVER VALLEY WILL HAVE PLENTY OF MOISTURE TO WORK
WITH AS PRECIPITABLE WATER VALUES RAMP UP TO BETWEEN 1.75 AND 2
INCHES BY SUNDAY NIGHT AND MONDAY MORNING.

TIMING AND AMPLITUDE DIFFERENCES CONTINUE TO EXIST WITH THE
LONGWAVE TROF EXPECTED TO MOVE ACROSS THE AREA ON MONDAY. THE
OPERATIONAL EURO SOLUTIONS CONTINUE TO BE SLOWEST/DEEPEST WITH THE
TROF...BUT ONLY ABOUT 6 HOURS SLOWER THAN GFS/NAM THROUGH TUESDAY.
SOUTHERN STREAM SHORTWAVE MOVES ACROSS THE AREA LATE SUNDAY NIGHT
WITH ACTUAL COLD FRONT ONLY JUST ENTERING NORTHWEST LOUISIANA BY
EARLY MONDAY MORNING. THUNDERSTORMS IN ADVANCE OF THE FRONT COULD
AFFECT WESTERN PORTIONS OF THE AREA BY SUNRISE ON MONDAY AS THE
SOUTHERN STREAM SHORTWAVE WEAKENS. A FEW OF THESE STORMS COULD BE
STRONG TO SEVERE NEAR THE ATCHAFALAYA RIVER LATE SUNDAY NIGHT. A
STRONGER NORTHERN STREAM SHORTWAVE WILL PUSH THE COLD FRONT
THROUGH THE AREA MONDAY AFTERNOON AND MONDAY NIGHT. LOW LEVEL WIND
FIELDS WILL BE MORE CONDUCIVE FOR SEVERE THUNDERSTORM DEVELOPMENT
WITH THE FIRST SHORTWAVE...WHILE THE INSTABILITY AND UPPER WINDS
WILL BE MORE CONDUCIVE WITH THE SECOND SHORTWAVE. SPC HAS
OUTLOOKED THE ENTIRE AREA FOR A SLIGHT RISK MONDAY AFTERNOON AND
EVENING WITH THE SECOND SHORTWAVE. MOST LIKELY MODE WOULD BE
SQUALL LINE WITH EMBEDDED SUPERCELLS. MAIN THREAT WOULD BE
DAMAGING WIND...WHILE HAIL AND AN ISOLATED TORNADO OR TWO CANNOT
BE RULED OUT. HEAVY RAIN COULD ALSO BECOME A PROBLEM WITH TWO
ROUNDS OF CONVECTION EXPECTED. BETWEEN SUNDAY NIGHT AND TUESDAY
MORNING...MUCH OF THE AREA COULD SEE TWO TO THREE INCHES OF
RAIN...WHICH WOULD LIKELY BRING SIGNIFICANT RISES TO AREA RIVERS
AGAIN.

MUCH COOLER AIR WILL RETURN TO THE AREA BEHIND THE FRONT FOR
TUESDAY AND WEDNESDAY. HIGHS ACROSS THE AREA TUESDAY AND LOWS
TUESDAY NIGHT ARE LIKELY TO BE 10-15 DEGREES BELOW NORMAL AND
15-20 DEGREES COOLER THAN WHAT WE SEE THIS WEEKEND. THIS COULD
BRING TEMPERATURES IN THE UPPER 30S TO NORMALLY COLDER LOCATIONS
WEDNESDAY MORNING.

BEYOND WEDNESDAY NIGHT...SIGNIFICANT DIFFERENCES ARISE IN THE
EXTENDED MODEL SOLUTIONS. GFS SOLUTION BRINGS CHANCES OF
PRECIPITATION BACK TO THE AREA FOR THURSDAY NIGHT THROUGH THE
WEEKEND...WHILE THE ECMWF SOLUTION IS DRY THROUGH THE EASTER
WEEKEND. EARLIER FORECAST HAD SMALL MENTIONS OF PRECIPITATION IN
FOR FRIDAY...WHICH WOULD FOLLOW THE GFS SOLUTION. WILL NOT MAKE
CHANGES FOR NOW AND WILL CONTINUE THOSE SLIGHT CHANCE/CHANCE
PRECIPITATION CHANCES INTO SATURDAY. 35

AVIATION...

HIGHLY VARIABLE CONDITIONS PREVAIL...HOWEVER A GREATER NUMBER OF
AIRPORTS WERE EXPERIENCING IFR TO LIFR DUE TO A COMBINATION OF LOW
VSBYS AND/OR CIGS. SATELLITE IMAGERY SHOWS THE LOW CLOUDS ARE
CONTINUING TO EXPAND ACROSS THE AREA...AND SOME OF THE STRATUS IS
BUILDING DOWN RESULTING IN A COMBINATION OF BOTH RADIATION AND
ADVECTION FOG. AREAS WITH MORE URBANIZATION...THICKER HIGHER BASED
CLOUDS...AND ALONG THE IMMEDIATE COAST AND TIDAL LAKES SHOULD
MAINTAIN THE HIGHER VSBYS THIS MORNING. FOG AND LOWER CLOUDS WILL
LIFT AND IMPROVE ALL AIRPORTS BACK THROUGH MVFR TO VFR BY LATE
MORNING...THEN VFR SHOULD PREVAIL THROUGH MOST OF THE EVENING. LOW
CLOUDS WITH CIGS 003-007 ARE LIKELY AGAIN LATE TONIGHT INTO SUNDAY
MORNING...HOWEVER HIGHER SURFACE/LOW LEVEL WINDS SHOULD KEEP MOST
VSBYS 2-3 MILES OR GREATER. 22/TD

MARINE...

MODERATE ONSHORE FLOW MAY REQUIRE EXERCISE CAUTION HEADLINES BY
SUNDAY AFTERNOON...BUT MORE LIKELY SUNDAY NIGHT AND MONDAY AHEAD
OF THE COLD FRONT. COLDER AIR SHOULD REACH THE COASTAL WATERS BY
DAYBREAK TUESDAY WITH SMALL CRAFT ADVISORIES LIKELY TUESDAY AND
TUESDAY NIGHT. AS HIGH MOVES EAST...MODERATE ONSHORE FLOW WILL
RETURN BY THURSDAY NIGHT AND FRIDAY WITH ADDITIONAL HEADLINES
LIKELY. 35

DECISION SUPPORT...

DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT
             MONITORING RIVER FLOODING.

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  78  60  79  66 /  10  10  10  60
BTR  81  63  82  68 /  10  10  10  60
ASD  79  61  79  67 /   0  10  10  50
MSY  79  65  79  68 /  10  10  10  40
GPT  76  64  76  67 /   0   0  10  40
PQL  78  59  77  65 /   0   0  10  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...DENSE FOG ADVISORY UNTIL 9 AM SATURDAY FOR THE FOLLOWING ZONES:
     ASCENSION...ASSUMPTION...EAST BATON
     ROUGE...IBERVILLE...LIVINGSTON...LOWER
     PLAQUEMINES...ORLEANS...SOUTHERN TANGIPAHOA...ST.
     CHARLES...ST. JAMES...ST. JOHN THE BAPTIST...UPPER
     JEFFERSON...UPPER LAFOURCHE...UPPER PLAQUEMINES...UPPER ST.
     BERNARD...UPPER TERREBONNE...AND WEST BATON ROUGE.

GM...NONE.
MS...NONE.
GM...NONE.
&&

$$








USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.