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

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799
FXUS64 KLIX 131344
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
844 AM CDT SUN APR 13 2014

.SOUNDING DISCUSSION...
SOME MINOR ISSUES WITH BASELINE PRIOR TO LAUNCH...OTHERWISE
NO PROBLEMS WITH FLIGHT. COLUMN MOISTURE INCREASING SLOWLY AS
PRECIPITABLE WATER HAS NOW RISEN TO 1.02 INCHES. A SURFACE BASED
INVERSION EXTENDS TO JUST UNDER 986 MB/1KFT...THEN ADIABATIC TO
THE BASE OF SUBSIDENCE INVERSION AT 820 MB. A WARM LAYER ABOVE 10C
TO 729 MB THEN DRY ADIABATIC TO A SECOND WARM LAYER LIKELY
ASSOCIATED WITH ADVANCING CIRRUS CLOUD DECK NEAR 500 MB/19KFT. A
PSEUDO LAPSE RATE TO A VERY HIGH TROPOPAUSE AT 182 MB WITH A RELATIVELY
WARM TEMPERATURE OF -65C. DEWPOINT DEPARTURES ARE GENERALLY 1-5C
FROM SURFACE TO BASE OF SUBSIDENCE INVERSION...THEN DRY ALOFT BUT
NARROWING NEAR CIRRUS LEVEL AROUND 24KFT. WINDS INDICATED A LOW
LEVEL JET STREAK SSW-SSE 25-30 KT JUST OFF SURFACE TO 5900FT...SW
10-25 KT TO A CALM LAYER AT 8700FT...THEN VEERING TO NW 15-80 KT
TO TROPOPAUSE. PEAK WIND 285/79KT AT 43.3KFT. LIFTED INDEX -4.7
WITH LOW LEVEL HELICITY NOW UP TO 185 M2/S2 DUE MAINLY TO SPEED
SHEAR. BOTH OF THESE VALUES WILL LIKELY INCREASE IN MAGNITUDE NEXT
24 HOURS WITH APPROACHING SYSTEM. FINALLY...BALLOON BURST OVER
WESTERN MISSISSIPPI SOUND NEAR GAP TO LAKE BORGNE 36 MILES DOWN
RANGE AND 8 MILES SOUTH OF PASS CHRISTIAN MS/WEST OF CAT ISLAND AT
10.77 MB OR 30555 M/19.0 MILES UP. 24/RR

&&

.PREV DISCUSSION... /ISSUED 439 AM CDT SUN APR 13 2014/

SYNOPSIS...

HIGH PRESSURE REMAINS ANCHORED OFF THE ATLANTIC COAST WITH AN AXIS
OF THE HIGH ALONG THE NORTHERN GULF COAST. LOW PRESSURE IS
CENTERED OVER IOWA AND THE OKLAHOMA PANHANDLE WITH A DRY LINE OVER
WEST TEXAS. A RATHER EXTENSIVE CIRRUS DECK HAS LIMITED THE
DEVELOPMENT OF LOW STRATUS TO THE MISSISSIPPI COAST AS OF 3 AM.
TEMPERATURES ARE GENERALLY IN THE 60S WITH DEW POINTS IN THE LOWER
AND MIDDLE 60S.

SHORT TERM...

TODAY THROUGH MONDAY NIGHT

WATER VAPOR SATELLITE IMAGERY SHOWS NEARLY PHASED ENERGY CARVING OUT
A DEEPENING LONGWAVE TROUGH FROM NEAR WESTERN MONTANA TO SOUTHERN
CALIFORNIA. OF PARTICULAR CONCERN IS A SHORTWAVE TROUGH THAT WILL
MOVE FROM SOUTHEAST ARIZONA AND ADJACENT NORTHERN MEXICO ACROSS NEW
MEXICO INTO WESTERN TEXAS THIS MORNING AND THE SOUTHERN PLAINS THIS
AFTERNOON ALONG WITH THE ATTENDANT DRY LINE AND COLD FRONT. ANOTHER
WARM/HUMID DAY IS IN STORE TODAY. MOISTURE REMAINS TOO SHALLOW TO
SUPPORT ANY SIGNIFICANT SHOWER DEVELOPMENT THROUGH THE DAY TODAY
BUT A FEW SHOWERS WILL BE POSSIBLE THIS EVENING. MAX TEMPS WILL
REACH THE UPPER 70S/LOWER 80S ONCE AGAIN.

THE SHORTWAVE TROUGH IS EXPECTED TO SHEAR OUT AS IT MOVES INTO THE
LOWER MISSISSIPPI VALLEY TONIGHT...HOWEVER THE COLD FRONT WILL SURGE
INTO THE ARKLATEX REGION LATE TONIGHT. A 30-40 KT LOW LEVEL JET WILL
DEVELOP THIS EVENING ACROSS SOUTHWEST TO NORTHEAST LOUISIANA AND
SOUTHWEST MISSISSIPPI AND THIS WIND AXIS WILL SHIFT EAST ACROSS THE
FORECAST AREA TONIGHT. PWS ARE STILL EXPECTED TO INCREASE TO 1.6-1.8
INCHES....AND DIFFLUENT FLOW WILL DEVELOP IN THE UPPER LEVELS AS A
100-110 KT JET STREAK AT 250 MB APPROACHES FROM THE WEST. A COMPLEX
OF SHOWERS/T-STORMS IS EXPECTED TO DEVELOP LATE SUNDAY AFTN OVER
NORTHEAST TEXAS/EASTERN OKLAHOMA AHEAD OF THE DRYLINE AND SHIFT EAST
ACROSS LOUISIANA SUNDAY EVENING. SOME OF THE ENERGY AND LIFT AT
VARIOUS LEVELS WILL BE A BIT DISJOINTED AND OUT OF PHASE
TONIGHT...SO CURRENT THINKING IS THE MORE NUMEROUS SHOWERS AND
THUNDERSTORMS WILL BE OVER THE FAR NORTH WITH MORE SCATTERED
ACTIVITY TO THE SOUTH NEAR I-12 AND I-10 AND ISOLATED TO THE SOUTH
OF I-10. FORECAST MODEL SOUNDINGS CONTINUE TO SHOW IMPRESSIVE LOW
LEVEL SHEAR THIS PERIOD WITH 0-3 KM HELICITIES OF 250-400 M2/S2
AROUND MIDNIGHT AND 150-300 M2/S2 AROUND 6 AM MONDAY. THIS WILL
SUPPORT A RISK OF A FEW SEVERE STORMS MAINLY LATE TONIGHT INTO MID
MORNING MONDAY OVER THE NORTHERN AND WESTERN ZONES...WITH DAMAGING
WINDS AND ISOLATED TORNADOES BEING THE MAIN THREATS.

THE FIRST SHORTWAVE WILL LIFT AWAY FROM THE AREA BY MIDDAY MONDAY. A
STRONGER LONGWAVE TROUGH WILL DEVELOP OVER THE PLAINS/MS VALLEY
MONDAY WITH AN ASSOCIATED COLD FRONT MOVING THROUGH SOUTHEAST
LOUISIANA AND SOUTHERN MISSISSIPPI MONDAY AFTERNOON/EVENING. PWS OF
1.6-1.8 INCHES WILL POOL AHEAD OF THE FRONT. SHEAR PROFILES ARE LESS
IMPRESSIVE MONDAY AFTN/EVENING BUT INSTABILITY IS GREATER DURING THE
EARLY AFTERNOON WITH CAPES 2000 TO 3000 J/KG AND LIS OF -4 TO -6.
HAVE LIKELY POPS BLANKETED ACROSS THE AREA MONDAY AFTN/EVENING WITH
A FEW SEVERE STORMS POSSIBLE. SPC HAS THE ENTIRE AREA HIGHLIGHTED IN
A SLIGHT RISK...WITH LOTS OF UNCERTAINTY ON HOW MESOSCALE BOUNDARIES
AND FORCING WILL PLAY OUT. LOCALLY HEAVY RAINFALL IS LIKELY TO OCCUR
AND COULD BECOME A CONCERN DUE TO THE POTENTIAL FOR STATIONARY BANDS
OF STRONGER CONVECTION DUE TO BACK-BUILDING. IT CURRENTLY IS NOT
ANTICIPATED THAT THE THREAT OF FLASH FLOODING WILL BE HIGH ENOUGH
FOR A WATCH...BUT THIS WILL HAVE TO BE MONITORED. 22/TD

LONG TERM...

TUESDAY THROUGH END OF FORECAST PERIOD.

WITH THE COLD FRONT WELL EAST OF THE AREA BY 12Z TUESDAY...CLOUDS
SHOULD DECREASE QUICKLY DURING THE MORNING HOURS. MUCH COLDER AIR
WILL BE MOVING INTO PLACE...AND TEMPERATURES WILL HAVE DIFFICULTY
GETTING MUCH PAST THE LOWER 60S TUESDAY AND MAY NOT GET OUT OF THE
50S IN SOME AREAS. WEDNESDAY MORNING WILL BE RATHER CHILLY WITH
ABOUT THE NORTHERN HALF OF THE AREA FALLING INTO THE 30S. HAVE
TRENDED TOWARD THE WARMER OVERNIGHT LOWS...GUIDANCE WAS A LITTLE
TOO COLD LAST FRONTAL SYSTEM. WILL STILL HAVE TO MONITOR THIS AS
LOW TEMPERATURE RECORDS ARE IN THE 30S OVER NORTHERN HALF OF THE
AREA AT MID WEEK. BEYOND WEDNESDAY...MEDIUM RANGE MODELS CONTINUE
TO HAVE DIFFICULTY RESOLVING IMPULSES MOVING THROUGH NORTHERN AND
CENTRAL PORTIONS OF THE COUNTRY. ECMWF SOLUTION CONTINUES TO BE
MAINLY DRY FOR NEXT WEEKEND...WHILE GFS PUSHES A COLD FRONT
THROUGH THE AREA ON FRIDAY. MAIN EMPHASIS OF SYSTEMS WILL BE TO
THE NORTH OF US IN EITHER CASE. PREVIOUS PACKAGES HAVE BEEN SHADED
TOWARD GFS WITH MENTION OF PRECIPITATION...AND WILL CONTINUE THAT
TREND FOR NOW. WEEKEND TEMPERATURES SHOULD BE NEAR NORMAL IN MOST
AREAS. 35

AVIATION...

CONDITIONS HAVE BEEN HARD TO PREDICT AGAIN EARLY THIS MORNING WITH
CONDITIONS RANGING FROM IFR ON PORTIONS OF THE MISSISSIPPI GULF
COAST TO VFR OVER MANY OF THE LARGER AIRPORTS. IT IS STILL EXPECTED
THAT IFR TO MVFR CIGS WILL BECOME MORE WIDESPREAD THROUGH ABOUT 14Z
BEFORE DAYTIME HEATING CAUSES THE CIGS TO LIFT ABOVE 030 BY MIDDAY.
AFTERNOON IMPROVEMENT WILL BE SHORT-LIVED HOWEVER AS VERY MOIST LOW
LEVELS SHOULD QUICKLY CREATE LOW CIGS TO MVFR OR IFR THIS EVENING
AND OVERNIGHT INTO MONDAY MORNING. THE OTHER CONCERN WILL BE
SHRA/TSRA THAT ARE EXPECTED TO START TO IMPACT AREAS FROM NEAR KMCB
TO KBTR AFTER 06Z MONDAY AND THE REMAINING AIRPORTS AFTER 12Z
MONDAY. LATER TAF ISSUANCES AT 12Z AND 18Z WILL HAVE TO CONSIDER
ADDING MENTION OF TSRA TO THE TAFS. 22/TD

MARINE...

MODERATE ONSHORE FLOW WILL APPROACH EXERCISE CAUTION LEVELS
TODAY...BUT WE ARE HOLDING OFF ON HEADLINES FOR NOW. HEADLINES A
LITTLE MORE LIKELY TONIGHT...BORDERLINE SMALL CRAFT ADVISORY. A
SMALL CRAFT ADVISORY DEFINITELY WILL BE NEEDED BEHIND THE COLD
FRONT MONDAY NIGHT THROUGH TUESDAY NIGHT. NOT TOTALLY OUT OF THE
QUESTION THAT A SHORT GALE WARNING COULD BE NEEDED AT SOME POINT
ON TUESDAY MORNING. WINDS WILL EASE WEDNESDAY MORNING BEFORE
MODERATE ONSHORE FLOW RETURNS ON THURSDAY. NEXT FRONT DUE ON
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  80  67  79  44 /  10  50  70  70
BTR  82  69  79  46 /  10  50  70  70
ASD  79  68  80  49 /  10  40  70  70
MSY  80  69  80  51 /  10  40  70  70
GPT  76  69  77  50 /  10  30  70  70
PQL  76  66  78  50 /  10  30  70  70

&&

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

$$









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