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

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FXUS64 KLIX 282059
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
359 PM CDT MON JUL 28 2014

.SHORT TERM...

AN UNUSUALLY AMPLIFIED UPPER LEVEL PATTERN WILL BE THE MAIN PLAYER
IMPACTING THE WEATHER ACROSS THE AREA THROUGH THURSDAY. A STRONG
UPPER LEVEL TROUGH WILL REMAIN FIXED OVER THE EASTERN THIRD OF THE
NATION...ALLOWING A STRONG MID-SUMMER COLD FRONT TO SWEEP INTO THE
AREA THIS EVENING AND OVERNIGHT. THE 12Z SOUNDING INDICATES A
POTENTIAL FOR STRONG WIND GUSTS TO GENERATE FROM ANY DEEPER
CONVECTION DUE TO SOME DRIER AIR IN THE MID-LEVELS...BUT THE OVERALL
SEVERE THREAT LOOKS LOWER THAN ORIGINALLY THOUGHT DUE TO A LACK OF
SHEAR AND WEAKER LAPSE RATES ALOFT. GIVEN THE MORE ISOLATED NATURE
OF THE CONVECTIVE ACTIVITY THIS AFTERNOON...HAVE LOWERED POPS
SLIGHTLY FOR THE EVENING HOURS.

BY TOMORROW MORNING...THE FRONTAL BOUNDARY SHOULD BE POSITIONED
ALONG THE LOUISIANA COAST. BEHIND THIS FRONT...A MUCH DRIER AND
MORE STABLE AIRMASS WILL BUILD IN...WITH DEWPOINTS FALLING INTO
THE MIDDLE TO UPPER 60S FOR AREAS NORTH OF INTERSTATE 10 BY
TOMORROW MORNING. HAVE KEPT IN SOME SLIGHT CHANCE POPS FOR COASTAL
LOUISIANA...INCLUDING THE NEW ORLEANS AREA DUE TO THE PROXIMITY OF
THE FRONTAL BOUNDARY AND SOME LINGERING LOW LEVEL MOISTURE.

THE DRIER AIR WILL CONTINUE TO ADVECT INTO THE AREA THROUGH
WEDNESDAY...WITH DEWPOINTS FALLING INTO THE UPPER 50S AND LOWER
60S BY WEDNESDAY AFTERNOON. PW VALUES WILL FALL TO AROUND 1.25
INCHES ON WEDNESDAY AND EXPECT TO SEE OVERNIGHT LOWS DIP INTO THE
MIDDLE TO UPPER 60S TUESDAY NIGHT DUE TO THE DRY AIR AND MOSTLY
CLEAR SKIES.

WEDNESDAY NIGHT INTO THURSDAY WILL SEE ANOTHER UPPER LEVEL VORT
MAX SLIDE DOWN FROM THE PLAINS INTO THE LOWER MISSISSIPPI VALLEY
ON THE BACK SIDE OF THE PERSISTENT UPPER LEVEL TROUGH OVER THE
EASTERN SEABOARD. INCREASING POSITIVE VORTICITY AND MOISTURE
ADVECTION INTO THE AREA ON THURSDAY WILL BRING ADDITIONAL CLOUD
COVER AND A RISK OF SOME ISOLATED AFTERNOON CONVECTION TO THE
REGION.

.LONG TERM...

THE VORT MAX AND ASSOCIATED LOW PRESSURE SYSTEM AND ATTENDANT
FRONT WILL SLIDE INTO THE FORECAST AREA THURSDAY NIGHT AND THEN
BECOME STALLED ALONG THE GULF COAST ON FRIDAY AS THE PARENT UPPER
LEVEL TROUGH LIFTS TO THE NORTHEAST AND A WEAK INVERTED TROUGH AXIS
TAKES HOLD OVER THE REGION. THE INVERTED TROUGH WILL PROVIDE JUST
ENOUGH LIFT TO SPARK OFF SCATTERED SHOWERS AND THUNDERSTORMS NEAR
THE STALLED OUT FRONTAL BOUNDARY THROUGH THE WEEKEND. HAVE
INCREASED POPS TO HIGH END CHANCE FOR EACH DAY.

GIVEN THE LACK OF STRONG WINDS ALOFT OVER THE AREA BEGINNING
FRIDAY AND PERSISTING THROUGH SUNDAY...STORM MOTIONS WILL TEND TO
BE FAIRLY SLOW AT 5 MPH OR LESS. IN ADDITION...A DEEP ONSHORE FLOW
REGIME WILL PUMP TROPICAL MOISTURE INTO THE REGION...PUSHING PW
VALUES UP TO 2 INCHES OR HIGHER ACROSS THE REGION. AS A
RESULT...THERE WILL BE A STREET FLOOD THREAT WITH ANY OF THE CELLS
THAT COME THROUGH.  THE CONVECTION WILL TEND TO BE DIURNAL IN
NATURE WITH THE GREATEST COVERAGE FROM LATE MORNING THROUGH EARLY
EVENING WHEN OVERALL INSTABILITY IS MAXIMIZED. FORTUNATELY...WITH
A WEAK SHEAR PROFILE IN PLACE...THE THREAT FOR SEVERE WEATHER
WILL BE VIRTUALLY NONEXISTENT.

&&

.AVIATION...
MAIN ISSUE IS COVERAGE AND TIMING OF TSRA WHICH REMAINED ONLY
ISOLATED THUS FAR. UNLESS COVERAGE INCREASES...IT IS LIKELY THAT
ONLY A FEW AIRPORTS WILL BRIEFLY EXPERIENCE SHRA/TSRA IN THE
VICINITY WITH A LOWER PROBABILITY OF LOWER THAN VFR CONDITIONS. TAF
AMENDMENTS MAY BE REQUIRED AS LATE AFTERNOON CONVECTIVE TRENDS ARE
ESTABLISHED. OTHERWISE...OUTSIDE OF CONVECTION EXPECT VFR CONDITIONS
TO CONTINUE TO PREVAIL THROUGH TUESDAY. 22/TD

&&

.MARINE...

A TIGHTER THAN NORMAL PRESSURE GRADIENT OVER THE EASTERN WATERS
HAS RESULTED IN PERSISTENT SMALL CRAFT EXERCISE CAUTION
CONDITIONS THROUGH THE DAY. THIS GRADIENT SHOULD LINGER THROUGH
THE OVERNIGHT HOURS IN ADVANCE OF AN APPROACHING FRONTAL
BOUNDARY...AND HAVE DECIDED TO KEEP THE EXERCISE CAUTION IN PLACE
FOR TONIGHT. ONCE THE FRONT MOVES INTO THE COASTAL WATERS
TOMORROW...WINDS WILL DECREASE TO AROUND 10 KNOTS AND SHIFT TO A
MORE NORTHERLY COMPONENT. THE FRONT WILL WASH OUT OVER THE COASTAL
WATERS BY TOMORROW NIGHT...WITH A MORE VARIABLE WIND REGIME TAKING
HOLD ON WEDNESDAY. ANOTHER FRONTAL BOUNDARY AND LOW PRESSURE
SYSTEM WILL THEN APPROACH ON THURSDAY...ALLOWING WINDS TO SHIFT
BACK TO THE SOUTH. THIS FRONT WILL STALL ALONG THE GULF COAST ON
FRIDAY AND LINGER THROUGH THE WEEKEND. WINDS WILL BE SOUTHERLY
OVER THE GULF COASTAL WATERS IN ADVANCE OF THIS FRONT...BUT WINDS
WILL BE MORE VARIABLE OVER THE TIDAL LAKES AND SOUNDS.

&&

.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  70  90  67  88 /  20  10  10  10
BTR  73  92  68  91 /  20  10  10  10
ASD  73  91  67  89 /  30  10  10  10
MSY  76  90  75  89 /  30  20  10  10
GPT  74  93  68  91 /  30  10  10  10
PQL  72  91  67  88 /  30  10  10  10

&&

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

$$

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