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

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514
FXUS64 KLIX 170815
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
315 AM CDT WED SEP 17 2014

.SHORT TERM...
THE FORECAST AREA HAS TRANSITIONED TO A NORTHWEST FLOW PATTERN
ALOFT WITH TROUGHING ALONG THE ATLANTIC COAST AND RIDGING OVER THE
INTER-MOUNTAIN WEST. MEANWHILE...REMNANTS OF HURRICANE ODILE
ENTERING THE DESERT SOUTHWEST AND WILL BE THE MAIN WEATHER
HEADLINER TODAY. CLOSER TO HOME...LAKE AND GULF BREEZE BOUNDARIES
SHOULD BECOME THE FOCUS OF CONVECTION BUT MAY BE DELAYED IN ONSET
INTO THE MID-AFTERNOON HOURS WITH NORTHWEST FLOW. THERE ARE SOME
CONCERNS OF NOCTURNAL CONVECTION WITH VORTICITY COMPLEX INDICATED
IN GFS DROPPING INTO THE REGION FROM TEXAS AS AN APPARENT
PERTURBATION EMANATING FROM THE ODILE ASSOCIATED TROUGH. THE ECMWF
SHOWS SIMILAR VORTICITY STREAK BUT VOID OF PRECIPITATION
OVERNIGHT. AT THIS TIME WILL MAINTAIN LOWER POPS BUT THIS MAY NEED
ADJUSTING BASED ON IN SITU CONDITIONS THIS EVENING. TEMPERATURES
WILL REMAIN NEAR NORMAL BUT HOURLY TEMPERATURES WILL BE SUBJECTED
TO RAIN COOLING AND THICK ANVIL CLOUD COVER AFTER CONVECTION TAKES
HOLD TODAY AND THURSDAY. MORNING CLOUD COVER THURSDAY MAY NEED TO
ERODE BEFORE GETTING DIURNAL TEMPERATURE TRENDS RE-ESTABLISHED.

.LONG TERM...
NORTHWEST FLOW REGIME WILL DICTATE WEATHER ACROSS THE FORECAST
AREA THROUGH THE WEEKEND. SUCH A REGIME IN SUMMER CAN BE
BOTHERSOME IN THAT SUBTLE VORTICITY STRUCTURES OR MESOSCALE
CONVECTIVE VORTICES /MCV/ DROPPING DOWN THE FACE OF RIDGING CAN
SUSTAIN CONVECTION IN AN UNCONVENTIONAL OFF-CLIMES MANNER.
PRECIPITATION ONSET IS TYPICALLY DELAYED UNTIL AFTER 3 PM IN THESE
REGIMES AND CAN PERSIST UNTIL AROUND OR SHORTLY AFTER MIDNIGHT.
THE GFS DOES INDICATE THIS NOTION FOR THURSDAY NIGHT. IF THIS
SCENARIO DOES OCCUR...THEN FRIDAY SHOULD SEE LESSER COVERAGE OVER
LAND AREAS BUT PRETTY ACTIVE IN THE COASTAL WATERS...ESPECIALLY
ASSOCIATED WITH THE PASSAGE OF AN EASTERLY WAVE ACROSS THE MIDDLE
GULF OVER THE WEEKEND. OF COURSE...PERSISTENT TROUGHING OVER THE
EASTERN UNITED STATES WILL FAVOR FRONTOGENESIS AND THIS APPEARS TO
BE WITH A STRONG CANADIAN HIGH PRESSURE SYSTEM THAT DROPS INTO THE
UPPER PART OF THE COUNTRY SUNDAY BEFORE SHUNTING EAST MONDAY. THIS
SHOULD HAVE ENOUGH DENSITY TO PUSH A FRONT INTO THE FORECAST AREA
MONDAY THAT WILL THEN BECOME SLUGGISH UNTIL THE SOUTHERN FRINGE OF
THE RIDGE GETS INDUCED FARTHER SOUTH BY MIDDLE OF NEXT WEEK. MORE
CONTINENTAL INFLUENCES MAY SUPPRESS GULF BREEZE CYCLE FOR A FEW
DAYS AND THE FRONTAL ZONE DISRUPTS THE STEADY STATENESS. DESPITE
THE NON-CLIMATOLOGICAL WEATHER REGIME...TEMPERATURES SHOULD REMAIN
SEASONABLY NEAR NORMAL FOR MUCH OF THE FORECAST PERIOD AND RAIN
CHANCES WILL LIKELY BE SOMEWHAT BELOW NORMAL FROM FRIDAY THROUGH
SUNDAY AND AGAIN ON TUESDAY. 24/RR

&&

.AVIATION...
SOME PATCHES OF MVFR VSBY IN LIGHT RADIATIONAL FOG AT A FEW
TERMINALS THIS MORNING. THESE CONDITIONS SHOULD IMPROVE BY MID-
MORNING FOR GENERAL VFR CONDITIONS. CONVECTIVE ONSET MAY BE
DELAYED UNTIL AFTER 19Z AT MOST LOCATIONS AND MAY CARRY OVER
03Z BEFORE ENDING WITH ANVIL DISSIPATION LIGHT RAINFALL AFTER
SUNSET.

&&

.MARINE...
A RATHER FLAT PRESSURE FIELD TODAY AND THURSDAY WILL UNDERGO SOME
GRADIENT TIGHTENING A BIT FRIDAY THAT SHOULD BE A SOLID EASTERLY
FLOW AROUND 15 KNOTS AS AN EASTERLY WAVE PASSES THROUGH THE MIDDLE
GULF. HIGH PRESSURE BUILDS SOUTHWARD THROUGH THE LOWER
APPALACHIANS OVER THE WEEKEND THAT MAY MAINTAIN THE EASTERLY FLOW
THROUGH THE WEEKEND BEFORE A COLD FRONT ENTERS THE NORTH GULF
MONDAY. THE INITIAL FRONTAL ZONE MAY BE TOO SHALLOW TO REALIZE ANY
SENSIBLE AFFECTS IN THE MARINE AREAS UNTIL MORE CONTINENTAL AIR
FINALLY NUDGES OFF THE COAST ON TUESDAY.

&&

.DECISION SUPPORT...
DSS CODE...GREEN.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT AND SUPPORTING USCG SSW OF PASCAGOULA.

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  90  72  90  69 /  20  10  20  20
BTR  90  73  88  70 /  30  10  40  20
ASD  89  73  86  70 /  30  10  30  20
MSY  88  76  84  74 /  30  10  30  20
GPT  89  74  87  71 /  30  10  20  20
PQL  90  70  88  67 /  30  10  10  20

&&

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

$$

24/RR







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