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

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139
FXUS64 KLIX 021346
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
746 AM CST MON MAR 2 2015

...SOUNDING DISCUSSION...
THERE IS A LOT OF MOISTURE IN THE SOUNDING THIS MORNING AS THE
PROFILE IS MOSTLY SATURATED FROM THE SFC TO 530 MB. PRECIPITABLE
WATER IS 1.88 INCHES... WHICH IS THE NEW RECORD FOR TODAY AS DEPICTED
IN THE SPC THREADED SOUNDING CLIMATOLOGY FOR LIX. THIS REPRESENTS
THE FOGGY CONDITIONS IN THE AREA AND OVERNIGHT DOWNPOURS WELL. SOUTHEAST
WINDS AT THE SFC HAVE BROUGHT IN GULF AIR AND THE MARITIME AIRMASS
WITH A 7 F TEMPERATURE INVERSION TO 015 FT. WINDS BECOME WESTERLY
ABOVE THE INVERSION WITH A 90 KT PEAK WIND AT 170 MB.

KRAUTMANN

&&

.PREV DISCUSSION... /ISSUED 417 AM CST MON MAR 2 2015/

SHORT TERM...
WEAK FRONTAL ZONE THAT IS IN THE PROCESS OF BECOMING STATIONARY
HAS PROVIDED A SYNOPTIC SCALE FOCUS FOR MOISTURE CONVERGENCE OVER
THE AREA TONIGHT. MEANWHILE...AN INVERTED TROUGH AXIS ASSOCIATED
WITH BAROCLINIC WARM FRONTAL ZONE IN THE WEST GULF WAS MIGRATING
NORTHWARD...ENRICHING THE MOISTURE OVER THE AREA. THIS HAS
RESULTED IN 1 TO 4 INCHES IN A FEW LOCATIONS SO FAR WITH HEAVY
RAINFALL STILL ONGOING FROM ROUGHLY PEARL RIVER TO POINTE A LA
HACHE...MOVING INTO COASTAL MISSISSIPPI THIS MORNING. EAST-WEST
ORIENTATION MAY RESULT IN SOME SHORT-TERM ECHO TRAINING BEFORE
EASING AS WARM FRONT MOVES FARTHER INLAND. THE ECMWF SEEMS TO HAVE
THE BETTER HANDLE ON THE CURRENT SITUATION. DEEP FETCHED MARITIME
AIR TO BECOME ESTABLISHED ACROSS THE GULF STATES TUESDAY AND
WEDNESDAY FOR WARM AND MUGGY CONDITIONS AND A CHANCE OF RAIN EACH
DAY...ALONG WITH SOME CONSIDERATIONS FOR SEA FOG DURING THE NIGHT
AND MORNING HOURS. WENT ON THE COOLER SIDE OF GUIDANCE
TEMPERATURES IN DEFERENCE TO COLD MARINE AIR RETURN...BUT STILL ON
THE WARM SIDE OF NORMAL THROUGH WEDNESDAY.

LONG TERM...
THINGS GET REALLY INTERESTING WEDNESDAY NIGHT AND THURSDAY
MORNING. STRONG ARCTIC COLD FRONT ADVANCES THROUGH THE PLAINS
STATES OVER ESTABLISHED SNOW PACK TO BRING A DRASTIC DROP IN
TEMPERATURES WITH ITS PASSAGE. MODEL GUIDANCE IS SHOWING
TEMPERATURES IN THE MID TO UPPER 70S WEDNESDAY THAT FALL AROUND
40F BY WEDNESDAY NIGHT. THERE A SEVERAL POINTS OF STRONG
CONSIDERATION WITH THIS SCENARIO. OVERALL PATTERN MAINTAINS
SOUTHWEST FLOW ALOFT THE ENTIRE TIME WHILE THE DENSE COLD AIR
UNDERCUTS. THIS WILL PROVIDE STRONG ISENTROPIC LIFT ALONG WITH
OTHER OMEGA FORCING FOR WIDESPREAD AND PERSISTENT RAINFALL DURING
THE TEMPERATURE TRANSITION. PAST SEVERAL SIMILAR SITUATIONS IN THE
MODEL DOMAINS HAVE STARTED OUT EXCEPTIONALLY COLD DAYS OUT ONLY TO
TREND WARMER CLOSER TO ACTUAL EVENT. THIS APPEARS TO BE NO
EXCEPTION. FINALLY...THICKNESSES NEVER FALL BELOW 552DM IN SW
MISSISSIPPI...WHICH SUGGESTS TEMPERATURES SHOULD REMAIN ABOVE
FREEZING IN THE LOWER LEVELS TO PRECLUDE A WINTER WEATHER
SITUATION THIS FAR SOUTH. WILL CONCEDE THAT THIS IS A CLOSE
CALL...BUT PAST TRENDS WORK IN FAVOR OF HOLDING OFF ON WINTER
PRECIPITATION WITHIN THE CWA BORDERS...THOUGH NEIGHBORING OFFICES
ARE PRUDENTLY TAKING THESE CONDITIONS JUST UP TO OUR JURISDICTION.
THERE WILL BE SUFFICIENT TIME FOR ADJUSTMENTS BUT CURRENT THINKING
IS THAT THE COLDEST AIR WILL HOLD OFF UNTIL AFTER PRECIPITATION
ENDS THURSDAY. COLD AIR MODERATES RATHER QUICKLY HEADING INTO THE
WEEKEND. MODELS DIVERGE ON SOLUTIONS FOR NEXT WEEKEND AS GFS
REMAINS RELATIVELY DRY WHILE ECMWF DEVELOPS A MECHANICAL LOW
PRESSURE TROUGH IN THE WEST GULF TO FOCUS MOISTURE RETURN ALONG
THE NORTH GULF NEXT SATURDAY. HAVE TRENDED CLOSER TO ECMWF FOR
NEXT WEEKEND TIME FRAME. 24/RR

AVIATION...
CEILINGS RANGING AROUND 500 FEET WILL KEEP IFR RESTRICTIONS IN PLACE
AT ALL OF THE TERMINALS THROUGH AROUND 14-15Z THIS MORNING.
CEILINGS SHOULD SLOWLY IMPROVE TO AROUND 1000 TO 1500 FEET AFTER
15Z...AND REMAIN AT THESE LEVELS THROUGH 00Z.  THE STRATUS DECK WILL
THEN START TO BUILD BACK DOWN TO AROUND 500 FEET AFTER 00Z...AND
VISIBILITIES WILL FALL BACK TO AROUND ONE MILE BY 03Z.  AS A
RESULT...PREVAILING IFR CONDITIONS ARE EXPECTED AT ALL OF THE
TERMINALS FROM 03Z THROUGH 12Z TOMORROW. 32

MARINE...
WEAK ONSHORE FLOW WITH WARM FRONTAL ZONE ALONG THE COAST TO MOVE
INLAND DURING THE DAY. ONSHORE FLOW BECOMES DEEPER AND LONGER-
FETCHED THROUGH WEDNESDAY TO DEVELOP A DECENT GROUND SWELL IN THE
GULF WATERS THROUGH MID-WEEK. STRONG COLD FRONTAL PASSAGE THURSDAY
WILL LIKELY BRING A PERIOD OF GALES OR AT LEAST HIGH END SMALL
CRAFT ADVISORY CONDITIONS THURSDAY. WINDS SHOULD RELAX WHILE
REMAINING OFFSHORE ORIENTED NEXT WEEKEND. 24/RR

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  67  60  74  65 /  60  30  30  30
BTR  72  61  76  65 /  60  30  30  30
ASD  72  61  75  63 /  50  30  20  20
MSY  70  62  75  65 /  50  30  20  20
GPT  69  59  72  62 /  40  30  20  20
PQL  66  58  73  62 /  50  30  10  20

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...DENSE FOG ADVISORY UNTIL 9 AM MONDAY FOR THE FOLLOWING ZONES:
     ASSUMPTION...LOWER JEFFERSON...LOWER LAFOURCHE...LOWER
     PLAQUEMINES...LOWER ST. BERNARD...LOWER
     TERREBONNE...ORLEANS...SOUTHERN TANGIPAHOA...ST.
     CHARLES...ST. JAMES...ST. JOHN THE BAPTIST...ST.
     TAMMANY...UPPER JEFFERSON...UPPER LAFOURCHE...UPPER
     PLAQUEMINES...UPPER ST. BERNARD...AND UPPER TERREBONNE.

GM...DENSE FOG ADVISORY UNTIL 9 AM MONDAY FOR THE FOLLOWING ZONES:
     BRETON SOUND...CHANDELEUR SOUND...COASTAL WATERS FROM
     BOOTHVILLE LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER OUT 20 NM...COASTAL WATERS FROM PORT FOURCHON TO
     LOWER ATCHAFALAYA RIVER OUT 20 NM...COASTAL WATERS FROM THE
     SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON
     OUT 20 NM...LAKE BORGNE...LAKE PONTCHARTRAIN AND LAKE
     MAUREPAS...AND MISSISSIPPI SOUND.

MS...DENSE FOG ADVISORY UNTIL 9 AM MONDAY FOR THE FOLLOWING ZONES:
     HANCOCK...HARRISON...AND JACKSON.

GM...DENSE FOG ADVISORY UNTIL 9 AM MONDAY FOR THE FOLLOWING ZONES:
     BRETON SOUND...CHANDELEUR SOUND...COASTAL WATERS FROM
     BOOTHVILLE LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER OUT 20 NM...COASTAL WATERS FROM PORT FOURCHON TO
     LOWER ATCHAFALAYA RIVER OUT 20 NM...COASTAL WATERS FROM THE
     SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON
     OUT 20 NM...LAKE BORGNE...LAKE PONTCHARTRAIN AND LAKE
     MAUREPAS...AND MISSISSIPPI SOUND.

&&

$$







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