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

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329
FXUS64 KLIX 250101
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
701 PM CST TUE FEB 24 2015

.SOUNDING DISCUSSION...

ROUTINE FLIGHT TERMINATED ABOUT 93 MINUTES AFTER LAUNCH OVER THE
GULF OF MEXICO ABOUT 5 MILES SOUTH OF DAUPHIN ISLAND ALABAMA.
FLIGHT REACHED 105.9K FEET...OR ABOUT 20 MILES IN ALTITUDE.

A RATHER STOUT INVERSION IN PLACE BETWEEN 2K AND 5K FEET...ABOUT 8
DEGREES CELSIUS...WITH MOST OF THE MOISTURE IN THE SOUNDING
TRAPPED IN THAT LAYER. ALTHOUGH THAT LAYER WAS MOSTLY
SATURATED...THERE WAS LITTLE IN THE WAY OF LOW CLOUD COVER AT
LAUNCH TIME. PRECIPITABLE WATER VALUE IS 1.10 INCHES WITH THIS
FLIGHT. LIGHT NORTH WINDS AT THE SURFACE BECAME WESTERLY BY ABOUT
4K FEET AND REMAINED WESTERLY THROUGH 100 MB. MAX WIND WAS 121
KNOTS AT 43.3K FEET. FREEZING LEVEL AT 13.5K FEET...AND THE -20C
LEVEL WAS AT 22.4K FEET. 35

&&

.PREV DISCUSSION... /ISSUED 430 PM CST TUE FEB 24 2015/

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...

SHORTWAVE TROUGH IS PUSHING EAST ACROSS THE EASTERN THIRD OF THE
U.S. WITH A MID/UPPER LEVEL SHORTWAVE RIDGE SLIDING EAST ACROSS THE
SOUTHERN PLAINS TOWARDS THE LOWER MISSISSIPPI VALLEY. ISENTROPIC
DOWNGLIDE AND SUBSIDENCE HAS ALLOWED THE LOW CLOUD DECK TO ERODE THE
LAST COUPLE HOURS AND LEAVE MUCH LESS CLOUD COVER THAN EARLIER
ANTICIPATED OVER MUCH OF THE FORECAST AREA. THESE DRIER CONDITIONS
ARE ONLY EXPECTED TO PERSIST MOST OF TONIGHT BEFORE A POTENT
SHORTWAVE TROUGH CURRENTLY OVER ARIZONA AND ADJACENT NORTHWEST
MEXICO MOVES QUICKLY EAST ACROSS TEXAS LATE TONIGHT AND WEDNESDAY
MORNING. THE MODELS ARE A BIT SLOWER BRINGING RAIN INTO THE AREA BY
A FEW HOURS...BUT THAT RESULTS IN QUITE A BIT LOWER RAIN CHANCES
TONIGHT THAN INDICATED IN PREVIOUS MODEL RUNS...ESPECIALLY FROM THE
MAV GUIDANCE. HAVE GENERALLY BLENDED THE LATEST MODEL GUIDANCE WITH
THE PREVIOUS FORECAST.

THE POTENT SHORTWAVE TROUGH WILL SWING ACROSS THE CENTRAL GULF COAST
REGION WEDNESDAY IN THE AFTERNOON AND EARLY EVENING. AN ASSOCIATED
AREA OF SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP OVER THE
NORTHWEST TO NORTH CENTRAL GULF OF MEXICO WEDNESDAY MORNING AND THIS
LOW WILL STRENGTHEN AS IT MOVES SOUTHEAST OF THE FORECAST AREA
ACROSS THE NORTHEAST GULF OF MEXICO AND EASTERN FLORIDA PANHANDLE
WEDNESDAY AFTERNOON AND EVENING. THE MODELS ARE FAIRLY CONSISTENT
WITH A LOW TRACK RANGING FROM JUST SOUTH OF THE MOUTH OF MISSISSIPPI
RIVER TO 30 TO 40 MILES SOUTH. EVEN WITH THIS BIT OF A RANGE IN THE
MODEL SOLUTIONS...THE FAR NORTHERN PORTION OF THE FORECAST AREA
SHOULD BE NO COLDER THAN THE MID 30S AT THE SURFACE WITH LOWER LEVEL
TEMPERATURE PROFILES NOT SUPPORTIVE OF ANYTHING BUT A COLD RAIN.
WIDESPREAD MODERATE TO LOCALLY HEAVY RAINFALL IS EXPECTED TO RAMP
PRETTY QUICKLY WEDNESDAY MORNING AND CONTINUE THROUGH ABOUT MID
AFTERNOON BEFORE ENDING QUICKLY WITH THE 700 MB TROUGH PASSAGE FROM
THE WEST IN MOST AREAS EXCEPT THE FAR EAST BY SUNSET...AND THE
MISSISSIPPI GULF COAST BY 8 OR 9 PM. MODEL SOUNDINGS ONLY SHOW SOME
MINOR...VERY ELEVATED CAPE LIFTING FROM WAY UP IN THE 750 TO 700 MB
LAYER...SO HAVE KEPT MENTION OF THUNDERSTORMS OUT OF THE FORECAST
ALTHOUGH IT WOULD NOT BE SURPRISING TO SEE A FEW BRIEF AND FAST
MOVING THUNDERSTORM CELLS. AFTER RAIN ENDS EARLY IN THE
EAST...WEDNESDAY NIGHT IS EXPECTED TO BE DRY BUT MOSTLY CLOUDY AND
COLD WITH LOWS DROPPING TO THE LOWER TO MID 30S.

LARGE POLAR SURFACE HIGH PRESSURE RIDGE...CENTERED OVER THE NORTHERN
PLAINS IS EXPECTED TO MOVE SOUTHEAST AND REINFORCE OR AT LEAST
MAINTAIN THE COLDER AIR OVER THE CENTRAL GULF COAST REGION THURSDAY
NIGHT.

LONG TERM /FRIDAY THROUGH TUESDAY/...

A LARGE SURFACE HIGH PRESSURE RIDGE IS EXPECTED TO COVER MOST OF THE
EASTERN HALF OF THE CONUS FRIDAY INTO THE WEEKEND. A FLATTER...MORE
ZONAL FLOW PATTERN ALOFT ON FRIDAY WILL START TO AMPLIFY OVER THE
WEEKEND AS A DIGGING TROUGH DIVES SOUTH NEAR THE CALIFORNIA COAST
TOWARDS BAJA. THIS WILL RESULT IN SOUTHWEST FLOW ALOFT OVER THE
SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY. THE HIGH PRESSURE
RIDGE SHOULD KEEP OUR AREA DRY FRIDAY INTO MOST OF SATURDAY
HOWEVER...SOME LOW RAIN CHANCES COULD RETURN OVER SOUTHERN AREAS
SATURDAY AFTERNOON OR NIGHT. THE NEXT SHORTWAVE TROUGH OR SERIES OF
DISTURBANCES MAY GET CLOSE ENOUGH FOR INCREASING RAIN CHANCES
SUNDAY...BUT THE MODELS ARE FOCUSING A BIT MORE ENERGY AND QPF ON
MONDAY INTO TUESDAY. 22/TD

AVIATION...

DRIER AIR HAS MIXED DOWN FROM ALOFT...ALLOWING FOR THE STRATUS DECK
TO CLEAR MORE THAN ORIGINALLY ANTICIPATED.  AS A RESULT...A PERIOD
OF VFR CONDITIONS HAS DEVELOPED THIS AFTERNOON.  STILL EXPECT TO SEE
THE ELEVATED INVERSION INTENSIFY OVERNIGHT...AND LOW STRATUS TO
REDEVELOP OVER ALL OF THE TERMINALS AFTER 06Z.  A POTENT LOW
PRESSURE SYSTEM WILL BRING WIDESPREAD LIGHT TO MODERATE RAINFALL AND
LOWER CEILINGS TO THE AREA TOMORROW...WITH IFR AND LIFR CONDITIONS
EXPECTED.  32

MARINE...

A PERIOD OF LIGHTER WINDS WILL BE SHORT LIVED THROUGH TONIGHT
BEFORE WINDS AND SEAS RAMP UP QUICKLY ON WEDNESDAY DUE TO THE LOW
PRESSURE AREA MOVING THROUGH THE NORTH CENTRAL GULF OF MEXICO.
COLDER AIR IN THE WAKE OF THIS LOW...THEN A REINFORCEMENT OF
COOLER AIR AND HIGH PRESSURE ON FRIDAY...WILL KEEP NORTH TO
NORTHEAST WINDS ON THE STRONGER SIDE WEDNESDAY NIGHT THROUGH
SATURDAY NIGHT. HAVE ISSUED A SMALL CRAFT ADVISORY STARTING AT 9
AM FOR DETERIORATING CONDITIONS SOUTH AND SOUTHWEST OF SOUTHWEST
PASS...AND SMALL CRAFT ADVISORY CRITERIA WILL THAN SPREAD ACROSS
MOST OF THE REMAINING COASTAL WATERS IN THE EARLY AFTERNOON. 22/TD

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 33 41 31 50 / 30 100 10 10
BTR 37 45 33 53 / 40 100 10 10
ASD 37 46 32 53 / 30 100 20 10
MSY 40 48 36 53 / 40 100 20 10
GPT 40 48 34 54 / 30 100 30 10
PQL 37 48 31 54 / 30 100 30 10

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  33  41  31  50 /  30 100  10  10
BTR  37  45  33  53 /  40 100  10  10
ASD  37  46  32  53 /  30 100  20  10
MSY  40  48  36  53 /  40 100  20  10
GPT  40  48  34  54 /  30 100  30  10
PQL  37  48  31  54 /  30 100  30  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY FROM 9 AM WEDNESDAY TO MIDNIGHT THURSDAY
     FOR THE FOLLOWING ZONES: COASTAL WATERS FROM BOOTHVILLE LA
     TO THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER OUT 20
     NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA
     FROM 20 TO 60 NM...COASTAL WATERS FROM PASCAGOULA MS TO
     STAKE ISLAND LA OUT 20 NM...COASTAL WATERS FROM PORT
     FOURCHON TO LOWER ATCHAFALAYA RIVER FROM 20 TO 60
     NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA
     RIVER OUT 20 NM...COASTAL WATERS FROM STAKE ISLAND LA TO
     THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60
     NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON FROM 20 TO 60 NM...AND
     COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER TO PORT FOURCHON OUT 20 NM.

MS...NONE.
GM...SMALL CRAFT ADVISORY FROM 9 AM WEDNESDAY TO MIDNIGHT THURSDAY
     FOR THE FOLLOWING ZONES: COASTAL WATERS FROM BOOTHVILLE LA
     TO THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER OUT 20
     NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA
     FROM 20 TO 60 NM...COASTAL WATERS FROM PASCAGOULA MS TO
     STAKE ISLAND LA OUT 20 NM...COASTAL WATERS FROM PORT
     FOURCHON TO LOWER ATCHAFALAYA RIVER FROM 20 TO 60
     NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA
     RIVER OUT 20 NM...COASTAL WATERS FROM STAKE ISLAND LA TO
     THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60
     NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON FROM 20 TO 60 NM...AND
     COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER TO PORT FOURCHON OUT 20 NM.

&&

$$







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