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

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659
FXUS64 KLIX 142041
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
341 PM CDT TUE APR 14 2015

.SHORT TERM...THE FLASH FLOOD WATCH CAME TO FRUITION TODAY WITH
NUMEROUS REPORTS OF FLASH FLOODING IN THE WATCH AREA. IN TERMS OF
RAINFALL AMOUNTS...ONE NWS EMPLOYEE MEASURED OVER 5 INCHES AND SOME
LOCATIONS COULD HAVE SEEN CLOSER TO 8 INCHES IF RADAR ESTIMATES ARE
CORRECT. COCORAHS REPORTS THAT WILL COME IN TOMORROW MORNING SHOULD
HELP TO VALIDATE OR CORRECT THESE ESTIMATES. GOOD NEWS IS RADAR AND
SATELLITE TRENDS INDICATE THAT WIDESPREAD HEAVY RAINFALL IS FINALLY
COMING TO AN END. IR/SAT SHOWS CLOUD TOPS WARMING AND THE ONLY
LOCATIONS WITH INTENSE RAINFALL IS ALONG A PQL TO BVE LINE AND
MOVING EAST. SO ALL FLASH FLOOD WARNINGS HAVE BEEN ALLOWED TO EXPIRE
ALTHOUGH LIKELY STILL SOME RESIDUAL FLOODING IN POOR DRAINAGE AREAS.
NIGHTTIME POPS STILL TO BE FAIRLY HIGH...50+% BUT INTENSITIES LIKELY
NOT TO BE TOO IMPACTFUL. HIGHER INSTABILITY WILL BE OFFSHORE OR
ALONG THE COAST TONIGHT. MESO AND MEDIUM RANGE MODELS SUGGEST NEXT
IMPULSE TO BE COMING ONSHORE ALONG THE LA COAST FROM THE SW EARLY
TOMORROW MORNING. MODEL SOUNDINGS SHOW PRECIP WATER VALUES TO REMAIN
NEAR RECORD FOR THIS TIME OF YEAR...AROUND 1.8 INCHES...BUT MUCH
LOWER INSTABILITY. THUS WILL CARRY SIMILAR POPS BUT NOT EXPECTING
QUITE AS MUCH INTENSITY WITH THESE STORMS. NEVERTHELESS...SATURATED
SOILS FROM TODAY WILL STRUGGLE TO ACCEPT HIGH RAINFALL RATES W/O
FLASH FLOOD RUNOFF. IN FACT...SOME FLASH FLOOD GUIDANCE FROM THE RFC
SHOWS PORTIONS OF LA SOUTH OF BATON ROUGE COULD FLOOD WITH AS LITTLE
AS A 1/4 OF AN INCH PER HOUR. WHILE THAT MAY BE ON THE CONSERVATIVE
SIDE...STILL FEEL THE THREAT FOR FLASH FLOODING CONTINUES AND THUS
HAVE EXTENDED THE FFA THROUGH TOMORROW AND ADDED PEARL RIVER
COUNTY TO THE LIST BASED ON HIGH RAINFALL AMOUNTS TODAY IN THE
SOUTHERN PORTION OF THAT COUNTY. ALSO LOWERED PREVIOUS FORECAST
HIGHS BY 3-5 DEGREES AS RAIN/CLOUDS COMBO HAS BEEN KEEPING TEMPS
FROM WARMING TOO MUCH.

MEFFER
&&

.LONG TERM...  NOT LOOKING LIKE ANY IMPROVEMENTS THROUGH THE
REMAINDER OF THE WEEK AS THE CWA WILL STILL BE W/IN SHEAR AXIS ZONE
BETWEEN UPPER RIDGE OVER THE NW CARIBBEAN AND TROUGH TO THE
NORTHWEST. KEPT POPS EACH DAY IN THE 80 TO 90 PERCENT RANGE AND
COULD SEE A DECENT AREAL COVERAGE OF 1 TO 3 INCHES. SO FAIRLY LIKELY
WILL HAVE TO EXTEND THRU FRIDAY. BEYOND FRIDAY MODEL CONTINUITY
BEGINS TO DEGRADE. GFS IS FASTER TO SWING AN UPPER LEVEL TROUGH
THROUGH TO CLEAR OUT THE AREA VS THE SLOWER ECMWF. FOR NOW HAVEN/T
MADE ANY CHANGES TO THE FCST BEYOND FRIDAY.

MEFFER
&&

.AVIATION... CURRENT CONDITIONS ARE HIGHLY VARIABLE FROM LIFR TO
MVFR DEPENDENT ON AREAL RAINFALL AND LOCATION OF THE TERMINAL. THE
LEAST IMPACTFUL PERIOD IN TERMS OF RAIN WILL LIKELY BE THE 00Z TO
06Z PERIOD AS CURRENT MCS MOVES NORTHEAST. SATURATED SOILS HOWEVER
COULD LEAD TO LIGHT FOG DEVELOPMENT BEFORE MORE RAIN MOVES IN TMR
MORNING. WILL HAVE SIMILAR CONDITIONS TODAY...TOMORROW.

MEFFER
&&

.MARINE... A PROLONGED PERIOD OF ONSHORE FLOW IS EXPECTED TO PREVAIL
THROUGH THE WEEKEND...GENERALLY AT LIGHT TO MODERATE LEVELS. A LONG
FETCHED SITUATION FROM THE YUCATAN CHANNEL GENERATES A DEEP SWELL
TRAIN ON FRIDAY AND FRIDAY NIGHT THAT SHOULD BRING SEAS CLOSE TO 6
FEET IN THE OPEN WATERS...WITH SOME 8 FOOT RANDOM WAVES IN THE OUTER
WATERS THAT COULD REQUIRE A SMALL CRAFT ADVISORY AT SOME POINT
FRIDAY INTO SATURDAY. 22/TD

&&

DECISION SUPPORT... DSS CODE...BLUE. DEPLOYED...NONE.
ACTIVATION...NONE. ACTIVITIES...MONITORING HEAVY RAINFALL/FLOODING
POTENTIAL.

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 TONIGHT RISK SVR         AND/OR DIRECT TROPICAL THREATS;
EVENTS OF NATIONAL          SIGNIFICANCE

&&

.PRELIMINARY POINT TEMPS/POPS... MCB 65 75 65 75 / 50 80 30 80
BTR 66 77 66 77 / 50 80 30 80 ASD 68 76 68 77 / 60 80 40 70 MSY 69
76 69 77 / 60 80 40 70 GPT 69 73 69 74 / 60 80 50 70 PQL 68 75 69
76 / 60 80 50 70

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FLASH FLOOD WATCH THROUGH WEDNESDAY EVENING FOR LAZ040-046>050-
     056>070-072.

GM...NONE.
MS...FLASH FLOOD WATCH THROUGH WEDNESDAY EVENING FOR MSZ077-080>082.

GM...NONE.
&&

$$



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