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

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964
FXUS64 KLIX 131743
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1243 PM CDT MON APR 13 2015

.UPDATE...

WELL DEFINED MCV MOVING NORTHWARD TOWARD THE RESTON AND MONROE
AREAS. THIS IS SWEEPING THE SHOWERS AND THUNDERSTORMS EASTWARD
WITH MOST ACTIVITY NOW OVER COASTAL MISSISSIPPI. EVEN THESE AREAS
SHOULD SEE AN END TO THUNDERSTORMS AND HEAVY RAIN PRIOR TO THE
ISSUANCE OF THE AFTERNOON FORECAST PACKAGE. WESTERN PORTIONS OF
THE AREA WILL SEE AT LEAST SOME SUNSHINE THIS AFTERNOON. CANNOT
RULE OUT SOME REDEVELOPMENT OF SHOWERS BEHIND THE IMPULSE AS THE
16Z HRRR INDICATES. EARLY LOOK AT 12Z GUIDANCE ALSO WOULD INDICATE
SOME LOWERING OF OVERNIGHT POPS IS WARRANTED. WILL NEED TO MONITOR
AFTERNOON TEMPERATURES AS WELL WITH SOME SUNSHINE INDICATED. 35

&&

.AVIATION...

CONVECTION DEPARTING MOST TERMINAL AREAS WITH VFR CONDITIONS AT
ALL SITES EXCEPT KGPT...WHERE IMPROVEMENT SHOULD OCCUR IN THE NEXT
COUPLE OF HOURS. VFR CONDITIONS LIKELY TO CONTINUE THROUGH AT
LEAST THE EVENING HOURS. CONCERN OVERNIGHT IS FOR DEVELOPMENT OF
FOG OR LOW STRATUS...AND MENTION OF LIGHT TO MODERATE FOG WILL BE
CARRIED IN THE FORECAST. NEXT ROUND OF CONVECTION LOOKS TO BE
DURING THE DAY ON TUESDAY...AND WILL LIKELY BE ADDRESSED IN THE
00Z FORECAST PACKAGE. 35/MEFFER

&&

.PREV DISCUSSION... /ISSUED 813 AM CDT MON APR 13 2015/

..SOUNDING DISCUSSION...
THE SOUNDING THIS MORNING IS UNSTABLE ABOVE THE TOP OF A SFC
INVERSION AT 950 MB. MIXED LAYER CAPE IS 1500 J/KG. MID LEVEL
LAPSE RATES HAVE STEEPENED SINCE YESTERDAY AND ARE AT ABOUT 6.3
C/KM. DUE TO A LOW LEVEL MESOSCALE BOUNDARY OVER THE AREA...
WINDS ARE EASTERLY IN THE INVERSION AND THEN SOUTH AT 018 FT.
ABOVE THE INVERSION WINDS BECOME WESTERLY. THIS CREATES SOME SHEAR
IN THE LOCAL ENVIRONMENT WITH LOW LEVEL SRH VALUES AROUND 200
M2/S2. THE PROFILE IS NEAR SATURATED AT POINTS THROUGHOUT...
RESULTING IN A RECORD MAX PW IN THE CLIMATOLOGY FOR TODAY AT 1.96
INCHES. THE STORMS COMING IN THIS MORNING WILL BE VERY EFFICIENT
RAIN MAKERS.
KRAUTMANN

PREV DISCUSSION... /ISSUED 321 AM CDT MON APR 13 2015/

SHORT TERM...
NEXT WEATHER PLAYER IS MCV MOVING OUT OF DEEP SOUTH TX INTO THE
GULF OF MEXICO TONIGHT. NO REAL SIGNS OF WEAKENING PER WSR88D AND
SATELLITE IMAGERY. MARGINAL RISK OF SEVERE WEATHER ASSOCIATED WITH
THE MCV IN THE FORM OF HIGH WINDS...FREQUENT LIGHTNING...AND
TORRENTIAL RAIN ASSOCIATED WITH THE STRONGER STORMS. LOOKING AT
THE 00Z SOUNDING ALSO INDICATES INSTABILITY IN THE POST WARM FRONT
ENVIRONMENT WITH PARCEL CAPE VALUES OF 900 TO 1000 J/KG AND BULK
SHEAR VALUES OF 22 M2/S2. PW MEASURED AT 1.94 INCHES INDICATES
RAIN THAT DOES FALL WILL BE QUITE EFFICIENT IN NATURE. HELICITY
IMPRESSIVE AT OVER 200 M2/S2. NOW THERE COULD BE SOME MODIFICATION
FROM 00Z TO THIS MORNING...WE WILL SEE ONCE WE LAUNCH THE 12Z
RADIOSONDE AND ADJUST IF NEEDED. EVEN THOUGH NOT WIDESPREAD...THERE
IS A NON- ZERO CHANCE OF A SOME WATERSPOUTS AND/OR BRIEF TORNADOES
ASSOCIATED WITH THE STRONGER STORMS AND ESPECIALLY WHEN THEY
INTERACT WITH MESOSCALE BOUNDARIES. I DID EXPAND AND EXTEND THE
FLASH FLOOD WATCH TO INCLUDE AREAS THAT RECEIVED HEAVY RAIN
YESTERDAY...IE THE MS GULF COAST WITH OVER 3 INCHES IN MANY AREAS
BETWEEN 00Z AND 06Z LAST NIGHT. ANY RAIN OVER THE WATCH AREA
BECOMES A PROBLEM AS ACCUMULATED RAINFALL TOTALS OVER THE LAST FEW
DAYS HAS LOWERED FFG VALUES TO AROUND 2 TO 2.5 INCHES PER HOUR
WHICH IS ATTAINABLE CONSIDERING THE THE CURRENT ENVIRONMENT.

HRRR TAKES THE MCV TO THE FORECAST AREA AROUND 13Z WITH SOME
SHRA DEVELOPING OUT AHEAD BEGINNING BETWEEN 8Z AND 9Z. RADAR
ALREADY SUPPORTING THIS FORECAST. THE MAIN MCV WILL REACH KBTR
AROUND 8AM...LAKE PONTCHARTRAIN BY 11AM/NOON... AND THE MS GULF
COAST AROUND 1 TO 2PM. /KEG/

LONG TERM...
WEATHER MODELS ARE ALL A LITTLE OFF IN TIMING AND COVERAGE OF
RAIN BUT WE CAN TAKE AWAY AT LEAST A VERY EL NINOESQUE WET
PATTERN CONTINUING FOR MUCH OF THE WEEK. ECMWF LOW AT 06Z LAST
NIGHT WAS PLOTTED CLOSE TO SATELLITE PER THE 3.9U CHANNEL
OBSERVATION. CLOSED LOW WAS IN SW NM WITH PLENTY OF FORCING AND
IMPULSES OUT AHEAD. DIFFLUENT FLOW ALOFT ALSO AIDING IN CURRENT
AND FUTURE SHRA/TSTM ACTIVITY OVER OUR AREA.

CURRENT LOW PROGGED OVER THE TX PANHANDLE AT 06Z TUE AS YET
ANOTHER TROUGH DIGS IN SOUTH OVER THE ROCKIES LATE IN THE WEEK.
A LOW CLOSES OFF AT THE BASE OF THE TROUGH OVER THE 4 CORNERS
AROUND 06Z THU. MODELS INDICATING THIS SETTING UP SIMILAR TO THE
CURRENT SITUATION WITH IMPULSES EJECTING EAST AND A DIFFLUENT
UPPER PATTERN. THIS SPELLS ADDITIONAL SHRA/TSTM CHANCES INTO
THU/FRI/SAT HOWEVER CONFIDENCE NOT QUITE AS HIGH ESPECIALLY
GETTING INTO NEXT WEEKEND. BY 18Z SUN THE CLOSED LOW HOVERS AROUND
WESTERN KS AND SHOULD BE PUSHING RAIN CHANCES EASTWARD WITH IT.
INTERESTING TO NOTE YET ANOTHER TROUGH AND ASSOCIATED CLOSED LOW
DIVES SOUTH OFF THE CA COAST PER THE GFS AND ECMWF AT THE 200 TO
240 HOUR MARK. LOTS OF UNCERTAINTY WITH THIS BUT DOES CONTINUE THE
CURRENT TREND OF A VERY ACTIVE SOUTHERN STREAM WITH SYSTEM LINED
UP FOR THE NEXT WEEK AND POSSIBLY BEYOND. /KEG/

MARINE...OUTSIDE OF CONVECTION WINDS SHOULD GENERALLY BE OUT OF THE
SE AND S THROUGH THE NEXT FEW DAYS. WINDS NEVER REALLY SEEM TO GET
VERY STRONG SO ONLY LOOKING FOR MODERATE ONSHORE AT TIMES...IN THE
10-15KT RANGE. B/C CONCERN WOULD BE IN THE NEXT 12 HRS WITH
CONVECTION CURRENTLY MOVING OVER THE NW GULF. THIS LINE OF STORMS IS
STRONG AND IF IT HOLDS WILL LIKELY PROMPT MARINE WARNINGS AS IT
MOVES INTO AND THROUGH THE COASTAL WATERS. /CAB/


DECISION SUPPORT...
DSS CODE...BLUE.
DEPLOYED...NONE
ACTIVATION...NONE.
ACTIVITIES...FLASH FLOOD WATCH AND MONITORING CONVECTIVE TRENDS.

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  75  67  74  65 / 100  40  80  60
BTR  77  68  75  66 / 100  40  80  50
ASD  77  69  77  67 / 100  30  80  50
MSY  78  70  76  68 / 100  30  70  50
GPT  74  71  74  70 / 100  30  70  50
PQL  77  71  78  70 / 100  30  70  50

&&

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

GM...NONE.
MS...FLASH FLOOD WATCH THROUGH TUESDAY EVENING FOR MSZ080>082.

GM...NONE.
&&

$$



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