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

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FXUS64 KLIX 300312
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1012 PM CDT FRI APR 29 2016

.UPDATE...
FORECAST FOR TONIGHT STILL APPEARS ON TRACK BUT IT IS
TOMORROW THAT APPEARS TO BE IN QUESTION NOW. THERE IS A LOT OF
INDICATION THE LAST FEW HRS THAT SUGGEST CONVECTION COULD MOVE INTO
THE REGION MUCH EARLIER THAN ANTICIPATED. FROM A MDL STANDPOINT THE
LAST 3-4 HRS OF THE HRRR HAS BEEN TRENDING STRONGER AND FASTER WITH
A SQUALL LINE EXPECTED TO DEVELOP IN THE TX HILL COUNTRY AND THEN
SURGE EAST POSSIBLY APPROACHING THE ATCHAFALAYA RIVER AS EARLY AS
15Z(MUCH LIKE LAST WEDNESDAY). WHAT COULD LEAD TO THIS...LOOKING AT
THE WV THE S/W MOVING OVER THE TX/OK PANHANDLES AND INTO KS APPEAR
LIKE IT COULD BE A TAD DEEPER WITH THE TROUGH AXIS TAKING A NEGATIVE
TILT AS IT MOVES THROUGH TX. IN ADDITION EVERY IMPRESSIVE DIVERGENCE
ALOFT OVER CNTRL AND ERN TX SHOULD LEAD TO VERY HEALTHY CONVECTION.
COMBINE THAT WITH POSSIBLY A STRONGER LLJ OVER OUR AREA TOMORROW
MORNING/MIDDAY(LEADING TO BETTER LL CONVERGENCE) AND ANOTHER RATHER
MOIST AND UNSTABLE ENVIRONMENT THERE IS A GOOD CHANCE THAT AS LONG
AS A LINE DEVELOPS IT WOULD CONTINUE DRIVING EAST. ADD IN THE FACT
THAT IF THERE ARE SEVERE SEGMENTS WITHIN THE LINE IT WILL IN ALL
LIKELIHOOD COLD POOL AND THUS LEAD TO AN EVEN FASTER ARRIVAL TIME
THAN WHAT WE ARE NOW GOING TO SHOW. HAVE MADE AN ADJUSTMENT TO BRING
CONVECTION INTO THE WRN PORTIONS OF THE CWA BY 15Z AND THE LINE IN
BTR BEFORE 18Z. AGAIN THIS COULD BE TOO SLOW.

THERE ARE TWO CAVEATS TO ALL OF THIS...FIRST A SOLID LINE MUST
DEVELOP IN TX AND SECOND THE S/W WILL PULL NNE AND WE COULD LOSE ALL
MID LVL SUPPORT WITH CONVECTION POSSIBLY DYING OFF JUST BEFORE
GETTING HERE. CAB

.SOUNDING DISCUSSION...
NO PROBLEMS WITH THE FLIGHT TONIGHT. IT TERMINATED AT 7 MB ABOUT
20.8 MILES ALOFT AND 50 MILES DOWNRANGE IN MISSISSIPPI SOUND ABOUT
8 MILES WEST OF CAT ISLAND BELOW PASS CHRISTIAN.

SOUNDING HAS AN ADIABATIC LAPSE RATE SURFACE TO BASE OF
SUBSIDENCE INVERSION NEAR 850 MB...ISOTHEMAL TO 814 MB...THEN A
FAIRLY STEEP LAPSE RATE ABOVE 700 MB TO TROPOPAUSE AT 137 MB WITH
A TEMPERATURE OF -72C. MOISTURE PROFILE IS SOMEWHAT SATURATED
BELOW INVERSION THEN QUITE DRY ALOFT...NOT TOO DISTANT FROM A
LOADED GUN SOUNDING WITH PLENTY OF DOWNDRAFT MOMEMENTUM AIR ALOFT
SHOULD A CONVECTIVE PROCESS GET UNDERWAY. WINDS ARE SE 10-15 KT TO
ABOUT 1500FT...S 25-30 KT TO 7900FT...THEN SW-NW 15-100KT ABOVE.
PEAK WIND 280/103KT AT 46.5KFT.

CHAP OUTPUT ON THIS SOUNDING IS QUITE DISTURBING FOR HEAVY
RAINFALL POTENTIAL ONCE AGAIN. USING MOST UNSTABLE LAPSE RATE
351K LIFT DOES YIELD NEARLY 100 PERCENT RAIN CHANCE...28% CHANCE
SEVERE WITH GUST POTENTIAL 52KT...MARBLE SIZED HAIL WITH A 64 VIL
AND SEVERE HAIL WITH 67 VIL. COMPUTED RAINFALL COMES UP 6.54
INCHES WITH POTENTIAL 10.01 INCHES! THIS WILL HAVE TO CLOSELY
MONITORED AS CONVECTION IS BLOSSOMING STEADILY OVER TEXAS AND
COULD MOVE INTO THE AREA UNDER STRONG DIFLUENT FLOW ALOFT
SATURDAY. 24/RR

&&

.PREV DISCUSSION... /ISSUED 413 PM CDT FRI APR 29 2016/

SYNOPSIS...
LATEST SURFACE ANALYSIS SHOWED A DEEP 1000MB LOW OVER SOUTHWEST
OKLAHOMA WITH A WARM FRONT EXTENDING EAST ALONG THE RED RIVER TO
NORTH MISSISSIPPI. A MODERATE SOUTHERLY FLOW WAS PRESENT FROM
CENTRAL TEXAS TO EAST MISSISSIPPI. PRECIPITABLE WATER PLOTS SHOWED MOISTURE
POOLING ALONG THE FRONTAL ZONE WITH 1.50 TO 1.75 INCHES FROM
NORTHEAST TEXAS TO CENTRAL MISSISSIPPI. UPPER AIR ANALYSIS SHOWED
A NEGATIVELY TITLED CYCLONIC CURVATURE FROM IDAHO TO NORTHERN NEW
MEXICO...CREATING A DIVERGENCE FLOW OVER ARKLATEX
REGION...SOUTHERN AND CENTRAL PLAINS. ISOTACH ANALYSIS AT 250MB
SHOWED THE SPLIT OVER CENTRAL AND DIVERGENCE EXTENDING NORTHEAST.
18

SHORT TERM...
WHILE TODAY IS QUIET ACROSS THE FORECAST AREA...SECOND HALF OF
THE WEEKEND AND FIRST HALF OF NEXT WEEK WILL BE UNSETTLED. UPPER
LEVEL TROUGH AXIS WILL CONTINUE TO ROTATE EAST OVER THE CENTRAL
PLAINS TONIGHT AND BECOME MORE CLOSED OFF OVER CENTRAL PLAINS ON
SATURDAY. SOUTHWEST TO WEST FLOW WILL ALLOW THE MOISTURE TO POOL
ALONG AN AXIS FROM WEST TENNESSEE TO CENTRAL TEXAS COAST BY
SATURDAY MORNING...PW VALUES 1.5 TO 1.8 INCHES ALONG THIS AXIS AND
1 TO 1.25 INCHES OVER THE FORECAST AREA ACCORDING TO GFS.
ERGO...RELATIVELY DRY FORECAST WILL HOLD OVERNIGHT AND SATURDAY
MORNING. SURFACE HEATING AND CLOSE PROXIMITY WILL YIELD SOME SCT
CONVECTION MAINLY ACROSS NORTHWEST ZONES FOR SATURDAY AFTERNOON.

WEST UPPER FLOW WILL ALLOW THE MOISTURE TO SAG SOUTH SATURDAY AND
MAINTAIN RAIN CHANCES OVERNIGHT INTO SUNDAY. MOISTURE AXIS WILL
LINE FROM SOUTHWEST LOUISIANA TO SOUTHWEST MISSISSIPPI WILL
VALUES 1.8 TO 2.0 INCHES INTO SUNDAY MORNING. CAPE VALUES WILL
REMAIN BETWEEN 900 TO 2500 J/KG THROUGH TUESDAY. THE MAIN JET
STREAM WILL REMAIN WELL NORTH OF THE FORECAST AREA. AS RESULT...LL
HELICITY VALUES REMAIN BELOW 250M/S WITH BEST VALUES SATURDAY
MORNING JUST NW OF FORECAST AREA. MOISTURE AXIS WILL ORIENT WEST
TO EAST FROM SOUTHWEST LOUISIANA TO JUST NORTH OF COASTAL
MISSISSIPPI. WILL MAINTAIN LIKELY POPS WITH HEAVY RAINFALL ACROSS
NORTH HALF OF FORECAST FOR SUNDAY. THIS AXIS WILL SLOWLY SAG SOUTH
SUNDAY THROUGH MONDAY AND RAIN CHANCES WILL REMAIN ELEVATED SUNDAY
THROUGH MONDAY AND AMOUNTS OF 2 TO 4 INCHES WITH ISOLATED HIGHER
AMOUNTS OVER A 2 TO 3 DAY PERIOD. LATER PACKAGES WILL EXAMINE FOR
POSSIBLE FLASH FLOOD WATCH ISSUANCE FOR PART OR ALL OF THE
FORECAST AREA SUNDAY THROUGH MONDAY. 18

LONG TERM...

GFS SLIGHTLY MORE AGGRESSIVE THAN EURO WITH WAVE IN THE
NORTHERN STREAM DIVING SOUTH OVER THE MISSISSIPPI VALLEY TUESDAY
INTO WEDNESDAY...EURO POSITIONED THE WAVE MORE EAST. EITHER
WAY...FORCING MAY YIELD STRONG STORMS OVER THE FORECAST AREA AND
POINT NORTHEAST ON TUESDAY. CLEARING IS EXPECTED WEDNESDAY TO THE
NEXT WEEKEND. 18

AVIATION...

EXPECT MVFR TO VFR CONDITIONS TO PREVAIL THROUGH THE REST OF THE
AFTERNOON AND EVENING. WE EXPECT CIGS TO LOWER TO MOSTLY MVFR TO
POSSIBLE IFR CONDITIONS LATER ON THIS EVENING. PATCHY FOG IS
POSSIBLE TONIGHT AND INTO THE MORNING HOURS SATURDAY. WINDS HAVE
BEEN FAIRLY BREEZY TODAY AND EXPECT THEM TO REMAIN ELEVATED TOMORROW
AS WELL AHEAD OF A COLD FRONT. THUNDERSTORMS WILL BE ON THE TABLE
LATE SATURDAY HAVE NOT PUT THEM IN THE FORECAST YET BUT LOOK FOR THE
MENTION OF THUNDERSTORMS TO BE INSERTED OVER THE NEXT ISSUANCE OR
THE FOLLOWING ISSUANCE. 13/MH

MARINE...

WILL RAISE EXERCISE CAUTION HEADLINES FOR THE REST OF OPEN WATERS
LATER TONIGHT INTO SATURDAY. THE EXERCISE CAUTION HEADLINES MAY
BE NECESSARY THROUGH MUCH OF THE WEEKEND...AT LEAST OVER THE
WESTERN WATERS. A STRONG COLD FRONT MAY YIELD SMALL CRAFT ADVISORY
CRITERIA TUESDAY NIGHT. 18

DECISION SUPPORT...
DSS CODE....BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...MINOR RIVER FLOODING.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  68  85  68  81 /  10  40  70  70
BTR  70  88  70  84 /  20  50  50  70
ASD  70  86  68  84 /  10  20  30  60
MSY  72  85  73  82 /  10  20  30  60
GPT  71  85  72  84 /  10  10  20  60
PQL  68  86  69  83 /  10  10  10  50

&&

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

$$



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