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

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000
FXUS64 KLIX 270210
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
910 PM CDT SUN APR 26 2015

.UPDATE...
INCREASED CHANCE OF SHOWERS AND THUNDERSTORMS TONIGHT IN RESPONSE
TO 250 MB JET STREAK MOVING ACROSS CENTRAL LOUISIANA AND
MISSISSIPPI PLACING FORECAST AREA IN RIGHT REAR QUADRANT WHICH IS
WHERE UPPER LEVEL DIVERGENCE IS BEING ENHANCED. 00Z SLIDELL
SOUNDING SHOWED PLENTY OF MID AND UPPER LEVEL MOISTURE AND
INSTABILITY ALSO.

&&

.SHORT TERM...
WITH SO MUCH INSTABLITY AND SHEAR DEVELOPING OVER THE AREA ON
MONDAY...CAN NOT RULE OUT THE POSSIBLITY OF HEAVY RAIN ALONG WITH
A SEVERE WEATHER THREAT. A FLASH FLOOD WATCH WILL PROBABLY BE NEED
FOR MONDAY AND MONDAY NIGHT.

&&

.PREV DISCUSSION... /ISSUED 846 PM CDT SUN APR 26 2015/

SOUNDING DISCUSSION...
ONLY ISSUE WITH LAUNCH THIS EVENING WAS LIGHT WINDS FIRST 5
MINUTES WITH BALLOON HOVERING OVERHEAD BEFORE WESTERLY WINDS WERE
REACHED AROUND 4KFT. CONDITIONALLY UNSTABLE SOUNDING WITH STEEP
LAPSE RATES IN THE MID LEVELS AND SUPPORTIVE OF OBSERVED ACCAS AND
ALTOCUMULUS FIELD AT LAUNCH...AND DETECTION OF ELEVATED CONVECTION
WITH ISOLATED LIGHTNING STRIKES TO THE SOUTHWEST OF KMSY DURING
FLIGHT. A RELATIVELY DRY SOUNDING WITH DRY LAYER ABOVE SHALLOW
MARINE LAYER UP TO ABOUT 600MB THEN SATURATED AT 555MB OR 16.2KFT.
WINDS...AS PREVIOUSLY MENTIONED...WERE NEAR CALM AT THE
SURFACE...A LAYER OF NE 2-5 KT TO JUST BELOW 4KFT...THEN SW TO NW
10-45KT TO 16KFT...THEN SW JET WINDS 60-126KT ABOVE...PEAK WIND
255/126KT AT 42.7KFT. PRECIPITABLE WATER 0.95 INCHES...LIFTED
INDEX -8 WITH A MOST UNSTABLE CAPE 2931 J/KG...NOT TOO SHABBY
GIVEN VERY LITTLE CONTRIBUTION TO SURFACE CONVECTIVE PROCESSES AT
THIS TIME.

RAN CHAP OUTPUT ON SOUNDING CONDITIONED ON ADVECTING LOW LEVEL
MOISTURE ADEQUATE TO PROVIDE A THETA-E AROUND 353K AT OR NEAR 850
MB. THIS YIELDS A RICKS INDEX OF 181 WITH A 71% CHANCE OF SEVERE
TSTMS. GUST POTENTIAL 74KT/85 MPH..HAIL 2.35" /HEN EGG/ WITH A VIL
OF ONLY 58. TORNADO POTENTIAL OF EF-4 POSSIBLE. BE MINDFUL THAT
THIS IS A CONDITIONAL CASE...NOT ACTUAL...BUT ALSO SHOULD BE NOTED
THAT PRESENCE OF ACCAS AND SOUNDING TO SUPPORT SUCH IS USUALLY A
12 HOUR PRECURSOR OF SEVERE WEATHER CONDITIONS. NAM ROS MODEL
OUTPUT OF CHAP INDICATING RI 162-164 WITH EF2 POTENTIAL MONDAY.

FINALLY...BALLOON BURST AT 5.8 MB AT AN ALTITUDE OF 21.5 MILES
ABOUT 87 MILES DOWNRANGE NEAR EASLEY ROAD NORTH OF HIGHWAY 28 IN
WESTERN ALABAMA. 24/RR

PREV DISCUSSION... /ISSUED 319 PM CDT SUN APR 26 2015/

DISCUSSION...
ALTHOUGH SHOWERS AND THUNDERSTORMS AFFECTED THE OUTER COASTAL
WATERS TODAY...MOST OF THE AREA EXPERIENCED A LULL IN
THUNDERSTORM ACTIVITY. THE QUIET WEATHER WILL BE SHORT LIVED AS
ACTIVE WEATHER RETURNS MONDAY THROUGH TUESDAY AS IMPRESSIVE UPPER
TROUGH OVER THE INTERMOUNTAIN REGION SWINGS EASTWARD ACROSS THE
SOUTHERN ROCKIES AND PLAIN DURING THE NEXT COUPLE OF DAY. MODELS
ARE IN GENERAL AGREEMENT WITH AN ASSOCIATED SURFACE LOW DEVELOPING
OVER TEXAS ON MONDAY AND MOVING EASTARD ACROSS THE NORTHERN GULF
COASTAL STATES MONDAY NIGHT AND TUESDAY. SEVERAL ROUNDS OF SHOWERS
AND THUNDERSTORMS WILL ACCOMPANY THIS POTENT WEATHER SYSTEM OVER
THE NEXT FEW DAYS. A STRONG UPPER JET SHOULD PROVIDE WIDESPREAD
SYNOPTIC SCALE LIFT...AND ALONG WITH LOW LEVEL INFLOW OF 20 TO 35
KNOTS AND AMPLE MOISTURE...PRECIP WATER IN THE 1.75 TO 2.0 INCH
RANGE BY LATE MONDAY...SHOULD LEAD TO POTENTIALLY HEAVY RAINFALL
OF 1 TO 3 INCHES ACROSS THE AREA. LATER FORECAST SHIFTS MAY HAVE
TO ISSUE FLASH FLOOD WATCH AS CONVECTIVE TRENDS AND TIMING ISSUES
ARE RESOVED. A FEW THUNDERSTORMS MAY BECOME SEVERE AS FORECAST
SOUNDINGS ESPECIALLY IN THE COASTAL AREA SUGGEST A SUFFICIENT
COMBINATION OF INSTBILITY AND SHEAR. THE FRONTAL BOUNDARY ACROSS
THE REGION POSITIONED IN THE VICINITY OF THE COAST AS THE SURFACE
LOW TRAVELS NEAR THE COAST MAY ENHANCE THE DIRECTION SHEAR
COMPONENET AND THUS THE SEVERE THREAT. THE STORM PREDICTION
CENTER HAS THE ENTIRE FORECAST AREA IN A SLIGHT RISK MONDAY AND
MONDAY NIGHT.

AS THE UPPER TROUGH MOVES EAST AND SURFACE LOW...LOW TO MID LEVEL
FLOW BECOMES WEST THEN NORTHWEST WITH MUCH COOLER AND DRIER
AIRMASS MOVING ACROSS THE AREA. DRY CONDITIONS AND TEMPS GENERALLY
BE 5 TO 10 DEGREE BELOW NORMAL ACROSS THE REGION WED THROUGH THU
BEFORE SLOWLY WARMING TO SEASONAL LEVELS BY THE WEEKEND. 21

MARINE...
REALTIVELY LIGHT WIND REGIME THIS AFTERNOON AND THIS EVENING WILL
BE SHORT LIVED AS SOUTHEAST FLOW INCREASES..TO NEAR 20 KNOTS BY
MONDAY AFTERNOON...AHEAD OF LOW PRESSURE FORECAST TO DEVELOP OVER
TEXAS ON MONDAY AND MOVE EASTWARD ALONG THE COASTAL AREA MONDAY
THROUGH TUESDAY. SEVERAL ROUNDS OF THUNDERSTORMS..POTENTIALLY
STRONG TO SEVERE...WILL LIKELY MOVE ACROSS THE MARINE IN ADVANCE
OF THE LOW PRESSURE SYSTEM. AS THE LOW MOVES EAST OF THE AREA ON
TUESDAY...NW WINDS WILL QUICKLY MOVE IN BEHIND IT AND RISE TO
20-30 KNOTS WITH HIGHER GUSTS. WIND SPEEDS ARE NOT EXPECTED TO
EASE BELOW 15-20KTS UNTIL THU NIGHT. 21

AVIATION...

OVERALL...VFR CONDITIONS WILL BE THE RULE AT ALL OF THE TERMINALS
THROUGH 06Z. WINDS WILL SLOWLY BACK THROUGH THE PERIOD...AND EXPECT
TO SEE A STRONGER EASTERLY WIND AFTER 12Z TOMORROW. BEFORE THIS WIND
INCREASES...ANOTHER INVERSION SHOULD DEVELOP AFTER 06Z...AND EXPECT
TO SEE A LOW STRATUS DECK RANGING FROM 300 TO 800 FEET FORM OVER THE
TERMINALS BY 09Z. THERE COULD BE SOME FURTHER STRENGTHENING OF THE
INVERSION AT KMCB...KHUM...AND KHDC...RESULTING IN A PERIOD OF
VISIBILITIES AND CEILINGS BELOW ONE HALF MILE AND 200 FEET
RESPECTIVELY BETWEEN 09Z AND 12Z AND THIS HAS BEEN MENTIONED AS A
TEMPO GROUP IN THE FORECAST. EXPECT TO SEE THE INVERSION QUICKLY
CLEAR AFTER 12Z...AS THE GRADIENT FLOW INCREASES AND THE BOUNDARY
LAYER TURNS MORE TURBULENT. A MIX OF MVFR AND VFR CEILINGS WILL
DEVELOP AROUND 14-15Z TOMORROW AS THIS INCREASED BOUNDARY LAYER
MIXING OCCURS.  AFTER 18Z...CONDITIONS WILL BEGIN TO DETERIORATE AS
CEILINGS FALL BACK INTO IFR RANGE AND NUMEROUS SHOWERS AND
THUNDERSTORMS MOVE INTO THE AREA. VCTS WORDING WILL LIKELY BE ADDED
FOR THE AFTERNOON HOURS TOMORROW. 32

DECISION SUPPORT...
DSS CODE...YELLOW
DEPLOYED...NAVY WEEK.
ACTIVATION...NONE. ACTIVITIES...MONITORING SEVERE WEATHER POTENTIAL
MONDAY AND TUESDAY.


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  63  72 /  30  50  70  60
BTR  68  77  65  76 /  30  70  80  50
ASD  69  76  65  80 /  30  60  80  60
MSY  72  77  68  80 /  30  70  80  50
GPT  70  74  67  76 /  30  50  70  60
PQL  68  77  65  78 /  30  50  60  60

&&

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

$$


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