Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 271706
AFDLCH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
1106 AM CST SAT DEC 27 2014


.AVIATION...SHOWERS, ISOLATED THUNDERSTORMS, STRATUS, AND AREAS
OF FOG WILL KEEP CONDITIONS IFR TO LIFR THROUGH MOST OF TODAY AND
TONIGHT. A COLD FRONT WILL MOVE ACROSS THE REGION FROM LATE THIS
AFTERNOON THROUGH LATE TONIGHT VEERING WINDS FROM SE NOW TO NW
BEHIND THE FRONT. STRATUS AND -RA WILL LINGER INTO SUNDAY BEHIND
THE FRONT.


&&

.PREV DISCUSSION... /ISSUED 946 AM CST SAT DEC 27 2014/

UPDATE...CERTAINLY A COMPLICATED WEATHER SCENARIO FOR THIS
AFTERNOON WITH A RATHER EXTENSIVE MARINE LAYER OVER SOUTHERN PARTS
OF FORECAST AREA.  THIS IS INHIBITING LARGE SCALE CONVECTIVE
DEVELOPMENT IN THE SHORT TERM BUT EXPECT INCREASING SHOWERS AND
THUNDERSTORMS BEGINNING LATE THIS MORNING THROUGH THE AFTERNOON.
BETTER INSTABILITY EXISTS OVER SOUTH CENTRAL LOUISIANA WITH SOME ECHO
TRAINING NOTED OVER FAR EASTERN PARTS OF THE COUNTY WARNING AREA.
SOME AREAS OF DENSE FOG ARE EXPECTED FOR THE NEXT SEVERAL HOURS BUT
BETTER MIXING IS FORECASTED FOR LATE THIS MORNING OVER THE LAND
AREAS.  FOR NOW...WILL HANDLE WITH SPS.

NO MAJOR CHANGES TO THE GRIDS ARE EXPECTED FOR THIS UPDATE...BUT MAY
BE MAKING SOME ADJUSTMENTS TO POPS/QPF FORECASTS IN THE SHORT
TERM.

FOR MARINE...WILL CONTINUE WITH FOG ADVISORY THROUGH NOON.  NO OTHER
UPDATES PLANNED AT THIS MOMENT.

PREV DISCUSSION... /ISSUED 334 AM CST SAT DEC 27 2014/

DISCUSSION...
THE BEGINNING OF WHAT IS EXPECTED TO BE A RATHER WET WEEKEND AS
THE FIRST...MAINLY LIGHT...SHOWERS ARE DEVELOPING ACROSS THE
FORECAST AREA THIS EARLY MORNING. THE MAIN CULPRIT IS A LARGE
UPPER LEVEL TROUGH EXTENDING FROM THE NORTH CENTRAL PLAINS DOWN
THROUGH THE SOUTHWEST U.S. THIS FEATURE WILL BE OPENING UP AND
MOVING ACROSS THE FORECAST AREA THIS WEEKEND. UNTIL THIS UPPER
LEVEL TROUGH MOVES PAST...CLOUDY...RAINY WEATHER CAN BE EXPECTED.

A NUMBER OF FACTORS ARE COMING TOGETHER THAT COULD MEAN A COOL
SEASON HEAVY RAINFALL POTENTIAL FOR A PORTION OF THE FORECAST
AREA.

FIRST...PLENTY OF GULF AND EAST PAC MOISTURE WILL BE TRANSPORTED
INTO THE FORECAST AREA FROM INCREASING SOUTHERLY WINDS IN THE LOW
LEVELS...AND MOIST SOUTHWEST FLOW A LOFT. PRECIPITABLE WATER ON
LATEST UPPER AIR SOUNDING WAS ALREADY NEAR 1.5 INCHES...WHICH IS
OVER 175 PERCENT OF NORMAL FOR LATE DECEMBER. MODERATE 30 TO 40
KNOT LOW LEVEL JET WILL CONTINUE THROUGH THE DAY...WITH PWAT
EXPECTED TO INCREASE TO BETWEEN 1.7 AND 1.9 INCHES THIS AFTERNOON
AND EVENING...AND THESE VALUES ARE OVER TWICE THE STANDARD DEVIATION.
MEAN RH WILL BE RATHER HIGH ALSO...OVER 90 PERCENT...WHICH WILL
MAKE FOR EFFICIENT RAIN PRODUCING SHOWERS AND STORMS.

SECOND...UPPER LEVEL TROUGH WILL PUSH A SURFACE COLD FRONT INTO
THE FORECAST AREA LATE THIS AFTERNOON...REACHING AN ALEXANDRIA TO
LAKE CHARLES LINE BY MIDNIGHT...AND MOVING SLOWLY ACROSS THE
REMAINDER OF THE FORECAST AREA DURING THE OVERNIGHT. WHILE A
FRONTAL WAVE DEVELOPS ALONG THE FRONT AND MOVES TO THE SOUTH
CENTRAL LOUISIANA COAST BY MIDNIGHT...THEN ACROSS THE ATCHAFALAYA
BASIN INTO SOUTHWEST MISSISSIPPI DURING THE OVERNIGHT. THESE
FEATURES WILL ALLOW FOR A LOW LEVEL MECHANISM TO HELP FOCUS THE
SHOWER AND STORM ACTIVITY. AND WITH MID LEVEL FLOW BECOMING
PARALLEL TO THE FRONT...STORM MOTION WILL BE RIGHT ALONG IT WITH
THE POSSIBILITY OF TRAINING.

THIRD...JET STREAK MOVING AROUND THE BASE OF THE UPPER LEVEL
TROUGH WILL PLACE THE FORECAST AREA IN THE FAVORABLE RIGHT
ENTRANCE REGION...THAT WILL CREATE GOOD UPPER LEVEL DIVERGENCE AND
ENHANCE SHOWER AND RAINFALL ACTIVITY.

THEREFORE...HPC HAS HIGHLIGHTED THE PORTION OF THE FORECAST AREA
ROUGHLY SOUTHEAST OF A MARKSVILLE TO SABINE PASS LINE IN A SLIGHT
RISK OF EXCESSIVE RAINFALL. A MIX OF QPF FROM HPC AND GLOBAL
MODELS SHOW STORM TOTAL RAINFALL ON AVERAGE IN THIS AREA BETWEEN 2
TO 4 INCHES...AND OF COURSE SOME LOCALLY HEAVY AMOUNTS WILL BE
POSSIBLE. DURING THE COOL SEASON...THIS COULD PROVIDE SOME RUN OFF
ISSUES. ALREADY INHERITED A FLOOD WATCH FROM EARLY SHIFT IN THE
REGION COVERED BY THE SLIGHT EXCESSIVE RAINFALL RISK...SO WILL
LEAVE THAT ALONE. HEAVIEST RAINFALL LOOKS TO TAKE PLACE BETWEEN
LATE SATURDAY AFTERNOON THROUGH THE OVERNIGHT.

ALSO...A LOW END OR MARGINAL RISK FOR SEVERE WEATHER HAS ALSO BEEN
OUTLINED FOR FORECAST AREA DURING THE AFTERNOON HOURS BY SPC. WARM
SECTOR WEDGE AHEAD OF FRONTAL WAVE WILL MAKE ITS WAY INLAND
INCREASING LOW LEVEL INSTABILITY WITH CAPES AROUND OR JUST ABOVE
1000 J/KG. ALSO...LOW LEVEL SHEAR WILL INCREASE WITH THE FRONTAL
WAVE. SO THERE IS THE POSSIBILITY OF SOME ROTATING UPDRAFTS TO
PRODUCE A BRIEF SEVERE STORM OR TWO. AT THIS POINT...WILL NOT
MENTION THE SEVERE WORDING IN THE WEATHER GRID AND MENTION IN THE HWO.

COLD FRONT WILL MOVE THROUGH THE FORECAST AREA BY SUNDAY MORNING.
BRINGING A MUCH COOLER AIR MASS. SOUTHERN JET STREAM ASSOCIATED
WITH THE UPPER LEVEL TROUGH WILL STILL BE ACTIVE. SO EXPECTED A
RAW DAY WITH OVER-RIDING RAIN...ENDING ON SUNDAY NIGHT AS THE
UPPER LEVEL TROUGH FINALLY MOVES OFF TO THE EAST.

LARGE CANADIAN HIGH PRESSURE SYSTEM WILL THEN SPILL DOWN THE
EASTERN ROCKIES INTO THE FORECAST AREA FOR THE EARLY TO MIDDLE
PART OF THE WEEK. THIS WILL PROVIDE A SPELL OF COLD NIGHT AND COOL
DAYS. AT-LEAST UPPER LEVEL CLOUDINESS WILL HANG AROUND...THAT WILL
HAMPER SOLAR RADIATION DURING THE DAYTIME...BUT MAY KEEP OVERNIGHT
LOWS IN CHECK.

CYCLE BEGINS ALL OVER AGAIN BY THE END OF THE WEEK...WITH NEXT
UPPER LEVEL TROUGH MOVING FROM THE WEST COAST INTO THE FORECAST
AREA...PROVIDING SHOWERS STARTING ON NEW YEARS DAY.

RUA

MARINE...
SOUTHERLY WINDS AHEAD OF A DEVELOPING STORM SYSTEM...WILL PROVIDE
AN INCREASE IN MOISTURE ACROSS THE MARINE AREA...WITH DEVELOPING
SHOWERS AND AREAS OF FOG UNTIL A COLD FRONT MOVES THROUGH DURING
THE OVERNIGHT AND SUNDAY MORNING. BEHIND THE FRONT...NORTH WINDS
ARE EXPECTED TO BRING A COOLER AIRMASS THAT WILL REDUCE THE CHANCE
FOR SEA FOG...ALTHOUGH OVER-RIDING RAIN SHOWERS WILL PERSIST UNTIL
SUNDAY NIGHT.

OFFSHORE FLOW WILL THEN CONTINUE THROUGH MID-WEEK. MODERATE TO
STRONG NORTH WINDS WILL BE POSSIBLE BY LATE TUESDAY INTO WEDNESDAY
AS PRESSURE GRADIENT INCREASES AS A STRONG CANADIAN HIGH NEAR THE REGION.

RUA

&&

.PRELIMINARY POINT TEMPS/POPS...
KLCH  74  52  56  42  59 /  90  90  80  30  10
KBPT  74  49  54  42  61 /  90  70  80  20  10
KAEX  71  51  53  40  56 /  90  90  80  30  10
KLFT  74  59  62  46  59 /  90  90  80  50  10

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR THE FOLLOWING ZONES:
     ACADIA...ALLEN...AVOYELLES...CALCASIEU...EAST CAMERON...
     EVANGELINE...IBERIA...JEFFERSON DAVIS...LAFAYETTE...LOWER
     ST. MARTIN...ST. LANDRY...ST. MARY...UPPER ST. MARTIN...
     VERMILION...WEST CAMERON.

TX...NONE.
GM...DENSE FOG ADVISORY UNTIL NOON CST TODAY FOR THE FOLLOWING ZONES:
     CALCASIEU LAKE...COASTAL WATERS FROM CAMERON LA TO HIGH
     ISLAND TX OUT 20 NM...COASTAL WATERS FROM INTRACOASTAL CITY
     TO CAMERON LA OUT 20 NM...COASTAL WATERS FROM LOWER
     ATCHAFALAYA RIVER TO INTRACOASTAL CITY LA OUT 20 NM...
     SABINE LAKE...VERMILION BAY.

&&

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&&

$$






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