FXUS64 KLCH 031136
AFDLCH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
536 AM CST THU DEC 3 2009
.AVIATION...
HIGH PRESSURE RIDGING SOUTH OVER THE REGION WILL MAINTAIN MODERATE
NORTH WINDS TODAY BETWEEN 8-12 KNOTS. SATELLITE IMAGES THIS
MORNING INDICATE PATCHY LOW CLOUDS OVER THE TOLEDO BEND AREA AND
ACROSS SOUTH CENTRAL LA. THESE CLOUDS ARE EXPECTED TO DISSIPATE BY
13Z...WITH VFR CONDITIONS PREVAILING THROUGH THE DAY TODAY. CLOUDS
EXPECTED TO INCREASE TONIGHT...BUT CIGS TO REMAIN VFR.
&&
.PREV DISCUSSION... /ISSUED 458 AM CST THU DEC 3 2009/
SYNOPSIS...
A WYOMING HIGH WILL BUILD SOUTHEAST THROUGH THE COLORADO FRONT RANGE
TO ACROSS DEEP SOUTH TEXAS...MOVING LITTLE OVER THE NEXT FEW DAYS.
FURTHER-UP...A DEEP POSITIVELY-TILTED WESTERLY TROUGH EXTENDS FROM
THE DAKOTAS SOUTHWEST TO ACROSS BAJA CALIFORNIA. THE WESTERLY
TROUGH SPLITS INTO A NORTHERN AND SOUTHERN STREAM BY FRIDAY...WITH
THE MORE VIRULENT SOUTHERN STREAM TRAVELING EASTWARD THROUGH WEST
TEXAS...BEFORE EXITING LOUISIANA BY SATURDAY MORNING.
A GULF COAST LOW WILL FORM JUST OFFSHORE BROWNSVILLE ON FRIDAY...
WITH THE APPROACH OF THE SOUTHERN STREAM TROUGH. THE LOW DEEPENS
WHILE TRAVELING THROUGH THE NORTHWEST GULF OF MEXICO...BEFORE
ENTERING THE NORTHEAST GULF OF MEXICO BY SATURDAY MORNING.
DISCUSSION...
UNSEASONABLY COOL WEATHER WILL PREVAIL FOR TODAY AND TONIGHT.
PROBLEMS WILL START BY FRIDAY AFTERNOON...AS CYCLONIC ASCENDING
AIR ASSOCIATED WITH THE DEEPENING GULF COAST LOW PHASES IN WITH
THE LIFT ASSOCIATED WITH THE ADVANCING WESTERLY TROUGH.
WIDESPREAD RAIN IS EXPECTED DURING THE AFTERNOON HOURS ON FRIDAY...
GIVING WAY TO SNOW DURING THE EVENING HOURS.
THE GFS MODEL IS PERSISTENT IN ITS SNOWY SOLUTION.
THE SURFACE RE-FREEZING LAYER WILL BE COLD ENOUGH...THE 1000-
850 MB THICKNESS CONTOURS RUNNING AT OR LOWER THAN 1290 METERS.
THE ELEVATED MELTING LAYER WILL REMAIN COLD WITH THE 850-700 MB
THICKNESS CONTOURS RUNNING AT OR LOWER THAN 1540 METERS. LITTLE
MELTING AS FLAKES ALOFT FALL THROUGH THIS LAYER.
THE ICE MULTIPLICATION LAYER IS MOST CONVINCING. SIGNIFICANT
SYNOPTIC LIFT ATTENDING THE ADVANCING WESTERLY TROUGH WILL UP-SWEEP
SUPER-COOLED LIQUID WATER DROPS...WHICH WILL RIME UPON
ENCOUNTERING FALLING ICE HABITS ABOVE...THEN SPLINTER. ABUNDANT ICE
SEEDING WILL PRODUCE ABUNDANT SNOW.
HOWEVER...HOW MUCH SNOW WILL FALL REMAINS THE PROBLEM. FOLLOWED
THE GFS 6-HOUR SNOWFALL ACCUMULATION AS GUIDANCE...WHICH KEEPS THE
TOTAL AMOUNTS BELOW THE 4-INCH WARNING LEVEL.
DECIDED TO ISSUE THE WINTER STORM WATCH MAINLY BECAUSE SNOW IS
EXPECTED TO FALL DURING THE NIGHT-TIME ON FRIDAY...LIMITED
VISIBILITY IS ALWAYS A PROBLEM...EVEN FOR RAIN.
ALL PRECIPITATION WILL BE ENDING ON SATURDAY.
MARINE...
VERY LARGE PRESSURE DIFFERENCES WILL SEPARATE THE GULF COAST LOW
FROM THE WYOMING-TO-TEXAS HIGH PRESSURE SYSTEM. STRONG NORTHERLY
WINDS WILL BE THE RESULT.
IN ADDITION...COLD CONTINENTAL AIR SLIDING OVER A RELATIVELY WARM
WATERS WILL MAKE FOR AN UNSTABLE MARINE LAYER. WINDS WILL BE
GUSTY AT TIMES. A GALE WATCH IS IN EFFECT.
&&
.PRELIMINARY POINT TEMPS/POPS...
KLCH 55 39 50 32 / 0 0 70 70
KBPT 55 38 48 29 / 0 0 80 60
KAEX 52 37 47 30 / 0 0 50 70
KLFT 55 34 51 28 / 0 0 50 70
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...WINTER STORM WATCH FROM FRIDAY EVENING THROUGH LATE FRIDAY NIGHT
FOR ACADIA-ALLEN-AVOYELLES-BEAUREGARD-CALCASIEU-CAMERON-
EVANGELINE-IBERIA-JEFFERSON DAVIS-LAFAYETTE-LOWER ST.
MARTIN-RAPIDES-ST. LANDRY-ST. MARY-UPPER ST. MARTIN-
VERMILION-VERNON.
TX...WINTER STORM WATCH FROM FRIDAY EVENING THROUGH LATE FRIDAY NIGHT
FOR HARDIN-JASPER-JEFFERSON-NEWTON-ORANGE-TYLER.
GM...NONE.
&&
$$
PUBLIC/MARINE...21
AVIATION...24
