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NATIONAL WEATHER SERVICE NEW ORLEANS/BATON ROUGE LA
356 AM CST WED DEC 22 2004
.DISCUSSION...LATEST UPPER AIR ANALYSIS CONTINUE TO SHOW A GENERAL
TROUGH ACROSS CONUS WITH A SHORT WAVE OVER NORTHERN WISCONSIN AND
ANOTHER OVER THE FOUR CORNERS REGION. ISOTACH ANALYSIS AT 250MB
REVEALED 110 KNOT JET MAX FROM IDAHO TO THE GREAT BASIS AND SPLIT
JET STREAM AHEAD OF THE TROUGH FROM ARIZONA TO GREAT LAKES AND FROM
ARIZONA TO NORTHERN GULF OF MEXICO. IR SATELLITE IMAGERY AND COASTAL
RADAR SITES SHOWED CONVECTION UNDERNEATH ONE THE JET STREAM OR OVER
LOUISIANA COASTAL WATERS. 00Z SOUNDING LCH REVEALED A STABLE TO
NEUTRAL ATM WITH A CAPE VALUE OF 45 J/KG AND LIX HAD A CAPE VALUE 17
J/KG. IN ADDITION...AT 00Z WED LCH AND LIX SOUNDINGS ARE SHOWING AN
INCREASE IN PRECIPITABLE WATER VALUES UP TO NEAR 1 INCH. LATEST
SURFACE ANALYSIS SHOWED A BOUNDARY FROM THE GREAT LAKES TO A LOW
OVER THE ARKLATEX REGION TO ANOTHER LOW OVER SOUTH TEXAS.
POSSIBLE SEVERE WEATHER THIS AFTERNOON AND THIS EVENING AND POSSIBLE
FROZEN PRECIPITATION FRIDAY ARE THE TWO MAIN FORECAST ISSUES FOR
THIS PACKAGE. SHORT WAVE OUT WEST WILL TRACK EAST ACROSS THE
SOUTHERN PLAINS TODAY AND BECOME NEGATIVELY TILTED ACROSS THE
ARKLATEX REGION TO THE MID SOUTH THIS EVENING. ACCORDING TO GFS AND
ETA...PRECIPITABLE WATER VALUES WILL INCREASE UP TO 1.5 TO 1.7
INCHES OVER SOUTHEAST LOUISIANA AND SOUTH MISSISSIPPI BY 00Z
THU...THIS EVENING. SOUTHERLY FLOW WILL CONTINUE TO INCREASE LOW
LEVEL MOISTURE. ETA BULKS UP CAPE VALUE TO NEAR 400 J/KG ACROSS
SOUTHWEST MISSISSIPPI AND 1200 J/KG BY NOON TODAY THROUGH THIS
EVENING BEFORE FRONTAL PASSAGE. OFF OF ALL THREE SHORT RANGE
MODELS...JET MAX OF 120 KNOTS DEVELOPS WEST TO EAST OVER CENTRAL
TEXAS THIS MORNING AND PROPAGATE EAST WITH TWO JETS SPLITTING OVER
FORECAST AREA. MODEL SOUNDING GENERALLY SHOW SPEED SHEAR AT 00Z THU
OVER THE AREA. WILL SEE STRONG TO ISOLATED SEVERE THUNDERSTORMS WITH
DAMAGING WINDS IN A SQUALL LATE THIS AFTERNOON AND THIS EVENING.
WITH -12 TO -14C...A FEW HAIL STORMS ARE POSSIBLE. FORECAST AREA
SURFACE HAS DRIED OUT SOME AND THE SPEED OF THE SHORT WAVE/PRECIP
FIELD WILL DECREASE THE THREAT OF A LONG DURATION OF HEAVY RAINFALL.
DO EXPECT WIDESPREAD 1 TO 2 INCH MAP WITH LOCAL 3 TO 4 INCH AMOUNTS
ARE EXPECTED ACROSS SOUTH MISSISSIPPI AND EAST CENTRAL LOUISIANA.
THIS COULD CAUSE A FEW PROBLEMS WITH URBAN/STREET AND SMALL STREAM
FLOODING...BUT THIS SHOULD NOT BE A WIDESPREAD ENOUGH PROBLEM TO
WARRANT A FLOOD WATCH LOOKING AT FLASH FLOOD GUIDANCE AT THIS TIME.
RAIN WILL BE TAPERING OFF AND ENDING WEDNESDAY EVENING. COLD AIR
ADVECTION WILL OCCUR BETWEEN 06 TO 12Z THU AND WILL QUIT PRECIP
EARLY THU.
MEANWHILE...A FULL LATITUDE POSITIVELY TILTED TROUGH DEVELOPS FROM
HUDSON BAY TO SOUTHWEST CONUS BY THURSDAY AND PUSH EAST THROUGH THE
WEEKEND ALTHOUGH A STRONG BRANCH OF THE UPPER JET WILL EXTEND FROM
MEXICO ACROSS THE NORTH GULF. THICKNESS VALUES WILL START TO
DECREASE THURSDAY. LOOKING AT MODEL SOUNDINGS...THE ETA IS COLDER
THAN THE GFS BUT DRY. THE GFS HAS A MOIST PROFILE SUPPORTIVE OF
PRECIPITATION...AND TEMPERATURES ARE SLIGHTLY ABOVE ABOVE 0C FROM
850 TO 725 UP TO 1C AT 18Z AT MSY. ETA AND GFS ARE COMING TOGETHER
WITH POSITIONING OF THE SURFACE LOW OVER THE CENTRAL GULF BY 00Z
SAT. HOWEVER...ETA IS MUCH COLDER AND QPF FIELDS ARE FARTHER SOUTH.
WITH CONTINUED CAA FRIDAY EVENING...WILL LIKELY SEE A CHANGE OVER TO
ALL SNOW BUT LIGHT TO VERY LIGHT AS COLD AIR BECOMES THICKER A LAYER
THUS DIMINISHING PRECIPITATION...EXCLUDING SOUTHEAST LOUISIANA COAST
WHERE A MIX IS POSSIBLE FRIDAY EVENING. MORE CONFIDENCE IN THE
FORECAST SHOULD COME THE NEXT COUPLE DAYS. HAVE LEFT POPS FOR THIS
EVENT AT 20 PERCENT CENTRAL TO 30 PERCENT NEAR THE SOUTHEAST LA
COAST FOR FRIDAY AND FRIDAY EVENING.
COLD AIR ADVECTION WILL INCREASE THROUGH SATURDAY AS THE MAIN TROUGH
MOVES THROUGH THE MISSISSIPPI VALLEY. ONCE AGAIN...FRIDAY NIGHT MAY
BE THE COLDEST NIGHT THUS FAR THIS SEASON WITH LOWER 20S EXPECTED
FROM SOUTHWEST MS TO THE MS COAST AND SOME ADJACENT PARISHES FROM
NEAR OR NORTH OF BTR TO THE NORTHSHORE. THIS SHOULD BE THE BEST
CHANCE THUS FAR FOR A KILLING FREEZE ON THE EAST BANK OF METRO NEW
ORLEANS AND SOME SOUTHEAST LA COASTAL AREAS WHERE WINDS DO NOT PASS
OVER TOO MUCH WATER. CHRISTMAS DAY SHOULD SEE SUN RETURN...BUT IT
WILL BE RATHER COLD WITH HIGHS ONLY IN THE MID 40S. &&
.PRELIMINARY POINT TEMPS/POPS...
MCB 66 38 44 25 / 100 70 00 00
BTR 69 39 46 28 / 100 60 00 00
MSY 73 44 47 33 / 90 70 00 00
GPT 68 42 49 29 / 90 80 00 00
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
MS...NONE.
SE LA AND MS COASTAL WATERS...SMALL CRAFT ADVISORY FROM PQL TO THE
ATCHAFALAYA RIVER OUT 60 NM EXCLUDING TIDAL LAKES.
&&
$$
18
Looks like rain and clouds for Baton Rouge Area
I want SNOW, not rain.