FXUS64 KLIX 072209
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
409 PM CST MON DEC 7 2009
.DISCUSSION...
LATEST SURFACE ANALYSIS CONTINUE TO SHOW A BROAD HIGH OVER THE
TENNESSEE AND OHIO VALLEYS AND AN INVERTED TROUGH/WARM FRONT FROM THE
LOWER TEXAS COAST TO SOUTH CENTRAL LOUISIANA COAST. IN
ADDITION...NORTHEAST FLOW WAS NOTED OVER EASTERN TEXAS...LOUISIANA
AND MISSISSIPPI. REGIONAL SOUNDINGS REVEALED A SOUTHWEST TO WEST FLOW
ABOVE 850MB. AIR MASS NORTH OF THE WARM FRONT WILL REMAIN OR
BECOME SATURATED AND PATCHY FOG WILL DEVELOP ACROSS THE AREA THIS
EVENING.
MARGINAL LESS THAN STEEP THAT-E LAPSE RATES WERE SUPPRESSED BY
SOUTHWEST FLOW WITH THIS MORNING'S SHORT WAVE. WATER VAPOR AND IR
SAT IMAGERY SOME CONVECTION OVER SOUTHWEST LOUISIANA COAST DUE TO
AN INCOMING JET. EXPECTING VERY LIMITED CONVECTION ALONG THE
INVERTED TROUGH OR WARM FRONT PASSAGE LATE TONIGHT WITH WARM WEST
WINDS ALOFT. UPPER AIR ANALYSIS REVEALED A VIGOROUS WAVE
APPROACHING THE GREAT BASIN. PROGRESSIVE FLOW WILL ALLOW THE WAVE
TO TRACK ACROSS THE ROCKIES OVERNIGHT INTO EARLY TUESDAY. WAVE
WILL BECOME NEGATIVELY TILTED OVER THE CENTRAL PLAINS TUESDAY
AFTERNOON. THESE ACTION WILL AMPLIFY THE RIDGE BUT ALSO PULL THE
INVERTED SURFACE TROUGH/WARM FRONT NORTH TONIGHT. WIDESPREAD SHOWERS
SHOULD BREAK OUT ALONG THIS BOUNDARY STARTING LATE TONIGHT FOR
WEST ZONES.
NO REAL FOCUS ONCE IN THE WARM SECTOR...AREA WILL SEE NUMEROUS
SHOWERS BUT VERY LITTLE CONVECTION UNTIL AFTERNOON. SURFACE
HEATING AND THE APPROACHING WAVE AXIS WILL ALLOW MOISTURE TO POOL
JUST AHEAD OF AXIS AND FOCUS MAY PROVIDE ENOUGH LIFT FOR
CONVECTION IN WIDESPREAD RAINS TUESDAY AFTERNOON AND TUESDAY
EVENING. THIS FORCING WILL BE NEEDED TO OVERCOME SOUTHWEST MID
LAYER FLOW AND 5H TEMPS AROUND -10C. SW LLJ OF 60 KNOTS WILL SET
UP FROM EAST TEXAS TO NORTH MISSISSIPPI TUESDAY AFTERNOON. AT THE
SAME TIME...FLOW ALOFT WILL BE FLATTENED AND AT THE BASE AND
BACKSIDE THE WAVE A 110 TO 130 JET WILL BE LOCATED FROM THE FOUR
CORNERS REGION TO SOUTHERN ARKANSAS LATE TUESDAY.
WITH LOW AND HIGH LEVEL WINDS IN PLACE...BEST HELICITY VALUES WILL
RESIDE ACROSS THE NORTH PART OF FORECAST AREA AND POINTS NORTH.
MARGINAL INSTABILITY WILL CONFINE THE SEVERE THREAT TO SLIGHT FOR
NOW. WITH PW VALUES APPROACHING 200 PERCENT FOR THIS TIME OF YEAR
AND WITH THESE HEIGHTS...DAMP CONDITIONS WITH AT LEAST SOME KIND
OF PRECIP WILL EXIST THROUGH TUESDAY NIGHT. ANY FOCUS WILL
INCREASE LIFT...RAIN CHANCES AND GOOD RAINFALL COVERAGE. AGREE
WITH HPC WITH AREAS RECEIVING 1 TO 2 INCHES WITH ISOLATED 3 INCHES
THROUGH WEDNESDAY NIGHT. A QUICK SHOT OF CAA WILL KNOCK TEMPS DOWN
THROUGH THURSDAY. HOWEVER...SHOT OF COLD AIR WILL BE SHORT LIVED AS
FLOW ALOFT REMAINS WEST TO SOUTHWEST THROUGH THE WEEKEND.
ERGO...THE ASSOCIATED SURFACE BOUNDARY WILL RETREAT NORTH OVER THE
AREA FRIDAY THROUGH TUESDAY...MAINTAIN THE BEST THREAT OF RAIN
ACROSS THE SOUTH HALF OF THE FORECAST
&&
.AVIATION...
THE UPPER LEVEL TROUGH IS CURRENTLY MOVING EAST OF THE AREA. ITS
DEPARTURE IS THE REASON WHILE THE BULK OF RAIN IS HAS ENDED OVER THE
REGION FOR NOW. LEFT BEHIND IS A WEAK STATIONARY SURFACE TROUGH
ALONG THE MCB...BTR AND LFT AXIS WHERE CEILINGS ARE BELOW 500 FEET
TO THE NORTHWEST OF THE TROUGH. TO THE SOUTHEAST OF THE TROUGH
CEILINGS ARE BETWEEN 2000 AND 3000 FEET. VISIBILITIES HAVE LOWERED
TO AROUND 1 MILE IN FOG THIS AFTERNOON NORTHWEST OF THE STATIONARY
BOUNDARY. LIFR CONDITIONS ARE EXPECTED TO BECOME WIDESPREAD BY 06Z
BETWEEN BTR...MCB AND ASD THIS EVENING. THESE LOW IFR CONDITIONS
WILL GRADUALLY SPREAD OVER THE REMAINDER OF THE AREA BY DAYBREAK.
ANOTHER UPPER LEVEL DISTURBANCE IS APPROACHING SOUTHWEST LA AT THIS
TIME. ITS PRODUCING AN AREA OF WIDESPREAD RAIN SHOWERS. THIS
DISTURBANCE WILL BE MOVING THROUGH SOUTHEAST LA AND SOUTHERN MS
REGION LATER TONIGHT. LOW IFR CONDITIONS WILL BE SLOW TO IMPROVE TO
IFR/MVFR TUESDAY MORNING UNTIL A WARM FRONT...WHICH IS CURRENTLY IN
THE NORTHERN GULF OF MEXICO...MOVES THROUGH THE AREA.
.COASTAL...
A PERIOD OF HIGHLY UNSETTLED WEATHER IS EXPECTED OVER THE COASTAL
WATERS THIS WEEK. SMALL CRAFT SHOULD EXERCISE CAUTION TONIGHT AS
SOUTHEAST GRADIENT FLOW WILL INCREASE AFTER MIDNIGHT. EXPECT SMALL
CRAFT CONDITIONS TO DEVELOP AHEAD OF AN ADVANCING STRONG COLD FRONT
AND LARGE LOW PRESSURE AREA ON TUESDAY. THE COLD FRONT SHOULD MOVE
THROUGH THE REGION TUESDAY NIGHT AND WEDNESDAY. THIS WILL ALLOW HIGH
PRESSURE TO DEVELOP OVER THE REGION WEDNESDAY NIGHT AND THURSDAY.
ANOTHER WARM FRONT AND LOW PRESSURE AREA IS EXPECTED TO FORM IN THE
NORTHWEST GULF COASTAL WATERS FRIDAY AND FRIDAY NIGHT. SMALL CRAFT
CONDITIONS SHOULD DEVELOP IN THE STRONG EASTERLY FLOW AS THE WARM
FRONT AND LOW PRESSURE AREA MOVE TOWARDS THE CENTRAL GULF COAST.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 57 74 55 64 / 60 90 60 10
BTR 61 75 56 65 / 80 90 60 10
MSY 63 76 63 70 / 60 90 80 10
GPT 60 70 62 69 / 40 80 80 20
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&
$$
