FXUS64 KLCH 230324
AFDLCH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
924 PM CST TUE DEC 22 2009
.UPDATE...
CONSIDERABLY WARMER THIS EVENING VERSUS YESTERDAY WITH
TEMPERATURES IN THE UPPER 50S AND 60S ACROSS THE AREA. WITH WAA
FORECAST TO STRENGTHEN THE REMAINDER OF THE NIGHT...TEMPERATURES
SHOULD REMAIN STEADY OR SLOWLY RISE THROUGH TOMORROW MORNING.
LATEST RADAR IMAGERY SHOWS SCATTERED SHOWER ACTIVITY CONTINUES
ACROSS MUCH OF THE WESTERN HALF OF THE FORECAST AREA...AND THE
ACTIVITY EXTENDS WELL SOUTHWARD INTO THE GULF. 00Z KLCH SOUNDING
SHOWS A DRY STABLE LAYER FROM THE SURFACE TO 850MB...WITH A
SATURATED LAYER FROM 850MB TO 700MB THEN AN EXTREMELY DRY LAYER
ABOVE THAT LEVEL. THUS MID LEVEL SHOWER ACTIVITY IS EXPECTED TO
CONTINUE THROUGH MUCH OF THE NIGHT AS CONDITIONS ARE TOO STABLE
FOR SURFACE BASED PARCELS. HOWEVER...NAM FORECAST SOUNDINGS
INDICATE SHOW THAT AS WAA CONTINUES TO INCREASE AND MOISTEN THE
NEAR SURFACE LAYER AFTER MIDNIGHT...SOME WEAK ELEVATED INSTABILITY
COULD ALLOW FOR A FEW ISOLATED THUNDERSTORMS OVER SOUTHEAST TEXAS
ZONES. CURRENT FORECAST HAS ALL OF THIS COVERED AND NO CHANGES
WERE MADE.
LATEST NAM FORECAST SOUNDINGS INDICATE THAT CONDITIONS WILL BECOME
MUCH MORE FAVORABLE FOR SURFACE BASED CONVECTION BY WEDNESDAY
AFTERNOON ACROSS OUR SOUTHEAST TEXAS ZONES. POINT FORECAST
SOUNDINGS FOR KBPT AND KJAS SHOW CAPE VALUES OF 700-1500 J/KG...NO
CAPPING INVERSION...SRH OF 300-400 M2/S2 AND VERY LOW CONVECTIVE
TEMPERATURES IN THE 60S WHICH ALL SUGGEST THE POTENTIAL OF
STRONG TO SEVERE THUNDERSTORMS POSSIBLY AS EARLY AS LATE
WEDNESDAY MORNING. MORE WIDESPREAD POTENTIAL FOR SEVERE WEATHER
ACROSS THE ENTIRE CWA STILL APPEARS TO BE IN THE CARDS WEDNESDAY
NIGHT INTO EARLY THURSDAY. INHERITED FORECAST ALSO HAS THIS WELL
COVERED.
SHAMBURGER
&&
.DISCUSSION...
&&
.PREV DISCUSSION... /ISSUED 544 PM CST TUE DEC 22 2009/
AVIATION...
PACIFIC SHORTWAVES...EMANATING OUT OF THE SIERRA MADRE OCCIDENTAL
RANGE OF DESERT MEXICO...WILL CONTINUE THEIR TRAVELS NORTHEAST
..PASSING THROUGH SOUTHEAST TEXAS AND INTO NORTHEAST LOUISIANA.
THE LIFT ASSOCIATED WITH THESE SHORTWAVES ARE CURRENTLY SETTING
OFF SCATTERED LIGHT SHOWERS ACROSS SOUTHEAST TEXAS.
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED AROUND MIDNIGHT...
MAINLY ACROSS SOUTHEAST TEXAS AND SOUTHWEST LOUISIANA. INCREASING
SOUTHERLY WINDS (AND THE ASSOCIATED ADVECTIVE INCREASE IN MOISTURE
AND INSTABILITY) WILL MAKE FOR A FRIENDLY ENVIRONMENT FOR CONVECTIVE
WEATHER. IFR CEILINGS ARE ALSO POSSIBLE AFTER MIDNIGHT...DUE
MAINLY TO THE CONVECTIVE WEATHER.
PREV DISCUSSION... /ISSUED 454 PM CST TUE DEC 22 2009/
DISCUSSION...
NOT MUCH CHANGE IN FORECAST THINKING FROM YESTERDAY WITH A STORMY
48-60 HOURS AHEAD.
ISOLATED MAINLY LIGHT SHOWERS ALREADY UNDERWAY THIS AFT ACROSS
PARTS OF EAST TX INTO WRN LA WITHIN REGION OF BEST LL WARM
AIR/MOISTURE ADVECTION. CONTINUED DEVELOPMENT IS EXPECTED IN THIS
AREA THROUGH THE EVENING AND OVERNIGHT HOURS WITH THUNDERSTORMS
COMING INTO THE MIX AS SYNOPTIC FORCING INCREASES W/ THE APPROACH
OF THE SOUTHERN STREAM JET. OVERNIGHT TEMPERATURES WILL BE RUNNING
WELL ABOVE NORMAL WITH THE ADDITIONAL CLOUD COVER AND SOUTHERLY
FETCH.
SHOWER AND THUNDERSTORM COVERAGE WILL CONTINUE TO INCREASE ON
WEDNESDAY AS THE MID/UPPER LEVEL TROF AND ASSOCIATED POLAR JET MAX
DROPS INTO NORTH TEXAS. THE THREAT OF SEVERE STORMS WILL START TO COME
INTO THE PICTURE BY TOMORROW AFTERNOON...PRIMARILY ACROSS EAST
TEXAS WHERE INSTABILITY AND LIFT WILL BE MAXIMIZED. BY TOMORROW
NIGHT...AS THE POLAR JET MAX ROUNDS THE BASE OF THE TROF...THE
TROF AXIS WILL TAKE ON AN INCREASINGLY NEGATIVE TILT. AT THE
SFC...A FRONTAL BOUNDARY IS EXPECTED TO ENTER EAST TEXAS AFTER
MIDNIGHT...AND PROGRESS RAPIDLY EAST THROUGH THE AREA DURING THE
OVERNIGHT AND THURSDAY MORNING HOURS. FORCING ALONG THE FRONT WILL
BE QUITE STRONG...AND AT THIS TIME...IT APPEARS THAT THUNDERSTORMS
WILL ORGANIZE INTO A SQUALL LINE ALONG OR JUST AHEAD OF THE FRONT.
FROM A KINEMATIC PERSPECTIVE...THIS SYSTEM CONTINUES TO LOOK
IMPRESSIVE...WHILE THERMODYNAMICALLY...JUST AVERAGE OR SLIGHTLY
LESS SO. NEVERTHELESS...THE LIMITED NATURE OF THE PROGGED
INSTABILITY CAN BE COMPENSATED FOR/OVERCOME BY THE DEGREE OF SHEAR
AND MAGNITUDE OF FORCING...AND I BELIEVE IT WILL BE. DAMAGING
WINDS WOULD SEEM TO BE THREAT NUMERO UNO...ESPECIALLY WITH THE LINEAR
CONVECTIVE MODE AND IMPRESSIVE LOW/MID LEVEL WINDS. HOWEVER...THERE
IS SUFFICIENT 0-2KM HELICITY PROGGED TO PRESENT A TORNADO
RISK...EITHER WITH ANY DISCRETE CELLS OR LEWPS WITHIN THE SQUALL
LINE. ALTHOUGH NO WIDESPREAD HEAVY RAINFALL/OR FLOODING IS
EXPECTED...THUNDERSTORMS WILL BE VERY EFFICIENT RAINFALL
PRODUCERS...SO LOCALLY HEAVY RAIN WILL ALSO BE A CONCERN.
WEATHER SHOULD RAPIDLY IMPROVE FROM WEST TO EAST AS THE SQUALL
LINE CLEARS THE AREA...AND THOUGH THERE ARE STILL SOME RELATIVELY
SMALL TIMING ISSUES TO WORK OUT...THE AREA SHOULD BE RAIN FREE NO
LATER THAN THURSDAY EVENING.
FORECAST FOR FRIDAY THROUGH THE WEEKEND CONTINUES TO BE DRY AND
COOL...WITH SLIGHT RAIN CHANCES RETURNING EARLY NEXT WEEK WITH THE
GLOBAL MODELS SHOWING ANOTHER SYSTEM AFFECTING THE AREA. DETAILS
CONTINUE TO CHANGE WITH THIS ONE...AS TO BE EXPECTED 7 TO 8 DAYS
OUT...SO MODIFICATIONS WERE KEPT MINIMAL.
MARINE...
A TIGHTENING PRESSURE GRADIENT BETWEEN HIGH PRESSURE TO THE EAST
AND A DEVELOPING LOW OVER THE SOUTHERN PLAINS WILL BRING
STRENGTHENING WINDS AND BUILDING SEAS OVER THE NORTHWEST GULF
TONIGHT AND WEDNESDAY. A COLD FRONT WITH SHOWERS AND THUNDERSTORMS
WILL ADVANCE ACROSS THE GULF WATERS THURSDAY MORNING WITH A
STRONG OFFSHORE FLOW DEVELOPING IN ITS WAKE. SMALL CRAFT
ADVISORIES ARE ALREADY IN PLACE FOR THE GULF WATERS PRIMARILY FOR
THE STRONG SOUTHERLY WINDS AHEAD OF THE FRONT. ADDITIONAL
ADVISORIES WILL LIKELY BE REQUIRED FOR THE STRONG NORTHWEST WINDS
AND ROUGH SEAS AFTER FRONTAL PASSAGE.
&&
.PRELIMINARY POINT TEMPS/POPS...
KLCH 62 71 60 65 36 / 40 50 80 80 10
KBPT 62 71 58 63 36 / 60 70 80 60 10
KAEX 57 69 58 63 34 / 30 50 90 90 10
KLFT 59 70 61 65 37 / 20 30 70 90 10
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL NOON CST THURSDAY FOR THE FOLLOWING
ZONES: 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...
WATERS FROM CAMERON, LA TO HIGH ISLAND, TX EXTENDING FROM
20 NM TO 60 NM...WATERS FROM INTRACOASTAL CITY, LA TO
CAMERON, LA EXTENDING FROM 20 NM TO 60 NM...WATERS FROM
LOWER ATCHAFALAYA RIVER TO INTRACOASTAL CITY, LA EXTENDING
FROM 20 NM TO 60 NM.
&&
$$
