FXUS64 KLIX 231242
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
642 AM CST WED DEC 23 2009
.UPDATE...
.SOUNDING DISCUSSION...
THE ATMOSPHERE IS GAINING MOISTURE BUT A DRY POCKET STILL REMAINS
IN THE MID LEVELS...PRECIPITABLE WATER VALUE IS 0.78 INCHES. AN
INVERSION IS PRESENT NEAR 1200 FEET AND A SECONDARY INVERSION IS
PRESENT NEAR 5200 FEET. WINDS ARE OUT OF THE SOUTHEAST UP TO 800 MB
AND OUT OF THE SOUTHWEST AND WEST ALOFT.
.PREV DISCUSSION... /ISSUED 403 AM CST WED DEC 23 2009/
SYNOPSIS...
MAIN SURFACE LOW IS LOCATED NEAR THE FOUR CORNERS REGION WITH COLD
FRONT EXTENDING SWWD ACROSS THE BAJA OF CA AND STATIONARY FRONT
EWD ACROSS THE TX PANHANDLE AND CENTRAL OK. A SECONDARY AND WEAKER
LOW EXISTS IN CENTRAL OK WITH WARM FRONT THROUGH NRN AR AND MS.
MOIST TONGUE IS EVIDENT IN EASTERN TX WITH TD/S IN THE MID 60S
BACKED UP TO DRYLINE IN WEST TX. LOCALLY...DEWPOINTS AND TEMPS
HAVE BEEN STEADILY RISING WITH WAA ONGOING. MAJORITY OF HEAVIER
RAIN ACROSS THE STATE HAS BEEN OCCURRING IN REGION OF GREATER
DIFFLUENCE AS SEEN ON 500MB WIND FIELD. UPPER LOW CONTINUES TO DIG
SEWD ACROSS THE WESTERN CONUS. A QUITE POTENT 300MB JET OF 175KTS
IS STREAKING ACROSS NRN MEXICO. WV IMAGERY INDICATES A DRY LAYER
IS SURGING EWD OVER TEXAS ON THE LEFT EXIT REGION OF THIS JET.
SHORT TERM...
WARM AND MOIST AIR WILL CONTINUE TO FILTER INTO THE AREA TODAY AS
A STEADY 12 TO 15 MPH SERLY WIND DEVELOPS FROM INCREASING PGF
BETWEEN STATIONARY SFC RIDGE TO THE EAST AND APPROACHING SFC
TROUGH. HIGHS SHOULD BE A DEGREE OR TWO WARMER THAN YESTERDAY WITH
ABOUT TWO THIRDS OF THE CWA AT OR ABOVE 70. TOOK A COMPROMISE ON
POPS BETWEEN THE WETTER MAV AND DRIER MET. ENDED UP WITH SLIGHT
CHANCE FOR EASTERN AREAS AND CHANCE SH/TS IN EXTREME WESTERN
ZONES.
COLD FRONT WILL BEGIN MAKING MORE SUBSTANTIAL PROGRESS ACROSS TX
LATER TONIGHT. RAIN CHANCES WILL BE INCREASING MORESO AFTER
MIDNIGHT. AT THIS TIME...THE AREA WILL BE IN THE WARM SECTOR EAST
OF COLD FRONT AND SOUTH OF WARM FRONT. LOW LEVEL JET LOOKS TO
INCREASE MOST AROUND SUNRISE ON CHRISTMAS EVE IN WESTERN PORTIONS
OF THE CWA WITH 50+KTS A FEW KFT OFF THE SFC AND STILL A SLIGHT
DIRECTIONAL SHEAR. MIXING DOWN THESE WINDS WILL POSE THE THREAT
FOR DAMAGING WINDS ALONG AN ONGOING SQUALL LINE. SRH OF AROUND
400 M2/S2 WILL BE THE PEAK IN THIS EARLY TO MID MORNING TIME OVER
THE WEST. SO...ISOLATED TORNADO THREAT WILL EXIST. MODELS ARE IN
GOOD AGREEMENT THAT THE FRONT/SQUALL LINE WILL IN INTO COASTAL MS
COUNTIES BY LATE AFTN AND THE EXIT THE CWA DURING THE EVENING HRS.
TOTAL QPF THROUGH THIS RAIN PERIOD SHOULD BE IN THE 1 TO 2 INCH
RANGE.
LONG TERM...
UPPER LEVEL LOW WILL SOMEWHAT STALL ACROSS THE CENTRAL CONUS THIS
WEEKEND. THIS WILL KEEP THE AREA IN NWRLY SFC FLOW REGIME AND THUS
TEMPS WILL STAY BELOW NORMAL. KEPT WITH MUCH OF PREVIOUS FORECAST
HIGHS IN THE LOWER 50S AND 3OS FOR THE LOWS. GFS AND ECMWF HAVE
SIGNIFICANTLY SLOWED THE TIMING OF A SFC LOW TO MOVE ACROSS THE
AREA NEXT WEEK FROM MON TO LATE WED.
MEFFER
AVIATION...
VFR MID LEVEL CEILINGS AND VSBY EXPECTED THROUGH ABOUT MID-MORNING
WITH PROGRESSIVELY LOWERING CEILINGS TO LOW END VFR THIS AFTERNOON.
WIDESPREAD MVFR CEILINGS IN WEST LOUISIANA INTO TEXAS WILL BE MOVING
INTO AREA BY THIS EVENING AND ACCOMPANIED WITH A FEW MARINE LAYER
SHOWERS OVERNIGHT. PRE-FRONTAL LINEAR MCS SQUALL LIKELY TO DEVELOP
AND MOVE INTO KBTR TERMINAL SPACE AROUND 15Z THURSDAY...KMCB AROUND
16Z...KMSY 17Z AND KGPT AROUND 19Z BUT WITH A WEAKENING TREND
FARTHER EAST. GFS BUFR SOUNDINGS RUN IN CHAP PROGRAM SHOWS MOST
UNSTABLE CONDITIONS AROUND THE 15Z TIME STEP WITH WINDS SWINGING
FROM SOUTHERLY TO WESTERLY WITH THE PASSAGE OF SQUALL LINE. 24/RR
MARINE...
ONSHORE FLOW STEADILY INCREASING AS GRADIENT TIGHTENS WITH MATURING
LOW PRESSURE SYSTEM MOVING INTO TEXAS FROM NEW MEXICO. VERY STRONG
UPPER LEVEL JET STREAM WITH VALUES 150KT OR HIGHER TO LIKELY INDUCE
A PRE-FRONTAL SQUALL LINE THAT MOVES ACROSS THE COASTAL WATERS
THURSDAY MORNING INTO THE EARLY AFTERNOON HOURS. GIVEN THE DEGREE OF
JET SUPPORT AND DRY AIR IN THE MID AND UPPER LEVELS...SQUALL GUSTS
MAY EXCEED 50KT WITH THE PASSAGE OF THIS FEATURE. THEREAFTER...THE
FRONT MOVES THROUGH THE COASTAL WATERS THURSDAY EVENING WITH COLD
HIGH PRESSURE BUILDING INTO THE GULF WITH SEVERAL RE-ENFORCEMENTS
THROUGH THE WEEKEND. WINDS AND SEAS WILL BECOME QUITE HAZARDOUS
BEGINNING LATER TODAY AND CONTINUING FOR THE WEEKEND BEFORE SETTLING
DOWN EARLY TO MID NEXT WEEK. 24/RR
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 68 58 62 35 / 30 90 100 20
BTR 73 59 61 36 / 30 90 100 10
MSY 73 61 70 42 / 20 80 100 10
GPT 67 59 66 41 / 30 70 100 30
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY FROM 6 AM THURSDAY TO 6 AM CST FRIDAY FOR
GMZ530.
SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM CST FRIDAY
FOR GMZ550-555-570-575.
MS...NONE.
GM... SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM CST FRIDAY
FOR GMZ555-570-575.
&&
$$
