FXUS64 KLIX 071845
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1245 PM CST MON DEC 7 2009
.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
1000 FEET TO THE NORTHWEST OF THE TROUGH. TO THE SOUTHEAST OF THE
TROUGH CEILINGS ARE BETWEEN 2000 AND 4000 FEET. VISIBILITIES ARE
MOSTLY UNRESTRICTED SINCE THE RAIN IS NO LONGER A SHORT TERM
FACTOR. THE IMPROVEMENT WILL BE TEMPORARY SINCE WIDESPREAD LOW IFR
CONDITIONS ARE EXPECTED TO DEVELOP BY 06Z BETWEEN BTR...MCB AND
ASD. THESE LOW IFR CONDITIONS WILL GRADUALLY SPREAD OVER THE
REMAINDER OF THE AREA BY DAYBREAK. ANOTHER UPPER LEVEL DISTURBANCE
WILL APPROACH THE AREA FRONT THE WEST AFTER MIDNIGHT. 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.
&&
.PREV DISCUSSION... /ISSUED 1141 AM CST MON DEC 7 2009/
UPDATE...
MADE A FEW CHANGES TO FIT OUR ONGOING TRENDS. UPPER LEVER SHORT
WAVE WILL CONTINUE TO PUSH THROUGH THE CENTRAL GULF COAST AND THE
BULK OF THE PRECIPITATION WAS OVER THE EAST HALF OF THE FORECAST
AREA. WILL MAINTAIN A SLIGHT CHANCE WEST AND CONTINUE AN INCREASE
IN RAIN CHANCE ACROSS THE AREA THIS EVENING AND OVERNIGHT.
PREV DISCUSSION... /ISSUED 706 AM CST MON DEC 7 2009/
UPDATE...
SOUNDING DISCUSSION...
LIGHT STRATIFORM RAIN OCCURRED AT LAUNCH. THE SOUNDING IS VERY
MOIST IN THE LOWER LEVELS WITH A SIGNIFICANT AMOUNT OF DRY AIR
ABOVE 500 MB...PRECIPITABLE WATER VALUE IS 1.38 INCHES. A STRONG
SURFACE INVERSION IS PRESENT AND ANOTHER INVERSION NEAR 3300 FEET.
WINDS ARE OUT OF THE EAST AT THE SURFACE SHIFTING SOUTH THEN WEST
ABOVE 750 MB.
PREV DISCUSSION... /ISSUED 433 AM CST MON DEC 7 2009/
ACTIVE WEATHER STILL IN STORE...
SHORT TERM...INTERESTING NIGHT IT HAS BEEN. LIGHT SHRA AND VIRGA
HAVE MOVED OVER MUCH OF THE AREA BUT BREAKS IN THE CLOUDS ACROSS OUR
NRN ZONES HAVE ALLOWED TEMPS TO DROP MUCH MORE THAN EXPECTED AS MCB
HAS GOTTEN AL THE WAY DOWN TO 45 BY 9Z. ALSO AT THAT TIME AN
INVERTED TROUGH WAS STRETCHING NNE FROM JUST OFF THE UPPER TX
COAST...JUST EAST OF TOLEDO BEND AND INTO THE ARKLAMISS. WV SHOWED
LIFT INCREASING OVER A LARGE AREA OF THE SW CONUS AND ACROSS THE
CNTRL PLAINS WHERE A LARGE WINTER STORM IS EXPECTED TO TAKE PLACE
OVER THE NEXT FEW DAYS. OVERALL THE GFS AND ECMWF SEEM TO HAVE
INITIALIZED WELL SO I WILL STICK CLOSE TO THE MAV GUI FOR THE MOST
PART MAKING ONLY SMALL CHANGES TO TEMPS AND POPS.
TODAY LIGHT SHRA AND MAYBE A STORM OR TWO WILL BE POSSIBLE. WEAK
WAA/ISENTROPIC LIFT WILL CONTINUE THROUGH THE DAY WITH THE STRONGEST
ISENTROPIC LIFT EXPECTED ACROSS THE NWRN/NRN HALF OF THE CWA TODAY
AND THIS IS WHERE THE HIGHEST POPS WILL BE. THAT SAID RAIN SHOULD
MOSTLY BE LIGHT TODAY WITH ONLY LIGHT ACCUMULATIONS OUTSIDE OF ANY
TSRA THAT DEVELOP. TONIGHT LOOK FOR RAIN TO INCREASE IN COVERAGE
AS THE MID LVL FLOW BECOMES A LITTLE MORE SWRLY WITH AN IMPULSE OR
TWO EXPECTED TO TRAVERSE ACROSS THE REGION.
AGAIN IT LOOKS LIKE THINGS WILL BE MOST ACTIVE ON TUE AND TUE NIGHT
AS WE WILL SEE ANOTHER COLD FRONT PUSH THROUGH THE AREA. AN UPPER
LOW CURRENTLY LOCATED OVER THE PAC NW WILL BEGIN TO KICK OUT TO THE
ESE LATE TODAY AND OVERNIGHT. AS IT CROSSES THE CONTINENTAL
DIVIDE CYCLOGENESIS WILL TAKE PLACE AROUND THE OK/TX PANHANDLES TUE
MORNING/MIDDAY. BOTH OF THESE FEATURES WILL CONTINUE TO PUSH EAST
THROUGH THE CNTRL PLAINS TUE AND TWRDS THE MID MS VALLEY THEN NE
INTO THE GRT LAKES REGION BY MIDDAY WED. THIS IS GOING TO SEND A
COLD FRONT ACROSS THE CWA LATE TUE NIGHT. AS THIS SFC LOW MOVES
ACROSS THOSE AFOREMENTIONED AREAS IT WILL DEEPEN AND TIGHTEN THE
PRESSURE GRADIENT ACROSS THE REGION. THE INCREASE IN SRLY WINDS
ALONG WITH WSW FLOW MID LVL FLOW WILL HELP TO TRANSPORT MORE
MOISTURE INTO THE AREA WITH PWS APPROACHING 2". THE SRLY LL WINDS
WILL ALSO HELP TO GET H85 THETA E AIR TO NEAR 336K AND DEWPOINTS
WELL INTO THE 60S. EVEN THOUGH THE BULK OF THE MID/UPPER LVL
SUPPORT WILL REMAIN OFF TO OUR N WE WILL SEE BROAD LIFT/ACCENT AS
HGHTS ARE EXPECTED TO FALL 8DM FROM TUE MORNING THROUGH WED
MORNING. ALSO WE WILL GET SOME FORCING FROM THE FRONT MOVING
THROUGH. SO WITH THAT AND THE AMOUNT OF MOISTURE EXPECTED WE
SHOULD SEE NUMEROUS TO WIDESPREAD SHRA ACROSS THE REGION BEGINNING
EARLY TUE MORNING THROUGH TUE NIGHT. ONCE THE FRONT STARTS TO PUSH
THROUGH EARLY TUE MORNING THINGS WILL BEGIN TO DRY OUT. THERE WILL
BE ISLTD TO SCT TSRA EVEN THOUGH THE ATMOSPHERE IS EXPECTED TO BE
MARGINALLY UNSTABLE.
NOW FOR THE SVR POTENTIAL. AGAIN I AM NOT OVERLY IMPRESSED MAINLY
B/C OF THE ANEMIC THERMODYNAMIC PROFILE BUT THE KINEMATIC FIELD IS
IMPRESSIVE. THAT SAID BOTH OF THESE ARE USUALLY THE CASE AS WE MOVE
INTO THE COLD SEASON. MID LVL LAPSE RATES ARE STILL EXPECTED TO BE
QUITE SHALLOW AROUND 5-5.3 C/KM. MLCAPE VALUES ARE ONLY EXPECTED TO
PEG OUT AROUND 400-700 J/KG WHILE VT 0F 23-24C AND SHOWALTERS AROUND
0 TO -2C MAY BE THE BEST WE SEE. THAT SAID THE SYNOPTIC PATTERN
AGAIN LOOKS FAVORABLE AND EVEN SLIGHTLY BETTER THAN WHAT WAS BEING
PORTRAYED THE PREVIOUS NIGHT. SFC PRESSURES WILL BE QUITE
LOW...POSSIBLY DOWN TO 1003MB AND MID LVL HGHTS WILL FALL INTO THE
FAVORABLE 572-576DM REGION. AGAIN THE LOCATION OF THE UPPER LVL JET
IS NOT OPTIMAL(WE WILL BE IN THE RFQ) THERE IS STILL BROAD
DIVERGENCE DURING THE DAY TUE. AS MENTIONED EARLIER THE KINEMATIC
FIELD IS IMPRESSIVE. WE WILL SEE A NICE INCREASE IN MID LVL WINDS
WITH H7 WINDS AROUND 50KTS AND H5 WINDS UP TO AS MUCH AS 70KTS. AS
THE SFC LOW CONTINUES TO DEEPEN AND PUSH INTO THE MID MS VALLEY THE
LL WINDS WILL RESPOND WITH A LL JET OF 50-60KTS OUT OF THE SW. WINDS
OF THIS MAGNITUDE WILL PROVIDE SUFFICIENT DEEP LAYER SHEAR OF
40-60KTS AND 0-1KM SHEAR OF 35-40KTS AND 0-1KM SREH AROUND 250M2/S2.
SO WHAT DOES ALL OF THIS SAY...WELL WITH THE AMOUNT OF MID LVL
FORCING AND BROAD ASCENT WE WILL SEE SHRA AND TSRA DEVELOP. THE
LACK OF INSTABILITY WILL KEEP THE AMOUNT OF TSRA LIMITED BUT WHAT
CAN DEVELOP AND BECOME DEEP WILL HAVE SOME THINGS WORKING FOR
THEM. THE AMOUNT OF SHEAR PRESENT SHOULD ALLOW ANY DEEP TSRA TO
ROTATE PRETTY NICELY WHICH WOULD LEAD TO SOME LONGEVITY AND
PROVIDE BOTH A DAMAGING WIND AND TORNADO RISK. AGAIN THANKS TO THE
LACK OF SOMETHING TO FOCUS ON THERE IS NO REAL LOCATION I CAN
DEFINE AT THIS TIME SO THE ENTIRE CWA APPEARS TO HAVE SOME RISK OF
STRONG TO SVR STORMS. TIMING LOOKS TO PRIMARILY BE DURING THE AFTN
AND EVN HOURS WITH THE RISK ENDING AFTER THE FRONTAL PASSAGE.
AGAIN WIDESPREAD STRONG/SVR STORMS LOOKS UNLIKELY BUT WE COULD SEE
A FEW IMPRESSIVE STORMS. /CAB/
LONG TERM...OVERALL THINGS HAVEN'T CHANGED TOO MUCH IN THE EXTENDED
BUT MEDIUM RANGE MDLS ARE NOT IN QUITE AS GOOD AGREEMENT AS THEY
WERE LAST NIGHT. THE GFS SEEMS TO HAVE PICKED UP THE PACE A LITTLE
BRINGING RAIN BACK INTO THE REGION FRI WHILE THE ECMWF IS STILL LATE
FRI NIGHT AND MOSTLY SAT. SINCE BOTH MDLS INITIALIZED DECENTLY I
WILL TRY TO TAKE A BLEND BUT PLAN TO STICK SOMEWHAT CLOSE TO THE 00Z
MEX. OVERALL CONFIDENCE IS NOT QUITE AS HIGH AS YESTERDAY BUT THINGS
STILL LOOK QUITE ACTIVE FOR OUR REGION.
WED AND THU WILL BE QUIET. THE COLD FRONT SHOULD PUSH INTO OUR
COASTAL WATERS BEFORE MIDDAY WED. THE MID LVLS WILL REMAIN MOSTLY
ZONAL AS THE L/W TROUGH FLATTENS OUT ACROSS MUCH OF THE SRN CONUS.
WITH MOSTLY ZONAL FLOW WE WILL LIKELY NOT SEE THE COLD TEMPS PLUNGE
AS FAR SOUTH. ON THE OTHER HAND THERE WILL LIKELY BE QUITE A BIT
OF SNOW ACROSS THE NRN/CNTRL PLAINS AND UPPER MS VALLEY. THIS WILL
KEEP THE AIRMASS FROM MODERATING MUCH UNTIL IT GETS DOWN INTO THE
LOWER MS VALLEY. SO EVEN WITH THE SFC HIGH NOT QUITE MAKING IT ALL
THE WAY DOWN TO THE NRN GULF WE SHOULD STILL COOLER TEMPS ONCE
AGAIN. COMBINE THAT WITH THE DRIER CONDITIONS AND WE WILL COOL DOWN
INTO THE 30S ONCE AGAIN OVER THE NRN HALF OF THE CWA. DUE TO THAT I
HAVE GONE A FEW DEGREES BELOW MEX WHICH AGREES MORE WITH THE ECMWF.
AS WE HEAD INTO FRI AND THROUGH THE WEEKEND WE WILL STILL BE IN
ZONAL TO WEAK WSWRLY FLOW. WEAK DISTURBANCES WILL PUSH ACROSS THE
REGION. AT THE SAME A WEAK SFC WAVE WILL DEVELOP IN THE NWRN GULF
AND TRACK ACROSS THE GULF COAST. MOISTURE WILL START TO RETURN AND
WE COULD SEE ISENTROPIC LIFT SHRA ONCE AGAIN FRI. THE GFS TRIES TO
BRING RAIN BACK IN AS EARLY AS THU NIGHT BUT I HAVE PUSHED BACK THE
CHANCES UNTIL AT LEAST FRI MORNING AS WE WILL LIKELY NEED TO RECOVER
FOR SOME TIME BEFORE RAIN ACTUALLY STARTS TO REACH THE SFC. WE WILL
REMAIN IN THE COOL SECTOR SO I WILL LEAVE THUNDER WORDING OUT OF THE
FCST. ALSO OF NOTE THIS TYPE OF SETUP WOULD CONCERN ME IF WE WERE A
LITTLE LATER IN THE COOL SEASON. AS WE WILL ACTUALLY HAVE THE COLD
AIR MOVE IN PLACE PRIOR TO A GULF LOW DEVELOPING AND THIS CAN LEAD
TO FREEZING RAIN...LUCKILY THE AIR WON'T BE EVEN REMOTELY COLD
ENOUGH FOR THAT SO WE WILL JUST DEAL WITH A COLD RAIN FRI NIGHT AND
PROBABLY THROUGH A MUCH OF SAT. /CAB/
AVIATION...A VIGOROUS SHORT WAVE TROUGH WILL IMPACT THE TERMINALS
TODAY INTO TONIGHT. THIS SHORT WAVE WILL ALLOW FOR PERIODS OF RAIN
TO PASS OVER ALL OF THE TERMINALS THROUGH THE DAY. DUE TO
THIS...HAVE PUT IN -RA THROUGH THE DAY FOR ALL TERMINALS.
VISIBILITIES ARE EXPECTED TO FALL INTO THE MVFR RANGE WHEN THESE
RAINS PASS THROUGH. IN ADDITION TO REDUCED VISIBILITIES...LOW
CEILINGS ARE ALSO EXPECTED AT
ALL TERMINALS. CURRENTLY...CEILINGS ARE MVFR RANGE...EXCEPT AT KBTR
WHERE CEILINGS HAVE FALLEN INTO THE IFR RANGE. CEILINGS SHOULD
REMAIN IN THE MVFR RANGE THROUGH TONIGHT. HOWEVER... A FEW PERIODS
OF IFR CEILINGS WILL BE POSSIBLE WITH HEAVIER SHOWERS. 32
COASTAL...VERY LITTLE CHANGE IN THINKING FROM THE PREVIOUS
FORECAST. PERSISTENT SOUTHERLY FLOW WILL TAKE HOLD TONIGHT AND
CONTINUE THROUGH TUESDAY NIGHT. WINDS WILL INCREASE TONIGHT INTO
TOMORROW...AS THE PRESSURE GRADIENT BETWEEN A DEEPENING LOW PRESSURE
SYSTEM OVER THE PLAINS AND A STRONG RIDGE OVER THE EASTERN SEABOARD
INCREASES. SMALL CRAFT EXERCISE CAUTION CONDITIONS ARE EXPECTED BY
TUESDAY OVER THE COASTAL WATERS. BY TUESDAY NIGHT...THE LONG
DURATION AND FETCH OF THE SOUTHERLY WINDS MAY ALLOW FOR A 1 TO 2
FOOT SWELL TRAIN TO INCREASE SEAS INTO THE SMALL CRAFT ADVISORY
RANGE. WINDS WILL SHIFT TO THE NORTHWEST WEDNESDAY...AS A COLD
FRONT SWEEPS THROUGH THE COASTAL WATERS. THIS FRONT WILL STALL OVER
THE NORTHERN GULF OF MEXICO WEDNESDAY NIGHT INTO THURSDAY. A PERIOD
OF SMALL CRAFT ADVISORY WINDS AND SEAS IS EXPECTED THURSDAY INTO
THURSDAY NIGHT...AS STRONG COLD AIR ADVECTION OVER THE WARMER WATERS
ALLOW FOR DECENT TURBULENT MIXING OF STRONGER WINDS ALOFT DOWN TO
THE SURFACE. ANOTHER AREA OF LOW PRESSURE SHOULD BEGIN TO FORM IN
THE WESTERN GULF OF MEXICO...IN A REGION OF ENHANCED BAROCLINICITY
ON FRIDAY. THIS WILL FORCE THE STATIONARY FRONT THROUGH THE REGION
AS A WARM FRONT. WINDS WILL BECOME SOUTHERLY AND INCREASE BACK INTO
AT LEAST EXERCISE CAUTION RANGE. 32
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 60 58 74 56 / 20 90 90 60
BTR 65 63 75 59 / 20 90 90 60
MSY 68 63 76 63 / 50 70 90 60
GPT 65 60 70 62 / 50 50 80 70
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&
$$
