FXUS64 KLIX 270114
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
714 PM CST THU NOV 26 2009
.UPDATE...
...SOUNDING DISCUSSION...
NO PROBLEMS WITH THE FLIGHT THIS EVENING. THE SOUNDING SHOWS THAT
THE ATMOSPHERE IS EXTREMELY DRY AND STABLE WITH A PW OF 0.2 INCHES
AND A LI OF 16.3. THIS WILL ALLOW FOR A CHILLY EVENING WITH
TEMPERATURES ALREADY IN THE LOWER 40S ON THE NORTHSHORE AND IN THE
LOWER 50S IN THE CITY OF NEW ORLEANS AND THE SURROUNDING AREAS ON
THE SOUTHSHORE. WINDS WERE LIGHT AND OUT OF THE NORTHWEST AT THE
SURFACE AT THE TIME OF LAUNCH BUT HAVE ALREADY GONE CALM AT THE
AIRPORT IN SLIDELL AS WELL AS AT HAMMOND...BATON ROUGE AND
MCCOMB. THIS WILL ALLOW FOR STRONG RADIATIONAL COOLING
OVERNIGHT...ESPECIALLY IN THE FREEZE WARNING AREA.
98/SO
&&
.PREV DISCUSSION... /ISSUED 259 PM CST THU NOV 26 2009/
SYNOPSIS...
SURFACE LOW CENTERED NORTH OF MICHIGAN WITH A COLD FRONT EXTENDING
SOUTHWARD ALONG THE APPALACHIANS AND INTO SOUTHEAST LOUISIANA.
SURFACE HIGH IS CENTERED OVER CENTRAL TEXAS. LOCALLY...REINFORCING
FRONT HAS MOVED THROUGH MOST OF THE AREA AS EVIDENT BY A SLIGHT
WIND SHIFT AND GUSTY CONDITIONS BEHIND THE FRONT. CLEAR SKIES AND
LOW DEWPOINTS WITH TEMPERATURES BARELY REACHING THE 60 DEGREE MARK
HAVE RESULTED IN A GORGEOUS THANKSGIVING DAY.
SHORT TERM...
COLDEST TEMPERATURES OF THE SEASON THUS FAR ARE EXPECTED TONIGHT
AS CLEAR SKIES...LOW DEWPOINTS AND CALM OR VERY LIGHT WINDS ALLOW
FOR EFFICIENT RADIATIVE COOLING. WITH THESE CONDITIONS...SHOWS
THAT TEMPERATURES WILL GENERALLY OVERACHIEVE AND DROP LOWER THAN
MODEL GUIDANCE SUGGESTS. WITH THAT SAID...AM FORECASTING
TEMPERATURES A DEGREE OR TWO BELOW GUIDANCE...AND SOME AREAS MAY
DROP EVEN LOWER THAN THAT CONSIDERING MCCOMB AND A FEW OTHER SITES
FELL A GOOD 4 TO 5 DEGREES BELOW GUIDANCE LAST NIGHT. RESULT IS
A FORECAST FOR A FEW HOURS OF TEMPERATURES BELOW FREEZING FOR
AREAS THAT ARE GENERALLY ALONG AND SOUTH OF A LINE FROM ST.
FRANCISVILLE TO HAMMOND TO SLIDELL TO PASCAGOULA.
AS THIS WILL BE THE FIRST FREEZE OF THE SEASON...A FREEZE WARNING
HAS BEEN ISSUED FOR THE AFFECTED AREAS FROM 3 AM UNTIL 7 AM CST.
THE COLDEST TEMPERATURES ARE EXPECTED ACROSS PIKE AND WALTHALL
COUNTIES...WHERE AN HOUR OR TWO OF TEMPERATURES IN THE UPPER 20S
CANNOT BE RULED OUT. SPENT QUITE A WHILE CONTEMPLATING WHETHER TO
INCLUDE EAST BATON ROUGE AND LIVINGSTON PARISHES IN THE FREEZE
WARNING. WHILE SOME OUTLYING RURAL AREAS IN THESE PARISHES MAY
EXPERIENCE A COUPLE HOURS OF FREEZING CONDITIONS...THE VAST
MAJORITY OF THE PARISHES SHOULD REMAIN JUST ABOVE FREEZING...SO
THEY WERE ULTIMATELY LEFT OUT.
ANOTHER COOL DAY ON TAP FOR FRIDAY WITH HIGHS AGAIN BARELY
EKING INTO THE 60S. BY SATURDAY...EXPECT A WARMING TREND TO
BEGIN AS THE SURFACE RIDGE SLIDES EASTWARD CAUSING WINDS TO BECOME
MORE SOUTHEASTERLY.
LONG TERM...
STILL SOME UNCERTAINTY CONCERNING THE EXTENDED PORTION OF THE
FORECAST. WHILE MODELS ARE SHOWING BETTER AGREEMENT WITH EACH
OTHER...WE ARE STILL SEEING SOME SIGNIFICANT RUN TO RUN CHANGES
CONCERNING THE TIMING AND EVENTUAL TRACK OF THE SURFACE SYSTEM.
HAVE GENERALLY GONE WITH A COMPROMISE BETWEEN THE ECMWF AND GFS
CONCERNING THIS SYSTEM...WHICH PUTS THE FORECAST IN GOOD AGREEMENT
WITH GUIDANCE FROM HPC.
BY SUNDAY...STRONG POSITIVELY TILTED UPPER TROUGH SHOULD BE
DIGGING INTO THE MIDDLE MISSISSIPPI VALLEY. AS IT DOES SO...A 500
MB CUT OFF LOW IS FORECAST TO DEVELOP OVER THE SOUTHWEST CONUS.
THIS CUT OFF LOW WILL HELP TO SLOW THE PROGRESSION OF THE SURFACE
COLD FRONT AS IT MOVES THROUGH THE AREA AND STALLS NEAR THE
NORTHERN GULF COAST. THE CHANCES OF RAIN ACROSS THE AREA WILL
GREATLY DEPEND ON EXACTLY HOW FAR INTO THE GULF THE FRONT STALLS.
HAVE GENERALLY FORECAST AT LEAST CHANCE POPS SUNDAY NIGHT THROUGH
TUESDAY WITH THE HIGHEST POPS ON MONDAY AS THE FRONT MOVES INTO
AND THROUGH THE LOCAL AREA.
AFTER THE FRONT STALLS...A SURFACE LOW IS FORECAST TO DEVELOP IN
THE WESTERN GULF IN RESPONSE TO THE UPPER LEVEL CUT OFF LOW
FINALLY BEGINNING TO PROGRESS EASTWARD. WHILE THE TIMING OF THIS
FEATURE IS CONSISTENT BETWEEN THE TWO MAJOR MODELS...THERE IS SOME
UNCERTAINTY CONCERNING THE TRACK OF THIS SURFACE LOW. THE GFS
KEEPS THE LOW MUCH FARTHER SOUTH BRINGING IT INTO THE FLORIDA
PANHANDLE BEFORE SHIPPING IT NORTHEASTWARD ALONG THE ATLANTIC
COAST. IN CONTRAST...THE ECMWF BRINGS THE LOW INTO SHORE NEAR
MOBILE SENDING IT MORE NORTHWARD INTO NEW ENGLAND. HAVE GENERALLY
GONE WITH A COMPROMISE BETWEEN THE TWO SOLUTIONS. AS THE TRACK OF
THE LOW WILL HAVE A HUGE IMPACT ON THE SENSIBLE WEATHER FOR THE
LOCAL AREA...HAVE GENERALLY ERRED ON THE SIDE OF CAUTION AND
INCLUDED THUNDERSTORMS ACROSS MOST OF THE AREA AS THE LOW MOVES
PAST THE REGION. THUNDERSTORMS WILL BE LESS LIKELY OVER LAND IF
THE LOW MOVES FARTHER TO THE SOUTH. IF THE LOW DOES TAKE A MORE
NORTHERLY ROUTE...THE LOCAL FORECAST AREA...ESPECIALLY EXTREME
SOUTHEAST LOUISIANA COULD SEE SOME STRONG THUNDERSTORMS FOR THE
TUESDAY NIGHT TIME FRAME. FUTURE FORECASTS WILL CONTINUE TO REFINE
THE DETAILS ACCOMPANYING THIS SYSTEM.
AS THE LOW PULLS AWAY FROM THE AREA...IT LOOKS LIKE THERE WILL BE
A PRETTY DECENT FIELD OF WRAP-AROUND MOISTURE ON THE BACK SIDE OF
THE LOW. THIS WILL KEEP COLD RAIN IN THE FORECAST EVEN AFTER THE
LOW MOVES OUT OF THE AREA WEDNESDAY. DRY HIGH PRESSURE SHOULD
BUILD INTO THE AREA FOR THURSDAY.
AVIATION...
VFR THROUGH FORECAST PERIOD. ONLY SHOT AT ANY CLOUDS THROUGH FRIDAY
WILL POSSIBLY BE SOME THIN HIGH CIRRUS LATE TONIGHT AND FRIDAY...BUT
THAT WILL NOT AFFECT GENERAL AVIATION.
MARINE...
SMALL CRAFT EXERCISE CAUTION WAS RAISED ON THE TIDAL LAKES THIS
MORNING AS COLD AIR ADVECTION ASSOCIATED WITH REINFORCING HIGH
PRESSURE TAKES HOLD. WHILE THERE MAY BE A FEW HOURS WHERE THESE
CONDITIONS DO NOT STRICTLY VERIFY...THE GENERAL TREND SHOULD BE IN
THE 15 TO 20 KNOT RANGE BOTH ON THE LAKES AND THE COASTAL WATERS.
WILL KEEP THE EXERCISE CAUTION THROUGH THE NIGHTTIME HOURS.
CONDITIONS WILL EASE FRIDAY MORNING...THEN QUIET WEATHER UNTIL THE
NEXT FRONT APPROACHES AROUND MONDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 30 61 38 68 / 0 0 0 10
BTR 33 62 41 69 / 0 0 0 10
MSY 38 62 44 69 / 0 0 0 10
GPT 34 62 37 67 / 0 0 0 10
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FREEZE WARNING FROM 3 AM FRIDAY TO 7 AM FRIDAY FOR THE FOLLOWING
ZONES: EAST FELICIANA...ST. HELENA...ST.
TAMMANY...TANGIPAHOA...WASHINGTON...AND WEST FELICIANA.
GM...NONE.
MS...FREEZE WARNING FROM 3 AM FRIDAY TO 7 AM FRIDAY FOR THE FOLLOWING
ZONES: AMITE...HANCOCK...HARRISON...JACKSON...PEARL
RIVER...PIKE...WALTHALL...AND WILKINSON.
GM...NONE.
&&
$$
