FXUS64 KLIX 060253
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
853 PM CST SAT DEC 5 2009
.UPDATE...
TEMPERATURES HAVE BEEN FALLING SIGNIFICANTLY FASTER THAN
PREVIOUSLY FORECAST. HAD TO DO A QUICK UPDATE TO DROP THE FORECAST
LOWS FOR TONIGHT. NEW FORECAST REQUIRES A HARD FREEZE WARNING FOR
PORTIONS OF SOUTHEAST LOUISIANA AND SOUTHERN MISSISSIPPI THAT ARE
GENERALLY NORTH OF A LINE FROM CENTREVILLE TO AMITE CITY TO
POPLARVILLE. WITH BELLE CHASSE ALREADY REPORTING 33 DEGREES...THE
FREEZE WARNING WILL ALSO BE EXTENDED EASTWARD TO INCLUDE THE NEW
ORLEANS METRO AREA.
&&
.PREV DISCUSSION... /ISSUED 750 PM CST SAT DEC 5 2009/
SOUNDING DISCUSSION...
NO PROBLEMS WITH THE FLIGHT THIS EVENING. A VERY DRY COOL AND DRY
AIR MASS IN PLACE WITH A PW OF ONLY 0.14 INCHES. CLEAR SKIES
PREVAIL AS DEW POINT DEPRESSIONS WERE AS HIGH AS 40 DEGREES
CELSIUS ABOVE 930 MILLIBARS. WINDS ARE LIGHT FROM THE NORTH IN THE
LOWEST LEVELS AND FAIRLY STRONG AND WESTERLY ALOFT.
PREV DISCUSSION... /ISSUED 349 PM CST SAT DEC 5 2009/
SHORT TERM...
COLD AND DRY AIRMASS WILL REMAIN ENTRENCHED ACROSS THE REGION
TONIGHT. CLEAR SKIES AND LIGHT WINDS WILL ALLOW STRONG RADIATIONAL
COOLING TO TAKE PLACE. AS A RESULT...EXPECT ANOTHER ROUND OF
FREEZING TEMPERATURES ACROSS MOST OF THE CWA. ONLY AREAS ALONG THE
IMMEDIATE LOUISIANA COAST AND SOUTH OF LAKE PONTCHARTRAIN SHOULD
REMAIN ABOVE FREEZING. WITH THIS IN MIND...HAVE ISSUED A FREEZE
WARNING FOR MOST OF THE AREA. HOWEVER...THE MISSISSIPPI/LOUISIANA
BORDER REGION FROM PEARL RIVER COUNTY WESTWARD WILL NOT HAVE A
FREEZE WARNING ISSUED FOR TONIGHT. THE AREA HAS EXPERIENCED TWO
PROLONGED FREEZE EVENTS THIS YEAR...WHICH HAS EFFECTIVELY KILLED
OFF MOST CROPS AND VEGETATION.
HEADING INTO TOMORROW...THE COLD AND DRY AIRMASS WILL BEGIN TO
PULL AWAY FROM THE REGION...ALONG WITH THE UPPER LEVEL TROUGH THAT
BROUGHT SNOW TO THE AREA FRIDAY NIGHT. AS THE SURFACE RIDGE AND
UPPER LEVEL TROUGH LIFT OUT...A MORE PROGRESSIVE ZONAL FLOW
PATTERN WILL DEVELOP ACROSS THE GULF SOUTH. IN THE LOW TO MID-
LEVELS OF THE ATMOSPHERE...DEEP SOUTHERLY FLOW WILL DEVELOP BY
SUNDAY AFTERNOON. STRONG WARM AIR AND MOISTURE ADVECTION ON THE
BACK OF THIS DEEP SOUTHERLY FLOW WILL STREAM INTO THE FORECAST
AREA. INCREASING CLOUD COVER CAN BE EXPECTED THROUGH THE DAY. IN
ADDITION...A FEW SHOWERS SHOULD DEVELOP BY LATE AFTERNOON OVER
WESTERN AND SOUTHERN ZONES. DAYTIME HIGHS WILL BE A GOOD 10
DEGREES WARMER THAN TODAY. THE FIRST IN A SERIES OF FAST MOVING
SHORT WAVE TROUGHS WILL THEN BEGIN TO PULL INTO THE AREA SUNDAY
NIGHT. A BROAD AREA OF POSITIVE VORTICITY ADVECTION AND UPPER
LEVEL LIFT WILL OVERSPREAD THE REGION. AS A RESULT...EXPECT AT
LEAST A CHANCE OF RAIN SUNDAY NIGHT INTO MONDAY. TEMPERATURES WILL
ALSO CONTINUE TO WARM ON MONDAY AS STRONG WARM AIR ADVECTION OFF
THE GULF OF MEXICO CONTINUES. HIGHS SHOULD CLIMB INTO THE MIDDLE TO
UPPER 60S...OR ABOUT NORMAL FOR THIS TIME OF YEAR.
ANOTHER VERY WEAK UPPER LEVEL IMPULSE AND AREA OF ENHANCED UPPER
LEVEL LIFT WILL SLIDE THROUGH MONDAY NIGHT INTO TUESDAY. THIS WEAK
AREA OF ENHANCED VORTICITY WILL BE A PREQUEL TO A MUCH STRONG
UPPER LEVEL VORT MAX SWINGING INTO THE CENTRAL PLAINS ON TUESDAY.
WITH A DIFLUENT FLOW PATTERN IN PLACE...AND PLENTY OF PVA
CONTINUING...EXPECT SHOWERS TO CONTINUE OVER THE AREA INTO MONDAY
NIGHT.
LONG TERM...
HEADING INTO TUESDAY AND TUESDAY NIGHT...THE STRONGER VORT MAX
MENTIONED PREVIOUSLY WILL PULL INTO THE CENTRAL PLAINS. STRONG LEE
CYCLOGENESIS OVER THE HIGH PLAINS OF EASTERN COLORADO AND WESTERN
KANSAS WILL OCCUR. ACROSS THE GULF SOUTH...DEEP SOUTHERLY FLOW
WILL CONTINUE TO KEEP AND WARM AND FAIRLY UNSTABLE AIRMASS IN
PLACE. EVEN THOUGH STRONG UPPER LEVEL DYNAMICS WILL NOT BE IN
PLACE ACROSS THE AREA TUESDAY INTO TUESDAY NIGHT...THERE SHOULD BE
ENOUGH INSTABILITY IN PLACE TO SPARK OFF A FEW THUNDERSTORMS. IN
ADDITION...A DECENT 50 KNOT LOW LEVEL JET AT AROUND 850 MB SHOULD
DEVELOP OVER THE AREA. STRONG SPEED SHEAR IN THE LOW TO MID-LEVELS
OF 35-40 KNOTS SHOULD BE ENOUGH TO ALLOW FOR ISOLATED STRONG AND
POSSIBLY SEVERE THUNDERSTORM DEVELOPMENT TUESDAY EVENING. THIS
SITUATION WILL HAVE TO BE MONITORED FOR THE NEXT COUPLE OF DAYS.
THE VORT LOBE AND ASSOCIATED SURFACE LOW WILL QUICKLY PULL TO THE
NORTHEAST ON WEDNESDAY...ALLOWING A FRONT TO PASS THROUGH THE AREA
WEDNESDAY MORNING. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT
FOR WEDNESDAY NIGHT AND REMAIN IN PLACE THROUGH THURSDAY.
HOWEVER...GIVEN THE PROGRESSIVE PATTERN IN PLACE...THIS WILL BE A
SHORT-LIVED BREAK. ANOTHER FAST MOVING UPPER LEVEL TROUGH WILL
SWEEP THROUGH FRIDAY...BRINGING ANOTHER CHANCE OF RAIN TO THE
REGION.
AVIATION...
SURFACE HIGH WILL SETTLE OVER THE AREA TONIGHT YIELDING LIGHT WINDS
AT ALL TAF SITES TONIGHT. HIGH SHOULD PRESS EAST PRODUCING A LIGHT
EAST FLOW AT EACH TAF SITE. WEST FLOW ALOFT WILL BRING IN MOISTURE
AND CEILINGS AT 15 KFT WILL AFFECT EACH TAF SITE FROM WEST TO EAST
SUNDAY MORNING. HOWEVER...VFR CONDITIONS SHOULD PREVAIL THROUGH 18Z
SUNDAY.
COASTAL...
WINDS HAVE DIMINISHED THIS AFTERNOON. WITH THE HIGH SHIFTING EAST
SUNDAY...WEAK RETURN FLOW WILL DEVELOP WITH AN INCREASE OF MOISTURE
BEGINNING OVER THE REGION. ANOTHER FRONTAL BOUNDARY WILL DEVELOP
OVER THE SRN PLAINS BY TUESDAY AND WINDS SHOULD PICK UP OUT OF THE
SOUTHEAST OVER COASTAL WATERS AHEAD OF FRONTAL BOUNDARY. EXPECTING
THE FRONT TO PUSH THROUGH THIS AREA BY WEDNESDAY. IN ADDITION...SEAS
ARE EXPECTED TO BUILD TUESDAY AHEAD OF THIS COLD FRONT AND REMAIN
HAZARDOUS AROUND THE FRONTAL PASSAGE.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 25 54 45 62 / 0 20 50 30
BTR 29 59 52 68 / 0 30 50 30
MSY 31 61 56 70 / 0 20 50 50
GPT 30 58 46 68 / 0 10 50 50
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FREEZE WARNING UNTIL 8 AM SUNDAY FOR THE FOLLOWING ZONES:
ASCENSION...ASSUMPTION...EAST BATON
ROUGE...IBERVILLE...LIVINGSTON...ORLEANS...ST.
CHARLES...ST. JAMES...ST. JOHN THE BAPTIST...ST.
TAMMANY...UPPER JEFFERSON...UPPER LAFOURCHE...UPPER
PLAQUEMINES...UPPER ST. BERNARD...UPPER TERREBONNE...AND
WEST BATON ROUGE.
HARD FREEZE WARNING FROM 3 AM SUNDAY TO 8 AM SUNDAY FOR THE
FOLLOWING ZONES: ST. HELENA...TANGIPAHOA...AND WASHINGTON.
MS...HARD FREEZE WARNING FROM 3 AM SUNDAY TO 8 AM SUNDAY FOR THE
FOLLOWING ZONES: AMITE...PEARL RIVER...PIKE...AND WALTHALL.
FREEZE WARNING UNTIL 8 AM SUNDAY FOR THE FOLLOWING ZONES:
HANCOCK...HARRISON...AND JACKSON.
GM...NONE.
&&
$$
UPDATE...95/DM
SOUNDING...GP
SHORT/LONG...32
AVIATION/MARINE...18/FZ
