FXUS64 KMOB 231729 AAB
AFDMOB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
1129 AM CST WED DEC 23 2009
.AVIATION...
18Z TAF CYCLE.
WHILE A FEW LOCATIONS ARE REPORTING MVFR CIGS IN THE NW FL
PANHANDLE...THE MAJORITY OF CIGS WILL BE IN THE VFR RANGE THROUGH
THIS EVENING...RANGING FROM 4000 FT AND HIGHER. AS WARM AIR
ADVECTION INCREASES OVERNIGHT...CIGS WILL BEGIN TO LOWER AND
ISOLATED SHOWERS WILL BEGIN TO DEVELOP. POTENTIAL FOR SOME FOG
CLOSER TO THE COAST...ESPECIALLY AT PNS AS WARMER AIR MOVES OVER THE
COOLER NEAR SHORE AND BAY WATERS. THE CHANCE FOR SHOWERS AND
THUNDERSTORMS INCREASE THURSDAY MORNING...ESPECIALLY LATE MORNING AS
A COLD FRONT BEGINS TO APPROACH FROM THE WEST. MVFR CIGS SHOULD BE
PREDOMINATE THROUGH 18Z...BUT MAY OCCASIONALLY LOWER TO IFR. 34/JFB
&&
/PREVIOUS DISCUSSION ISSUED 430 AM CST WED DEC 23 2009/
.SHORT TERM...(TODAY AND TONIGHT)...A SURFACE RIDGE WILL GRADUALLY
EASE OFF TO THE NORTHEAST AS THE NEXT FRONTAL SYSTEM MOVES EAST OUT
OF TEXAS LATER TONIGHT. CLOUDINESS WILL BE ON THE INCREASE FROM THE
WEST THROUGH THE DAY AS THE SURFACE AND UPPER LOW BECOME BETTER
ORGANIZED. FIRST ROUND OF SHOWERS AND THUNDERSTORMS...CURRENTLY
ACROSS NORTHERN LOUISIANA WILL REMAIN WELL OFF TO THE NORTHWEST OF
THE AREA TODAY...BUT WE DO HAVE A SLIGHT CHANCE TO CHANCE OF LIGHT
RAIN IN FOR THIS AFTERNOON OVER MOST OF THE AREA AS THE WARMER MOIST
SOUTHEAST FLOW RIDES UP AND OVER THE DEPARTING WEDGE OF COOLER AIR.
POPS INCREASE TONIGHT AS PWATS INCREASE TO AN INCH AND A QUARTER.
WILL LIMIT THE THUNDERSTORMS TO THE MARINE AREA FOR TONIGHT AS
BETTER INSTABILITY REMAIN OVER THE MARINE AREA. WILL ALSO HAVE A
CHANCE FOR SOME FOG OVER THE NEAR SHORE WATERS TONIGHT BUT THE
FORECAST DEW POINTS ARE NOT THAT HIGH ONLY IN THE LOWER 60S. /11
(THURSDAY AND FRIDAY)...MAIN FOCUS THIS PERIOD WILL BE ON THE
POTENTIAL FOR STRONG TO SEVERE THUNDERSTORMS ALONG A COLD FRONT
THURSDAY AFTERNOON INTO THURSDAY EVENING. TIMING DIFFERENCES
BETWEEN MODELS ARE RATHER SMALL AND ALL INDICATE CYCLOGENESIS IN THE
VICINITY OF THE ARKLATEX THURSDAY MORNING AS A STRONG SHORTWAVE
EJECTS INTO THE SOUTHERN PLAINS AND BECOMES NEGATIVELY TILTED. THE
LOW WILL THEN RAPIDLY MOVE NORTHEASTWARD THROUGH THE DAY. THE
TRAILING COLD FRONT WILL MOVE TO THE EAST WITH AN ASSOCIATED SQUALL
LINE MOVING INTO OUR SOUTHEAST MISSISSIPPI COUNTIES DURING THE LATE
AFTERNOON AND MOVING EASTWARD ACROSS THE AREA THROUGH THE EVENING
HOURS. AHEAD OF THE FRONT ON THURSDAY...THE PRESSURE GRADIENT WILL
TIGHTEN AS THE SFC LOW DEEPENS...CREATING BREEZY CONDITIONS AT THE
SFC THROUGH THE DAY. THE DEEPENING SFC LOW...NEGATIVE TILT OF THE
UPPER TROUGH ALONG WITH A STRONG LOW LEVEL AND UPPER LEVEL JET ALL
POINT TO THE POTENTIAL OF SEVERE THUNDERSTORM DEVELOPMENT.
HOWEVER...ALL MODELS POINT TO A LACK OF GOOD INSTABILITY ACROSS THE
CENTRAL GULF COAST WITH DEWPOINTS STRUGGLING TO REACH THE LOWER 60S
BY THE AFTERNOON. THIS MAKES SENSE LOOKING AT BUOY OBS ACROSS THE
GULF. THIS LACK OF QUALITY SFC MOISTURE ALONG WITH WEAK MID LEVEL
LAPSE RATES INDICATE CAPE VALUES WILL BE RATHER LOW...GENERALLY
BELOW 400 TO 500 J/KG. THE SREF INDICATES ABOUT A 10 TO 20 PERCENT
PROBABILITY OF CAPE VALUES GREATER THAN 500 J/KG REACHING EXTREME
SOUTHERN PORTIONS OF THE AREA. THE GREATEST POTENTIAL FOR SEVERE
THUNDERSTORM DEVELOPMENT WILL BE OVER EXTREME SOUTHWEST ALABAMA AND
THE FLORIDA PANHANDLE WHERE THE HIGHEST CAPE VALUES WILL COEXIST
WITH THE STRONGER SHEAR VALUES. THIS IS WHERE SPC HAS OUTLOOKED A
SLIGHT RISK FOR SEVERE THUNDERSTORMS. THE GREATEST THREAT WILL BE
DAMAGING WINDS ALONG THE SQUALL LINE AS IT WILL NOT TAKE MUCH TO MIX
DOWN THE STRONGER WINDS JUST OFF THE SFC. IF STORMS ARE ABLE TO
DEVELOP AHEAD OF THE LINE AND TAP INTO GREATER INSTABILITY THEY WILL
POSE A RISK OF ISOLATED TORNADOES. THE SEVERE THREAT WILL DECREASE
LATE THURSDAY NIGHT AS THE SFC LOW OCCLUDES AND THE LOW LVL JET
SHIFTS NORTH.
THE FRONT WILL BE EAST OF THE AREA FRIDAY MORNING WITH CLEARING
SKIES AND A MUCH COOLER AND DRIER AIRMASS MOVING INTO THE REGION.
HIGHS WILL ONLY BE IN THE LOW TO MID 50S ON FRIDAY AFTER BUMPING 70
ON THURSDAY IN SOME SPOTS. 13/JC
.LONG TERM...(SATURDAY THROUGH TUESDAY)...THE UPPER LEVEL LOW WILL
STALL ACROSS THE NORTHERN PLAINS THEN MOVE SLOWLY EASTWARD THROUGH
EARLY NEXT WEEK. MEANWHILE...HIGH PRESSURE WILL GRADUALLY BUILD IN
FROM THE WEST. THIS WILL MAINTAIN A NORTHWESTERLY SFC FLOW PATTERN
AND KEEP TEMPS BELOW NORMAL THROUGH THE PERIOD. HIGHS IN THE LOW TO
MID 50S WITH LOWS IN THE UPPER 20S TO MID 30S. THE GLOBAL MODELS
HAVE SLOWED THE TIMING ON THE GULF LOW FORECAST TO DEVELOP EARLY
NEXT WEEK TO LATE IN THE PERIOD. THUS...THE POPS FOR NEXT WEEK HAVE
BEEN LOWERED. 13/JC
.MARINE...HAVE SMALL CRAFT ADVISORIES STARTING THIS EVENING AND
THINK THAT IS STILL ON TRACK...HOWEVER WINDS HAVE BEEN NEAR 20 KNOTS
SINCE MIDNIGHT BUT BELIEVE THEY WILL EASE UP A BIT AFTER DAYLIGHT
AND THE THERMAL GRADIENT RELAXES A BIT. A STRONG SOUTHEAST WIND
TONIGHT CONTINUING UNTIL AFTER FRONTAL PASSAGE THURSDAY EVENING.
SEAS BUILDING TO AROUND 10 FEET IN ADVANCE OF THE FRONT THEN SLOWLY
SUBSIDING AS THE WINDS BECOME WESTERLY. AREAS OF FOG DEVELOPING
TONIGHT AND PERSISTING INTO THURSDAY MORNING OVER THE NEAR SHORE
WATERS AND BAYS. WINDS AND SEAS EASE UP FRIDAY AFTERNOON AND REMAIN
NORTH TO NORTHWEST OVER THE WEEKEND AT 10 TO 15 KNOTS. SHOWERS
POSSIBLY AS EARLY AS THIS AFTERNOON OVER PORTIONS OF THE COASTAL
WATERS WITH COVERAGE INCREASING TONIGHT ALONG WITH THE CHANCE OF
ISOLATED THUNDERSTORMS THEN THURSDAY SHOWERS AND THUNDERSTORMS
THROUGH THE DAY ENDING LATE THURSDAY NIGHT. /11
&&
.PRELIMINARY POINT TEMPS/POPS...
MOBILE 67 59 68 41 / 20 70 100 50
PENSACOLA 65 58 68 45 / 20 50 100 80
DESTIN 64 58 66 50 / 10 40 90 80
EVERGREEN 63 53 66 41 / 20 30 90 80
WAYNESBORO 62 55 64 36 / 40 60 100 40
CAMDEN 61 52 65 39 / 20 30 100 80
CRESTVIEW 66 52 68 44 / 10 40 90 80
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
FL...NONE.
MS...NONE.
GM...SMALL CRAFT ADVISORY FROM 9 PM WEDNESDAY TO 9 AM FRIDAY FOR THE
FOLLOWING ZONES: COASTAL WATERS FROM DESTIN TO PENSACOLA FL
OUT 20 NM...COASTAL WATERS FROM PENSACOLA FL TO PASCAGOULA
MS OUT 20 NM...MOBILE BAY...WATERS FROM DESTIN TO PENSACOLA
FL FROM 20 TO 60 NM...AND WATERS FROM PENSACOLA FL TO
PASCAGOULA MS FROM 20 TO 60 NM.
&&
$$
