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FXUS62 KILM 141722
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1222 PM EST SUN DEC 14 2014

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO MOVE OVERHEAD AND THEN OFFSHORE BY
MONDAY. TEMPERATURES WILL RISE ABOVE NORMAL MONDAY AND TUESDAY
BEFORE A COLD FRONT PUSHES THROUGH TUESDAY NIGHT. SLIGHTLY COOLER
TEMPERATURES WILL FOLLOW FOR MID WEEK. A STORM SYSTEM WILL
APPROACH THE AREA FROM THE WEST LATE IN THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1000 AM SUNDAY...FORECAST ON TRACK SO FAR...BUT LITTLE
CONCERNED WITH TEMP AND DEWPOINT FORECAST FOR THIS AFTERNOON.
ADJUSTED THE DEWPOINT TEMPS DOWN SLIGHTLY AS SOUNDING PROFILES
SHOW DROP OFF OF DEWPOINT TRACE ABOVE THE SURFACE WITH VERY DRY
AIR IN PLACE. ONCE MIXING OCCURS SHOULD BE ABLE TO DRAG SOME MORE
OF THAT DRY AIR DOWN AS IN PREVIOUS DAYS WHERE GUIDANCE WAS WAY
TOO HIGH WITH DEWPOINT TEMPS. THERE IS ONE CAVEAT THOUGH...THE
WINDS WILL HAVE MORE OF A NORTHERLY COMPONENT OVER THE WESTERLY
WINDS OF YESTERDAY. THEREFORE THERE MAY NOT BE AS MUCH
DOWNSLOPING. THIS COULD KEEP DEWPOINTS UP A BIT HIGHER BUT MAY
ALSO KEEP TEMPS A LITTLE COOLER. OVERALL EXPECT A SUNNY DRY AND
SEASONABLE DAY WITH TEMPS RIGHT AROUND 60 MOST PLACES AND INTO THE
MID 60S OVER NORTHEAST SOUTH CAROLINA.

OTHERWISE...AS MENTIONED IN PREVIOUS DISCUSSION...BOTH THE LOW TO
OUR NORTHEAST AND THE RIDGE TO OUR WEST WILL FINALLY PROGRESS
EASTWARD WITH LOCAL AREA FALLING UNDER THE INFLUENCE OF HIGH
PRESSURE FROM THE SURFACE UP THROUGH THE MID TO UPPER LEVELS. THE
RIDGE AXIS WILL BE ALIGNED N TO S ACROSS THE EASTERN SEABOARD BY 
MONDAY MORNING. THE SFC HIGH WILL BE SHIFTING CLOSER OVERHEAD
THROUGH THE NIGHT ALSO. THEREFORE EXPECT PLENTY OF SUBSIDENCE AND
DRY AIR IN PLACE THROUGH TONIGHT. THE SFC WINDS WILL BEGIN TO SHIFT
AROUND TO THE N-NE ALLOWING FOR A BIT MORE OF A MARINE INFLUENCE
BUT OVERALL REMAINING VERY LIGHT TO CALM AND THEREFORE DO NOT
EXPECT TOO MUCH MOISTURE ADVECTION. BASICALLY LOOKING AT A
SUNNY/CLEAR FORECAST THIS PERIOD. WITH CLEAR SKIES AND NEAR CALM
WINDS...EXPECT ANOTHER DECENT RADIATIONAL COOLING NIGHT WITH TEMPS
DROPPING TO RIGHT AROUND FREEZING AGAIN.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 3 AM SUNDAY...SURFACE AND MID LEVEL RIDGE AXIS SHIFT OFFSHORE 
MON AS SOUTHERN STREAM SYSTEM LIFTS NORTHEAST THROUGH THE MS VALLEY. 
ALTHOUGH THIS SYSTEM WILL BE WEAKENING AS IT LIFTS NORTHEAST IT WILL 
BE RESPONSIBLE FOR PUSHING A WEAK COLD FRONT ACROSS THE AREA TUE. 
ALTHOUGH PRECIP MAY DEVELOP IN ASSOCIATED WITH THE FRONTAL PASSAGE 
DO NOT THINK MEASURABLE PRECIP HAS MUCH OF A CHANCE. DEEP DRY AIR 
REMAINS IN PLACE AHEAD OF THE FRONT WITH ONLY A RIBBON OF DEEPER 
MOISTURE ASSOCIATED WITH THE FRONT. THE DEPTH OF THIS MOISTURE IS 
RATHER SHALLOW AND IS BOUNDED BY SIGNIFICANT LAYERS OF DRY AIR. 
PRECIPITABLE WATER VALUES STRUGGLE TO REACH AN INCH WHILE ALOFT 
THERE IS A LACK OF ANY FORCING. MID LEVEL LAPSE RATES REMAIN 
UNIMPRESSIVE THROUGH THE EVENT WHICH MAY END UP BEING NOTHING MORE 
THAN A SIGNIFICANT INCREASE IN CLOUD COVER ACCOMPANIED BY ISOLATED 
SPRINKLES. ONLY THE ECMWF GENERATES ANY MEASURABLE PRECIP WHILE THE 
NAM/GFS/CANADIAN ARE ALL DRY. WILL HOLD ONTO INHERITED SILENT POP 
FOR TUE BUT DO PLAN TO TREND NUMBERS DOWN CLOSER TO 15%.

TEMPERATURES WILL RUN ABOVE CLIMO MON AND MON NIGHT. WARM ADVECTION 
AHEAD OF THE ADVANCING FRONT ON TUE WILL PUSH HIGHS WELL ABOVE 
CLIMO...MID TO UPPER 60S IN MOST AREAS. COLD AIR ASSOCIATED WITH THE 
INCOMING HIGH LAGS WELL BEHIND THE FRONT AND BOUNDARY LAYER WINDS 
WILL HELP KEEP LOWS WELL ABOVE CLIMO TUE NIGHT.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 3 AM SUNDAY...PROGRESSIVE MID LEVEL PATTERN DEVELOPS OVER THE 
EASTERN CONUS MID WEEK. MEANWHILE HIGH PRESSURE OVER CENTRAL CANADA 
WILL SPILL SOUTH...BUILDING OVER THE CAROLINAS MID TO LATE WEEK. 
WEAK COLD ADVECTION WILL KNOCK TEMPS BACK TO SEASONABLE ON WED AND 
THU. LATE NEXT WEEK ANOTHER SOUTHERN STREAM SYSTEM WILL EMERGE FROM 
THE SOUTHWEST. 

AS WAS THE CASE WITH THE LAST SYSTEM THERE IS CONSIDERABLE 
DIFFERENCE BETWEEN OPERATIONAL GFS/ECMWF. MOST OF THE GFS ENSEMBLES 
ARE IN LINE THE 00Z GFS LIFTING THE SYSTEM NORTHEAST THROUGH THE 
OH/TN VALLEYS AS THE PERIOD ENDS. THE ECMWF HAS A MORE AMPLIFIED 
SOUTHERN STREAM SYSTEM. THIS MEANS THE SYSTEM EXITS THE SOUTHWEST A 
BIT LATER. THIS LATER TIMING ALLOWS IT TO INTERACT WITH A NORTHERN 
STREAM SHORTWAVE DROPPING SOUTH ACROSS THE UPPER MIDWEST. THE RESULT 
IS A MUCH MORE SIGNIFICANT MID LATITUDE SYSTEM. ALTHOUGH EITHER 
SOLUTION WOULD RESULT IN INCREASING PRECIP CHANCES FRI NIGHT AND SAT 
THE TEMPERATURE PROFILES WOULD BE QUITE DIFFERENT. GFS LIFTS A WEAK 
COASTAL TROUGH NORTH OF THE AREA AS A WARM FRONT WHILE SFC LOW 
PASSES NORTHWEST...DRAGGING A COLD FRONT ACROSS THE AREA LATE SAT. 
ECMWF MOVES THE SURFACE LOW ACROSS THE AREA SAT NIGHT WITH AN 
EXTENDED PERIOD OF ISENTROPIC LIFT COINCIDENT WITH DEEP MOISTURE 
AHEAD OF THE LOW. 

THE FINER DETAILS DEPEND ON THE BEHAVIOR OF THE 2 SHORTWAVES IN 
QUESTION...AND UNTIL THESE FEATURES CAN BE SAMPLED BY THE UPPER AIR 
NETWORK THERE IS LIKELY TO BE SIGNIFICANT SPREAD ALONG WITH A LACK 
OF RUN TO RUN CONSISTENCY WITHIN THE MEDIUM RANGE GUIDANCE. THUS DO 
NOT PLAN ANY CHANGES TO THE INHERITED FORECAST WHICH KEEPS TEMPS 
NEAR CLIMO AND INDICATES INCREASING PRECIP CHANCES LATE IN THE WEEK.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AS OF 18Z...VFR WILL PREVAIL AT ALL TERMINALS THROUGH THIS VALID TAF 
PERIOD. THE REST OF TODAY WILL BE SUNNY WITH LIGHT N-NW WINDS AROUND 
5 KT. HIGH PRESSURE WILL MOVE EASTWARD OVER THE CAROLINAS TONIGHT... 
RESULTING IN CALM CONDITIONS DURING THE OVERNIGHT HOURS. SOME LIGHT 
BR CANNOT BE RULED OUT BEFORE DAYBREAK...BUT DO NOT ANTICIPATE ANY 
FOG ISSUES BASED ON THE LATEST FORECAST SOUNDINGS. AS HIGH PRESSURE 
SLIDES OFFSHORE DURING THE DAY MON...LIGHT/VRBL WINDS WILL BECOME 
EASTERLY AROUND 5 KT BY MIDDAY.  

EXTENDED OUTLOOK...SLIGHT CHANCE OF SHOWERS TUE AS A COLD FRONT 
PUSHES THROUGH THE REGION. OTHERWISE VFR THROUGH FRI.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/... 
AS OF 1000 AM SUNDAY...THE LOCAL WATERS CONTINUE TO REMAIN IN
BETWEEN LOW PRESSURE SYSTEM MOVING FARTHER OFF FROM THE NEW
ENGLAND COAST AND AN EASTWARD PROGRESSING AND WELL AMPLIFIED UPPER
RIDGE FROM THE CENTRAL UNITED STATES. AT THE SFC...CENTER OF HIGH
PRESSURE WILL PUSH ACROSS THE APPALACHIANS INTO NORTH CAROLINA BY
DAYBREAK MON. THE OVERALL SFC PRESSURE PATTERN TO YIELD NW WINDS
SHIFTING TO N-NE THROUGH THE NIGHT. A SLOWLY RELAXING GRADIENT
WILL ALLOW WINDS UP TO 10 TO 15 KTS THIS MORNING TO DIMINISH TO 5-10
KT FOR THE REMAINDER OF THE NEAR TERM FORECAST. SIGNIFICANT SEAS
WILL RUN 2 FT OR LESS...WITH A FEW 3 FOOTERS POSSIBLE ACROSS THE
OUTER WATERS OFF CAPE FEAR. THE SIGNIFICANT SEAS WILL BE COMPRISED
OF A LONGER PERIOD UP TO 12 SECONDS...1-2 FOOT EASTERLY GROUND
SWELL AND SHORTER PERIOD WIND DRIVEN WAVES.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 3 AM SUNDAY...LIGHT NORTHERLY FLOW AT THE START OF THE PERIOD 
WILL BECOME LIGHT AND VARIABLE DURING MON AS SURFACE RIDGE AXIS 
MOVES OVERHEAD. RETURN FLOW DEVELOPS LATE MON NIGHT AS RIDGE MOVES 
FARTHER OFF THE COAST. APPROACHING COLD FRONT WILL TIGHTEN THE 
GRADIENT TUE...PUSHING SOUTHWEST FLOW TO A SOLID 15 KT LATE TUE. 
FRONT MOVES ACROSS THE WATERS DURING THE EVENING WITH OFFSHORE FLOW 
DEVELOPING AROUND MIDNIGHT. LACK OF STRONG COLD ADVECTION OR STRONG 
GRADIENT WILL KEEP OFFSHORE FLOW IN THE 10 TO 15 KT RANGE THROUGH 
THE END OF THE PERIOD. SEAS AROUND 2 FT MON INTO TUE WILL BUILD TO 2 
TO 4 FT LATE TUE DUE TO THE INCREASED SOUTHWEST FLOW. OCCASIONAL 5 
FT SEAS WILL BE POSSIBLE IN EASTERN PORTIONS OF AMZ252 LATE TUE.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 3 AM SUNDAY... NORTH TO NORTHWEST FLOW WILL DOMINATE THE 
PERIOD AS HIGH PRESSURE BUILDS SOUTH FROM CENTRAL CANADA AND THE 
UPPER MIDWEST. LACK OF STRONG COLD ADVECTION AND MARGINAL GRADIENT 
WILL KEEP SPEEDS 10 TO 15 KT THROUGH THE PERIOD. OFFSHORE WIND 
COMPONENT COMBINED WITH RELATIVELY LIGHT WIND SPEEDS WILL KEEP SEAS 
WITHIN 20 NM 2 FT OR LESS.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.

&&

$$

NEAR TERM...RGZ
SHORT TERM...III
LONG TERM...III
AVIATION...BJR