FXUS62 KILM 150540
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1240 AM EST TUE DEC 15 2009
.SYNOPSIS...
A STRONG COLD FRONT WILL MOVE THROUGH THE AREA TUESDAY AFTERNOON.
CANADIAN HIGH PRESSURE WILL FOLLOW AND BUILD ACROSS THE CAROLINAS
FOR THE REMAINDER OF THE WEEK. LOW PRESSURE DEVELOPING OFF THE
CAROLINA COASTS MAY BRING SOME RAIN CHANCES BY SATURDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 930 PM MONDAY...WEAK ONSHORE FLOW INITIALLY NEAR THE COAST
WILL RESULT IN SEA FOG PARTIALLY AFFECTING THE IMMEDIATE
COAST...MAINLY IN THE VICINITY OF CAPE FEAR INTO THE EARLY MORNING
HRS OF MONDAY. SSTS IN THE LOW TO MID 50S AND SFC DEWPOINTS OVER 60
PARTIALLY MOVING OVER THESE COOLER WATERS...PATCHES OF SEA FOG WILL
LIKELY BE IN THE NEIGHBORHOOD AND POSSIBLY MOVE ONSHORE. AS WINDS
BECOME MORE OF A WESTERLY COMPONENT LATER OVERNIGHT INTO
TUESDAY...SEA FOG SHOULD BECOME LESS OF AN INFLUENCE.
AN OLD FRONTAL BOUNDARY LIES OVER THE WATERS JUST SOUTH OF THE
AREA...WHICH THEN EXTENDS INLAND IN THE VICINITY OF SAVANNAH AND
WESTWARD TO THE SOUTHERN PORTIONS OF THE GULF COAST STATES. DURING
THE OVERNIGHT...WEAK UPPER IMPULSES WILL INTERACT WITH THIS SFC
BOUNDARY AND WILL RESULT IN OVERRUNNING TYPE PCPN NORTH OF THE
BOUNDARY...AND CONVECTION IMMEDIATELY ALONG THIS BOUNDARY. THIS HAS
BEEN THE MAINSTAY FOR THIS EVENING AND OVERNIGHT...WITH THE PCPN
SHIELD SLOWLY CREEPING NE-WARD TOWARD THE ILM CWA. AS A RESULT WITH
CLOUDINESS FROM THIS PCPN RACING WELL AHEAD AND ACROSS THE ILM
CWA...THE DENSE FOG POSSIBILITIES HAVE LOWERED BUT WILL CONTINUE TO
MENTION AREAS OF FOG. OVERNIGHT MIN TEMPS HAVE BEEN ADJUSTED 1-3
DEGREES HIER DUE TO FAVORED 18Z MAV MOS GUIDANCE AND LATEST HOURLY
TEMP TRENDS RUNNING A BIT HIER. HAVE INDICATED ISOLATED RW+...NO
THUNDER AS OF YET...DUE TO THE CLOSER PROXIMITY OF THE SFC FRONT
LATER TONIGHT INTO TUE MORNING AS IT LIFTS SLITELY NORTHWARD IN
RESPONSE TO THE IMPULSE ALOFT MOVING ALONG IT.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 PM MONDAY...COLD FRONT TO ENTER WESTERN ZONES BY ABOUT 18Z.
SHOWERS PRECEDING AND ACCOMPANYING ITS ARRIVAL WITH LIKELY CHANCE
POPS SEEMINGLY WARRANTED AREA-WIDE DUE TO DEEP MOISTURE PROFILE.
LACK OF DEEP FORCING FOR ASCENT SUGGESTS A LOW QPF EVENT HOWEVER.
LOW LEVEL THERMAL PROFILES SUPPORTIVE UP MID TO UPPER 60S FOR HIGHS
EVEN DESPITE WEAK LAPSE RATES AND PLENTY OF CLOUD COVER. STRONG COLD
AIR ADVECTION BEHIND THE BOUNDARY TUESDAY NIGHT INTO WEDNESDAY...THE
LATTER HAVING HIGHS STUCK IN THE LOW 50S. GOOD RADIATIONAL COOLING
EXPECTED WEDNESDAY NIGHT AS WINDS DROP OFF. LOWS GENERALLY IN THE
UPPER 20S.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 3 PM MONDAY...LITTLE CHANGE IN THE EXTENDED FORECAST THIS
AFTERNOON AS THE FIRST COUPLE OF DAYS WILL FEATURE AN ARCTIC AIRMASS
FOLLOWED BY A GLANCING BLOW FROM A SOUTHERN STREAM SYSTEM AND ENDING
UP WITH ANOTHER ARCTIC AIR MASS FOR GOOD MEASURE. REGARDING THE
INITIAL AIR MASS...MID AND HIGH LEVEL CLOUDS SHOULD KEEP
TEMPERATURES UP A FEW AND POSSIBLY SEVERAL DEGREES WARMER THAN
PREVIOUS THINKING FOR FRIDAY MORNING WITH THURSDAY MORNING NOW
LOOKING LIKE THE COLDEST ...AT LEAST OF THESE TWO DAYS.
THE GFS...GEM AND ECMWF ARE COMING INTO GENERAL AGREEMENT WITH
REGARDS TO THE SOUTHERN STREAM SYSTEM...KEEPING IT MOSTLY TO THE
SOUTHEAST AS THE PHASING WITH THE NORTHERN BRANCH IS NOW GONE. NO
CHANGE TO THE POPS WHICH ARE CONFINED MOSTLY TO THE COAST AND IN THE
SLIGHT CATEGORY.
MID LEVEL CYCLONIC FLOW GETS REINFORCED LATER SUNDAY AS A POTENT
CUTOFF DROPS DOWN INTO THE GREAT LAKES AREA. THIS BRINGS WITH IT THE
COLDEST AIR MASS OF THE SEASON WITH 850MB TEMPERATURES DROPPING TO
THE MIDDLE TEENS OR AROUND -10 DEGREES C. AT FIRST TAKE...THIS IS
SHAPING UP TO BE ONE OF THOSE SCENARIOS WHERE NUMERICAL GUIDANCE IS
TOO WARM BY SEVERAL DEGREES...ESPECIALLY FOR HIGHS. THIS COULD MEAN
MONDAYS HIGHS STRUGGLE TO GET OUT OF THE 30S. HOWEVER STILL A LONG
WAY OUT AND THE TIMING OF THE COLD AIR ADVECTION IS BOUND TO CHANGE
SEVERAL TIMES.
&&
.AVIATION /06Z TUESDAY THROUGH FRIDAY/...
TIME HEIGHT AND SATELLITE SHOW ABUNDANT LOW LEVEL MOISTURE COVERS
THE AREA. KLBT AND KFLO WILL REMAIN WITHIN OR BELOW IFR FOR MOST OF
THE TAF PERIOD. INCREASED MIXING IN ASSOCIATION WITH COLD FRONTAL
PASSAGE SHOULD ALLOW CEILINGS TO FINALLY RISE...TO PERHAPS VFR AFTER
22Z. FOR THE COASTAL SITES...BETTER MIXING HAS ALLOWED CEILINGS TO
RISE TO MVFR THIS EVE AND WE EXPECT MVFR CONDITIONS TO DOMINATE FOR
MOST OF THE TAF PERIOD. VFR CONDITIONS SHOULD DEVELOP AT KILM/KCRE/
KMYR 00-02Z. LIGHT RAIN IS BEGINNING TO DEVELOP ACROSS THE AREA AS
WEAK ISENTROPIC LIFT INCREASES. STRATIFORM RAIN IS EXPECTED TO
TRANSITION TO CONVECTIVE SHOWERS THIS MORNING. PRECIPITATION WILL
REMAIN IN THE FORECAST UNTIL PASSAGE OF THE COLD FRONT LATE DAY AND
THIS EVE. SW WINDS WILL SHIFT TO THE NW AND THEN N WITH FRONTAL
PASSAGE.
EXTENDED OUTLOOK...VFR WEDNESDAY THROUGH FRIDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 12 AM TUESDAY...WINDS WILL VEER FROM SW TO A WSW
DIRECTION A FEW HRS AFTER SUNRISE. AN IMPULSE ALOFT HAS INTERACTED
WITH A STATIONARY BOUNDARY THAT LIES SOUTH OF THE AREA...WHICH THEN
EXTENDS WEST ACROSS SAVANNAH TO THE SOUTHERN PORTIONS OF THE GULF
STATES. AM CONCERNED THAT A WEAK SFC LOW COULD DEVELOP AND QUICKLY
MOVE NE ACROSS THE AREA EARLY TUESDAY. MODELS AT THIS POINT SAY
NO...BUT LATEST CONVECTION CURRENTLY ALONG THIS BOUNDARY WAS NOT
PAINTED WELL BY PREVIOUS MODEL RUNS AND THUS THE POTENCY OF THE
IMPULSE(S) ALOFT. WILL KEEP SEAS ON THE HIER SIDE OF GUIDANCE DUE TO
CONTINUED RESIDUAL SE-S MEDIOCRE SWELL BUT MORESO FOR THE
POSSIBILITY OF SLITELY STRONGER/HIER WINDS.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 PM MONDAY...BRIEF PRE-FRONTAL REGIME TO BE FOLLOWED BY
AFTERNOON PASSAGE OF STRONG COLD FRONT. THE SURGE THAT FOLLOWS WILL
PROBABLY REQUIRE A SMALL CRAFT ADVISORY. COOLER SSTS AND THE
NON-ALIGNMENT OF THE FLOW CASTING JUST ENOUGH UNCERTAINTY HOWEVER TO
RAISE FLAG AT THIS TIME. AFTER SHORT-LIVED PINCHED GRADIENT WINDS
ABATE WEDNESDAY NIGHT AS 1030MB HIGH BUILDS IN FOR THE REMAINDER OF
THE PERIOD.
LONG TERM /THURSDAY THROUGH SATURDAY/...
AS OF 3 PM MONDAY...FAIRLY BRISK NORTHERLY FLOW OF 15-20 KNOTS
INITIALLY WILL SUBSIDE QUICKLY TO AROUND 10 KNOTS OR POSSIBLY LESS
BY FRIDAY MORNING. CAVEAT TO THIS FORECAST IS HOW STRONG THE
SOUTHERN STREAM LOW GETS AND FINAL PLACEMENT...ALTHOUGH WITH THE 10
KNOTS CURRENTLY ADVERTISED...STILL A LOT OF WIGGLE ROOM EVEN TO GET
TO SMALL CRAFT CONDITIONS. NORTHERLY FLOW PICKS BACK UP SLIGHTLY
SATURDAY AS SYSTEM PULLS AWAY. BENIGN SEAS THROUGHOUT THE PERIOD.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
NEAR TERM...DCH/RJD
SHORT TERM...MBB
LONG TERM...SHK
AVIATION...RJD/HDL
