Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 310233
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1033 PM EDT THU OCT 30 2014

.SYNOPSIS...
HIGH PRESSURE WILL NUDGE INTO THE AREA THROUGH FRIDAY BETWEEN AN
APPROACHING COLD FRONT TO THE WEST AND A WEAK AREA OF LOW PRESSURE
ALONG A STALLED FRONT OFFSHORE. A POWERFUL COLD FRONT WILL CROSS THE
REGION ON SATURDAY AS COLD CANADIAN HIGH PRESSURE BUILDS IN
THROUGH THE REST OF THE WEEKEND. THIS AREA OF HIGH PRESSURE WILL
THEN BECOME THE DOMINANT WEATHER FEATURE THROUGH THE FIRST HALF OF
NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
AS OF 1030 PM THURSDAY...RADAR AND SATELLITE IMAGERY IMPLY THAT
ISENTROPIC LIFT IS INCREASING 20-40 MILES OFF THE SOUTHERN AND
CENTRAL SOUTH CAROLINA COAST. THIS AREA IS MOVING NORTHEAST AND
SHOULD MISS THE POINT OF CAPE FEAR BY A COMFORTABLE MARGIN. HOWEVER
ADDITIONAL ISENTROPIC LIFT DEVELOPING IN THE 06-12Z TIMEFRAME MAY
STILL SPREAD SOME SHOWER ACTIVITY INLAND ALONG THE COAST. BESIDES
ADJUSTING FORECAST TEMP/WIND/SKY GRIDS OVER THE NEXT FEW HOURS TO
ACCOUNT FOR LATEST OBSERVED TRENDS...NO CHANGES HAVE BEEN MADE TO
THE FORECAST. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS...

LAST NIGHT`S COLD FRONT IS STALLING ABOUT 200 MILES OFF THE COAST.
THE FLOW ALOFT STILL HAS A SIGNIFICANT CYCLONIC CURVATURE...AND A
SERIES OF SHORTWAVES ARE ANALYZED UPSTREAM OF THE CAROLINAS. ONE
DISTURBANCE CURRENTLY OVER COASTAL GEORGIA WILL MOVE NORTHEASTWARD
ALONG THE COAST OVERNIGHT...INDUCING SURFACE LOW PRESSURE TO DEVELOP
ALONG THE STALLED FRONT OFFSHORE. IN RESPONSE TO THE APPROACHING
DISTURBANCE SHALLOW ISENTROPIC LIFT SHOULD DEVELOP ALONG THE COAST
BETWEEN THE 295K-300K SURFACES... ROUGHLY BETWEEN 4000-8000 FT
AGL...WITH CLOUDS AND SOME PATCHY LIGHT RAIN PROBABLY DEVELOPING
AFTER MIDNIGHT. I HAVE INCREASED RAINFALL CHANCES TO 20-30 PERCENT
ACROSS COASTAL SE NORTH CAROLINA BUT MAINTAINED A DRY FORECAST
ELSEWHERE AS IT APPEARS THE ISENTROPIC LIFT WILL BE WEAKER AND
SHOULD INVOLVE MAINLY DRY/UNSATURATED PARCEL MOTION.

WITH CLOUDS EXPECTED TO DEVELOP ALONG THE COAST I HAVE NUDGED
FORECAST LOWS UP BY A COUPLE OF DEGREES...ESPECIALLY NEAR
WILMINGTON...WITH SMALLER OR NO CHANGES MADE ELSEWHERE. LOWS SHOULD
REACH THE MID 40S INLAND ALONG I-95...WITH UPPER 40S TO LOWER 50S
EXPECTED ALONG THE COAST.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
AS OF 300 PM THURSDAY...FRIDAY AND FRIDAY NIGHT...FRIDAY WILL MAINLY
BE A TRANSITIONAL DAY AHEAD OF THE THE POWERFUL COLD FRONT THAT WILL
BEGIN TO PUNCH IN TO THE AREA FROM THE WEST LATE FRIDAY NIGHT.
ALOFT...THE UPPER TROUGH AXIS WILL SHIFT EASTWARD AND BEGIN TO
AMPLIFY AS A VIGOROUS AND DEEP UPPER LOW DIGS IN AND DIVES SOUTHWARD
OUT OF THE GREAT LAKES REGION. BY LATE FRIDAY NIGHT THE UPPER LOW
SHOULD BE POSITIONED ALMOST DIRECTLY OVER TOP OF THE SOUTHERN
APPALACHIANS. AT THE SURFACE...FRIDAY WILL SEE THE REMNANT FRONT
SITTING JUST OFFSHORE WITH A WEAK AREA OF LOW PRESSURE BEGINNING TO
DEVELOP ALONG IT. MODELS ARE CONSISTENT IN SHOWING SHOWER ACTIVITY
BRUSHING THE COASTAL WATERS AND PERHAPS BRUSHING AREAS NEAR
SOUTHPORT AND ALONG BRUNSWICK/NEW HANOVER COUNTIES.
OTHERWISE...FRIDAY WILL BE QUIET WITH HIGHS REACHING INTO THE UPPER
60S IN MOST AREAS. OVERNIGHT...THE VERY STRONG COLD FRONT WILL BEGIN
APPROACHING THE AREA AND EVEN MOVING THROUGH FAR INLAND AREAS LATE.
POPS BEGIN TO INCREASE FROM THE WEST AFTER MIDNIGHT AS THE DEEP
FORCING ASSOCIATED WITH THE POWERFUL UPPER LEVEL DYNAMICS INCREASES.
HOWEVER...THE BULK OF ANY PRECIPITATION AND ESPECIALLY THE ARRIVAL
OF THE COLD AIR WILL BE MORE INTO THE SATURDAY TIME FRAME.

SATURDAY THROUGH SUNDAY...OVERALL IT WILL BE A CHILLY AND AT TIMES
BLUSTERY WEEKEND AS A STRONG COLD FRONT MOVES THROUGH THE AREA AND
COLD CANADIAN HIGH PRESSURE BUILDS IN. ALOFT...A POWERFUL AND DEEP
UPPER LOW WILL SWING THROUGH THE BASE OF THE DEEP UPPER TROUGH
SATURDAY MORNING AND THEN LIFT AWAY FROM THE AREA THROUGH SUNDAY. AT
THE SURFACE...A VERY STRONG COLD FRONT WILL PUSH THROUGH EARLY
SATURDAY AND THE STRONG UPPER FORCING ALOFT WILL PROMOTE
CYCLOGENESIS OFF THE OUTER BANKS. THE FIRST FORECAST ISSUE REVOLVES
AROUND THE PRECIPITATION POTENTIAL ON SATURDAY. VERY IMPRESSIVE DEEP
LAYER FORCING WITH THIS SYSTEM WILL SPREAD ACROSS THE AREA INCLUDING
STRONG PVA...UPPER LEVEL JET DYNAMICS...EVEN A SLOT OF LOW LEVEL
FRONTOGENESIS LATER ON SATURDAY. FURTHERMORE...THE ARRIVAL OF THE
IMPRESSIVE COLD POOL ALOFT...500 MB TEMPS AROUND -26C...WILL HELP
STEEPEN MID LEVEL LAPSE RATES THROUGH THE DAY. POPS HAVE BEEN
INCREASED INTO THE CATEGORICAL RANGE THROUGH THE DAY AS A RESULT.
ONE THING TO WATCH FOR IS THE STEEPENING MID LEVEL LAPSE RATES AND
FALLING FREEZING LEVELS WILL LIKELY ALLOW FOR SOME PRECIPITATION TO
FALL AS GRAUPEL AT TIMES ESPECIALLY LATER ON SATURDAY. THE TOP OF
THE MOIST LAYER WILL DEFINITELY REACH INTO THE DENDRITIC CRYSTAL
GROWTH ZONE...THEN UNDERGO AT LEAST PARTIAL MELTING AS IT FALLS
THROUGH THE ABOVE FREEZING NEAR SURFACE LAYER. GRAUPEL WILL
CERTAINLY NOT BE THE PREDOMINANT PRECIPITATION TYPE AND THE WEATHER
GRIDS ONLY MENTION LIQUID RAIN...BUT IT IS WORTH MENTIONING
NONETHELESS. PRECIPITATION WILL COME TO AN END STARTING SATURDAY
EVENING AS THE FORCING BEGINS TO EXIT THE REGION. THE NEXT FORECAST
ISSUE IS THE ARRIVAL OF WELL BELOW NORMAL TEMPERATURES AND THE
POTENTIAL FOR AN ADVECTIVE FREEZE INLAND SATURDAY NIGHT. 850 MB
TEMPS ARE VERY COLD...RUNNING ABOUT 5 STANDARD DEVIATIONS BELOW
NORMAL...AND THE LINGERING GRADIENT WILL KEEP WINDS STRONG ENOUGH TO
PRECLUDE MUCH IN THE WAY OF FROST CONCERNS. SUNDAY HIGHS WILL BE
QUITE COOL WITH MID 50S IN MOST AREAS...AND WILL THREATEN RECORD LOW
MAXIMUM TEMPERATURE RECORDS AT THE CLIMATE SITES. SUCH HIGH
TEMPERATURES ARE ALMOST 20 DEGREES BELOW FOR EARLY NOVEMBER.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 300 PM THURSDAY...SUNDAY NIGHT WILL BE THE COLDEST NIGHT OF
THE PERIOD AS THE PRESSURE GRADIENT WEAKENS SUFFICIENTLY TO ALLOW
FOR GOOD RADIATIONAL COOLING CONDITIONS. THERE APPEARS TO BE A
LINGERING FEW MPH OF NE WINDS THAT MAY SPARE INLAND ZONES FREEZING
TEMPS WHEREAS WEAK OCEAN INFLUENCE SHOULD FAVOR UPPER 30S COAST. THE
CENTER OF THE HIGH IS HESITANT TO GET EAST OF THE REGION ON TUESDAY
PRECLUDING BONA FIDE RETURN FLOW AND SO THE CLIMO TEMPS SEEN IN MOS
BULLETINS SEEM TOO OPTIMISTIC...AND HAVE BEEN UNDERCUT BY JUST A FEW
DEGREES. THE ACTUAL RETURN FLOW SHOULD GET UNDERWAY TUESDAY NIGHT
INTO WEDNESDAY. WILL ADD SOME LOW POPS IN THE RETURN FLOW BUT MOST
OF THE MOISTENING MAY STILL BE DEDICATED TO PW RECOVERY FROM THE
COLD AIRMASS AS OPPOSED TO ACTUAL RAINFALL.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AS OF 00Z...EXPECT VFR THROUGH THE VALID PERIOD AS HIGH PRESSURE
REIGNS OVER THE AREA.

VFR PREVAILS THIS EVENING WITH LIGHT NORTHEAST WINDS. EXPECT THIS
TREND TO PERSIST THROUGH THE OVERNIGHT HOURS...WITH LINGERING
SCT/BKN MID TO HIGH CLOUDS AT TIMES. ON FRIDAY...VFR WILL CONTINUE
NORTH-NORTHEAST WINDS INCREASING TO AOB 12 KTS...BECOMING LIGHT
TOWARDS THE EVENING HOURS. SCT/BKN MID TO HIGH LEVEL CLOUDS ARE
EXPECTED THROUGHOUT THE DAY.

EXTENDED OUTLOOK...MVFR/POSSIBLE IFR WITH SHOWERS AND INCREASED
WINDS SATURDAY INTO SUNDAY WITH COLD FRONT. VFR ON MONDAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 PM THURSDAY...NO SIGNIFICANT CHANGES HAVE BEEN MADE TO
THE FORECAST. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS...

A COLD FRONT IS STALLING OUT BEYOND THE GULF STREAM ABOUT 200 MILES
OFFSHORE. LOW PRESSURE IS EXPECTED TO DEVELOP ALONG THE FRONT
OVERNIGHT...WITH A BACKING TREND IN WIND DIRECTIONS AND INCREASING
TREND IN WIND SPEEDS EXPECTED. CURRENTLY WIND SPEEDS RANGE FROM ONLY
5-10 KNOTS ON THE BEACHES TO 15-20 KNOTS OUT AT 20 MILES DISTANCE
FROM SHORE...WITH SEAS 2-4 FEET. MODELS HAVE TRENDED A BIT FARTHER
WESTWARD WITH THE PRECIPITATION SHIELD ON THE WEST SIDE OF THE UPPER
LOW...AND I HAVE THEREFORE ADDED SHOWER CHANCES TO THE
FORECAST...MAINLY AFTER MIDNIGHT...WITH THE HIGHEST CHANCES IN THE
CAPE FEAR WATERS DUE TO THEIR MORE EASTWARD LOCATION.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 300 PM THURSDAY...FRIDAY THROUGH TUESDAY...THE BULK OF THE
SIGNIFICANT MARINE CONDITIONS WILL OCCUR STARTING EARLY SATURDAY AS
A VERY STRONG COLD FRONT BEGINS TO IMPACT THE LOCAL WATERS. UP UNTIL
THAT POINT...NORTH WINDS MAY SURGE INTO THE 15-20 KT RANGE WITH SEAS
UP TO 4-5 FT OUT NEAR 20 NM AT TIMES.

BEGINNING SATURDAY MORNING...THE COLD FRONT WILL BEGIN TO SWEEP
ACROSS THE WATERS WITH A SIGNIFICANT INCREASE IN WINDS/SEAS THROUGH
THE DAY. THE AIRMASS BEHIND THE FRONT IS QUITE COLD AND WITH WATER
TEMPERATURES STILL IN THE LOW 70S...IDEAL MIXING CONDITIONS WILL BE
IN PLACE ESPECIALLY SATURDAY NIGHT AS THE COLD ADVECTION REACHES IT
PEAK. THE DEEPENING MIXING OVER THE WATERS WILL BE HAPPENING
COINCIDENT WITH A DEEPENING AREA OF LOW PRESSURE PULLING AWAY TO THE
NORTHEAST OFF THE OUTER BANKS. MODEL GUIDANCE SHOWS 1000 MB
GEOSTROPHIC WINDS INCREASING TO 70 KT ACROSS MUCH OF THE WATERS
SATURDAY EVENING AND EARLY SATURDAY NIGHT. WITH THE EXPECTED MIXING
THIS WILL EASILY SUPPORT GALE CONDITIONS ACROSS ALL OF THE WATERS.
IN FACT...GIVEN THE MOST RECENT MODEL SOUNDINGS IT IS NOT OUT OF THE
QUESTION TO SEE A VERY BRIEF PERIOD OF STORM FORCE GUSTS WITH THE
INITIAL PUNCH OF WIND BEHIND THE FRONT IN THE 00-03Z SUNDAY TIME
PERIOD. AS SUCH...A GALE WATCH HAS BEEN HOISTED STARTING AT 13Z
SATURDAY FOR THE SOUTH CAROLINA WATERS AND 17Z FOR THE NORTH
CAROLINA WATERS. GALES WILL CONTINUE THROUGH SATURDAY NIGHT AND THEN
BEGIN TO DIMINISH TO JUST SMALL CRAFT ADVISORY WINDS BY SUNDAY
MORNING.

LONG TERM /SUNDAY THROUGH TUESDAY/...
AS OF 300 PM THURSDAY...THE GRADIENT WILL STILL BE QUITE STRONG
SUNDAY MORNING ESPECIALLY OVER NORTHERN ZONES. HOWEVER THERE WILL BE
A MARKED ABATING TREND AS THE DAY WEARS ON DUE TO THE RAPID
NORTHEASTERLY MOVEMENT OF THE STILL DEEPENING LOW THAT AFFECTED US
DIRECTLY SATURDAY AND SATURDAY NIGHT. IN FACT AS IT APPEARS NOW
THERE MAY BE NO HEADLINES NEEDED BY MIDDAY OR SO. FOR MUCH OF MONDAY
HIGH PRESSURE WILL ELONGATE UP AND DOWN THE CAROLINAS WITH A LATE
DAY SHIFT TOWARDS THE COASTLINE. N WINDS WILL VEER TO THE NE AND
GROW LIGHTER. HIGH PRESSURE WILL BUILD IN EARLY NEXT WEEK AND MUCH
QUIETER CONDITIONS ARE EXPECTED.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...GALE WATCH FROM SATURDAY MORNING THROUGH LATE SATURDAY
NIGHT      FOR AMZ254-256.

     GALE WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY MORNING FOR
     AMZ250-252.

&&

$$

NEAR TERM...TRA
SHORT TERM...99/CHS
LONG TERM...99/CHS
AVIATION...SGL





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