Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 201640
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1240 PM EDT SUN APR 20 2014

.SYNOPSIS...
SLOW MOVING LOW PRESSURE ABOUT 150 MILES SOUTHEAST OF CAPE FEAR WILL
MOVE SLOWLY EASTWARD AND AWAY FROM THE CAROLINAS TONIGHT AND MONDAY.
A COLD FRONT MAY BRING ANOTHER ROUND OF SHOWERS LATE TUESDAY...
FOLLOWED BY A GRADUAL WARMUP FOR THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1230 PM SUNDAY...SLUG OF ISENTROPIC LIFT IS MOVING SOUTHWEST
ACROSS THE CAPE FEAR REGION ACCOMPANIED BY SHOWERS. ILM HAS PICKED
UP ABOUT A TENTH OF AN INCH OF RAIN IN THE PAST TWO HOURS. SINCE
THESE SHOWERS ARE BEING GENERATED SO LOW IN THE ATMOSPHERE WHERE
TEMPERATURES ARE WELL ABOVE FREEZING...THIS IS A "TROPICAL" WARM
RAIN/COALESCENCE PRECIPITATION PROCESS. DROP SIZE IS VERY SMALL AND
IT IS NOT TAKING A LOT OF RAIN TO LOWER THE VISIBILITY
SUBSTANTIALLY. THE BULK OF THIS PRECIPITATION SHOULD STICK TO
REGIONS WITHIN 40 MILES OF THE COAST WHERE SURFACE DEWPOINTS ARE >45
DEGREES F. FARTHER INLAND ALONG THE I-95 CORRIDOR TEMP-DEWPOINT
SPREADS ARE APPROACHING 20 DEGREES F IN SPOTS...MAKING MEASURABLE
PRECIPITATION TOUGHER TO COME BY. PREVIOUS DISCUSSION FROM 1000 AM
FOLLOWS...

VERTICALLY STACKED LOW PRESSURE (1011 MB) IS CENTERED APPROXIMATELY
125 MILES SOUTHEAST OF CAPE FEAR. MODEL ANALYSIS FIELDS STILL
INDICATE A COLD CORE ALOFT WITH THIS SYSTEM...BUT DEEP CONVECTION
HAS DEVELOPED WITHIN THE CENTER OF THIS LOW WITH NLDN LIGHTNING
DISPLAYS SHOWING SEVERAL HUNDRED LIGHTNING STRIKES PER HOUR
OFFSHORE. BREEZY NORTH WINDS WILL CONTINUE IN THE BROAD OUTER
CIRCULATION AROUND THIS LOW TODAY OVER LAND...WITH GUSTS INLAND
AROUND 30 MPH...POSSIBLY APPROACHING 40 MPH AT THE COAST.

CURRENT RADAR COMPOSITES SHOW THE BULK OF THE RAIN CONFINED TO
COASTAL NORTH CAROLINA FROM WILMINGTON NORTHEASTWARD ACROSS THE
SOUTHERN OUTER BANKS. MOVEMENT OF THIS PRECIPITATION IS TOWARD THE
SOUTHWEST WHICH PLACES ITS SOURCE REGION RATHER LOW IN THE
ATMOSPHERE ON THE 290K ISENTROPIC SURFACE. SATURATION IS INDICATED
ON THE NAM AND GFS TO CONTINUE ON THE 290K SURFACE THROUGH THE
DAY...WITH LIFT PERHAPS INCREASING EAST OF I-95 THIS AFTERNOON. FOR
THIS REASON I AM RELUCTANT TO TRIM BACK POPS BELOW 60-70% (LIKELY)
FOR BURGAW...WILMINGTON...SOUTHPORT...AND MYRTLE BEACH. FARTHER
INLAND THERE IS A LOT OF VERY DRY AIR (SURFACE DEWPOINTS IN THE 30S)
WHICH IS NOT WELL REPRESENTED IN THE MODELS. THIS COULD MAKE IT VERY
DIFFICULT FOR RAIN TO OCCUR ALONG AND WEST OF I-95 TODAY...AND I
HAVE TRIMMED BACK POPS TO NO HIGHER THAN 20% (SLIGHT CHANCE) HERE.

WHERE PRECIPITATION CHANCES ARE HIGHEST NEAR THE COAST I HAVE
TRIMMED BACK HIGHS TO BARELY 60 DEGREES...WITH LOWER 60S POSSIBLE
FARTHER INLAND. THIS IS A GOOD 15 DEGREES BELOW NORMAL FOR THIS DATE
AND WILL HELP TO CANCEL OUT SOME OF THOSE UNUSUALLY WARM DAYS WE HAD
THE FIRST HALF OF APRIL. MONTHLY TEMPERATURE DEPARTURES THROUGH
YESTERDAY WERE +2.6 DEGREES IN WILMINGTON...+0.7 DEGREES IN
FLORENCE...AND +1.1 DEGREES IN MYRTLE BEACH. PREVIOUS DISCUSSION
FROM 600 AM FOLLOWS...

ANOTHER DREARY AND COOL DAY IS IN STORE FOR THE EASTERN CAROLINAS.
THE STIFF NE WINDS WILL ADD INSULT TO INJURY. EXPECT CLOUDS WILL
HANG ON THROUGH THE DAY...WITH CLEARER SKIES HOLDING NOT TOO FAR TO
OUR W AND SW...BUT UNABLE TO MAKE ANY DECENT EASTWARD PROGRESSION AS
ATLANTIC LOW PRESSURE AND ITS ASSOCIATED TROUGH...CUTOFF FROM THE
MEAN FLOW...DRIFT EVER SO SLOWLY SEAWARD THROUGH TONIGHT. THE COLUMN
DOES SLOWLY DRY OUT ABOVE A PRONOUNCED NEAR SURFACE INVERSION.
HOWEVER...THE SATURATED LAYER NEVER SHRINKS TO A DEPTH LESS THAN
ABOUT 2 KFT...THUS EXPECT CLOUDS WILL AGAIN HANG ON THROUGH THE
PERIOD. ALTHOUGH WE WILL LARGELY BE ON THE BACKSIDE OR SUBSIDENT
SIDE OF THE LOW CENTER...PROXIMITY OF SURFACE TROUGH AND WEAK
PERTURBATIONS ROTATING AROUND THE UPPER LOW WILL NECESSITATE KEEPING
MENTION OF POPS IN THE FORECAST INTO TONIGHT. HIGHEST POPS SEEM
WARRANTED THROUGH MIDDAY...UP TO CATEGORICAL WITH POPS TRENDING
LOWER THROUGH THE AFTERNOON. TONIGHT...THE CIRCULATION AROUND THE
UPPER LOW MOVES PROGRESSIVELY FURTHER AWAY FROM THE AREA WITH SOME
RIDGING BUILDING TO THE COAST LATE AT NIGHT AND ON MON. THUS THE
DOWNWARD TREND IN POPS WILL CONTINUE WITH ONLY A SLIGHT CHANCE
INLAND DURING THE EVE. POPS ALONG THE COAST WILL ALSO TREND TO
SLIGHT CHANCE...ALTHOUGH AT A SLIGHTLY SLOWER PACE.

THERE WILL BE A TIGHT PRESSURE GRADIENT BETWEEN THE LOW CENTER AND
TROUGH OFFSHORE AND THE STRONG HIGH PRESSURE CENTER ACROSS EASTERN
NEW ENGLAND...RIDGING INTO THE CAROLINAS. THE RESULT...NE WINDS ON
THE ORDER OF 15 TO 25 MPH WITH GUSTS IN EXCESS OF 30 MPH. THE
BEACHES MAY EXPERIENCE WIND GUSTS NEAR 40 MPH. THESE WINDS WILL BE
TRENDING LOWER THROUGH THE LATE AFTERNOON AND EVE...BUT EVEN
TONIGHT...WINDS WILL BE 10 TO 20 MPH MOST OF THE TIME.

TEMPS TODAY WILL BE WELL BELOW NORMAL...WILL CAP THEM IN THE LOWER
60S GIVEN THERE WILL BE NO HELP FROM THE SUN TO BOOST THEM ANY
HIGHER. TONIGHT...CLOUD COVER AND WINDS...ALLOWING FOR A RATHER WELL
MIXED ENVIRONMENT...SHOULD PREVENT TEMPS FROM DROPPING BELOW THE MID
AND UPPER 40S.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...RAIN-FREE ON MONDAY AS MID LEVEL RIDGING AND
WESTERLY DOWNSLOPING KEEP THINGS VERY DRY. AT THE SURFACE HOWEVER
THERE WILL STILL BE SOME MOISTURE IN THE NNE FLOW. THUS EXPECT AN
EAST-WEST GRADATION IN CLOUD COVER. OVERALL CLOUD COVER WILL
DECREASE THROUGH THE DAY THOUGH AS THE PREVIOUSLY CUTOFF ATLANTIC
SYSTEM CONTINUES TO OPEN UP AND MOVE EASTWARD. MID LEVEL HEIGHT
FALLS SPREAD ACROSS THE REGION ON TUESDAY AS THE RIDGE GIVES WAY TO
TROUGHINESS DROPPING OUT OF THE GREAT LAKES AREA.  LOW LEVEL
MOISTURE ADVECTION THEN FOLLOWS LATE DAY WITH THE APPROACH OF A COLD
FRONT. THIS BOUNDARY IS A LITTLE SLOWER THAN PREV PROGGED. SHOWERS
WILL BE WIDELY SCATTERED AND INSTABILITY QUITE MEAGER. MONDAY HIGHS
HELD BELOW CLIMO BY THE NORTHERLY COMPONENT BUT TEMPS SNAP BACK TO
SEASONABLE IF NOT A LITTLE WARMER IN THE PREFRONTAL SRLY FLOW ON
TUES.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...PRESSURE PATTERN QUITE POORLY DEFINED ON
WEDNESDAY AS THE POST FRONTAL HIGH IS QUITE WEAK AND MOSTLY CENTERED
WELL TO OUR NORTH. THIS PRECLUDES ANY COOL ADVECTION AND FAIRLY
SEASONABLE WEATHER IS EXPECTED. WE MAY SEE A BUMP OF A FEW DEGREES
ON THURSDAY AS HIGH MOVES OFF THE COAST. THIS VERY SLIGHT WARMING
TREND WILL CONTINUE FOR THE REMAINDER OF THE PERIOD. LOW LEVELS WILL
MOISTEN GRADUALLY BASICALLY JUST CHANGING THE MOSTLY SUNNY SKIES OF
WED AND THU TO PARTLY SUNNY BY FRIDAY OR THEREABOUTS...AGAIN A
GRADUAL PROCESS. THE UPTICK IN MOISTURE PAIRED WITH THE DEVELOPMENT
OF A PIEDMONT TROUGH CALLS FOR SOME SLIGHT CHC POPS BY SATURDAY.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AS OF 18Z...THE LOW OFFSHORE WILL MOVE SLOWLY AWAY FROM THE
TERMINALS THIS TAF VALID PERIOD. THERE WILL CONTINUE TO BE A GOOD
CHANCE OF WRAP AROUND BANDS OF RAIN AT LEAST THROUGH
00Z...ESPECIALLY NEAR THE COAST. FLIGHT CONDITIONS NOW ARE
MVFR/TEMPO IFR AT KILM AND MVFR AT KCRE. VFR IS OCCURRING ELSEWHERE.
A BAND OF LIGHT TO OCCASIONALLY MODERATE RAIN WAS MOVING SWWD FROM
THE ILM VCNTY. PATCHY LIGHT RAIN OR SPRINKLES WERE OCCURRING
INLAND.

MVFR WILL BE POSSIBLE AT ALL COASTAL TERMINALS THIS AFTERNOON WITH
CIGS AROUND 1K. THE CHANCE OF IFR IS LOW BUT CIGS 800-900 AND VSBYS
1-3 SM ARE POSSIBLE IN THE BRIEF HEAVIER SHOWERS. SFC WINDS WILL BE
N-NE GUSTING TO 25-30 KTS...HIGHEST AT THE COASTAL TERMINALS. TEMPO
MVFR CIGS/-RA COULD OCCUR AT KFLO/KLBT BUT THE LOWER CIGS APPEAR TO
BE MORE LIKELY EAST OF THE TERMINALS.

AFTER THE PRECIPITATION ENDS AROUND 00Z CONFIDENCE IS HIGHEST FOR
VFR CIGS AT KFLO/KLBT AND MVFR CIGS AT THE COASTAL TERMINALS AS COLD
AIR ADVECTION DEVELOPS A LOW LEVEL INVERSION AROUND 1K. CIGS WILL
BECOME VFR AT ALL TERMINALS 13-15Z.

EXTENDED OUTLOOK...VFR MONDAY. CHANCE OF SHOWERS/TEMPO MVFR ON
TUESDAY WITH A COLD FRONT. VFR WEDNESDAY AND THURSDAY. CHANCE OF
SHOWERS/TEMPO MVFR ON FRIDAY.



&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1230 PM SUNDAY...VERY LITTLE CHANGE HAS OCCURRED IN THE PAST
SEVERAL HOURS WITH MARINE WEATHER CONDITIONS. GUSTS CONTINUE TO
REACH 30 KNOTS AT THE NC BEACHES...25 KT AT THE SC BEACHES...AND
JUST SHY OF 40 KNOTS OUT AT THE FRYING PAN SHOALS BUOY. PREVIOUS
DISCUSSION FROM 1000 AM FOLLOWS...

WINDS AT THE FRYING PAN SHOALS BUOY HAVE GUSTED AS HIGH AS 41 KNOTS
THIS MORNING...WITH COASTAL OBSERVATIONS SHOWING GUSTS AS HIGH AS 30
KNOTS AT WRIGHTSVILLE BEACH AND BALD HEAD ISLAND. IN THE
SEMI-PROTECTED WATERS SOUTHWEST OF CAPE FEAR WINDS ARE RUNNING 5-7
KNOTS LESS NEARSHORE...BUT ARE PROBABLY STILL QUITE STRONG AWAY FROM
SHORE. 1011 MB LOW PRESSURE ABOUT 125 MILES SOUTHEAST OF CAPE FEAR
HAS BEEN PRODUCING AN IMPRESSIVE AMOUNT OF DEEP CONVECTION WITH NLDN
LIGHTNING NETWORK DISPLAYS SHOWING SEVERAL HUNDRED LIGHTNING STRIKES
PER HOUR NEAR THE CENTER OF THE CIRCULATION. SINCE THIS LOW IS
FORECAST TO ONLY DRIFT EASTWARD THROUGH TODAY LOOK FOR ONLY A SLOW
IMPROVING TREND IN WINDS/SEAS TO BEGIN LATE TODAY AND TONIGHT.
PREVIOUS DISCUSSION FROM 600 AM FOLLOWS...

LOW PRESSURE WAS BROADLY CENTERED OFF THE SOUTHEAST COAST. A TROUGH
EXTENDED FROM THE CENTER OF THE LOW AND UP ALONG THE THE CAROLINA
COAST. AT THE SAME TIME...STRONG HIGH PRESSURE...CENTERED ACROSS
EASTERN NEW ENGLAND...WAS RIDGING DOWN THE COAST AND ACROSS THE
CAROLINAS. THIS CONTINUES TO RESULT IN A VERY TIGHT PRESSURE
GRADIENT...PRODUCING GALE FORCE WINDS ACROSS THE WATERS...UP TO 25
TO 35 KT WITH GUSTS NEAR 40 KT. WINDS ARE EXPECTED TO SLOWLY
DIMINISH TONIGHT. THE DIRECTION WILL REMAIN NE TODAY WITH A SLOW
BACKING TO THE N AS THE LOW CENTER AND TROUGH SLOWLY MOVE SEAWARD.
SEAS WILL BE HIGHEST INTO THIS AFTERNOON...UP TO 7 TO 12 FT. SEAS
WILL SUBSIDE TONIGHT...DOWN TO 6 TO 9 FT BY DAYBREAK MON. WAVE
HEIGHTS ACROSS THE NEAR SHORE WATERS OF LONG BAY WILL BE
CONSIDERABLY LOWER DUE TO THE VERY LIMITED FETCH ON NE TO N WINDS.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...SHORT TERM WILL START WITH A SMALL CRAFT
ADVISORY AS WE CONTINUE TO RAMP DOWN FROM THE GALES OF THE NEAR TERM
PERIOD. GRADIENT WILL EASE AS LOW PRESSURE PULLS AWAY SLOWLY TO THE
EAST AND A WEAK HIGH TRIES TO GET ESTABLISHED ACROSS THE SOUTHEAST.
THE LATTER DOES NOT HAVE MUCH LUCK TO LOCAL WINDS WILL ALMOST
EXCLUSIVELY BE A FUNCTION OF THE EXITING LOW. SOUTHERLY FLOW
OVERSPREADS THE REGION FROM WEST TO EAST ON TUESDAY AS A COLD FRONT
APPROACHES FROM THE NORTHWEST. THIS WILL SLIGHTLY REVERSE THE
ABATING TREND IN WAVE HEIGHT BUT NO FLAGS OR CAUTIONARY HEADLINES
EXPECTED AS WIND REMAINS QUITE LIGHT BOTH AHEAD OF AND FOLLOWING A
TUESDAY NIGHT FROPA.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 300 AM SUNDAY...FOLLOWING THE PASSAGE OF A COLD FRONT
WEDNESDAYS WILL BRING DECREASING AND VEERING WINDS AND ABATING
SEAS. HIGH PRESSURE NORMALLY BUILDS IN BEHIND A COLD FRONT BUT THIS
TIME THE AIRMASS PRETTY MUCH WASHES OUT AS IT BUILDS SOUTHWARD. A
STRONGER HIGH FORMS WEDNESDAY NIGHT UP IN NY/PA AND IT WILL EXTEND A
RIDGE AXIS DOWN INTO THE CAROLINAS. THIS WILL INITIALLY YIELD A
LIGHT ONSHORE FLOW BUT AS THURSDAY PROGRESSES THE HIGH WILL SPLIT
SLIGHTLY WITH ONE CENTER ANCHORING OFF HATTERAS. WIND WILL
EVENTUALLY TURN SOUTHERLY OR SOUTHWESTERLY.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...HIGH RIP CURRENT RISK THROUGH THIS EVENING FOR SCZ056.

NC...HIGH RIP CURRENT RISK THROUGH THIS EVENING FOR NCZ106-108.

MARINE...GALE WARNING UNTIL 11 PM EDT THIS EVENING FOR
AMZ250-252-254-     256.

&&

$$

NEAR TERM...RJD/TRA
SHORT TERM...MBB
LONG TERM...MBB
AVIATION...MRR/TRA





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