Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 260541
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
141 AM EDT SUN APR 26 2015

.SYNOPSIS...
A COLD FRONT WILL SINK SOUTH ACROSS THE AREA TODAY AND TONIGHT.
DRY HIGH PRESSURE WILL MOVE INTO THE REGION MONDAY AND TUESDAY
BEFORE A STORM SYSTEM IMPACTS THE AREA MID WEEK. SEASONABLE AND
DRY HIGH PRESSURE IS EXPECTED TO RETURN FRIDAY INTO NEXT WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 140 AM SATURDAY...SLIGHT TO LOW CHANCE FOR CONVECTION
ACROSS ALL LOCATIONS...ALL NIGHT. THIS A RESULT OF AN OSCILLATING
SFC BOUNDARY ACROSS THE ILM CWA FOR THE REMAINDER OF THE OVERNIGHT
PERIOD. THE DEEPER AND MAIN AREA OF CONVECTION THAT CROSSES THE
NC- VA MOUNTAINS...SHOULD REMAIN JUST NORTH OF THE FA AS IT TRACKS
TO THE ESE OVERNIGHT. HAVE TWEAKED OVERNIGHT MINS BASED ON WHERE
THE SFC FRONT IS EXPECTED TO LIE BY DAYBREAK SUN. HAVE ADDED
PATCHY/AREAS OF FOG TO THE OVERNIGHT PERIOD...ESPECIALLY ALONG AND
NORTH OF THE SFC FRONTAL BOUNDARY.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 PM SATURDAY...A WARM FRONT WILL BE SITUATED VERY NEAR
OR JUST N OF THE AREA SUNDAY MORNING. MODEL PROFILES SHOW A DEEP
WESTERLY FLOW WITH SIGNIFICANT MOISTURE RELEGATED TO THE LOWEST 3
KFT OR SO IN THE WARM SECTOR. A 50 KT JET WILL BE LOCATED 3-5 KFT
AGL SUNDAY. THE GFS SHOWS LITTLE IN THE WAY OF INSTABILITY ON SUN
WHILE THE NAM PORTRAYS MIXED LAYER CAPE VALUES UP TO AROUND 1500
J/KG AND THIS SEEMS MUCH MORE REASONABLE. THE INSTABILITY WILL BE
SHRINKING SOUTHWARD WITH TIME AS THE LAST OF THE WEAK WAVES OF LOW
PRESSURE MOVES OFFSHORE TO CONSOLIDATE AND STRENGTHEN WELL OFF THE
NC COAST. MODEL SOUNDINGS ACTUALLY SHOW A STRONG FRONTAL INVERSION
DEVELOPING FROM N TO S...LASTLY ACROSS THE SOUTHERN GRAND STRAND
AND SOUTH SANTEE RIVER AREAS BY MID AFTERNOON SUN. CONFIDENCE IN
TIMING IS NOT HIGH...BUT TRENDS LOOK TO BE ON THE RIGHT TRACK.
GIVEN MAGNITUDE OF DRY AIR IN STRONG AND DEEPENING WESTERLY FLOW
ALOFT...WOULD EXPECT COVERAGE OF CONVECTION TO BE ISOLATED TO
SCATTERED. CAN NOT RULE OUT AN ISOLATED STRONG OR SEVERE
THUNDERSTORM TO INCLUDE HAIL AND/OR STRONG TO DAMAGING WIND GUSTS.
THE SEVERE WEATHER RISK WILL BE PRIMARILY ACROSS THE SOUTHERN
REACHES OF OUR FORECAST AREA...WHERE INSTABILITY WILL BE
GREATEST...AS WELL AS PERHAPS WHERE SEABREEZE INTERACTS WITH THE
FRONT. ANY SEVERE WEATHER WILL INCLUDE STRONG TO DAMAGING WIND
GUSTS WILL SHOW POPS TRENDING LOWER FROM N TO S LATE IN THE
AFTERNOON AND THROUGH THE EVE HOURS.

A SERIES OF SHORTWAVE TROUGHS ROUNDING A RETROGRADING AN UPPER LOW
OFF THE NEW ENGLAND COAST WILL HELP TO REINFORCE THE COOLER AND
DRIER AIR ADVECTING INTO THE FORECAST AREA MON AND MON NIGHT. A
GOOD DEAL OF SUNSHINE MON WILL BE BATTLING THE COOL NW FLOW WITH
850 MB TEMPS DROPPING TO AROUND 3 DEG C.

HIGHS SUN WILL LIKELY VARY FROM N TO S AND DEPENDING ON CLOUD
COVER...THERE COULD BE A SIGNIFICANT TEMP GRADIENT ACROSS THE
AREA. WILL FORECAST LOWER TO MID 80S ACROSS THE SOUTH SANTEE
RIVER AREA WITH MID AND UPPER 70S ELSEWHERE. HOWEVER...THE
NORTHERN REACHES OF THE AREA COULD BE STYMIED IN THE LOWER 70S
GIVEN THEIR PROXIMITY TO THE BOUNDARY AND GREATER CLOUD COVER.
HIGHS ON SUN WILL BE IN THE LOWER 70S FOR THE MOST PART...ONE TO
TWO CATEGORIES BELOW NORMAL FOR THE WANING DAYS OF APRIL. AFTERNOON
RELATIVE HUMIDITY LEVELS WILL BE FALLING THROUGH THE 40S AND 30S
ON MON AS DRY AND COOL HIGH PRESSURE TO THE NW BUILDS INTO THE
EASTERN CAROLINAS. THE COOLEST NIGHT...MON NIGHT...WILL BE IN THE
MID AND UPPER 40S.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 PM SATURDAY....MEDIUM RANGE GUIDANCE CONTINUES TO
STRUGGLE WITH THE EVOLUTION OF A MID LEVEL SYSTEM THAT WILL AFFECT
THE AREA TO SOME EXTENT FOR MIDWEEK. SEVERAL MODELS KEEP THE
TROUGH MORE PROGRESSIVE WHILE OTHERS PHASE THE SYSTEM WITH
NORTHERN STREAM ENERGY CREATING A MORE DYNAMIC SYSTEM AND PROLIFIC
RAIN MAKER FOR OUR AREA. UNTIL THE MODELS CONVERGE ON A DEPENDABLE
SOLUTION...PRUDENCE CALLS FOR KEEPING POPS IN THE FORECAST FROM
LATE TUESDAY THROUGH THURSDAY. NO CHANGES TO TEMPERATURE FORECAST
WHICH WILL BE A LITTLE BELOW CLIMATOLOGY.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 06Z...A WARM FRONT IS LOCATED FROM KLBT TO N OF KILM EARLY
THIS MORNING. FURTHER N A COLD FRONT ORIENTATED NE-SW AND IS JUST N
OF KLBT. LIFR/IFR CIGS ARE OCCURRING N OF THESE FRONTS WITH MOSTLY
VFR TO THE SOUTH. ANY LINGERING SHOWERS SHOULD DISSIPATE OVER THE
NEXT FEW HOURS WITH ONLY ISOLATED ACTIVITY THROUGH SUNRISE.
IFR/LIFR EARLY THIS MORNING WILL HINGE HIGHLY ON THE POSITION OF THE
FRONTS AT KILM/KLBT. KLBT APPEARS MOST LIKELY TO ENCOUNTER THESE LOW
CIGS. ELSEWHERE...CLEAR SKIES...LIGHT WINDS AND SUBSIDENCE BEHIND THE
SHOWER AREA SHOULD ALLOW FOR FOG TO DEVELOP. VSBYS SHOULD BEGIN TO
DECREASE OVER THE NEXT SEVERAL HOURS TO MVFR/IFR. TOWARDS DAYBREAK
VSBYS MAY IMPROVE AS WSW WINDS INCREASE...LIFTING THE FOG INTO AN
LIFR/IFR LAYER. ALTHOUGH CONFIDENCE OF OCCURRENCE IS MODERATE THERE
IS LOW CONFIDENCE IN TIMING AND DURATION.

MODELS DIFFER HIGHLY ON TIMING OF THE FRONTAL PASSAGE LATER TODAY AND
THE AMOUNT OF ASSOCIATED LOW LEVEL CLOUDS. THUS CONFIDENCE IN CIG
HEIGHTS AND CLOUD AMOUNTS IS LOW FOR SUNDAY. THE COLD FRONT SHOULD
MOVE THROUGH THE NORTHERN TERMINALS DURING THE MORNING AND DURING
THE AFTERNOON AT THE SOUTHERN TERMINALS WITH WINDS SHIFTING TO THE W-
NW. SHOWERS POSSIBLE DURING THE DAY WITH ISOLATED THUNDERSTORMS AT
THE SOUTHERNMOST TERMINALS.

EXTENDED OUTLOOK...VFR MONDAY AND TUESDAY. SHOWERS POSSIBLE WEDNESDAY
AFTERNOON THROUGH THURSDAY MORNING.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 140 AM SATURDAY...RAISED A SMALL CRAFT EXERCISE CAUTION FOR
ALL WATERS DUE TO COMBINED 15 TO 20 KT WINDS AND SIGNIFICANT SEAS
RANGING FROM 2 TO 4 FT...UP TO 5 FT ACROSS THE OUTER WATERS. THE
EXCEPTION WILL BE FOR THE WATERS BETWEEN CAPE FEAR SOUTH TO LITTLE
RIVER INLET WHERE A SOLID 3 TO 5 FT WILL EXIST THRUOUT.

LATEST SFC ANALYSIS HAS THE SFC FRONTAL BOUNDARY JUST NORTH OF
CAPE FEAR. PREFER THE LATEST 00Z NAM MODEL RUN...HAVE SLIGHTLY
SLOWED THE MOVEMENT OF THE FRONTAL BOUNDARY BACK TO THE SOUTH
OVERNIGHT. THIS WILL ALLOW A SW-WSW WIND AT 10 TO 20 KT TO OCCUR
FOR A SLIGHTLY LONGER TIME FRAME AND COVERING A BIT MORE ACREAGE
THAN EARLIER THOUGHT. THIS INCREASED COVERAGE AND TIME WILL RESULT
IN 3 TO 5 FT SIGNIFICANT SEAS...ESPECIALLY FROM CAPE FEAR
SOUTHWARD. CURRENT 41013 BUOY WITHIN THE WARM SECTOR INDICATES A
SOLID SW 20G25 KT WIND AND SIG. SEAS HAVING BUILT TO 5.9 FT. AS
EXPECTED WIND DRIVEN WAVES TO PRIMARILY POPULATE SIGNIFICANT SEAS
WITH DOMINANT PERIODS AROUND 6 SECONDS.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 PM SATURDAY...THE WIND DIRECTION WILL BE FROM THE W OR
SW SUN MORNING...THEN VEER TO THE NW AND N AS A FRONT SINKS BACK
TO THE S THROUGH THE DAY. THE FRONT MAY NOT MOVE S OF THE
SOUTHERNMOST WATERS TIL LATE AFTERNOON. THERE WILL BE A MODEST
SURGE SUN NIGHT AND THEN A SLIGHTLY STRONGER ONE MON NIGHT AS A
SERIES OF SHORTWAVE TROUGHS ROTATE AROUND UPPER LOW RETROGRADING
OFF THE NEW ENGLAND COAST. WINDS WILL BE STRONGEST WHEN THE WIND
DIRECTION IS FROM THE N OR NNW...UP TO 15 TO 20 KT MON NIGHT.
SEAS WILL BE 2 TO 4 FT MOST OF THE TIME. HOWEVER...EXPECT SEAS TO
BUILD UP TO 5 FT DURING THE SURGES...WITH THE GREATEST COVERAGE OF
5 FT SEAS MON NIGHT.

LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 300 PM SATURDAY...DESPITE AN INTERESTING AND POSSIBLY
DYNAMIC SYNOPTIC WEATHER SCENARIO AT THE MID LEVELS...THE SURFACE
FEATURES DRIVING THE WINDS AND SEAS WILL BE RATHER BENIGN IN
COMPARISON. HIGH PRESSURE TO THE NORTH WILL MAINTAIN A NORTH TO
NORTHEASTERLY FLOW ACROSS THE WATERS THROUGH WEDNESDAY WITH SPEEDS
GENERALLY TEN KNOTS OR LESS. FORECAST CHALLENGE THEN ARISES AS
MODELS ARE STILL UNSURE HOW TO HANDLE LOW PRESSURE IN THE GULF OR
UP THE EAST COAST BOTH IN A PLACEMENT AND STRENGTH PERSPECTIVE.
WILL MAINTAIN THE MODEST OFFSHORE FLOW FOR THURSDAY DUE TO
UNCERTAINTY. SIGNIFICANT SEAS WILL BE 2-4 FEET.

&&

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

&&

$$


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