Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 262237
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
635 PM EDT WED AUG 26 2015

.SYNOPSIS...
A FRONT WILL OSCILLATE ACROSS THE COAST INTO THURSDAY WHILE
GRADUALLY LOSING IDENTITY. HIGH PRESSURE WILL SLOWLY BUILD INTO
THE CAROLINAS THIS WEEKEND. ERIKA IS EXPECTED TO APPROACH THE
BAHAMAS AND SOUTH FLORIDA LATE IN THE WEEKEND INTO EARLY NEXT
WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 312 PM WEDNESDAY...CONVECTION HAS YET TO EVOLVE AS ROBUSTLY
AS PREVIOUSLY ANTICIPATED...BUT THE ENVIRONMENT STILL APPEARS TO
BE RIPE FOR TSTMS THIS AFTN THROUGH TONIGHT.

STATIONARY FRONT ALIGNED VERY NEAR THE COAST IS SLOWLY BEING
ABSORBED/COMBINED WITH THE SEA BREEZE WHICH IS JUST NOW BEGINNING TO
DEVELOP. THIS LATE START TO HEATING IS DUE TO THE PRONOUNCED CLOUD
COVER FROM THIS MORNING (POST FRONTAL STRATUS AND ANVIL DEBRIS) THAT
ONLY RECENTLY ERODED. WHILE HEATING HAS BEEN SLOW...IT IS STILL VERY
UNSTABLE OUTSIDE WITH SPC MESOANALYSIS SHOWING 2000-3000 J/KG OF
SBCAPE ALONG THE EASTERN COUNTIES. THIS IS HIGHLY UNSTABLE...SO ANY
UPDRAFTS FORCED BY SURFACE BASED CONVERGENCE ALONG THE SEA
BREEZE...FRONT...OR DIFFERENTIAL HEATING BOUNDARIES...ARE STILL
EXPECTED TO RISE QUICKLY INTO TSTMS. ADDITIONALLY...A SHORTWAVE
EVIDENT ON WV IMAGERY LIFTING NE FROM THE GULF COAST WILL COMBINE
WITH ENHANCING DIFFLUENCE AT 300 MB TO PROVIDE UPPER SUPPORT. IN
OTHER WORDS...ALL SIGNS STILL POINT TO CONVECTION BLOSSOMING THIS
EVENING...AND HIGH RES GUIDANCE...WHILE NOT AS AGGRESSIVE AS EARLIER
STILL SHOWS SCATTERED TO WIDESPREAD CONVECTION DEVELOPING THROUGH
THIS EVENING. HAVE TRIMMED POP BACK TO HIGH CHC FROM THE EARLIER
LIKELY...BUT MANY PLACES STILL FACE THE RISK OF TORRENTIAL RAINFALL
WITH ISOLATED FLOODING...SIGNIFICANT LIGHTNING...AND MAYBE AN
ISOLATED DAMAGING WIND GUST.

POP WILL WANE SLOWLY AFTER DARK WITH LOSS OF HEATING...BUT THE
PRESENCE OF THE UPPER FEATURES WILL HAVE THE POTENTIAL TO MAINTAIN
CONVECTION THROUGH THE OVERNIGHT HOURS...ALTHOUGH IN A WEAKER AND
LESS WIDESPREAD FASHION.

TEMPS TONIGHT WILL FALL SLOWLY AS CLOUDS AND SOUTHERLY WINDS EAST OF
THE FRONT MAINTAIN A VERY WARM AND HUMID AIRMASS. A SIGNIFICANT TEMP
GRADIENT IS FORECAST ACROSS THE CWA FOR MINS...DROPPING TO AROUND 69
WELL INLAND...BUT STAYING AS WARM AS 75 ALONG THE IMMEDIATE COAST.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 312 PM WEDNESDAY...LOCAL ATMOSPHERIC CONDITIONS WILL REMAIN
FAVORABLE FOR CONVECTION ALONG THE COAST AND COASTAL INTERIOR
THURSDAY AND FRIDAY...AS A WAVERING BUT DECAYING FRONTAL BOUNDARY
REMAINS QUASI-STATIONARY NEAR THE LAND-SEA INTERFACE. TROPICAL
MOISTURE WILL REMAIN DEEPEST OFFSHORE BUT RICH ENOUGH TO SERVE AS
FUEL IN LATE AUGUST HEATING ACROSS THE EASTERN ZONES. EXPECTATION
OF SEA-BREEZE CONVERGENCE MAY VERY WELL CO-MINGLE WITH THE
DETERIORATING FRONT TO ADD ADDITIONAL UPDRAFT FOCUS BY THE
AFTERNOON BOTH DAYS. TIME HEIGHT DEPICTIONS OF RH IN THE COLUMN
SUGGEST GRADUAL DRYING AND ANTICYCLONIC TURNING OF THE ATMOSPHERE
AS AN UPPER RIDGE BUILDS FROM THE SE FRIDAY...AND COULD REDUCE
POP POTENTIAL FRIDAY COMPARED TO THURSDAY. TEMPERATURES OF MAX/MIN
WILL HOLD CLOSE TO NORMALS FOR LATE AUGUST BOTH DAYS...ALTHOUGH
CLOUD COVER AND WEAK POST FRONTAL AIR MAY RESULT IN MIDDLE 80S
MOST LOCATIONS.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 312 PM WEDNESDAY...BY SATURDAY ERIKA...OR REMNANTS OF...MAY
BE MOVING INTO THE FAR EASTERN BAHAMAS. CURRENT MODEL SPREADS BY
DAY 5 MONDAY BECOME HIGHLY DIVERGENT...PLACING ERIKA ANYWHERE FROM
THE EASTERN GULF OF MEXICO TO SEVERAL HUNDRED MILES EAST OF
FLORIDA. IN LIGHT OF THE PRESENT UNCERTAINTY...COUPLED WITH A
DECENT CONSENSUS THAT UPPER RIDGING WILL STRENGTHEN INTO THE
CAROLINAS...THE EXTENDED FORECAST DOES NOT REFLECT ANY DIRECT
IMPACTS FROM ERIKA. EXCEPTION POTENTIALLY COULD BE ARRIVAL OF
SWELL WAVE ENERGY...PROVIDED ERIKA INTENSIFIES AS DEPICTED BY THE
OFFICIAL NHC TRACKS...THOUGH EVEN THIS PARAMETER CARRIES LIMITED
CONFIDENCE. AS A RESULT...FORECAST IN DAYS 4-7 REPRESENTS NEAR
CLIMATOLOGICAL CONDITIONS FOR LATE AUGUST WITH MAXIMUMS IN THE
UPPER 80S TO AROUND 90...MINIMUMS IN THE LOW 70S...DOTTED WITH
ISOLATED TO SCATTERED SHOWERS AND TSTMS. A LOCAL ELEVATED RIP
CURRENT THREAT COULD ARRIVE ON OUR BEACHES BY THIS WEEKEND.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 00Z...CONVECTION IS WANING...ALTHOUGH THIS IS COUNTER TO WHAT
THE NAM IS SHOWING WITH CONVECTION ONGOING THROUGH 06Z. THINK THIS
SCENARIO IS TOO PESSIMISTIC AS THE CELLS WERE TRAINING AND WORKED
THE ATMOSPHERE OVER PRETTY GOOD. DEBRIS CLOUDS WILL KEEP FOG ALONG THE
COAST AT A MINIMUM...HOWEVER WITH ALL THAT WATER ON THE GROUND AT
MYR WHERE THE FLOODING OCCURRED...IF THEY CLEAR OUT COULD SEE SOME
IFR CONDITIONS. WILL REEVALUATE IN A FEW HOURS AND AMEND IF NECESSARY.
SOME LIGHT FOG INLAND WITH MVFR STRATUS EXPECTED. WEDNESDAY...PREDOMINATELY
VFR WITH NORTHEAST FLOW. A SLIGHT CHANCE OF CONVECTION AROUND MAX
HEATING.

EXTENDED OUTLOOK...PREDOMINATELY VFR WITH ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS THROUGH THE EXTENDED. BRIEF MORNING
FOG/STRATUS IS ALSO EXPECTED EACH DAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 312 PM WEDNESDAY...COLD FRONT/SEA BREEZE HYBRID IS SLOWLY
LIFTING  BACK TO THE NW...WITH A WEAK GRADIENT REMAINING IN PLACE
ACROSS THE WATERS. WINDS HAVE BEEN VARIABLE ACROSS THE
WATERS...BUT ARE TURNING TO A PREDOMINANT SOUTHERLY
DIRECTION...STRONGEST WITHIN THE SEA BREEZE CIRCULATION WHERE
SPEEDS MAY REACH UP TO 15 KTS...10 KTS ELSEWHERE. LATEST BUOY OBS
CONTINUE TO SHOW AN 10-11 SEC PERIOD SE SWELL AS THE DOMINANT WAVE
GROUP...AND THIS WILL PERSIST THROUGH TONIGHT WITH WAVE HEIGHTS
REMAINING AROUND 2-3 FT.


SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 312 PM WEDNESDAY...MANAGEABLE MARINE CONDITIONS THURSDAY
AND FRIDAY...WITH ONSHORE E-SE WINDS 10-15 KT BOTH DAYS OUTSIDE OF
TSTMS. SEA SPECTRUM WILL CONSIST OF ESE WAVE 2-3 FEET EVERY 10
SECONDS ACCOMPANIED BY A LIGHT TO MODERATE ONSHORE DIRECTED CHOP.
TSTMS WILL BE SCATTERED OVER THE 0-20 NM WATERS AND MARINERS
SHOULD GET A RADAR UPDATE BEFORE HEADING OUT...AS SOME STORMS
BECOME STRONG AND CAPABLE OF PRODUCING MORNING WATER SPOUTS.

LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 312 PM WEDNESDAY...SATURDAY THROUGH MONDAY THERE APPEARS
AGREEMENT AMONG GFS/ECMWF PLOTS THAT DESPITE THE SPECIFIC
ARRANGEMENT OR CONFIGURATION OF THE SYNOPTIC PATTERN...THE
PRESSURE GRADIENT/PATTERN WILL BE A FLAT ONE. THIS SUGGEST
LIGHT WINDS. SEAS HOWEVER DEPENDING ON HOW ERIKA INTENSITY
TRENDS PAN-OUT...MAY BE LACED WITH AN UNDERLYING LONG PERIOD
SWELL THAT COULD ACCOMPANY THE LIGHT WIND-WAVES. THIS MAY INDUCE
ENHANCED SHOALING PROCESSES IN SHALLOW WATER AREAS. ISOLATED TO
SCATTERED SHOWERS AND TSTMS WILL REMAIN IN THE EXTENDED MARINE
FORECAST BASED ON EXPECTED ATMOSPHERIC MOISTURE AVAILABILITY.

&&

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

&&

$$

SYNOPSIS...MJC
NEAR TERM...JDW
SHORT TERM...MJC
LONG TERM...MJC
AVIATION...43


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