Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 260658
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
158 AM EST THU FEB 26 2015

.SYNOPSIS...
LOW PRESSURE WILL BRING MOSTLY RAIN TO THE AREA TONIGHT. SNOW WILL
FALL MAINLY WEST OF INTERSTATE 95...WITH A COUPLE INCHES POSSIBLE.
ARCTIC HIGH PRESSURE WILL BUILD IN THURSDAY INTO THE WEEKEND
BRINGING COLD TEMPERATURES AND EVENTUALLY SOME CLEARING SKIES.
MOISTURE WILL RETURN FOR THE NEW WEEK WITH TEMPERATURES CONTINUING
TO SHOW QUITE A BIT OF DAY TO DAY VARIABILITY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 130 AM THURSDAY...NEW UPDATES SENT TO REMOVE ALL MENTION ALL
SNOW OR SLEET FROM THE FORECASTS. WILL CONTINUE TO MENTION LIGHT
FREEZING RAIN OR LIGHT FREEZING DRIZZLE POSSIBLE FROM ROUGHLY
DAYBREAK THU THRU MID-MORNING FOR THE COUNTIES WITHIN THE WINTER
WX ADVISORY. TEMPS SHOULD BE ABOVE 32 BY LATE MORNING...ELIMINATING
THE THREAT FOR ANY ICING.

PREVIOUS DISCUSSION..............................................
AS OF 820 PM WEDNESDAY...SLEET IS FALLING AS FAR EAST AS WILMINGTON
THIS EVENING...WITH A MIX OF SLEET AND SNOW REPORTED AS FAR EAST AS
WHITEVILLE. THIS APPEARS TO BE DUE TO A POCKET OF VERY DRY AIR
BETWEEN 2,000 AND 10,000 FEET AGL--MUCH DRIER THAN ANY MODEL
FORECAST. THE 00Z SOUNDINGS FROM MHX AND GSO SHOWED DEWPOINT
DEPRESSIONS ANOTHER 10 DEGREES F WIDER THAN THE 18Z NAM OR GFS
THROUGH THAT LAYER. EVAPORATIONAL COOLING WITH THIS INITIAL WAVE OF
PRECIPITATION COOLED THE COLUMN SUFFICIENTLY TO MAKE A WRECK OF MY
PREVIOUS FORECAST.

STRONG WARM ADVECTION IN THE 850-700 MB LAYER SHOULD RAISE AIR
TEMPERATURES WELL ABOVE FREEZING IN THE NEXT 1-2 HOURS...ALONG WITH
A CONSIDERABLE INFLUX OF GULF AND ATLANTIC MOISTURE WHICH WILL
REMOVE ANY REMAINING EVAPORATIONAL COOLING POTENTIAL. BY LATE
EVENING I ANTICIPATE FROZEN PRECIPITATION TO BE CONFINED TO WESTERN
PORTIONS OF MARLBORO AND DARLINGTON COUNTIES...PERHAPS AFFECTING
MAXTON IN WESTERN ROBESON COUNTY AS WELL.

I AM GROWING MORE CONCERNED ABOUT THE POTENTIAL FOR WRAP-AROUND COLD
AIR AROUND SUNRISE THURSDAY MORNING CHANGING THE LAST OF THE RAIN
OVER TO FREEZING RAIN. I HAVE ADDED A CHANCE OF FREEZING RAIN TO THE
FORECAST ACROSS NORTHERN FLORENCE...MARION AND COLUMBUS
COUNTIES...AND MAY NEED TO CONSIDER RAISING AN ADVISORY FOR FREEZING
RAIN IF THIS THREAT GROWS OVERNIGHT.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...ACTIVE WEATHER WILL BE LIMITED TO THE FIRST
FEW HOURS OF THE PERIOD AS LOW PRESSURE RACES AWAY FROM THE
REGION. THE MAIN FORCING WILL BE LONG GONE LEAVING LOW LEVEL
MOISTURE IN THE FORM OF LIGHT RAIN SHOWERS AND MOSTLY DRIZZLE FOR
THE MORNING HOURS. I DID LEAVE AN HOUR OR TWO OF FREEZING RAIN FOR
THE NORTHERN PARTS OF THE ADVISORY AREA BUT TEMPERATURES SHOULD
SLOWLY PLOD TO ABOVE FREEZING IN THESE AREAS BY MID MORNING.
BEYOND THIS ARCTIC HIGH PRESSURE BUILDS INTO THE AREA THROUGH THE
REMAINDER OF THE PERIOD. CLOUDS WILL BE VERY SLOW TO SCOUR OUT
WITH LOW CEILINGS TRAPPED BELOW THE INVERSION. SOME SUNSHINE
SHOULD BREAK OUT FOR FRIDAY AFTERNOON. FOR THIS REASON I HAVE
OPTED FOR SLIGHTLY COOLER DAYTIME HIGHS AND SLIGHTLY MODERATED
OVERNIGHT LOWS VS THE MOS GUIDANCE.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 300 PM WEDNESDAY...NOT SURE WHEN WE`LL SEE SUNSHINE AGAIN.

AFTER A RAIN-FREE BUT PROBABLY CLOUDY DAY SATURDAY THE LONG TERM
WILL BECOME INCREASINGLY UNSETTLED. SATURDAY THOUGH BRINGS ZONAL MID
LEVEL FLOW BUT ALSO LOW LEVEL MOISTURE TRAPPED BENEATH DEEP
INVERSION OR PERHAPS NEARLY ISOTHERMAL LAYER AS LARGE SURFACE HIGH
PROGRESSES EAST WITH ITS CENTER WELL TO OUR NORTH. SUNDAY THE HIGH
TAKES ON MORE OF A WEDGE-LIKE ELONGATION INTO THE CAROLINAS.
TROUGHINESS DEVELOPS OFFSHORE AS WELL BUT NOW APPEARS MUCH WEAKER.
AS SUCH MODELS HAVE BACKED OFF ON RAIN CHANCES FOR SUNDAY BUT SOME
LOW POPS STILL LIKELY WARRANTED FOR COASTAL AREAS. SUNDAY HIGHS HAD
TO BE LOWERED CONSIDERABLY AS THE WEDGE WILL LIKELY SPONSOR A DREARY
DAY WITH TEMPS MIRED IN THE 40S (MEANWHILE THE NORMAL HIGH CONTINUES
TO CREEP UPWARDS...NOW 63 FOR ILM). SPEAKING OF HIGHS IN THE
60S...MONDAY MAY BE OUR BEST CHANCE TO SEE AS SUCH. THE WEDGE BREAKS
DOWN ONLY TO GIVE WAY TO A DECELERATING COLD FRONT. HIGHS MAY CLIMB
CLOSE TO SEASONABLE DESPITE FAIRLY HIGH RAIN CHANCES. UNSETTLED
WEATHER WILL LAST INTO TUESDAY INTO WEDNESDAY BUT THE TEMPERATURES
BUST POTENTIAL APPEARS LARGE ESPECIALLY TUESDAY. HIGH PRESSURE WEDGE
ON TUESDAY COULD BRING ANOTHER COOL AND RAINY DAY INSTEAD OF THE
SEASONABLE WEATHER IN THE CURRENT FORECAST (IN ONE RUN THE MEX FCST
WENT FROM 65 TO 52!). FOR WEDNESDAY THE SETUP IS RATHER SIMILAR TO
MONDAY WHEREIN THE WEDGE MAY BREAK DOWN FOR A NEAR IMMEDIATE ARRIVAL
OF A COLD FRONT, THE END RESULT BEING A RAINY BUT SEASONABLE DAY.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 00Z...PRECIPITATION MOVING INTO THE AREA FROM THE SW WITH
-RAPL MIX ACROSS FLORENCE AND ROBESON COUNTIES BUT NOT AT THE ASOS
SITES. WILL MENTION AT KFLO AND KLBT IN TEMPO GROUP A -RAPL MIX.
EXPECT ALL RAIN EVENT ACROSS THE COASTAL TERMINALS THROUGHOUT THE
NIGHT WITH MAX UVM BETWEEN 04Z-08Z HAVE BROUGHT DOWN SITES TO LIFR
IN TEMPO GROUPS TO ACCOUNT FOR THIS. MODEL SOUNDING DATA ALONG THE
COASTAL SITES STILL SHOW DRY AREA BETWEEN H9 AND H7 BUT THIS QUICKLY
MOISTEN UP AND BY 02Z COLUMN IS SATURATED AND STAYS THAT WAY TO
ABOUT 12Z WHEN DRY SLOT WORKS ITS WAY ACROSS THE TERMINALS. WILL CUT
OFF PRECIPITATION AROUND THIS TIME BUT KEEP TERMINALS IN MVFR WITH
CEILING AND VSBY THROUGHOUT THE DAY. FOR KLBT WILL HAVE A TEMPO
GROUP FROM 04Z-08Z FOR -SNPL WITH A PREVAILING GROUP AT 08Z FOR
-SNPL BEFORE MIXING BACK WITH -RA BY 10Z. WILL NOT HAVE -FZRA OR -PL
AT FLO AFT 03Z. WINDS WILL BE MAINLY FROM THE NE TO E AT 10-15 KTS
WITH SOME HIGHER GUSTS AS 60-70 KT JET IS LOCATED AT H7 THROUGHOUT
THE NIGHT WITH 95 KT WINDS AT H5. WOULD EXPECT SOME TURBULENCE
THROUGHOUT THIS LEVEL WITH WIND SPEED SHEAR. HIGH CONFIDENCE
OVERNIGHT IN IFR CONDITIONS AT TERMINALS ESPECIALLY FROM 04-08Z.

EXTENDED OUTLOOK...MVFR/IFR ON THURSDAY AND AGAIN ON SUNDAY.
OTHERWISE EXPECT VFR.

&&

.MARINE...
.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 PM WEDNESDAY...THE ONLY CHANGE TO THE FORECAST WAS TO SLOW
DOWN THE RATE OF INCREASE IN FORECAST SEA HEIGHTS OVERNIGHT. OUR
LOCAL SWAN WAVE MODEL HAS A WELL-KNOWN BIAS OF INCREASING SEAS MUCH
TOO QUICKLY IN PERIODS OF STRENGTHENING WIND. NO OTHER SIGNIFICANT
CHANGES ARE NECESSARY. DISCUSSION FROM 300 PM FOLLOWS...

LOW PRESSURE WILL MOVE OUT OF THE GULF OF MEXICO THIS EVE AND THEN
UP THE CAROLINA COAST...INTENSIFYING OFF THE NORTH CAROLINA COAST
TOWARD DAYBREAK AND ON THU. THE PRESSURE GRADIENT IS EXPECTED TO
BECOME SUFFICIENTLY TIGHT TO SUPPORT 20 TO 25 KT WINDS. THE
DIRECTION WILL BE NE THROUGH THE EVE...BACKING TO THE N OVERNIGHT.
SEAS WILL RESPOND TO THE INCREASING WINDS...BUILDING UP TO 6 TO 9
FT...10 FT SEAS ARE POSSIBLE AROUND FRYING PAN SHOALS. SEAS WILL BE
LOWER ACROSS THE VERY NEAR SHORE WATERS.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...ARCTIC HIGH PRESSURE WILL BUILD IN BEHIND
DEPARTING LOW PRESSURE AND WILL BE THE MAIN PLAYER DURING THE SHORT
TERM FOR THE MARINE COMMUNITY. INITIALLY A NORTHERLY FLOW OF 15-20
KNOTS WILL BE IN PLACE. BY THURSDAY AFTERNOON SPEEDS DROP TO 10-15
KNOTS LEANING HEAVILY TO THE HIGHER SIDE OF THE RANGE. WITH THE
SPRAWLING HIGH MOVING SLOWLY...THE COLD AIR ADVECTION ARRIVES IN THE
SAME MANNER AND WINDS WILL REMAIN HERE UNTIL BASICALLY THE END OF
THE PERIOD. THERE MAY BE A SUBTLE BUT BRIEF LULL EARLY SATURDAY
FOLLOWED BY AN INCREASE ONCE AGAIN AS THE EARLY STAGES OF A COASTAL
TROUGH FORM. SEAS WILL BE HIGHEST EARLY WITH 5-8 FEET CONTINUING. BY
LATER THURSDAY AFTERNOON...A MORE MODERATE RANGE OF 2-4 FEET
DEVELOPS. THE EXPIRATION OF THE SMALL CRAFT ADVISORY LATE IN THE DAY
LOOKS OK.

LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 PM WEDNESDAY...LARGE AREA OF EASTBOUND HIGH PRESSURE ON
SATURDAY SLIDING ACROSS OHIO VALLEY. THIS LEADS TO A BROAD SWATH OF
NORTHEASTERLY FLOW ALONG MUCH OF THE EAST COAST. CONDITIONS MAY GET
CLOSE TO SCEC/SCA CUTOFF ESPECIALLY ALONG THE LESS SHELTERED NC
WATERS. SUNDAY THIS HIGH MOVES FURTHER EAST BUT LEAVES BEHIND A
RIDGE AXIS INTO THE CAROLINAS. AT THE SAME TIME AN OFFSHORE
TROUGHINESS SHOULD WEAKEN AND VEER THE FLOW. PRETTY COMPLEX SETUP
HEADING INTO MONDAY WITH THE WEDGE BREAKING DOWN LEAVING BEHIND HIGH
DUE EAST OF THE REGION AND A COLD FRONT DROPPING INTO THE UPSTATE
REGION OF THE CAROLINAS WHILE DECELERATING. SOUTHWESTERLY FLOW
AHEAD OF THE FRONT VEERS CONSIDERABLY OVER AT LEAST NORTHERN WATERS
DEPENDING ON THE SPEED OF THE BOUNDARY. A NE FLOW RETURNS AREA-WIDE
BY MONDAY NIGHT.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR SCZ017-023-
     024.

NC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ087-096-
     105.

MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR AMZ250-
     252-254-256.

&&

$$
SYNOPSIS...SHK
NEAR TERM...RJD/TRA
SHORT TERM...SHK
LONG TERM...MBB
AVIATION...DCH






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