National Weather Service United States Department of Commerce

 


000
FXUS62 KILM 280508
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
108 AM EDT SAT MAR 28 2015

.SYNOPSIS...
SHARPLY COLDER TEMPERATURES WILL SETTLE INTO THE AREA OVER THE
WEEKEND...AND A FREEZE WATCH REMAINS POSTED FOR EARLY SUNDAY. A
WEAK COLD FRONT WILL PASS THROUGH MONDAY BRINGING A CHANCE OF
SHOWERS...WITH SEASONABLE TEMPERATURES FOLLOWING THROUGH MID WEEK.
A WARMING TREND IS EXPECTED LATE NEXT WEEK AHEAD OF A COLD FRONT.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...

AS OF 115 AM SATURDAY...I HAVE MADE UPDATES TO FORECAST LOW
TEMPERATURES TONIGHT...RAISING THEM BY 3-5 DEGREES ESPECIALLY
INLAND. COLD ADVECTION IS PRODUCING VERY STEEP LOW-LEVEL LAPSE RATES
WHICH WILL KEEP SURFACE WINDS COUPLED UP WITH THE REST OF THE DEEP
BOUNDARY LAYER OVERNIGHT. FAIRLY DENSE CLOUDS ARE OBVIOUSLY HELPING
TOO. MOS FORECASTS ARE NEVER TO BE TRUSTED IN THESE SITUATIONS
ALTHOUGH THE RAW MODELS THEMSELVES USUALLY PERFORM QUITE WELL.
FORECAST LOWS RANGE 38-40 ALONG THE I-95 CORRIDOR TO 42-44 ON THE
BEACHES. OTHERWISE PATCHY LIGHT RAIN WILL CONTINUE TO ADVECT
EASTWARD AS THE CORE OF THE UPPER LEVEL DISTURBANCE REACHES THE
COAST AROUND DAYBREAK. DISCUSSION FROM 1000 PM FOLLOWS...

NO MAJOR CHANGES FOR THE EVENING UPDATE. BASED ON RADAR
TRENDS...WILL RAISE PROBABILITY OF PRECIPITATION LATE EVENING AND
OVERNIGHT TO SCATTERED AS SHORT-WAVE IMPULSES EJECT NE FROM THE
UPPER TROUGH BASE...AND THE TROUGH AXIS TRAVERSE THE AREA. AS A
RESULT WILL MAINTAIN MENTIONABLE POPS INTO DAYBREAK. HAVE HELD OFF
ON ANY SMALL HAIL MENTION DESPITE THE PASSING OF THE COLD POOL
ALOFT...AND NO THUNDER PLANNED SINCE LOW-LEVEL COLD AIR ADVECTION
WILL OFF-SET H9-85 LAPSE RATES SOMEWHAT. THE PREVIOUS EVENING
DISCUSSION FOLLOWS.

BULK OF RAINFALL AND COLD FRONT HAS PASSED SOUTH AND EAST OF THE
AREA. COLDER TEMPERATURES WILL TREND WITH UPPER 30S TO LOW 40S BY
DAYBREAK SATURDAY. HIGHLY AMPLIFIED UPPER TROUGH AND ASSOCIATED
AXIS REMAIN POISED WEST OF THE AREA EDGING THIS WAY. A VORTICITY
CENTER CRADLED IN THE BASAL PORTION OF THE TROUGH WILL SCOOT
ACROSS NE SC AND SE NC BETWEEN 6Z/2AM-12Z/8AM AND WILL BRING
ISOLATED TO SCATTERED COLD-CORE SHOWERS AS AN H7 COLD FRONT SWEEPS
THROUGH. THE POTENCY OF THE UPPER TROUGH MAY WARRANT INCLUSION OF
SMALL HAIL WITH THE SHOWERS AND A CLOSER LOOK WILL BE TAKEN IN 00Z
MODEL DATA TO DETERMINE IF THUNDER SHOULD BE CARRIED
OVERNIGHT...ELEVATED AND NOT ROOTED TO THE SURFACE WITH SURFACE
DEWPOINTS DROPPING IN THE 30S. TIME HEIGHTS POINT TO A SLIGHT
DEEPENING OF COLUMN MOISTURE DURING TRANSIT. BRISK NW WINDS TO
ACCOMPANY THIS PASSAGE/FEATURE...AND IN THE PREDAWN HOURS FOR THE
28TH DAY OF MARCH...WIND CHILLS IN THE LOWER 30S DURING THE WEE
HOURS OF SATURDAY. FOR THE EVENING HOURS TONIGHT ISOLATED SHOWERS
ONLY...AS AIR TEMPERATURES FALL STEADILY THROUGH THE 40S BENEATH A
LINGERING CLOUD COVER.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
AS OF 330 AM FRIDAY...A COOL DOWN IS IN STORE WITH THE PASSAGE
OF THIS LATE SEASON COLD FRONT. IN THE MID-LEVELS THE SHARP 500
MILLIBAR TROUGH AXIS WILL HAVE SHIFTED EAST OF THE FORECAST AREA
WITH HIGH PRESSURE BUILDING AT THE SURFACE. THIS COLD AIR
ADVECTION WILL BE SPILLING INTO THE REGION WITH 850 MILLIBAR
TEMPERATURE FALLING TO -6 TO -8 DEGREES CELSIUS. AT THE SURFACE
LOW TEMPERATURES ON SUNDAY MORNING ARE EXPECTING TO REACH 27
DEGREES F INLAND TO AROUND FREEZE ON THE BEACH STRANDS. THUS A
FREEZE WATCH HAS BEEN ISSUED THIS AFTERNOON AS THE CHANCES FOR A
HARD FREEZE APPEAR LIKELY FOR OUR INLAND AREAS LATE NIGHT SATURDAY
INTO THE 1ST FEW HOURS AFTER SUNRISE.

HIGH TEMPERATURES BOTH DAYS ARE EXPECTED TO BE IN THE 50S AND THE
LOW ON SUNDAY NIGHT INTO MONDAY WILL MODERATE INTO THE UPPER 30 TO
LOW 40S ALONG THE BEACH STRANDS OF NORTHEAST SOUTH CAROLINA.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 340 PM FRIDAY...SPRING-LIKE PATTERN UPCOMING FOR ALL OF
NEXT WEEK AS THE NORTHERN STREAM REMAINS ACTIVE...DRIVING COLD
FRONTS ACROSS THE AREA...SEPARATED BY WARM TEMPERATURES.

BROAD TROUGH WILL PERSIST OVER THE EASTERN CONUS THROUGH MID-WEEK
WITH A SHORTWAVE DIVING THROUGH THE MID-ATLANTIC MONDAY NIGHT. THIS
WILL PUSH A WEAK COLD FRONT ACROSS THE AREA WITH A GOOD CHANCE FOR
SHOWERS...BUT ONLY LIMITED POST-FRONTAL CAA. THUS...TUESDAY WILL
LIKELY BE WARMER THAN MONDAY EVEN THOUGH THE AREA WILL BE BEHIND THE
FRONT. THEREAFTER...A SIGNIFICANT WARMING TREND LOOKS TO BEGIN AS
THE MID-LEVEL TROUGH GETS DISPLACED BY RIDGING...AND EVEN A WEAK
SHORTWAVE THURSDAY WILL DO LITTLE TO IMPEDE THE WARMER TEMPERATURES.
AT THE SURFACE...HIGH PRESSURE BUILDS DOWN BEHIND THE COLD FRONT
TUESDAY...AND THEN PARKS OFFSHORE WED-FRI. INCREASING AIR-MASS
SHOWER ACTIVITY WILL OCCUR THU/FRI AHEAD OF A MORE SIGNIFICANT COLD
FRONT AS AN EARLY-SUMMER PATTERN SETS UP...FOR AT LEAST A FEW DAYS.
STRONG COLD FRONT WILL BE ON THE DOORSTEP AT THE END OF THE
PERIOD...BUT LOOKS TO HOLD OFF UNTIL JUST BEYOND THE EXTENDED...AND
WILL MAINTAIN THE WARMING TREND WITH TEMPS RISING TO ABOVE NORMAL
FOR THE LATTER HALF OF THE PERIOD.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...

AS OF 06Z...AN AREA OF LIGHT RAIN WILL MOVE ACROSS THE TERMINALS
EARLY THIS MORNING. AT KFLO/KLBT FAIRLY CONFIDENT FLIGHT CONDITIONS
WILL BE VFR BASED ON CURRENT TRENDS AND UPSTREAM OBSERVATIONS.
CANNOT RULE OUT TEMPO MVFR SINCE RAIN WILL BE OCCURRING BUT
CONFIDENCE IS LOW. AT THE COASTAL TERMINALS CIGS WILL BE VFR BUT
WITH A BETTER CHANCE OF TEMPO MVFR.

VFR EXPECTED ALL TERMINALS AFTER DAYBREAK. WINDS WILL BE NW AND
GUSTY AT TIMES. BY LATE AFTERNOON WINDS SHOULD BECOME LIGHT.

EXTENDED OUTLOOK...VFR SATURDAY. A SLIGHT CHANCE OF SHOWERS
MONDAY...OTHERWISE VFR EXPECTED.

&&

.MARINE... NEAR TERM /THROUGH TONIGHT/...

AS OF 115 AM SATURDAY...NORTHWESTERLY WINDS CURRENTLY RANGE FROM 10-
15 KT NEARSHORE TO 20+ KNOTS OUT AT THE FRYING PAN SHOALS BUOY.
CHANGES WITH THE WIND FORECAST ARE VERY MINOR. HOWEVER I HAVE MADE
SUBSTANTIAL UPDATES TO SEA HEIGHT FORECASTS THROUGH
MORNING...RAISING THEM SUBSTANTIALLY IN THE CAPE FEAR VICINITY BASED
ON DATA FROM BOTH NEARSHORE BUOYS AND FRYING PAN SHOALS. WAVEWATCH
MODEL FORECASTS SUGGESTS SEA HEIGHTS NEEDED TO BE LOWERED SOUTH OF
CAPE FEAR IN LONG BAY WHERE LESSER AMOUNTS OF BACKSWELL AFFECT THE
SHALLOWER NEARSHORE WATERS. DISCUSSION FROM 1000 PM FOLLOWS...

SCA REMAINS IN EFFECT FOR THE ILM NC WATERS...AND A SCEC
FOR THE ILM SC WATERS THROUGH TONIGHT. SEAS 5-7 FEET ACROSS THE NC
WATERS AND GENERALLY 4-5 FT OVER THE SC WATERS. SEAS WILL LIKELY
DROP A BIT OVERNIGHT AS WINDS TURN TO MORE OF AN OFFSHORE
TRAJECTORY...BUT WIND GUSTS WILL LIKELY ENDURE INTO EARLY SATURDAY.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 340 PM FRIDAY...THE COLD FRONT WILL HAVE SHIFTED WELL OFF
THE COAST BY SATURDAY MORNING AND NORTHWEST WINDS OF 15 TO 20
KNOTS WILL BE BLOWING OFFSHORE SATURDAY. THE WINDS WILL VEER TO
THE NORTH AND CONTINUE IN THE 15 TO 20 KNOT RANGE THROUGH EARLY
SUNDAY WITH A DECREASE IN SPEEDS TO 10 TO 15 KNOTS OVERNIGHT
SUNDAY. ON SUNDAY NIGHT WINDS WILL BE FROM THE WEST AT 10 TO 15
KNOTS AS HIGH PRESSURE SHIFTS OFF THE COAST. WAVE HEIGHTS WILL
FALL FROM 3 TO 5 FEET ON SATURDAY TO AROUND 2 FEET BY SUNDAY
NIGHT. NO ADVISORIES ARE EXPECTED DURING THIS PERIOD.

LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 340 PM FRIDAY...GUSTY SW WINDS GREET MONDAY AHEAD OF A COLD
FRONT WHICH WILL CROSS THE WATERS MONDAY NIGHT. SPEEDS OF 15-20
KTS WILL BE COMMON...DRIVING WAVE HEIGHTS TO 3-4 FT THROUGH MONDAY
EVE. THE FRONT WILL CROSS THE WATERS FROM NORTH TO SOUTH MONDAY
NIGHT TURNING WINDS QUICKLY TO THE NORTH AT 15-20 KTS...BEFORE
EASING QUICKLY TUESDAY MORNING AS HIGH PRESSURE BUILDS OVERHEAD.
SEAS WILL REMAIN CHOPPY JUST BEHIND THE FRONT...BUT THE OFFSHORE
WINDS WILL PUSH SEAS DOWN TO 2-3 FT EARLY TUESDAY...AND THEN THESE
WILL FALL FURTHER ON THE LIGHT WINDS DURING THE DAY. THIS HIGH
PRESSURE WILL MOVE OFFSHORE DURING THE MIDDLE OF THE WEEK...AND AS
SOUTHERLY RETURN FLOW DEVELOPS...WINDS WILL RISE TO 10-15 KTS LATE
IN THE PERIOD WITH SEAS INCREASING AGAIN TO 2-4 FT.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
FOR SCZ017-023-024-032-033-039-053>056.
NC...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
FOR NCZ087-096-099-105>110.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR AMZ250-252.

&&

$$

NEAR TERM...MJC/TRA
SHORT TERM...DRH
LONG TERM...JDW
AVIATION...MRR