Area Forecast Discussion
Issued by NWS Wilmington, NC

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537
FXUS62 KILM 070905
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
405 AM EST SUN FEB 7 2016

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL RAPIDLY INTENSIFY AS IT TRACKS
NORTHEAST OFFSHORE OF THE CAROLINAS TODAY. THIS SYSTEM MAY BRING
A MIX OF RAIN AND SNOW TO INLAND LOCATIONS TODAY. THE STRONG LOW
WILL TRACK FARTHER OUT TO SEA TONIGHT THRU MONDAY. WEAK HIGH
PRESSURE WILL PREVAIL MONDAY FOLLOWED BY A COLD FRONTAL PASSAGE
MONDAY NIGHT. A DRY ARCTIC AIR MASS WILL FOLLOW INTO MID WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 945 PM SATURDAY...FORECAST CONTINUES AS BEFORE. MONITORING
00Z GUIDANCE AS IT COMES IN TO SEE HOW IT INITIALIZES WITH CURRENT
REALITY AND TO SEE IF WE NEED TO MAKE ANY ADJUSTMENTS TO OUR
THINKING. LATEST OBS SHOW MID 40S ABOUT EVERYWHERE WITH LIGHT RAIN
OR DRIZZLE FALLING OVER LARGE PORTIONS OF THE FORECAST AREA.
PREVIOUS DISCUSSION FOLLOWS:

HAVE RAISED POPS FOR THIS EVENING GIVEN LATEST RADAR REFLECTIVITY
TRENDS...WHICH SHOW A GRADUAL INCREASE IN COVERAGE.
HOWEVER...PRECIP IS STILL VERY LIGHT DESPITE INCREASED
COVERAGE...SO HAVE NOT CHANGED QPF VALUES SIGNIFICANTLY. OTHERWISE
FORECAST REMAINS ON TRACK. PREVIOUS DISCUSSION FOLLOWS:

DETERIORATING WEATHER CONDITIONS TO PREVAIL LATE TONIGHT INTO
SUNDAY AS WIND...RAIN...AND SNOW DEVELOP IN RESPONSE TO AN
EVOLVING UPPER LOW AND ATTENDANT...BOMBING SURFACE LOW OFF THE
CAROLINA COAST. ISENTROPIC OMEGA WAS ALREADY UNDERWAY THIS
AFTERNOON OVER E GA AND SC AND THE CAROLINA COASTS...WHERE LIGHT
PCPN AMOUNTS WERE NOTED. SURFACE TEMPERATURES ACROSS NE SC AND SE
NC WILL NOT ALLOW FROZEN PCPN UNTIL THE PRE- DAWN HOURS SUNDAY
MAINLY ALONG AND WEST OF I-95. TEMPERATURES SUPPORT A MIX OF RAIN
AND SNOW...OR WET SNOW WITH LOW SNOW-RATIO VALUES. THROUGH 12Z
SUNDAY SNOW AMOUNTS OF A 1/4 INCH ARE POSSIBLE WEST OF I- 95.
NORTH WINDS WILL REMAIN IN PLACE TONIGHT AND INCREASE TO 10-20 MPH
BY DAYBREAK OVER LAND WITH STRONGER GUSTS AT THE COAST EARLY
SUNDAY...AS A RAPIDLY DEEPENING LOW BECOMES POSITIONED A FEW
HUNDRED MILES OFF CHARLESTON SC. THROUGH 12Z SUNDAY UP TO A HALF
OF RAIN IS POSSIBLE ALONG THE COAST...ESPECIALLY SOUTH OF CAPE
FEAR. MINIMUM TEMPERATURES AT DAYBREAK SUNDAY 32-38...COLDEST WEST
AND MILDEST AT THE COAST.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 3 AM SUNDAY...IMPRESSIVE SHORTWAVE DROPPING SOUTH THROUGH THE
UPPER MIDWEST SUN INTO MON WILL BRING ANOTHER CHANCE OF WINTRY
PRECIP TO THE AREA LATE MON AND MON NIGHT. DYNAMICS WITH THE
SHORTWAVE ARE IMPRESSIVE...AS IS THE ABUNDANCE OF THE COLD AIR. THE
ONLY LIMITING FACTOR WILL BE THE AMOUNT OF MOISTURE...SPECIFICALLY
THE LOW LEVEL MOISTURE. FORECAST SOUNDINGS SHOW STRONG UPWARD MOTION
IN THE DENDRITIC GROWTH ZONE WITHIN A LAYER OF INCREASED MOISTURE.
HOWEVER...BELOW 5K FT OR SO THE DRY AIR BECOMES AN OBSTACLE. STRONG
SHORTWAVES ALWAYS MANAGE TO WRING WHAT LITTLE MOISTURE IS AVAILABLE
OUT OF THE ATMOSPHERE BUT IN THIS CASE THE QPF IS GOING TO BE RATHER
LOW. SO WHILE THERE IS POTENTIAL FOR RAIN...POSSIBLY WITH SNOW
SHOWERS MIXED IN...DO NOT THINK EVENT WILL BE THAT SIGNIFICANT.
LATEST SOUNDINGS SUGGEST ALL RAIN FOR THE FORECAST AREA BUT THE COLD
AIR IS NOT FAR AWAY AND GIVEN THE STRENGTH OF THE WAVE THERE IS
DEFINITELY POTENTIAL FOR DYNAMIC COOLING. WILL KEEP FORECAST ALL
RAIN FOR NOW (ESPECIALLY SINCE LOCAL TOP DOWN METHODOLOGIES YIELD
ALL RAIN) BUT CANNOT RULE OUT THE ADDITION OF SNOW AS ZERO HOUR
APPROACHES. WILL CONTINUE TO CARRY LOW CHC POP WITH MINIMAL QPF.
SHORTWAVE HELPS DRIVE THE FIRST OF 2 COLD FRONT ACROSS THE AREA MON
NIGHT. NEAR CLIMO TEMPS MON DROP BELOW CLIMO MON NIGHT AS COLD
ADVECTION GETS GOING.

CONTINUED STRONG COLD ADVECTION TUE AND TUE NIGHT WILL RESULT IN
TEMPERATURES BELOW TO WELL BELOW CLIMO FOR THE SECOND HALF OF THE
PERIOD. SECOND COLD FRONT CROSSES THE AREA LATER TUE REINFORCING THE
ALREADY COLD AIR MASS IN PLACE. THIS COLD FRONT IS BEING DRIVEN BY
ANOTHER SHORTWAVE ROTATING AROUND THE BASE OF THE TROUGH. ALTHOUGH
LOW LEVEL MOISTURE REMAINS QUITE LIMITED THERE WILL BE ENOUGH MID
LEVEL MOISTURE TO SUPPORT AN INCREASE IN CLOUD COVER AND POSSIBLY
SOME VIRGA.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 3 AM SUNDAY...REGION WILL BE IN THE GRIP OF AN ARCTIC AIR MASS
AS THE PERIOD BEGINS. BROAD 5H TROUGH OVER THE EASTERN CONUS WED
INTO THU WILL MAINTAIN TEMPERATURES 10 TO 15 DEGREES BELOW CLIMO.
HIGHS EACH DAY WILL STRUGGLE TO REACH MID 40S. LOWS AT NIGHT WILL
NOT BE QUITE AS COLD AS ONE WOULD EXPECT GIVEN 850 TEMPS APPROACHING
-14C AT TIMES. CENTER OF THE SURFACE HIGH NEVER SETTLES OVER THE
AREA WITH THE BITTERLY COLD AIR IN PLACE. SO WHILE THIS MEANS COLD
ADVECTION NEVER WANES IT ALSO MEANS BOUNDARY LAYER MIXING NEVER
CEASES. LOWS WILL END UP IN THE MID 20S WED NIGHT. RATHER BALMY
COMPARED TO WHAT -14C 850 TEMP ON A STRONG RADIATIONAL COOLING NIGHT
WOULD YIELD...LOWS APPROACHING SINGLE DIGITS. THE MIXING WILL COME
AT A PRICE THOUGH...WIND CHILL VALUES WILL DROP WELL INTO THE TEENS.

MID LEVEL PATTERN REMAINS AMPLIFIED THU THOUGH HEIGHTS STARTS
BUILDING AS SHORTWAVE EXITS. AIR MASS STARTS TO MODIFY BUT THE
SURFACE LAYER WILL REMAIN ISOLATED AND SENSIBLE WARMING IS NOT
LIKELY TO BE REALIZED UNTIL THU NIGHT AT THE EARLIEST. BRIEF PERIOD
OF RETURN FLOW LATER THU AND THU NIGHT ENDS WITH COLD FRONT CROSSING
THE AREA DURING FRI. THIS FRONT IS FOLLOWED BY ANOTHER ROUND OF
ARCTIC AIR AS THE PERIOD ENDS. THE BEST...AND REALLY ONLY CHANCE FOR
PRECIP WILL BE LATE IN THE PERIOD AHEAD OF THE AFOREMENTIONED COLD
FRONT. ALTHOUGH SYSTEM DOES NOT APPEAR TO BE ALL THAT SPECIAL A COLD
FRONT/SHORTWAVE COMBO WITH MOISTURE IS USUALLY A RECIPE FOR AT LEAST
SOME LIGHT PRECIP. WILL CARRY A SILENT POP LATE IN THE PERIOD FOR
NOW.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
AS OF 06Z...SHOULD BE AN INTERESTING NEXT 24 HOURS TO SAY THE
LEAST. CURRENTLY...SURFACE CYCLOGENESIS OCCURRING OFFSHORE FROM
THE FLORIDA EAST COAST. A STRONG UPPER TROF WILL CATCH UP WITH THE
SFC LOW THIS MORNING...RESULTING IN EXPLOSIVE DEEPENING OF THE SFC
LOW JUST OFFSHORE FROM THE NC AND SC COASTS THRU THIS AFTERNOON
AND EVENING.

LOOK AT INITIALLY REDUCED VISIBILITY FROM LIGHT RAIN...VFR TO
MVFR...WITH POCKETS OF MODERATE TO HEAVY RAIN...MVFR TO IFR...
REDUCING VSBY TO LESS THAN 1 MILE AND ASSOCIATED CEILINGS
AT OR BELOW 1200 FT. THE HEAVIEST PCPN WILL OCCUR DURING DAYTIME
SUNDAY MORNING THRU MID-AFTERNOON. THE HIGHER PCPN AMOUNTS WILL
OCCUR CLOSER TO THE COAST...IE MYR...CRE AND ILM. SFC TEMPS AND
THE LOW LEVELS REMAIN MILD ENOUGH TO KEEP THE PCPN TYPE TO JUST
PLAIN RAIN. THE ENDING OF THIS PCPN COULD BE A MIXTURE OF RAIN OR
SNOW OR POSSIBLY ALL SNOW DEPENDING ON HOW MUCH WRAP AROUND COLD
AIR MAKES IT INTO THE AREA PRIOR TO THE DEPARTURE OF THE MOISTURE.
FOR NOW...ENDING THE PCPN AS PLAIN RAIN.

THE MAJOR EFFECTS FROM THIS STORM SYSTEM WILL BE THE GUSTY NE
WINDS INITIALLY...BACKING TO THE NORTH TODAY...AND NW LATE THIS
AFTERNOON AND EVENING. THE SFC PG WILL TIGHTEN RAPIDLY THIS
MORNING AS THE SFC LOW NEARLY BOMBS JUST OFFSHORE FROM THE
CAROLINAS LATER THIS MORNING AND AFTERNOON...AND PASSES BY CAPE
FEAR EARLY THIS EVENING...AND OFF CAPE HATTERAS BY SUNRISE MON.
PEAK GUSTS WILL RUN 20 TO 30 KT ACROSS THE INLAND TERMINALS...
AND 30-40 KT ACROSS THE COASTAL TERMINALS...AND OCCUR LATE THIS
MORNING THRU EARLY THIS EVENING.

EXTENDED OUTLOOK...CONDITIONS IMPROVE TO VFR SUNDAY EVENING AND
OVERNIGHT...AND CONTINUING THRU MON. A CHANCE OF PRECIPITATION
WITH MVFR CONDITIONS POSSIBLE LATE MONDAY INTO TUESDAY. ARCTIC
AIR MASS WILL PROVIDE VFR CONDITIONS WEDNESDAY AND THURSDAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 945 PM SATURDAY...WE CONTINUE TO SEE A GRADUAL INCREASE IN
WINDS AND SEAS...WITH 5 FT SEAS NOW REACHING THE NEAR-SHORE
WATERS. GALE WARNING CONTINUES FOR ALL WATERS. PREVIOUS DISCUSSION
FOLLOWS:

MARINE CONDITIONS WILL BECOME PERILOUS INTO EARLY SUNDAY AS N
WINDS RAPIDLY INTENSIFY AS A SURFACE LOW DEEPENS QUICKLY OFFSHORE
OF SC EARLY SUNDAY. GALE WARNINGS ARE POSTED FOR SUNDAY AND
ADVISORY CONDITIONS WILL CERTAINLY PRECEDE THE GALE STARTING
TONIGHT. MARINERS ARE DISCOURAGED FROM VENTURING OFFSHORE THE NEXT
36 HOURS AS CONDITIONS WILL TURN DANGEROUS. ALTHOUGH SUNDAY WILL
SEE THE WORSE OF CONDITIONS...WAVE HEIGHTS DAYBREAK SUNDAY WILL
REACH 4 TO 7 FEET AND GROWING...WITH DOMINANT WAVE PERIODS OF 5-6
SECONDS...MAKING FOR STEEP-FACED WAVE-SETS. WIND-DRIVEN RAIN LATE
TONIGHT AND EARLY SUNDAY WILL REDUCE VISIBILITIES TO 2NM OR LESS
AT TIMES.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 3 AM SUNDAY...SOUTHWEST FLOW WILL DROP UNDER 20 KT FOR A
PERIOD ON MON BUT APPROACH OF STRONG COLD FRONT LATE IN THE DAY
WILL PUSH WINDS BACK OVER 20 KT BY LATE AFTERNOON. PASSAGE OF COLD
FRONT MON NIGHT IS FOLLOWED BY DEVELOPMENT OF WESTERLY
FLOW...ENHANCED BY PINCHED GRADIENT AND STRONG COLD ADVECTION.
SPEEDS MON NIGHT WILL APPROACH 30 KT SUSTAINED WITH GUSTS OF 35 TO
40 KT. COLD ADVECTION CONTINUES TUE AND TUE NIGHT WITH WINDS
REMAINING IN THE 25 TO 30 KT RANGE THROUGH THE END OF THE PERIOD.
SEAS RANGING FROM 3 TO 6 FT MON MORNING START BUILDING IN THE
AFTERNOON...PEAKING BETWEEN 4 AND 8 FT MON NIGHT AND STAYING 4 TO
8 FT THROUGH THE END OF THE PERIOD.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 3 AM SUNDAY...STRONG WEST TO NORTHWEST FLOW CONTINUES ON
WED THEN STARTS TO WEAKEN THU AS COLD ADVECTION WEAKENS AND
GRADIENT RELAXES. OFFSHORE FLOW DURING THE FIRST HALF OF THE
PERIOD WILL BE AROUND 25 KT WITH GUSTS APPROACHING GALE FORCE.
ELONGATED SURFACE RIDGE STARTS BUILDING IN FROM THE WEST LATE WED
NIGHT AND THU. SPEEDS DROP UNDER 20 KT WED NIGHT AND UNDER 15 KT
BY THE END OF THU. ALTHOUGH FLOW WILL BE OFFSHORE ELEVATED WIND
SPEEDS WILL KEEP SEAS OVER 6 FT THROUGH WED NIGHT. GRADUAL
REDUCTION IN WIND SPEEDS LATE WED NIGHT AND THU ALLOWS SEAS TO
DROP TO 2 TO 4 FT THU AND THU NIGHT.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...FLOOD WATCH THROUGH THIS EVENING FOR SCZ053>056.
     WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR SCZ053>056.
NC...FLOOD WATCH THROUGH THIS EVENING FOR NCZ099-105>110.
     WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR NCZ105>110.
MARINE...STORM WARNING UNTIL 10 PM EST THIS EVENING FOR AMZ250-252-254-
     256.

&&

$$

NEAR TERM...MJC
SHORT TERM...III
LONG TERM...III
AVIATION...DCH



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