Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 191041
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
640 AM EDT SUN APR 19 2015

.SYNOPSIS...
AN APPROACHING FRONTAL SYSTEM WILL BRING SHOWERS AND SCATTERED
THUNDERSTORMS TODAY THROUGH MONDAY. A FEW OF THESE STORMS COULD
BE STRONG TO SEVERE TODAY AND MONDAY. DRY AND SEASONABLE HIGH
PRESSURE WILL BUILD INTO THE AREA TUESDAY AND WEDNESDAY. WARMER
TEMPERATURES ARE EXPECTED THURSDAY AHEAD OF THE NEXT COLD FRONT.
MUCH COOLER TEMPERATURES ARE POSSIBLE LATE WEEK AND INTO NEXT
WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 645 AM SUNDAY...SURFACE LOW PRESSURE OVER THE MID-MISSISSIPPI
VALLEY WILL DEEPEN AND MOVE NORTH TODAY. THIS IS IN RESPONSE TO AN
INCOMING STRONG UPPER DISTURBANCE IN THE CENTRAL PLAINS STATES
INTERSECTING A REGION OF LOW-LEVEL BAROCLINICITY. ACROSS THE
CAROLINAS THE LOW-LEVEL FLOW WILL BE VEERING TODAY IN RESPONSE TO
THE DEEPENING LOW...WITH A DIFFUSE WARM FRONT EXPECTED TO TRANSIT
THE REGION FROM SOUTH TO NORTH THIS AFTERNOON. DEEP MOISTURE WILL BE
INCREASING RAPIDLY THROUGH THE DAY AND BY THIS EVENING THE 00Z GFS
SHOWS PRECIPITABLE WATER IN EXCESS OF 1.8 INCHES ALONG THE COAST...A
VALUE TYPICAL OF A SUMMERTIME TROPICAL AIRMASS.

A SERIES OF WEAK UPPER DISTURBANCES WILL MOVE OVERHEAD FROM
SOUTHWEST TO NORTHEAST TODAY. THE FIRST OF THESE DISTURBANCES SHOULD
ARRIVE ACROSS THE CENTRAL CAROLINAS BY MID TO LATE MORNING...
SPREADING A ZONE OF RAIN WITH EMBEDDED ELEVATED CONVECTIVE ELEMENTS
ACROSS THE AREA. AS THE WARM FRONT ARRIVES DURING THE AFTERNOON
MUCAPE VALUES WILL INCREASE TO OVER 1000 J/KG ACROSS SOUTH
CAROLINA...WITH 500-750 J/KG EXPECTED ACROSS NORTH CAROLINA. ALONG
AND SOUTH OF A LINE FROM DARLINGTON TO FLORENCE TO CONWAY THIS
INSTABILITY SHOULD BECOME SURFACE-BASED. BULK SHEAR COMPUTED ACROSS
THE 0-6KM LAYER SHOULD REACH 25-30 KT...WITH 0-1 KM HELICITY
REACHING 100-150 M^2/S^2. NONE OF THESE VALUES REACH CRITICAL
THRESHOLD VALUES FOR SIGNIFICANT SEVERE WEATHER...HOWEVER THE ODDS
OF SEVERE WEATHER ARE PROBABLY NON-ZERO TODAY. IF ANY SEVERE STORMS
WERE TO OCCUR THE TIME OF CONCERN WOULD BE THIS AFTERNOON UNTIL
AROUND SUNSET...WITH WIND DAMAGE OR A BRIEF SPIN-UP TORNADO POSSIBLE.

HEAVY RAINFALL MAY END UP BEING THE BIGGER THREAT. WITH SUCH HIGH
PRECIPITABLE WATER VALUES AND A SECOND UPPER DISTURBANCE MOVING
OVERHEAD DURING THE EARLY EVENING...A QUICK 0.5 TO 1.0 INCH OF RAIN
CANNOT BE RULED OUT. BEHIND THE LAST DISTURBANCE THE FORCING FOR
RAIN OR CONVECTION ENDS...AND I HAVE SHOWN A DIMINISHING TREND IN
POPS FROM MIDNIGHT THROUGH DAYBREAK MONDAY MORNING.

HIGHS TODAY SHOULD REACH THE MID 70S EXCEPT ~5 DEGREES COOLER AT THE
BEACHES. LOWS TONIGHT SHOULD ONLY FALL INTO THE MID TO UPPER 60S
WITH MILD SOUTHWEST BREEZES CONTINUING.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...INTERESTING START TO THE WORK WEEK AS A
SHORTWAVE EMBEDDED WITHIN A DEEPENING TROUGH WILL CREATE THE
POTENTIAL FOR STRONG THUNDERSTORMS ON MONDAY.

WARM FRONT WILL BE WELL NORTH OF THE AREA MONDAY MORNING...AND MOST
OF THE HEAVY RAINFALL ANTICIPATED SUNDAY NIGHT WILL BE
NORTH/OFFSHORE BY THE BEGINNING OF THE PERIOD. SOME RESIDUAL SHOWERS
MAY PERSIST ON THE COAST EARLY...BUT ACTUALLY EXPECT THE MORNING
HOURS TO BE DRY FOR THE MOST PART LOCALLY. THE COLUMN WILL DRY
CONSIDERABLY FROM SUNDAY AS THE BEST MOISTURE DEPARTS TO THE
NE...AND SOME SUBSIDENCE IS EXPECTED BEHIND AN EXITING SHORTWAVE.
THIS WILL LEAVE AT LEAST PARTIAL INSOLATION...AND AS WARM/MOIST
ADVECTION CONTINUES THE ATMOSPHERE WILL BECOME QUITE UNSTABLE MONDAY
AFTN/EVE. FORECAST MLCAPE VALUES RISE TOWARDS 2000 J/KG...WITH THE
SREF MEAN AROUND 1500 J/KG. AT THE SAME TIME...A SHORTWAVE WILL RIDE
THROUGH THE DEEPENING TROUGH SO PVA COMBINED WITH HEIGHT FALLS
/STEEPENING MID-LEVEL LAPSE RATES/ WILL DRIVE AN ENVIRONMENT
CONDUCIVE TO STRONG CONVECTION. ADDITIONALLY...LFQ OF A SUBTROPICAL
250MB JET WILL APPROACH FROM THE SW. HOWEVER...SURFACE FORCING IS
MOSTLY WEAK AND THE MID-LEVELS REMAIN QUITE DRY DURING THE MOST
UNSTABLE PART OF THE DAY. THIS SUGGESTS THAT ACTIVITY WILL BE
ISOLATED OR SCATTERED MONDAY AFTN/EVE...BUT ANY STORM WILL HAVE
THE POTENTIAL TO BECOME STRONG AND SPC HAS THE AREA IN A SLIGHT
RISK FOR MONDAY. DO NOT EXPECT WIDESPREAD STRONG/SEVERE
STORMS...AND ATTM THE BEST FOCUS MAY BE ALONG THE PIEDMONT TROUGH
AND WESTERN PORTIONS OF THE CWA.

COLD FRONT WILL APPROACH SLOWLY FROM THE NW DRIVEN BY THE DEEPENING
UPPER TROUGH...AND IS NOW SLATED FOR A CROSSING JUST BEFORE DAWN
TUESDAY. THIS FRONT WILL BE ACCOMPANIED BY MORE WIDESPREAD SHOWER
ACTIVITY...BUT NOT EXPECTING STRONG CONVECTION WITH ITS PASSAGE.
COLD ADVECTION LAGS THE FRONT CONSIDERABLY...SO WHILE TUESDAY WILL
BE DRY WITH MUCH MORE SUNSHINE AS HIGH PRESSURE BUILDS ACROSS THE
REGION...TEMPS WILL NOT BE SIGNIFICANTLY COOLER THAN MONDAY.

ON THE DISCUSSION OF TEMPERATURES...MONDAY WILL LIKELY BE WELL ABOVE
NORMAL WITH WIDESPREAD 80S AWAY FROM THE BEACHES ON STRONG WARM
ADVECTION AHEAD OF THE FRONT. A RELATIVELY WARM NIGHT EXPECTED
MONDAY NIGHT AS FROPA OCCURS LATE...AND LOWS WILL DROP ONLY INTO THE
LOW 60S. SLIGHTLY COOLER TUESDAY WITH HIGHS REACHING WELL INTO THE
70S TO NEAR 80...BEFORE COOL DRY HIGH PRESSURE ALLOWS FOR TEMPS TO
CRASH TO AROUND 50 TUESDAY NIGHT.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...MID-LEVELS EVOLVE INTO A DECIDEDLY WINTER-LIKE
APPEARANCE THROUGH THE EXTENDED WITH A LARGE VORTEX CUTOFF ACROSS
SOUTHEAST CANADA WHICH WILL SLOWLY DROP ACROSS NEW ENGLAND BY THE
WKND. INITIALLY THIS PRODUCES BENIGN AND SEASONABLE WEATHER ACROSS
THE CAROLINAS...AS THE FLOW BECOMES ZONAL BENEATH THE CUTOFF...SO
SURFACE HIGH PRESSURE WILL BECOME THE DOMINANT FEATURE WED/THU. THIS
HIGH WILL MOVE OFFSHORE THURSDAY AHEAD OF THE NEXT COLD
FRONT...DRIVEN BY A PIECE OF VORT ENERGY ROTATING AROUND THE LARGE
MID-LEVEL VORTEX. MID-LEVEL FLOW REMAINS W/NW HOWEVER...SO ALTHOUGH
PRECIP CHANCES INCREASE WITH THE COLD FRONT...SIGNIFICANT SHOWER
ACTIVITY IS NOT ANTICIPATED. THE BIGGER STORY COULD BE MUCH COOLER
TEMPS BEHIND THIS FRONT FRI/SAT THANKS TO 1000-500MB THICKNESSES
DROPPING TOWARDS -2 SD`S FROM CLIMO...AND HIGHS/LOWS BY SATURDAY
COULD FALL WELL BELOW NORMAL. A LOW PRESSURE SYSTEM MAY BEGIN TO
EMERGE FROM THE GULF COAST STATES AND MOVE TOWARDS THE AREA AT THE
END OF THE PERIOD...AND WILL MAINTAIN INHERITED LOW-CHC POP FOR
SATURDAY.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
AS OF 12Z...A WARM FRONT WILL WAVE NORTH TODAY...WITH GOOD
ISENTROPIC LIFT WITH DEEP MOISTURE SPREADING INTO THE AREA BY
MIDDAY. EXPECT MODERATE TO HEAVY SHOWERS TO INUNDATE THE REGION BY
16Z...WITH INTERMITTENT IFR CONDITIONS IN THE HEAVIER CONVECTION. A
RUMBLE OF THUNDER IS POSSIBLE...BUT LEFT OUT A MENTION AT THIS TIME.
CEILINGS WILL LIKELY LOWER TO IFR FOR THE DURATION OF THE TAF TIME
AFTER 00Z. WINDS WILL BE EAST NORTHEAST INITIALLY...SHIFT TO THE
SOUTHEAST THEN SOUTH LATER THIS AFTERNOON...GUSTY AT TIMES.

EXTENDED OUTLOOK...MVFR/IFR POSSIBLE INTO MONDAY WITH SHOWERS AND
ISOLATED THUNDERSTORMS. A COLD FRONT WILL PUSH THROUGH THE AREA
MONDAY NIGHT WITH SHOWERS POSSIBLE FOLLOWED BY MAINLY VFR CONDITIONS
TUESDAY. POSSIBLE SHOWERS RETURNING LATER IN THE WEEK.

&&

.MARINE... NEAR TERM /THROUGH TONIGHT/...
AS OF 645 AM SUNDAY...LOW PRESSURE OVER THE MID-MISSISSIPPI VALLEY
WILL DEEPEN TODAY. THE INCREASING SOUTHERLY WIND AHEAD OF THIS
SYSTEM WILL DRAG A WARM FRONT THROUGH THE COASTAL CAROLINAS THIS
AFTERNOON. GENERALLY EASTERLY WINDS THIS MORNING WILL VEER
SOUTHEASTERLY THIS AFTERNOON...THEN SOUTHERLY TONIGHT. WINDS WILL
INCREASE BUT NOT EXCESSIVELY SO GIVEN THE PRETTY LARGE DISTANCE FROM
HERE BACK TO THE LOW...AND ALSO THE FACT THAT THE INCOMING AIRMASS
WILL BE SIGNIFICANTLY WARMER THAN THE OCEAN SURFACE LEADING TO MOST
OF THE WIND ENERGY RIDING UP AND OVER A COOL AND STABLE LAYER OF AIR
AT THE SURFACE.

WIDESPREAD SHOWERS AND EMBEDDED T-STORMS SHOULD AFFECT THE COASTAL
WATERS THIS AFTERNOON AND TONIGHT. REDUCED VISIBILITY IN HEAVY
RAINFALL AND ALSO OCCASIONAL LIGHTNING STRIKES WILL BE THE MOST
SIGNIFICANT IMPACTS. SEAS WILL GRADUALLY BUILD DUE TO THE ONSHORE
FLOW...WITH THE WORST CONDITIONS EXPECTED NORTH OF CAPE FEAR. THERE
IS A 4-6 HOUR WINDOW LATE THIS EVENING INTO EARLY MONDAY MORNING
WHERE A SMALL CRAFT ADVISORY MAY BE NEEDED NORTH OF CAPE FEAR DUE TO
6 FOOT SEAS...BUT GIVEN SOME REMAINING UNCERTAINTY ABOUT HOW LONG
SOUTHERLY WINDS BLOW BEFORE VEERING SOUTHWESTERLY AND WEAKENING...I
WILL DELAY RAISING THE ADVISORY JUST YET.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...COLD FRONT APPROACHING FROM THE WEST WILL
PINCH THE GRADIENT MONDAY...AND GUSTY SW WINDS WILL REACH 15-20
KTS WITH SLIGHTLY HIGHER GUSTS. THIS WILL PERSIST ALL OF MONDAY
SINCE THE COLD FRONT IS NOT EXPECTED TO CROSS OFFSHORE UNTIL FIRST
LIGHT TUESDAY...AND THUS A CHOPPY SEA STATE IS EXPECTED. WAVE
HEIGHTS WILL RISE TO 4-5 FT...AND A SCEC MAY BE NEEDED MUCH OF
MONDAY. WINDS WILL SHIFT QUICKLY TO THE W AND THEN NW BEHIND THE
FRONT TUESDAY MORNING...AND THEN SLOWLY DECREASE IN SPEED FROM
10-15 KTS...TO AROUND 5 KTS AS HIGH PRESSURE BUILDS TOWARDS THE
AREA REDUCING THE PRESSURE GRADIENT. SEAS WILL FALL INITIALLY ON
THE OFFSHORE WIND TO 2-4 FT...BEFORE DROPPING FURTHER TO 1-2 FT
TUESDAY NIGHT.

LONG TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 300 AM SUNDAY...BROAD HIGH PRESSURE WILL SKIRT ACROSS THE
WATERS AND OFFSHORE WEDNESDAY...SO LIGHT AND VARIABLE WINDS WILL
GRADUALLY TRANSITION TO A SW DIRECTION WEDNESDAY NIGHT AS RETURN
FLOW DEVELOPS. THIS SW FLOW WILL PERSIST MOST OF THURSDAY BUT WITH
SPEEDS INCREASING TO 10-15 KTS AHEAD OF A COLD FRONT WHICH WILL
CROSS THE WATERS AT THE END OF THE PERIOD. WAVE HEIGHTS OF 1-2 FT
WILL BUILD SLOWLY ONCE THE WIND BECOMES PREDOMINANTLY FROM THE SW
LATE WEDNESDAY...AND THEN CONTINUE TO SLOWLY RISE THURSDAY TO 3-4
FT BEFORE THE COLD FRONTAL PASSAGE.

&&

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

&&

$$

SYNOPSIS...JDW
NEAR TERM...TRA
SHORT TERM...JDW
LONG TERM...JDW
AVIATION...43
MARINE...TRA/JDW


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