000
FXUS62 KILM 230527
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
127 AM EDT THU MAY 23 2013
.SYNOPSIS...
SHOWERS AND THUNDERSTORMS WILL INCREASE AHEAD OF AN APPROACHING
COLD FRONT. THE FRONT WILL CROSS THE REGION EARLY FRIDAY MORNING.
CANADIAN HIGH PRESSURE WILL BRING COOLER AND DRIER CONDITIONS OVER
THE WEEKEND. THE HIGH WILL MOVE OFF THE COAST EARLY NEXT WEEK AND
WILL ALLOW TEMPERATURES TO WARM TO NORMAL READINGS FOR LATE MAY.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
AS OF 10 PM WEDNESDAY...CONVECTION IS EXPECTED TO DEVELOP/EXPAND
ACROSS THE WATERS AS A WEAK MID-LEVEL IMPULSE MOVES UP THE CAROLINA
COAST...PASSING E OF THE AREA OVERNIGHT AND EARLY THU MORNING.
SEVERAL OF THE MODELS ARE PORTRAYING THIS SCENARIO AND BASED ON
RECENT NIGHTS...THERE IS A GOOD LEVEL OF CONFIDENCE THAT THE
CONVECTION WILL AFFECT THE CAPE FEAR REGION...ESPECIALLY VERY CLOSE
TO THE COAST...WITH THE GREATEST COVERAGE ACROSS THE WATERS.
THEREFORE...WILL SHOW A SIGNIFICANT GRADIENT AT THE COAST...WITH
POPS AS HIGH AS 80 PERCENT.
CONVECTION WELL W OF THE AREA...AND ASSOCIATED MORE CLOSELY WITH THE
UPSTREAM TROUGH AND MID-LEVEL SHORTWAVE...IS STILL GOING STRONG LATE
THIS EVE...BUT IS EXPECTED TO VERY SLOWLY WIND DOWN AS THE
ENVIRONMENT BEGINS TO STABILIZE WITH LOSS OF HEATING. WILL OPT TO
KEEP POPS BELOW THRESHOLD FOR OUR MOST INLAND AREAS OVERNIGHT...BUT
WILL CONTINUE TO EYE TRENDS FOR ANY ADJUSTMENTS THAT MAY BE
NECESSARY SHOULD THE SHOWERS AND THUNDERSTORMS TO OUR W ADVANCE
FURTHER E THAN CURRENTLY EXPECTED.
PRECIPITABLE WATER VALUES ACTUALLY CLIMB TO ALMOST 2 INCHES
ALONG/NEAR THE COAST OVERNIGHT AND WILL INCLUDE MENTION OF HEAVY
RAIN IN ISOLATED THUNDERSTORMS. WELL INLAND...WET GROUND MAY AGAIN
BE CONDUCIVE FOR MAINLY PATCHY FOG AND HAVE INTRODUCED FOG...
ESPECIALLY TOWARD MORNING.
THE AIRMASS WILL NOT APPRECIABLY CHANGE UNTIL A COLD FRONT MOVES
THROUGH LATE THU NIGHT AND FRI MORNING. THUS...MINIMUM TEMPS WILL BE
RATHER SIMILAR TO THE PAST SEVERAL NIGHTS. GIVEN DEWPOINTS HAVE
CREPT HIGHER...WILL GO WITH MAINLY UPPER 60S TO AROUND 70 DEGREES...
HIGHEST ALONG THE COAST.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
AS OF 3 PM WEDNESDAY...PERIOD WILL BE MARKED BY 2 DISTINCT AIR
MASSES. TROPICAL AIR MASS IN PLACE THU WILL SUPPORT PLENTY OF
SHOWERS AND THUNDERSTORMS AHEAD OF APPROACHING COLD FRONT. DEEP
SOUTH TO SOUTHWEST FLOW WILL SUPPLY ABUNDANT MOISTURE TO THE REGION
WITH PRECIPITABLE WATER VALUES IN THE 1.6 TO 1.8 INCH RANGE. VERY
LITTLE IN THE WAY OF FACTORS LIMITING UPWARD MOTION FOR THU SO
DIURNAL HEATING SHOULD PRODUCE STORMS IN THE MORNING. SEABREEZE AND
PREFRONTAL TROUGH...AS WELL AS OUTFLOW FROM ONGOING STORMS...WILL
HELP ENHANCE CONVECTION AND EXPAND COVERAGE. HOWEVER BEHIND THE
PREFRONTAL TROUGH WESTERLY MID AND UPPER LEVEL FLOW WILL CUTOFF DEEP
MOISTURE FEED WHICH MAY LEAD TO A REDUCTION IN STRENGTH AND COVERAGE
OF CONVECTION DURING MID TO LATE AFTERNOON HOURS. HIGHS WILL BE NEAR
TO SLIGHTLY ABOVE CLIMO.
COLD FRONT ARRIVES IN THE AREA THU NIGHT...PUSHED INTO AND ACROSS
THE AREA BY LONGWAVE 5H TROUGH. ALTHOUGH FORECAST SOUNDINGS SHOW
COLUMN DRYING AHEAD OF THE FRONT...PWATS DROP BY ALMOST HALF AN
INCH...STRONG CONVERGENCE ALONG THE FRONT SHOULD LEAD TO A SECOND
ROUND OF SHOWERS AND THUNDERSTORMS THU EVENING/NIGHT. DO NOT THINK
SEVERE WEATHER WILL BE A CONCERN ON THU. MID LEVEL LAPSE RATES ARE
WEAK AND THE WARM LAYER IS DEEP/MOIST HOWEVER FLOODING COULD BE A
CONCERN. BEHIND THE PREFRONTAL TROUGH THINGS COULD BE A DIFFERENT.
MID LEVEL DRYING AND SOME COOLING...STEEPENING LAPSE RATES...MAY
INCREASE HAIL AND STRONG WIND POTENTIAL. LATE TIMING OF FROPA WILL
LIMIT LOW LEVEL INSTABILITY AND WHILE THERE WILL BE SOME DIVERGENCE
ALOFT AHEAD OF THE TROUGH AXIS IT IS NOT PARTICULARLY STRONG. COLD
ADVECTION ARRIVES LATE SO FOR MOST AREAS TEMPERATURES THU NIGHT WILL
CONTINUE TO RUN ABOVE CLIMO.
MUCH DRIER/COOLER AIR ARRIVES FRI AS CANADIAN HIGH BUILDS IN FROM
THE NORTHWEST. 5H TROUGH AXIS MOVES IN FRI AFTERNOON WITH COLD POOL
ALOFT OVERHEAD DURING MAX HEATING. SOME WEAK ENHANCEMENT FROM
SHORTWAVE ROTATING AROUND BASE OF TROUGH IS EXPECTED BUT FORECAST
SOUNDINGS SHOW A SIGNIFICANT AREA OF SUBSIDENCE AROUND 700 MB AND
VERY DRY AIR ABOVE 10K FT. CANNOT RULE OUT AN ISOLATED LOW TOPPED
SHOWER BUT THINK COVERAGE OF PRECIP WILL BE LOW THOUGH PLENTY OF
FLAT CU IS LIKELY. HAVE TRIMMED BACK INHERITED POP BASED ON DEEP DRY
AIR AND/INVERSION...A CHANGE SUPPORTED BY LATEST MOS NUMBERS.
LOTS OF ERROR POTENTIAL FOR FRI WITH RESPECT TO TEMPS. COLD
ADVECTION WILL BE SOMEWHAT OFFSET BY DOWNSLOPE COMPONENT AND HIGH
SUN ANGLE...THOUGH INCREASING CLOUD COVER WILL LIMIT INSOLATION.
ACROSS COASTAL SC HIGHS MAY STILL END UP ABOVE CLIMO BUT REMAINDER
OF THE AREA WILL BE NEAR TO SLIGHTLY BELOW CLIMO. COLD ADVECTION
DECREASES FRI NIGHT THOUGH CLEARING SKIES AND DEEP DRY AIR MAY ALLOW
FOR SOME RADIATIONAL COOLING. LOWS END UP BELOW CLIMO WITH UPPER 40S
TO LOW 50S POSSIBLE.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 3 PM WEDNESDAY...CANADIAN HIGH PRESSURE WILL BUILD DOWN
INTO THE COASTAL CAROLINAS OVER THE WEEKEND. LOCAL AREA WILL
REMAIN IN COOLER AND DRIER NORTHERLY FLOW ON FRONT END OF SYSTEM
THROUGH SATURDAY INTO SUNDAY. THE CENTER DRIFTS CLOSER OVERHEAD
SUNDAY AND THEN SHIFTS OFF SHORE ON MONDAY. THE HIGH WILL SHIFT
FURTHER OFF SHORE KEEPING A WARMER AND MOISTER RETURN FLOW OVER
THE AREA THROUGH MID WEEK NEXT WEEK.
ABOVE THE SURFACE...A DEEP NW FLOW WILL CONTINUE ON THE BACK END OF
THE MID TO UPPER TROUGH SLOWLY EXITING OFF TO THE NORTHEAST THROUGH
TUES AS RIDGE BUILDS UP THE CENTRAL STATES AND SHIFTS SLOWLY EAST.
OVERALL A DEEP COOLER AND DRIER FLOW WILL PREVAIL THROUGH EARLY NEXT
WEEK. SOME UPPER LEVEL MOISTURE WILL SPILL OVER THE RIDGE EARLY TO
MID WEEK NEXT WEEK AS RIDGE MOVES EAST AND BUILDS UP THE EASTERN SEA
BOARD BY WEDNESDAY. THEREFORE MAY SEE SOME HIGH CLOUDS STREAMING
ACROSS THE COASTAL CAROLINAS...BUT OVERALL PLENTY OF SUNSHINE
THROUGH THE LONG TERM PERIOD.
ESSENTIALLY A COOLER START WITH UNSEASONABLY COOLER TEMPS OVER THE
WEEKEND BUT PLENTY OF WARM MAY SUNSHINE TO BRING TEMPS INTO THE MID
TO UPPER 70S. CAN ALSO EXPECT LARGER DIURNAL SWINGS WITH PLENTY OF
DRY AIR IN PLACE AND COOL START TO THE DAYS UP THROUGH MONDAY...WITH
OVERNIGHT LOWS DOWN CLOSER TO 50 TO 55 DEGREES. AS RETURN FLOW SETS
UP MON THROUGH WED WARMER AND MOISTER CONDITIONS WILL RETURN WITH
TEMPS REACHING BACK INTO THE LOW TO MID 80S DURING THE DAY AND
CLOSER TO 60 OVERNIGHT ON TUES AND WED. WILL ALSO SEE CU BUILDUP IN
THE AFTERNOON SEA BREEZE AND A CHC OF CONVECTION BACK IN THE
FORECAST BY MON AFTN.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 06Z...PERIODS OF MVFR/POSSIBLE IFR OVERNIGHT AND INTO THE
MORNING HOURS DUE TO LOWERED CIGS/AREAS OF FOG/LOWERED VSBYS AS WELL
AS SCATTERED CONVECTION ALONG THE COAST. VFR WILL PREVAIL BY LATE
MORNING WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ON
THURSDAY...WITH REDUCED RESTRICTIONS POSSIBLE IN HEAVIER DOWNPOURS.
VFR WITH AREAS OF MVFR WITH VCSH ARE ON TAP TONIGHT WITH SOUTH WINDS
AOB 10 KTS. EXPECT MVFR/POSSIBLE IFR TO DEVELOP AS GUIDANCE IS IN
GOOD AGREEMENT WITH REDEVELOPMENT OF SHOWERS ALONG THE COAST GIVEN
AN EXTREMELY SATURATED ATMOSPHERIC PROFILE. CANNOT RULE OUT ISOLATED
THUNDERSTORMS THROUGH THE ENTIRE PERIOD BUT HAVE OPTED TO NOT
INCLUDE ATTM GIVEN LOWERED CONFIDENCE. AFTER DAYBREAK...CIGS WILL
GRADUALLY LIFT ALLOWING FOR RESTRICTIONS TO RETURN TO VFR STATUS.
EXPECT SCT/BKN CLOUDS WITH SHOWERS AND ISOLATED THUNDERSTORMS.
SOUTHERLY WINDS WILL CONTINUE WITH SUSTAINED SPEEDS AOB 12 KTS AND
GUSTS UP TO 20 KTS. INTO THE EVENING HOURS ON THURSDAY...ANY
LINGERING CONVECTION WILL TAPER OFF AND WINDS WILL BECOME LIGHT.
EXTENDED OUTLOOK...SHOWERS AND THUNDERSTORMS POSSIBLE THURSDAY
THROUGH EARLY FRIDAY. OTHERWISE VFR.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 10 PM WEDNESDAY...BERMUDA HIGH PRESSURE WILL REMAIN ANCHORED
OVER THE WESTERN ATLANTIC. A WEAK MID-LEVEL IMPULSE WILL MOVE UP THE
CAROLINA COAST...ACROSS THE OFFSHORE WATERS. SHOWERS AND ISOLATED
THUNDERSTORMS LATE TONIGHT AND THU MORNING WILL RESULT IN REDUCED
VISIBILITIES IN HEAVY RAIN. WINDS WILL BE FROM THE S AT 10 TO 15 KT.
A WEAK 7 TO 8 SECOND SE SWELL WILL PERSIST. SEAS WILL RANGE FROM 2
TO 4 FT...BUT LOCALLY HIGHER IN AND NEAR THE MORE ROBUST CONVECTION.
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 3 PM WEDNESDAY...SOUTHERLY FLOW ACROSS THE WATERS THU INTO THU
NIGHT WILL INCREASE TO 15 TO 20 KT BY AFTERNOON AS COLD FRONT
APPROACHES FROM THE WEST. INCREASE IN SPEEDS COMBINED WITH PROLONGED
SOUTHERLY FLOW WILL GENERATE LARGER WIND WAVE ON TOP OF SOUTHERLY
SWELL...BUILDING SEAS TO 3 TO 5 FT BEFORE COLD FRONT PASSES EARLY
FRI MORNING. FOR THU/THU NIGHT IT DOES NOT SEEM LIKE A SCA HEADLINE
WILL BE NEEDED BUT A SCEC MAY BE IN THE CARDS. OFFSHORE FLOW
DEVELOPS BEHIND THE FRONT FOR FRI WITH COMBINATION OF COLD ADVECTION
AND GRADIENT PUSHING WIND SPEEDS TO A SOLID 20 KT AT TIMES. OFFSHORE
WIND COMPONENT WILL LIKELY KEEP SEAS WITHIN 20 NM UNDER 6 FT BUT
WILL CREATE TREACHEROUS CONDITIONS WITH A VERY SHORT PERIOD WEST TO
NORTHWEST WIND WAVE ON TOP OF A LONG PERIOD SOUTHEAST SWELL. WINDS
DECREASE TO A SOLID 15 KT FRI NIGHT AS THEY VEER TO NORTHERLY.
LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 3 PM WEDNESDAY...AS COOL CANADIAN HIGH PRESSURE BUILDS IN
EARLY SATURDAY THE WINDS WILL BE UP TO 15 TO 20 KTS EARLY IN COOL
SURGE AND TIGHTENED GRADIENT. WINDS WILL LIGHTEN AS HIGH PRESSURE
SHIFTS CLOSER OVERHEAD LATE SATURDAY THROUGH SUNDAY. THEREFORE
EXPECT WINDS AROUND 15 KTS OUT OF THE NORTH LATE SATURDAY THROUGH
EARLY SUNDAY AND THEN WEAKENING FURTHER TO 10 KTS OR LESS THROUGH
SUNDAY.
SEAS WILL BE ENTIRELY WIND-WAVE DOMINATED BETWEEN 3 AND 5 FT THROUGH
EARLY SATURDAY. BY LATE SATURDAY INTO SUNDAY...THE SEAS WILL SUBSIDE
AND WINDS LIGHTEN AS HIGH SHIFTS CLOSER OVERHEAD. EXPECT SEAS DOWN
TO 3 FT OR LESS BY SAT NIGHT INTO SUNDAY AND SLIGHTLY LOWER SUN
NIGHT INTO MONDAY IN LIGHT WINDS. BY MONDAY THE WINDS WILL COME
AROUND AS A LIGHT RETURN FLOW SETS UP AS HIGH PRESSURE BEGINS TO
SHIFT OFF SHORE. BASICALLY W TO SW FLOW THROUGH MONDAY BECOMING MORE
SOUTHERLY BY TUESDAY REMAINING 10 KTS OR LESS.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
NEAR TERM...RJD/8
SHORT TERM...III
LONG TERM...RGZ
AVIATION...SGL/8
