National Weather Service United States Department of Commerce

 


000
FXUS62 KILM 291441
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
930 AM EDT WED JUL 29 2015

.SYNOPSIS...
HIGH PRESSURE WILL SLOWLY WEAKEN THROUGH MID WEEK. A PIEDMONT
TROUGH WILL FORM THIS AFTERNOON AND LINGER ON THURSDAY AS WEAK
LOW PRESSURE REMAINS OFF THE SOUTHEAST COAST. A COLD FRONT WILL
MOVE INTO THE AREA FRIDAY AND STALL DURING THE WEEKEND BEFORE
DISSIPATING MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 930 AM WEDNESDAY... 12Z RAOBS SHOWED AN INVERSION AT AROUND
900MB THAT HAS RECENTLY BEEN OVERCOME DUE TO MIXING. DRY AIR ABOVE
THIS LAYER MEANS THAT CUMULUS CLOUDS WILL BE SLOW TO DEVELOP IN MOST
AREAS. MEANWHILE FAR WESTERN ZONES HAVE A MORE STRATOCU APPEARANCE
ON VIS SAT IMAGERY WHERE A BIT OF MOISTURE HAD RESIDED ABOVE THIS
INVERSION. HEATING WILL MAKE THESE CLOUDS TAKE ON A MORE CELLULAR
APPEARANCE AND THEY INDICATE THE ONLY REAL AREAS THAT HAVE ANY SHOT
AT PRECIPITATION. THE LATEST 12Z WRF KEEPS THIS ACTIVITY LARGELY TO
OUR WEST BUT FEEL THAT THE CLOUD LINE REPRESENTS WHERE 20 POPS ARE
WARRANTED. THIS IS VERY MUCH IN LINE WITH THE PREVIOUS FORECAST AND
NOT ANTICIPATING ANY CHANGES AT THIS TIME.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 3 AM WEDNESDAY...PRECIP CHANCES WILL BE ON THE INCREASE
DURING THE PERIOD AS 5H RIDGE BREAKS DOWN AND 5H TROUGH STARTS TO
SET UP. ILL DEFINED SURFACE PATTERN ON THU WILL ALLOW SEA BREEZE
AND PIEDMONT TROUGH CONVECTION BUT LACK OF SIGNIFICANT SURFACE OR
MID LEVEL TRIGGERS WILL KEEP COVERAGE LIMITED. PRECIP CHANCES
START TO INCREASE THU NIGHT AS WEAKENING COLD FRONT MOVES IN FROM
THE NORTHWEST. FRONT ARRIVES AS INSTABILITY IS WANING WHICH SHOULD
KEEP COVERAGE FOR THU NIGHT IN SLIGHT CHC RANGE AT MOST DESPITE
THE PRESENCE OF LOW LEVEL CONVERGENCE AND DEEP MOISTURE.

FRONT REMAINS IN THE AREA FRI...SERVING AS A FOCAL POINT FOR
CONVECTION. DIURNAL INSTABILITY WILL HAVE PLENTY OF DEEP MOISTURE TO
WORK WITH...PRECIPITABLE WATERS EXCEED 2 INCHES LATER IN THE DAY.
WEAKENING SUBSIDENCE AND INSTABILITY ALONG WITH WHAT APPEARS TO BE
SOME SLIGHT PVA FRI AFTERNOON INCREASES PRECIP CHANCES FRI INTO FRI
NIGHT. WILL CONTINUE WITH INHERITED LIKELY POP BUT WONDER IF MID
LEVEL RIDGING MIGHT HOLD ON A BIT LONGER THAN GUIDANCE IS
SUGGESTING. SHOULD THAT BE THE CASE LINGERING SUBSIDENCE COULD KEEP
CONVECTION IN CHECK...RESULTING IN SLIGHTLY LOWER POP THAN WHAT
IS CURRENTLY FORECAST FOR THE SECOND HALF OF THE PERIOD.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 3 AM WEDNESDAY...STALLED FRONT AND DEEP MOISTURE LINGERS OVER
THE AREA SAT KEEPING WEATHER UNSETTLED THROUGH THE WEEKS END. AT
THIS POINT UNCERTAINTY IN THE FORECAST REALLY STARTS TO INCREASE.
BOTH GFS AND ECMWF SHOW A 5H TROUGH DIGGING DOWN THE EAST COAST. MID
LEVEL TROUGH PUSHES THE DEEP MOISTURE OFF THE COAST FOR THE START OF
NEXT WEEK WITH THE REGION DRYING OUT. SURFACE PATTERN REMAINS ILL
DEFINED AND WHATS LEFT OF THE SURFACE BOUNDARY WILL LINGER IN THE
AREA. HOWEVER THE LACK OF DEEP MOISTURE KEEPS PRECIP CHANCES AT OR
BELOW THE TYPICAL SUMMERTIME AFTERNOON 30 POP TO START THE WEEK.

PREVIOUSLY GUIDANCE HAD BEEN SHOWING A STRONGER SHORTWAVE DROPPING
ACROSS THE AREA IN THE DEEP NORTHWEST FLOW TUE. WHILE THIS FEATURE
IS STILL DISCERNIBLE...JUST BARELY...IT IS IN A WEAKER STATE. AS
THESE SHORTWAVES ARE FREQUENTLY CONVECTIVELY INDUCED/INFLUENCED WILL
NOT GO ABOVE CLIMO POP FOR THE END OF THE PERIOD GIVEN THE
HEIGHTENED UNCERTAINTY. TEMPERATURES WILL BE NEAR TO SLIGHTLY ABOVE
CLIMO...GENERALLY NEAR CLIMO BY DAY AND SLIGHTLY ABOVE BY NIGHT.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 12Z...A COASTAL LOW AND TROUGH WILL KEEP CONVECTION OFFSHORE
TODAY. VERY LITTLE MOISTURE TO WORK WITH TODAY...ALTHOUGH LOW LEVEL
MOISTURE MAY PRODUCE A BRIEF MVFR CEILING THIS MORNING. ONSHORE FLOW
WILL KEEP THINGS FAIRLY PLEASANT TODAY...WITH SLIGHTLY BELOW NORMAL
TEMPERATURES ALONG THE COAST. LIGHT WINDS THIS EVENING WITH LIGHT
FOG POSSIBLE TOWARD DAYBREAK.

EXTENDED OUTLOOK...PREDOMINANTLY VFR THROUGH THE PERIOD WITH A
SLIGHT CHANCE AFTERNOON SHRA/TSRA. BEST CHANCE SHRA/TSRA FRIDAY AND
SATURDAY.

&&

.MARINE...

NEAR TERM /THROUGH TONIGHT/...

AS OF 930 AM WEDNESDAY...ONSHORE FLOW QUASI-STEADY TODAY. NOT
EXPECTING ANY CHANGES TO THE FORECAST. THE PREVIOUS DISCUSSION
FOLLOWS.

AS OF 538 AM WEDNESDAY...E WIND 10-15 KT TO PREVAIL TODAY AND
TONIGHT...ACCOMPANIED BY 3-3.5 FOOT SEAS. OCCASIONAL GUSTS TO 20
KT OUGHT TO BE ANTICIPATED...ESPECIALLY IN THE AFTERNOON
NEARSHORE. SEAS PRIMARILY A MIX OF SE WAVES 2-3 FT EVERY 6 SECONDS
AND MODERATE EASTERLY CHOP. SHOWERS AND TSTMS ARE EXPECTED TO
REMAIN WELL BEYOND THE 0-20 NM WATERS TODAY AND NO RESTRICTIONS TO
VISIBILITY ARE EXPECTED.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 3 AM WEDNESDAY...ILL-DEFINED GRADIENT AND WEAK SURFACE WAVE
PASSING EAST OF THE WATERS THU WILL INDUCE LIGHT NORTH TO
NORTHEAST FLOW INTO THU NIGHT. WAVE MOVES OFF TO THE NORTHEAST THU
NIGHT INTO FRI AS WEAK SURFACE FRONT DROPS IN FROM THE NORTHWEST.
LIGHT AND VARIABLE WINDS THU NIGHT GAIN A SOUTHWEST COMPONENT FRI
AND FRI NIGHT BUT LACK OF ANY REAL GRADIENT KEEPS SPEEDS AROUND 10
KT THROUGH THE END OF THE PERIOD. SEAS 2 TO 3 FT THROUGH THE
PERIOD.


LONG TERM /SATURDAY THROUGH SUNDAY/...
AS OF 3 AM WEDNESDAY...SOUTHWEST FLOW WILL CONTINUE OVER THE
WATERS THROUGH THE WEEKEND. THE REMAINS OF A STALLED FRONT WILL
LINGER NEAR THE COAST AS BERMUDA HIGH TRIES TO BUILD BACK WEST.
GRADIENT WILL REMAIN ON THE WEAK SIDE WITH SPEEDS NO MORE THAN 10
TO 15 KT AT ANY POINT DURING THE PERIOD. DAILY SEA BREEZE WILL
RESULT IN ENHANCED ONSHORE FLOW NEAR THE COAST BOTH DAYS. SEAS
WILL RUN 2 TO 3 FT ON SAT AND 2 TO 4 FT SUN.

&&

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

&&

$$

NEAR TERM...MBB
SHORT TERM...III
LONG TERM...III
AVIATION...43