Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KPHI 021318
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
918 AM EDT SAT MAY 2 2015

.SYNOPSIS...
LOW PRESSURE OFF THE NORTH CAROLINA COAST WILL MOVE FARTHER OUT TO
SEA TODAY. AN EXPANSIVE AREA OF HIGH PRESSURE WILL REMAIN IN CONTROL
OF THE EASTERN THIRD OF THE COUNTRY THIS WEEKEND. THE CENTER OF THE
HIGH WILL SHIFT OFFSHORE SUNDAY NIGHT AND MONDAY. A COLD FRONT WILL
APPROACH FROM THE NORTHWEST MONDAY NIGHT. THIS FRONT IS EXPECTED TO
WEAKEN AND STALL OVER THE AREA TUESDAY INTO WEDNESDAY. HIGH PRESSURE
BUILDS BACK INTO THE AREA LATE IN THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
MORNING CLOUDS HAVE PRETTY MUCH DISSIPATED ACROSS OUR CWA. MORNING
SOUNDINGS DO SHOW CONVECTIVE TEMPS BEING REACHED. MODELING STILL
SHOWING A LEE SIDE TROF DEVELOPING THIS AFTERNOON, BUT LAST FEW
RAP AND HRRR NOT THAT ENTHUSED ABOUT SHOWERS. WE SCALED BACK
COVERAGE, TIMING AND AMOUNTS. GIVEN YESTERDAY`S RESULTS WERE LESS
THAN EXPECTED, IF MESOSCALE MODELING TREND CONTINUES, WE MAY DO
FURTHER SCALING BACK WITH NEXT UPDATE. 12Z SOUNDINGS SHOWING MAX
TEMPS IN THE 60S FOR TODAY. GIVEN CONTINUED AIR MASS MODIFICATION
AND CONVECTIVE TEMPS IN THE 60S, WE SHOULD GET TO CURRENT HIGH
TEMPS AND NO CHANGES WERE MADE.

HIGH PRESSURE WILL SLOWLY BUILD INTO THE REGION FROM THE W AS LOW
PRES OFF THE COAST MOVES AWAY FROM THE REGION. AS A RESULT, MAINLY
DRY WX AND WARMING TEMPS ARE IN STORE TODAY. WITH LIGHT FLOW,
TEMPS WILL BE COOLER ALG THE CST WHERE A SEABREEZE IS EXPECTED TO
DEVELOP.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
THE SFC RIDGE WILL MOVE FURTHER INTO THE REGION TONIGHT AND
EXPECT A GENLY CLEAR SKY AND NOT MUCH WIND.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
THE LARGE-SCALE PLAYERS NEXT WEEK INCLUDE PERSISTENT TROUGHING OVER
THE WESTERN CONUS AND DOWNSTREAM RIDGING OVER MUCH OF THE EASTERN
CONUS AND WESTERN ATLANTIC. THIS PATTERN WILL RESULT IN WARMER
THAN NORMAL TEMPS AND FEW OPPORTUNITIES FOR PRECIPITATION FOR THE
MID-ATLANTIC REGION FOR THE LONG-TERM PERIOD. MAX TEMPS GENERALLY
RANGE FROM THE MID 70S TO LOWER 80S EACH DAY (EXCEPT COOLER ALONG
THE COAST AND IN THE POCONOS).

THE CENTER OF THE SURFACE HIGH PRESSURE AND H8 ANTICYCLONE WILL BE
POSITIONED OVER THE SOUTHEAST STATES ON SUNDAY. THESE FEATURES WILL
PROGRESS DOWNSTREAM TOWARD THE EAST COAST SUNDAY NIGHT AND THEN OVER
THE WESTERN ATLANTIC ON MONDAY. SOUTHWESTERLY RETURN FLOW AROUND
THE HIGH WILL DRAW EVEN WARMER AND SLIGHTLY MORE HUMID AIR UP THE
EASTERN SEABOARD.

A COLD FRONT IS EXPECTED TO DROP SOUTHWARD INTO THE REGION TUESDAY
MORNING. THE COMBINATION OF UNIDIRECTIONAL W-SW FLOW ALOFT THAT
BECOMES ORIENTED PARALLEL TO THE BOUNDARY AND DOWNSTREAM BLOCKING
(FROM THE HIGH OVER THE WESTERN ATLANTIC AND CAROLINAS) WILL
LIKELY CAUSE THE FRONT TO STALL OVER THE FORECAST AREA THRU
WEDNESDAY. THE BOUNDARY WILL ALSO BECOME INCREASINGLY DIFFUSE
DURING THIS TIME. THE BEST, IF NOT THE ONLY APPRECIABLE CHANCE
FOR PRECIPITATION NEXT WEEK WILL BE TUESDAY-WEDNESDAY. WHILE
FORCING FROM THIS DECAYING BOUNDARY ITSELF WILL BE WEAK, WE WILL
HAVE TO WATCH FOR MID-LEVEL SHORTWAVE ENERGY THAT EJECTS OUT OF
THE SOUTHWEST CONUS TROUGH TO RIDE ATOP THE DOWNSTREAM RIDGE AND
EVENTUALLY MOVE INTO OUR AREA SOMETIME DURING THE TUESDAY
AFTERNOON- WEDNESDAY MORNING PERIOD. THIS WOULD ENHANCE COVERAGE
OF SHOWERS. HOWEVER, THE TIMING AND STRENGTH OF ANY SUCH IMPULSE
IS STILL UNCERTAIN THIS FAR OUT, SO POPS WERE KEPT GENERALLY LOW.
THE 00Z GUIDANCE PROGS THE GREATER INSTABILITY THAT MAY BE
SUFFICIENT FOR CONVECTION TO BE CONFINED TO NEAR THE FRONT OWING
TO MOISTURE POOLING ALONG THE BOUNDARY. KEPT CHANCES FOR
THUNDERSTORMS LOW AREA WIDE DUE TO UNCERTAINTY IN THE LOCATION OF
THE BOUNDARY.

THE REMNANTS OF THE OLD FRONTAL BOUNDARY IS FORECAST TO BECOME
WASHED OUT ACROSS THE AREA BY WEDNESDAY NIGHT. UPPER RIDGE BUILDING
WILL OCCUR OVER THE MIDWEST AND MID ATLANTIC LATE IN THE WEEK. THIS
ALLOWS THE WARMTH TO PERSIST ACROSS THE FORECAST AREA THRU THE END
OF THE WEEK. MODELS ARE IN GOOD AGREEMENT WITH A CUTOFF LOW
FORMING OFF THE SOUTHEAST COAST THURSDAY. WITH WEAK STEERING FLOW
UNDERNEATH THE UPPER RIDGE, THE LOW IS NOT EXPECTED TO MAKE MUCH
ADVANCEMENT TOWARD OUR AREA, RESULTING IN A DRY FORECAST FOR
THURSDAY AND FRIDAY.

&&

.AVIATION /13Z SATURDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

VFR CONDS ARE EXPECTED THRU THE TAF PD AS HIGH PRES BUILDS IN
FROM THE W. THERE WILL BE SOME LINGERING SC AT TIMES THRU THE DAY
BEFORE THE SKY BECOMES MAINLY CLR OVERNIGHT. WIND WILL SHIFT FROM
NELY TO ELY AND EVENTUALLY S DURG THE DAY AND BECOME LIGHT
OVERNIGHT. SPEEDS WILL REMAIN LESS THAN 10 KT. A SEA BREEZE FRONT
IS EXPECTED TO WORK ITS WAY INLAND FROM THE CST DURG THE AFTN.

OUTLOOK...

SUNDAY AND MONDAY...VFR. LIGHT NW WINDS SUNDAY WILL BECOME SWLY AND
INCREASE ON MONDAY. GUSTS TO 20 KT POSSIBLE MONDAY AFTERNOON.

TUESDAY AND WEDNESDAY...PREDOMINATELY VFR. BRIEF/LOCAL RESTRICTIONS
IN SCT SHOWERS AND ISO TSTMS AS A COLD FRONT DROPS SOUTHWARD AND
THEN STALLS OVER THE AREA. BEST CHANCE FOR PRECIP WOULD BE TUESDAY
AFTERNOON THRU WEDNESDAY MORNING.

&&

.MARINE...
WE WILL EXTEND THE SCA FOR A FEW MORE HOURS AS OBSERVED SEAS
ARE ABOUT A FOOT ABOVE WAVE WATCH GUIDANCE.

ONCE THIS CURRENT SCA COMES DOWN, NO ADDITIONAL MARINE HEADLINES
ARE EXPECTED IN THE NR OR SHORT TERM PDS.


OUTLOOK...
SUNDAY THROUGH WEDNESDAY...WINDS AND WAVES WILL PREDOMINATELY
STAY BELOW SCA CRITERIA. S-SW FLOW WILL INCREASE TO 15-20 KT
MONDAY AFTERNOON THRU WEDNESDAY BUT THE WARM AIR ATOP THE COLDER
WATERS WILL NOT PROVIDE MUCH OPPORTUNITY FOR STRONGER WINDS ALOFT
TO MIX DOWN TO THE SURFACE.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR
     ANZ452>455.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ451.

&&

$$
SYNOPSIS...KLEIN
NEAR TERM...GIGI/NIERENBERG
SHORT TERM...NIERENBERG
LONG TERM...KLEIN
AVIATION...KLEIN/NIERENBERG
MARINE...GIGI/KLEIN/NIERENBERG



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.