Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Home | 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 080139
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
939 PM EDT TUE JUL 7 2015

.SYNOPSIS...
OVERNIGHT A COLD FRONT WILL SLOWLY MOVE TOWARDS OUR REGION. THE
TROUGH TO OUR SOUTH WILL MERGE WITH THIS FRONTAL BOUNDARY ON
THURSDAY, STALLING THE FRONT OVER OUR AREA. SEVERAL AREAS OF LOW
PRESSURE WILL MOVE ALONG THE FRONTAL BOUNDARY ON THURSDAY AND
FRIDAY. HIGH PRESSURE WILL BRIEFLY MOVE INTO THE REGION FOR THE
WEEKEND, BEFORE A WARM FRONTAL BOUNDARY MOVES TO OUR NORTH ON
MONDAY. A TROUGH LOOKS TO PERSIST OVER OUR AREA THROUGH MOST OF
NEXT WEEK, AS A RESULT OF A DOMINANT RIDGE OVER THE MIDWEST.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
EARLIER CONVECTIVE ACTIVITY HAS MOVED OUT OF OUR REGION AND
DISSIPATED. WILL NEXT TURN OUR ATTENTION TO THE FRONT AND
ASSOCIATED CONVECTION JUST AHEAD OF THE FRONT. CLOUD COVER SHOULD
INCREASE ACROSS THE WESTERN HALF OF THE CWA OVER THE NEXT FEW
HOURS. RADAR TRENDS/USING A TIME OF ARRIVAL TOOL, WOULD SUGGEST
THE NEXT ROUND OF SHOWERS/STORMS TO ARRIVE BETWEEN 04 AND 06Z.
HOWEVER, DO EXPECT SOME OF THE CONVECTIVE ACTIVITY ALONG THE LINE
(IF NOT MOST OF IT) TO DISSIPATE AS THE BOUNDARY LAYER
STABILIZES/NOCTURNAL TEMPERATURE INVERSION SETS UP. STILL, HAVE
INCREASED POPS IN THE 04 TO 09Z TIME PERIOD FOR A FEW SHOWERS THAT
MAY MOVE INTO OUR REGION.

IT WILL REMAIN HUMID TONIGHT WITH MINIMUM TEMPERATURES FORECAST TO
RANGE FROM THE UPPER 60S TO THE MIDDLE 70S.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
A FRONTAL BOUNDARY IS FORECAST TO EXTEND FROM THE CATSKILLS ACROSS
NORTHEASTERN PENNSYLVANIA TO AROUND PITTSBURGH EARLY ON WEDNESDAY
MORNING. THE BOUNDARY IS EXPECTED TO SINK SLOWLY INTO OUR
NORTHWESTERN COUNTIES AS THE DAY PROGRESSES. MEANWHILE, A SURFACE
TROUGH IS ANTICIPATED TO DEVELOP TO THE LEE OF THE APPALACHIANS IN
THE SOUTHWESTERLY FLOW.

THE CONVECTION THAT WAS OVER THE EASTERN GREAT LAKES AND THE LOWER
OHIO RIVER VALLEY THIS AFTERNOON SHOULD REACH OUR REGION ON
WEDNESDAY. AS A RESULT, WE WILL INDICATE AN INCREASING CHANCE OF
SHOWERS AND THUNDERSTORMS FROM NORTHWEST TO SOUTHEAST.

THE MODEL GUIDANCE IS SUGGESTING ONLY MARGINAL INSTABILITY FOR
WEDNESDAY. HOWEVER, PRECIPITABLE WATER VALUES WILL LIKELY INCREASE
TO 2 INCHES OR MORE. IN ADDITION, UPPER LEVEL WINDS BY TOMORROW
EVENING MAY BE NEARLY PARALLEL TO THE SLOW MOVING FRONT. THIS
PATTERN THUS, LOOKS SOMEWHAT SIMILAR TO A MADDOX HEAVY RAIN
FRONTAL PATTERN. HOWEVER, ONE POTENTIAL NEGATING FACTOR MAY BE THE
LACK OF MUCH UPPER LEVEL SUPPORT FOR SUSTAINED CONVECTION. ALL
THAT CONSIDERED, WE WILL CONTINUE TO MENTION THE POSSIBILITY OF
LOCALLY HEAVY RAINFALL IN THE HWO.

MAXIMUM TEMPERATURES ON WEDNESDAY ARE ANTICIPATED TO BE MAINLY IN THE
80S WITH SOME UPPER 70S IN THE FAR NORTH AND SOME LOWER 90S IN THE
FAR SOUTH.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
HEMISPHERIC WAVE GUIDANCE SHOWS DEEP SOUTHWESTERLY FLOW ACROSS THE
EASTERN HALF OF THE U.S. AT THE START OF THE LONGTERM PERIOD. BY THE
WEEKEND THE WAVELENGTH ACROSS THE CONTIGUOUS U.S. BECOMES LONGER
ALLOWING THE SOUTHEAST RIDGING TO RETROGRADE TOWARDS THE CENTRAL
U.S. THIS SETS UP A PSEUDO-HIGH LATITUDE OMEGA BLOCK, WITH OUR
REGION ON THE PERIPHERY OF AN EAST COAST TROUGH. THIS PATTERN LOOKS
TO REMAIN IN PLACE, WHILE LIFTING AND WEAKENING A BIT, GOING INTO
NEXT WORK WEEK, ADDING TO OUR DAILY CHANCES FOR SHOWERS AND
THUNDERSTORMS.

THURSDAY - FRIDAY NIGHT...THE SLOW SAGGING COLD FRONT THAT BEGINS TO
CROSS THE REGION ON WEDNESDAY LOOKS TO MAKE IT AS FAR SOUTH AS
DELMARVA ON THURSDAY AND REMAIN NEARLY IN PLACE THROUGH FRIDAY.
MULTIPLE WAVES MOVE ALONG THIS BOUNDARY AS IT PRESSES SOUTHWARD
ADDING TO THE INCREASED CHANCES FOR SCATTERED SHOWERS AND EMBEDDED
THUNDER. GUIDANCE TRIES TO ADVECT IN MORE INSTABILITY FROM THE SOUTH
ON THURSDAY AHEAD OF THE FRONT BUT THE TIMING DOESN`T LOOK LIKE IT
OVERLAPS THE FRONTAL PASSAGE. THAT BEING SAID PWATS WILL STILL BE
WELL ABOVE NORMAL, POSSIBLY 2+ INCHES GIVING US MORE LOCALIZED
FLOODING ISSUES...SAME AS IT EVER WAS. WE CONTINUE WITH THE HEAVY
RAIN WORDING IN THE FORECAST THURSDAY NIGHT INTO FRIDAY MORNING, BUT
CONFINE IT TO OUR NORTHERN HALF...BETTER LIFT/DYNAMICS AND SOME
ELEVATED INSTABILITY TO WORK WITH. AFTER WHAT COULD BE A GREAT LAKES
MCS PASSAGE FRIDAY MORNING ACROSS OUR NORTH, THE FRONT CONTINUES TO
SAG SOUTHWARD DURING THE DAY WITH ISOLATED SHOWERS AND THUNDERSTORMS
POSSIBLE ACROSS DELMARVA...DRYING OUT BEHIND THE FRONT ACROSS THE
NORTH. IT SHOULD BE NOTED THAT FFG ACROSS THE NORTHERN ZONES IS
RUNNING QUITE LOW WITH A LOT OF AREAS ONLY NEEDING 1.5 INCHES IN AN
HOUR TO CAUSE ISSUES...SOMETHING TO WATCH.

SATURDAY...THE AFOREMENTIONED FRONT SHOULD BE FARTHER TO OUR SOUTH
THIS WEEKEND WHILE LARGE SCALE SUBSIDENCE TAKES OVER...THE LONGWAVE
RIDGING RETROGRADING ALL THE WHILE. WE STILL EXPECT SATURDAY TO BE
RAIN FREE BUT THERE COULD BE LINGERING MID-LEVEL ENERGY MOVING BY TO
OUR SOUTHWEST THAT MAY TOUCH OFF A FEW ISOLATED TO SCATTERED SHOWERS
IN OUR EXTREME SOUTHWEST ZONES...HAVE TIME TO BETTER DEFINE THESE
CHANCES IF ANY.

SUNDAY - TUESDAY...WARM FRONT PASSAGE, FROM WHAT WAS ONCE THE COLD
FRONT EARLIER IN THE PERIOD, MOVES BACK TOWARDS THE NORTH ON SUNDAY
NIGHT INTO MONDAY. COLD FRONT THEN NEARS FROM THE NORTHWEST LATE
ON MONDAY INTO TUESDAY AS TROUGHING TAKES BACK OVER AGAIN.
NORTHWEST FLOW ALOFT LOOKS TO PREVAIL AS CENTRAL U.S. RIDGING
AMPLIFIES. THIS MAY SEND SEVERAL SHORTWAVES THROUGH THE REGION
FROM LATE MONDAY ONWARD...NORTHERN PLAINS MCS SEASON.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

VFR CONDITIONS SHOULD CONTINUE THROUGH 06Z. A FEW SHRA MAY MOVE
INTO WESTERN PORTIONS OF THE REGION, INCLUDING KRDG AND KABE
BETWEEN 04 AND 06Z. HOWEVER, COVERAGE IS EXPECTED TO BE QUITE
LIMITED, TOO LIMITED TO MENTION IN THE TAFS AT THIS TIME (AT LEAST
FOR THE FIRST ROUND OF SHRA). WILL SEE INCREASING MID LEVEL CLOUDS
ACROSS THE REGION OVERNIGHT.

A SLOW MOVING COLD FRONT WILL APPROACH FROM THE NORTHWEST AFTER
09Z. MVFR CEILINGS ALONG WITH MORE SHRA AND POSSIBLY TSRA SHOULD
ARRIVE AT KRDG AND KABE NEAR 12Z. THE LOWERING CONDITIONS AND
PRECIPITATION SHOULD REACH THE DELAWARE VALLEY (INCLUDING KPHL,
KPNE, KILG, KTTN) BETWEEN 15 AND 21Z. IT IS UNCLEAR IF THE
PRECIPITATION WILL PROPAGATE AS FAR SW AS KMIV AND KACY BY 00Z.

A LIGHT SOUTHWESTERLY WIND IS EXPECTED OVERNIGHT. THE SLOW MOVING
COLD FRONT WILL BRING A SHIFT TO WNW AND EVENTUALLY NW WINDS
TOMORROW FOR MOST TAF SITES (THE FRONT MAY NOT REACH KMIV OR KACY
BEFORE 00Z).

OUTLOOK...

THURSDAY...POTENTIAL MVFR AND IFR RESTRICTIONS IN SHOWERS AND
THUNDERSTORMS, HIGHEST CHANCES EACH AFTERNOON AND EVENING. WEST-
SOUTHWEST WIND GUSTS AT OR UNDER 20 KNOTS.

FRIDAY - SATURDAY NIGHT...VFR. WINDS AT OR UNDER 10 KNOTS, MAINLY
NORTHERLY.

SUNDAY...MOSTLY VFR. SOME SCATTERED SHOWERS AND EMBEDDED THUNDER
POSSIBLE.

&&

.MARINE...
SOUTHWESTERLY WINDS MAY AT TIMES GUST NEAR OR JUST ABOVE 20 KT
OVERNIGHT, BUT SHOULD DECREASE TOWARDS DAYBREAK. A SLOW MOVING
COLD FRONT IS FORECAST TO APPROACH FROM THE NORTHWEST LATE
WEDNESDAY AFTERNOON, WHICH COULD BRING A SHIFT TO WESTERLY AND
EVENTUALLY NORTHWESTERLY WINDS, PRIMARILY FOR THE NORTHERN NJ
ATLANTIC WATERS.

WAVE HEIGHTS ON OUR OCEAN WATERS WILL GENERALLY RANGE BETWEEN 3
AND 4 FT OVERNIGHT INTO TOMORROW MORNING, BUT SHOULD BEGIN TO
DECREASE MID DAY TOMORROW. WAVES ARE EXPECTED TO BE 2 FEET OR
LESS ON DELAWARE BAY.

OUTLOOK...

SUB-SCA WINDS AND SEAS EXPECTED. ANY WIND GUSTS LOOK TO REMAIN
BELOW 20 KNOTS, MORE NORTHERLY THROUGH SATURDAY NIGHT. SEAS
AROUND FOUR FEET ON WEDNESDAY AND THURSDAY. THE HIGHEST CHANCE OF
THUNDERSTORMS IS WEDNESDAY AFTERNOON AND EVENING THEN AGAIN LATER
THURSDAY.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...SPIVEY
NEAR TERM...IOVINO/JOHNSON
SHORT TERM...IOVINO/JOHNSON
LONG TERM...GAINES/HEAVENER
AVIATION...IOVINO/HEAVENER/JOHNSON
MARINE...IOVINO/HEAVENER/JOHNSON


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