Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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173
FXUS61 KPHI 290145
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
945 PM EDT THU APR 28 2016

.SYNOPSIS...
LOW PRESSURE IN NORTH CAROLINA GRADUALLY SHIFTS OUT TO SEA OFF THE
MID ATLANTIC COAST LATER FRIDAY OR FRIDAY NIGHT. HIGH PRESSURE WILL
THEN BUILD DOWN FROM THE NORTH SATURDAY INTO SUNDAY. LOW PRESSURE IS
FORECAST TO TRACK ACROSS OUR AREA SUNDAY NIGHT AND MONDAY BEFORE
SHIFTING OFFSHORE MONDAY NIGHT INTO TUESDAY. HIGH PRESSURE MAY EXTEND
INTO OUR AREA TUESDAY INTO WEDNESDAY. THE NEXT COLD FRONT ARRIVES ON
THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
930PM ESTF: POPS ADJUSTED HIGHER ON THE DELMARVA OVERNIGHT (03Z-
07Z) PER DYING CONVECTION MOVING EWD FROM VA. ADDED PATCHY DRIZZLE/FOG
TO THE FCST. A DAMP COOL NIGHT. THE HEAVIER RAINS OF EARLIER THIS
EVENING WERE DIMINISHING ACROSS PA AND NJ.

MANY REPS OF .1 TO .3 INCHES SO FAR THIS AFTN/EVE ECENTRAL PA THROUGH
CENTRAL NJ.

TEMPS SHOULD BE STEADY TONIGHT.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
THE NEXT UPPER LEVEL SHORT WAVE TROUGH CROSSES ESEWD ALONG I-80
LATE TOMORROW AND IS SOMEWHAT IMPRESSIVE (TIGHT 500MB VORT) DESPITE
MINOR 30 METER 12 HR 500 MB HFC. HAVE RAISED POPS 30-40 PCT N OF
I-78 FRIDAY AFTERNOON PER GFS/EC SUGGESTION OF .1-.2 INCHES.

ADJUSTED TEMPS DOWN 2-3F IN SOME PLACES PER OVC CONDITION AND
LITTLE IN THE WAY OF MIXING WITHIN THIS FAIRLY MOIST BOUNDARY
LAYER.

WITH CONTINUED ONSHORE FLOW AND PERSISTENT LOW AND MID LEVEL CLOUDS,
KEPT TOMORROWS HIGHS SIMILAR TO WHAT WE`VE SEEN TODAY AND YESTERDAY...
GENERALLY UPPER 40S TO MID 50S FOR MOST OF THE REGION...PROBABLY
AROUND 12F BELOW NORMAL....POSSIBLY COLDER THAN THAT.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
THE SYNOPTIC PATTERN IS FORECAST TO BE COMPRISED OF A STRONG CLOSED
LOW THAT CONTINUES TO SLOWLY EXIT THE CANADIAN MARITIMES FRIDAY
NIGHT INTO SATURDAY. THIS ALLOWS THE UPPER-LEVEL FLOW TO BACK MORE
WESTERLY/ZONAL OVER THE WEEKEND AS A WEAK RIDGE AXIS MOVES ACROSS. A
CLOSED LOW IN THE PLAINS IS FORECAST TO OPEN UP AS IT LIFTS
NORTHEAST AND EASTWARD OVER THE WEEKEND. THIS FEATURE IS SCHEDULED
TO CROSS OUR AREA SUNDAY NIGHT AND MONDAY. THIS WILL DRIVE LOW
PRESSURE EASTWARD, WHICH LOOKS TO TRACK ACROSS OUR AREA ON MONDAY
BEFORE SHIFTING OFFSHORE. AS A RIDGE BUILDS OUT WEST, A TROUGH LOOKS
TO AMPLIFY INTO THE EAST TUESDAY THROUGH THURSDAY. A COLD FRONT
ASSOCIATED WITH THE LEADING EDGE OF THIS LOOKS TO APPROACH LATER
WEDNESDAY THEN MOVE THROUGH OUR AREA THURSDAY. WE USED A
MODEL/CONTINUITY BLEND THROUGH SUNDAY, THEN BLENDED IN THE 12Z WPC
GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING
ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES.

FOR FRIDAY NIGHT AND SATURDAY...AN UPPER-LEVEL FEATURE IS FORECAST
TO TRANSLATE ACROSS OUR AREA TO START FRIDAY NIGHT. THIS SHOULD KEEP
SOME SHOWERS GOING, HOWEVER THEY SHOULD BE ON THE WANE AS SOME
RIDGING ARRIVES LATER FRIDAY NIGHT AND TO START SATURDAY. THE UPPER-
LEVEL FLOW THEN BACKS SOME AS A TROUGH TAKES ON SOME AMPLIFICATION
IN THE GREAT LAKES LATE SATURDAY. THIS WILL ALLOW FOR WAA AND
INCREASING ISENTROPIC LIFT TO START OVERSPREADING OUR AREA SATURDAY
NIGHT. THIS MAY RESULT IN SOME RAIN ARRIVING LATER SATURDAY NIGHT,
AND THE MODEL GUIDANCE OVERALL APPEARS TO BE FASTER IN BRINGING IN
THE PRECIPITATION. AS A RESULT, WE SPED UP THE POP INCREASE SATURDAY
NIGHT. DUE TO SOME BRIEF DRYING SATURDAY, TEMPERATURES SHOULD MODIFY
SOME DURING THE DAY.

FOR SUNDAY AND MONDAY...AS AN UPPER-LEVEL TROUGH AMPLIFIES EASTWARD,
SURFACE LOW PRESSURE IS FORECAST TO ARRIVE IN OUR AREA LATER SUNDAY
AND MONDAY. HOWEVER, THERE APPEARS TO BE PLENTY OF WAA AND
ISENTROPIC INDUCED LIFT AS A WARM FRONT EDGES CLOSER DURING SUNDAY.
GIVEN THE FLOW BACKING TO THE SOUTHWEST, PRECIPITATION MAY QUICKLY
MOVE ACROSS THE AREA. LINGERING SURFACE HIGH PRESSURE TO OUR
NORTHEAST THOUGH WILL RESULT IN SOME SORT OF A WEDGE INITIALLY AND
COULD ALLOW ENOUGH DRY LOW-LEVEL AIR TO HOLD ON A LITTLE LONGER.
OVERALL THOUGH, MOISTURE INCREASING FROM THE SOUTHWEST SHOULD
OVERTAKE THIS. AS A RESULT, THIS TIME FRAME LOOKS RATHER UNSETTLED
WITH RAIN AT TIMES.

THE STEADIER RAIN MAY THEN BECOME SHOWERY ON MONDAY AS THE BETTER
OVERRUNNING STARTS TO SHIFT TO OUR NORTHEAST. SOME GUIDANCE SUGGESTS
LESS PRECIPITATION ON MONDAY WHICH WOULD OCCUR IF THE SURFACE LOW IS
FASTER. IT APPEARS THE WARM SECTOR MAY EDGE INTO OUR SOUTHERN AREAS
SUNDAY INTO MONDAY. WHILE SOME THUNDER CANNOT BE RULED OUT WITHIN
THE WARM SECTOR /PERHAPS SOME ELEVATED INSTABILITY NORTH OF THE WARM
FRONT/, IT IS LESS CERTAIN IF IT WOULD BE ENOUGH FOR THUNDER. AS A
RESULT, NO THUNDER WAS ADDED ATTM. THE SHOWERS SHOULD END MONDAY
NIGHT AS THE SYSTEM SHIFTS OFFSHORE AND THE LOW-LEVEL FLOW TURNS
MORE FROM THE NORTH AND NORTHWEST.

FOR TUESDAY THROUGH THURSDAY...AN UPPER-LEVEL TROUGH IS FORECAST TO
AMPLIFY INTO THE EAST TUESDAY AND WEDNESDAY. AS THIS STARTS TO
OCCUR, THE MONDAY FRONTAL BOUNDARY MAY HAVE A WAVE OF LOW PRESSURE
RUNNING UP THE FRONT. THIS COULD AT LEAST BRUSH OUR EASTERN AND
SOUTHERN ZONES TUESDAY, HOWEVER THERE IS LOW CONFIDENCE WITH THIS.
AS THE AFOREMENTIONED TROUGH AMPLIFIES MORE INTO THURSDAY, A COLD
FRONT LOOKS TO ARRIVE. THERE SHOULD BE ENOUGH HEATING AND WAA TO
ALLOW TEMPERATURES TO MODIFY SOME PRIOR TO THE ARRIVAL OF THE COLD
FRONT.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG,KMIV, KACY AND SURROUNDING AREAS.

REMAINDER OF TONIGHT...CONDITIONS GENERALLY MVFR OR IFR IN ST/DRIZZLE
FOG AND GROUPS OF SHOWERY RAINS. LIGHT NE WIND. HIGH CONFIDENCE.

FRIDAY...CONDITIONS PROBABLY IMPROVING TO MVFR OR VFR CIGS DURING
MIDDAY. MODERATE CONFIDENCE BUT MAY LOWER IN RAIN DURING THE
AFTERNOON, ESPECIALLY KRDG/KABE AND KTTN. NE WIND WITH A FEW
GUSTS 15-20 KT POSSIBLE I-95 EASTWARD.


OUTLOOK...
FRIDAY NIGHT...MVFR CONDITIONS IN THE EVENING WITH SOME SHOWERS
SHOULD THEN IMPROVE TO VFR. NORTHEAST WINDS 10 KNOTS OR LESS.

SATURDAY...VFR DURING THE DAY, THEN LOWER TO MVFR AT NIGHT AS SOME
RAIN APPROACHES. EAST-SOUTHEAST WINDS AROUND 10 KNOTS OR LESS.

SUNDAY AND MONDAY...MVFR TO POTENTIALLY IFR CONDITIONS ALONG WITH
RAIN AT TIMES. THE CONDITIONS MAY START IMPROVING MONDAY NIGHT.

TUESDAY...VFR OVERALL.

&&

.MARINE...
930 PM: DELAYED THE START OF THE SCA LOWER DE BAY AND NJ COAST.
CONFIDENCE BELOW AVERAGE ON SEAS REACHING 5 FT NJ ATLC WATERS OR
GUSTS 25 KT LOWER DE BAY AND NJ ATLC WATERS...BUT ITS STILL
POSSIBLE.

OUTLOOK... FRIDAY NIGHT...NORTHEASTERLY WIND GUSTS OF 20 TO 25
KNOTS ON THE OCEAN ZONES ALONG WITH SEAS TO AROUND 5 FEET. THESE
SHOULD SUBSIDE DURING THE NIGHT AND THEREFORE THE SMALL CRAFT
ADVISORY WAS KEPT UNTIL 06Z SATURDAY.

SATURDAY AND SUNDAY...THE WINDS AND SEAS SHOULD BE BELOW ADVISORY
CRITERIA DESPITE INCOMING LOW PRESSURE LATE SUNDAY.

MONDAY AND TUESDAY...NORTHEAST WINDS MONDAY SHOULD SHIFT TO
NORTHWEST AT NIGHT INTO TUESDAY BEFORE SHIFTING BACK EASTERLY. IT
APPEARS THAT THE WINDS REMAIN UNDER 25 KNOTS, HOWEVER SEAS MAY BUILD
TO 5 FEET FOR A TIME ON THE OCEAN ZONES.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 AM FRIDAY TO 2 AM EDT SATURDAY FOR
     ANZ450>453.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT SATURDAY FOR ANZ454-455.
     SMALL CRAFT ADVISORY FROM 4 AM TO 10 AM EDT FRIDAY FOR ANZ431.

&&

$$
SYNOPSIS...DRAG/GORSE
NEAR TERM...DRAG 945P
SHORT TERM...DRAG/JOHNSON 945P
LONG TERM...GORSE
AVIATION...DRAG/GORSE 945P
MARINE...DRAG/GORSE 945P



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