Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 312214
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
614 PM EDT SUN MAY 31 2015

.SYNOPSIS...
A COLD FRONT HAS SETTLED SOUTH ACROSS ACROSS NORTHERN PENNSYLVANIA
AND NORTHERN NEW JERSEY LATE TODAY WITH AREAS OF LOW PRESSURE IN
SOUTHERN PENNSYLVANIA AND EASTERN OHIO. THIS COLD FRONT AND AREAS
OF LOW PRESSURE WILL INCH ITS WAY SOUTHEASTWARD THROUGH THE REMAINDER
OF OUR FORECAST AREA MONDAY AND TUESDAY. HIGH PRESSURE WILL BUILD
SOUTHEASTWARD BEHIND FOR THE MIDDLE AND LATTER HALF OF NEXT WEEK.
THIS HIGH WILL BE FOLLOWED BY ANOTHER COLD FRONT DROPPING SOUTHEAST
INTO THE REGION BY NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
630 PM ESTF: EXPANDED WATCH SWD AROUND ONE TIER OF COUNTIES. MORE
LATER AS TIME PERMITS. WATCH THE RADAR AND MONITOR OUR STMTS/WARNINGS
/ADVISORIES.

WE COULD BENEFIT FROM RAINFALL REPORTS OF GREATER THAN 1 INCH IN
30 MINUTES OR STORM TOTALS OVER 2 INCHES. PLS POST FACEBOOK.
THANKS.

WWW.WEATHER.GOV/PHI

530 PM ESTF: A COLD FRONT HAS SETTLED SOUTH TO NEAR I-78 AND
WILL PROBABLY BECOME NEARLY STATIONARY ABOUT 20 MILES SOUTH OF
THIS POSITION LATE THIS EVENING. OVERRUNNING HEAVY SHOWERS AND
TSTMS WERE OCCURRING NEAR AND NORTH OF THE FRONT AND THE FLOOD
WATCH CONTINUES WITH PWAT NEAR 1.7 INCHES AND MODEL GUIDANCE
SUGGESTING EXPANSION AND INTENSIFICATION OF RAINFALL BETWEEN NOW
AND 10 PM.

MEANWHILE CUT THE POPS THROUGH 04Z FROM NEAR KBLM TO KTTN AND
KPHL SEWD TO THE COASTS WHERE AM NOT EXPECTING ANY SHOWERS AND
STORMS BEFORE MIDNIGHT.

AS FOR A SEVERE THUNDERSTORM THREAT, THE BEST BULK SHEAR IS TO
OUR NORTH AND WEST, HOWEVER WITH PLENTY OF INSTABILITY INTO THIS
EVENING ANY ROBUST CONVECTIVE CORES COULD PRODUCE A LOCAL
DOWNBURST/DAMAGING WIND GUST IN COMBINATION WITH VERY HEAVY RAIN.
THIS IS MAINLY FOR OUR WESTERN TO NORTHWESTERN ZONES.

AS FOR THE LOW TEMPERATURES, WE MAINLY USED A NAM/GFS MOS BLEND.
THE HOURLY TEMPERATURE AND DEW POINT GRIDS HAD THE LAMP/LAV
GUIDANCE INCORPORATED INTO THEM.

DID LOWER THE TEMPS SHARPLY N OF I-80 IN NNJ THIS EVENING IN
OUTFLOWS AND BACKDOOR COLD FRONT.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
     FLASH FLOOD WATCH MAY BE NEEDED FOR E PA AND MUCH OF THE NRN
THIRDS OF NJ MONDAY...

AS PER BELOW WE WILL NOT ISSUE TODAY TRAINING OF BANDS OF 1.8 INCH
PWAT TSTORMS MONDAY AFTN/EVENING COULD BECOME A SERIOUS PROBLEM
FOR URBAN AREAS THAT THEY TRAVERSE.

CENTRAL A FRONTAL BOUNDARY SHOULD BE BISECTING OUR AREA FROM WEST
TO EAST DURING THE COURSE OF THE DAY. THE FRONT IS NOT EXPECTED TO
SAG ALL THE WAY TO THE SOUTH DUE TO ENOUGH RIDGING HOLDING ON
COMBINED WITH A SLOW MOVING WEAK SURFACE LOW. AN UPPER-LEVEL
TROUGH IS FORECAST TO UNDERGO SOME AMPLIFICATION ACROSS THE GREAT
LAKES, AND THIS SHOULD TEND TO HOLD THE BOUNDARY AND WEAK SURFACE
LOW IN OUR AREA THROUGH THE DAY. AS A RESULT, AT LEAST THE
SOUTHERN HALF OF OUR AREA WILL BE WITHIN THE WARM SECTOR ALTHOUGH
THE NORTHERN ZONES WILL BE MUCH COOLER WITH AN EASTERLY WIND. THIS
MAY TEND TO HOLD IN LOWER CLOUDS THROUGH MUCH OF THE DAY, WITH
MORE INSTABILITY FARTHER SOUTH. AS A RESULT, A POTENTIALLY TRICKY
HIGH TEMPERATURE FORECAST. WE BLENDED THE NAM/GFS MOS OVERALL.

FOR AREAS ALONG AND SOUTH OF THE FRONT, A HIGH PW AIRMASS REMAINS
AND WITH ENOUGH LIFT AND FOCUS WITH THE SURFACE FRONT COMBINED WITH
WEAK SURFACE LOW PRESSURE IS EXPECTED TO RESULT IN NUMEROUS SHOWERS
AND THUNDERSTORMS ACROSS MUCH OF THE AREA. THIS MAY BE FOCUSED
INITIALLY ALONG THE INTERSTATE 95 CORRIDOR BEFORE DRIFTING SOUTH,
HOWEVER THEN MORE DEVELOPMENT NORTHWARD IS POSSIBLE WITH LIFT OVER
THE FRONT WITH THE ARRIVAL OF WEAK SURFACE LOW PRESSURE. IT IS
ACROSS THE SOUTHERN AREAS WHERE ENOUGH INSTABILITY COMBINED WITH
FORCING COULD BUILD CONVECTIVE CORES ENOUGH TO ALLOW FOR LOCALLY
STRONG WINDS AND PERHAPS SOME HAIL. THIS WILL DEPEND ON HOW MUCH
INSTABILITY CAN DEVELOP PRIOR TO CONVECTIVE INITIATION OR LEFTOVER
EARLIER CONVECTION.

THERE IS THE POTENTIAL FOR TRAINING CELLS WITH CONVECTIVE
ORGANIZATION AND THEREFORE STRONGER CORES COULD BE CAPABLE OF
PRODUCING LOCALLY EXCESSIVE RAINFALL RATES. DEPENDING ON HOW THE
CONVECTIVE ORGANIZATION BEHAVES, A FLASH FLOOD WATCH MAY BE NEEDED
FOR PORTIONS OF THE CWA ESPECIALLY FOR THE URBAN AREAS ALONG THE
INTERSTATE 95 CORRIDOR.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
MONDAY NIGHT THROUGH TUESDAY NIGHT:

MID-LEVEL FLOW WILL CONTINUE TO SLOW DOWN  MONDAY NIGHT, ALMOST
ALLOWING THE FRONT TO STALL OUT. SEVERAL FACTORS SUGGEST HEAVY,
POTENTIALLY TRAINING SHOWERS AND A FEW THUNDERSTORMS WILL OCCUR
MONDAY NIGHT INTO TUESDAY. SEVERAL AREAS OF LOW PRESSURE AND
ASSOCIATED MID LEVEL DISTURBANCES WILL PASS THROUGH THE REGION.
MOISTURE WILL CONTINUE TO STREAM NORTHWARD AHEAD OF THE FRONT
LEADING TO SURGING PW VALUES CLOSE TO 2 INCHES. A TALL SKINNY CAPE
PROFILE IS ALSO MODELED ALONG WITH VERY SLOW STORM MOTIONS.
HOWEVER, AS STATED IN THE OVERNIGHT DISCUSSION THE SATURATION OF
ATMOSPHERIC PROFILE DOES NOT HAVE A IDEAL LOOK FOR HEAVY RAINFALL
WHICH MAY LIMIT THE EXCESSIVENESS OF THE RAIN SOMEWHAT.

WITH MORE IN THE WAY OF SHOWERS OVERALL, INSTABILITY WILL BE LESS
LEADING TO A MORE ISOLATED THREAT FOR ANY STRONG THUNDERSTORMS. THE
HIGHEST CHANCES FOR RAIN  WILL GRADUALLY SHIFT SOUTHEASTWARD MONDAY
NIGHT AND TUESDAY. THE FRONTAL BOUNDARY SHOULD BEGIN TO TRANSITION
EASTWARD BY TUESDAY NIGHT WITH GRADUALLY DECREASING CHANCES OF RAIN
FROM NORTHWEST TO SOUTHEAST. COMPARED TO YESTERDAY, RAINFALL
AMOUNTS LOOK SLIGHTLY HIGHER IN THESE PERIODS THAN WITH THE LAST
FEW FORECAST UPDATES. THIS MAKES SENSE LOOKING AT ENVIRONMENTAL
FACTORS IN PLACE AND THE POTENTIAL FOR DECENT SYNOPTIC LIFT AHEAD
OF A MORE ORGANIZED AND SLOWER MOVING LOW PRESSURE SYSTEM. THIS
FORECAST GOES WITH THE RFC QPF AS A STARTING POINT, WITH TIMING ON
THE ECMWF AND UKMET MODELS FACTORED IN AS WELL, WHICH ARE SLOWER
COMPARED TO THE GFS/CMC. WILL MAINTAIN CATEGORICAL POPS FOR MONDAY
NIGHT AND RAISE POPS SOME ON TUESDAY AS WELL. TRENDS CONTINUE TO
SHOW SOME SHOWERS MAY LINGER THROUGH TUESDAY NIGHT IN THE DELMARVA
AND SOUTHEAST NJ.

TOTAL RAINFALL MONDAY NIGHT AND TUESDAY IS LIKELY TO RANGE FROM 1 TO
3 INCHES WITH LOCALLY HIGHER AMOUNTS.  A GENERAL CONSENSUS AT THIS
TIME YIELDS THE HIGHEST RAINFALL TOTALS ACROSS EASTERN PA AND
NORTHERN NJ. MET/MAV MOS ARE STARTING TO PICK UP ON THE POTENTIAL
FOR TEMPERATURES TO BE KEPT UP AT NIGHT AND LOWER DURING THE DAY
DUE TO CLOUDS AND PRECIPITATION.

WEDNESDAY THROUGH FRIDAY: HIGH PRESSURE BUILDS OVER THEN PASSES EAST
OF THE REGION FOR THE MIDDLE AND LATER HALF OF THE WEEK. COOL
REFRESHING AIRMASS TO START THEN WARMER AND MUGGY BY WEEKS END. THE
POTENTIAL STILL DOES EXIST FOR AN AREA OF LOW PRESSURE TO DEVELOP WELL
TO OUR SOUTHEAST NEAR THE FRONTAL BOUNDARY WHICH PASSES THROUGH
OUR REGION TUESDAY. RIGHT NOW FOR THIS TIMEFRAME IT STILL LOOKS
LIKE THE HIGH PRESSURE HAS ENOUGH PUSH TO KEEP OUR WEATHER PARTLY
TO MOSTLY CLOUDY WITH THE MOST CLOUDS ACROSS THE SOUTHERN DELMARVA
REGION.

FRIDAY NIGHT THROUGH SUNDAY: ANOTHER COLD FRONT IS LIKELY TO MOVE
INTO THE REGION POSSIBLY DECAYING OVER THE REGION. TIMING
DIFFERENCES AS USUAL ARE PRESENT WITH THIS FEATURE WITH THE
FASTER, STRONGER GFS AND THE SLOWER ECMWF. WARM AND MORE HUMID
CONDITIONS ARE LIKELY PRECEDE THE FRONT. SOME SCATTERED
THUNDERSTORMS MAY FORM AHEAD OF THE FRONT AS WELL. OPTED FOR LOW
CHANCE POPS ATTM CENTERED ON SATURDAY AFTERNOON AND EVENING,
CLOSER TO THE ECMWF TIMING. GIVEN THE UNCERTAINTY WITH THE
FRONTAL TIMING AND THE POTENTIAL FOR MORE CLOUDS, KEPT
TEMPERATURES FAIRLY CLOSE TO THE GFS/ECMWF/WPC ENSEMBLE SETS.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

THROUGH 00Z...VFR EVERYWHERE EXCEPT IFR IN SHOWERS AND THUNDERSTORMS
CLOSEST TO KABE TO KRDG WHERE GUSTY NE WINDS MAY DEVELOP THIS EVENING.
OTHERWISE SOUTH- SOUTHWEST WINDS GUSTY 20 KT IN SE PA AND S NJ
THROUGH DE.

TONIGHT...A COLD FRONT WILL SETTLE SOUTHWARD BUT PROBABLY STALL.
THIS SHOULD ALLOW FOR SHOWERS AND THUNDERSTORMS TO ARRIVE FROM THE
WEST, BUT THEN WEAKEN AFTER 04Z/01. THE TIMING AND OVERALL
ORGANIZATION/PLACEMENT CARRIES SOME LOWER CONFIDENCE, AND
THEREFORE ONLY CARRIED THUNDER IN THE FAR INLAND TERMINALS TO
START THE EVENING.

PLEASE SEE TAFS FOR DETAILS. HAVE DELAYED SHOWERS FOR ABOUT 6 HRS
IN THE TAFS FOR KTTN KPHL AREA.

MVFR TO NEAR IFR CEILINGS ARE ANTICIPATED FOR MANY OF THE
TERMINALS OVERNIGHT. SOUTH-SOUTHWEST WINDS BECOMING SOUTHEAST AT
LESS THAN 10 KNOTS, ALTHOUGH EASTERLY AT KABE AND KTTN.

MONDAY...SHOWERS AND THUNDERSTORMS EXPECTED, WITH THE MOST
WIDESPREAD ACTIVITY DURING THE AFTERNOON. AS A RESULT, MVFR AND
LOCALIZED IFR ESPECIALLY DURING SHOWERS AND THUNDERSTORMS. SOUTHEAST
OR EAST WIND UP TO 10 KNOTS.

OUTLOOK...
MONDAY NIGHT THROUGH TUESDAY NIGHT: MVFR AND IFR RESTRICTIONS IN
SHOWERS AND SCATTERED THUNDERSTORMS.  EAST TO NORTHEAST WINDS UNDER
10 KNOTS.

WEDNESDAY THROUGH FRIDAY: VFR. EAST WINDS UNDER 10 KNOTS BECOMING
MORE SOUTHERLY BY FRIDAY.

&&

.MARINE...
ISSUED MARGINAL SCA THROUGH MIDNIGHT TONIGHT.

A SOUTHERLY FLOW WILL CONTINUE AHEAD OF A COLD FRONT DRIFTING SOUTHWARD
THROUGH MONDAY. THIS BOUNDARY WILL ALLOW FOR A WIND SHIFT FROM THE
SOUTH TO SOUTHEAST AND THEN EAST ESPECIALLY LATE TONIGHT AND
MONDAY ACROSS THE NORTHERN COASTAL WATERS. THE FLOW IS EXPECTED TO
BE LIGHT ENOUGH TO KEEP THE WINDS BELOW 25 KNOTS. SOME GUSTINESS
IS EXPECTED INTO THIS EVENING THOUGH ESPECIALLY NEARSHORE WITH
BETTER MIXING AND ONCE AGAIN ON MONDAY SOUTH OF THE FRONT. THE
SEAS ARE EXPECTED TO BE AT OR BELOW 4 FEET THROUGH MONDAY.

OUTLOOK...

MONDAY NIGHT THROUGH FRIDAY: SEAS THREE TO FOUR FEET FOR MOST OF THE
WEEK. WINDS SHIFTING TO THE EAST AND NORTHEAST WITH GUSTS UNDER 20
KNOTS THROUGH TUESDAY NIGHT. SOME LOCALIZED GUSTS FROM 20-25 ARE
POSSIBLE WEDNESDAY MORNING. WINDS SHIFTING TO MORE SOUTHERLY ON
FRIDAY. STILL SOME UNCERTAINTY WITH SEAS GIVEN THE POTENTIAL FOR
LOW PRESSURE TO FORM SOUTHEAST OF THE REGION FOR THE MIDDLE OF THE
WEEK, ATTM IT DOES NOT LOOK LIKE A INCREASE IN SEAS FROM THIS.

&&

.RIP CURRENTS...
THE RIP CURRENT RISK FOR THE JERSEY SHORE AND THE DELAWARE BEACHES
IS MODERATE THROUGH THIS EVENING, BASED ON THE CONTINUED SOUTHERLY
FLOW AND LONGER WAVE PERIOD.

&&

.CLIMATE...
NOTE: SEE BOTTOM OF THIS SECTION ON KPHL FIRST 90 OF THE SEASON.

MAY 2015...A TOP 4 WARMEST ON RECORD FOR LARGE PORTIONS OF OUR AREA,
AND RATHER DRY THOUGH WE STILL HAVE POTENTIAL FOR SIGNIFICANT
RAINFALL THIS EVENING WHICH WOULD SIGNIFICANTLY ALTER THE FINAL
MONTH OF MAY PRECIPITATION RANKING.


ALL ACTUAL AND FORECAST INFORMATION CHECKED THROUGH AROUND 2 PM
TODAY - SUNDAY MAY 31.

ALLENTOWN WILL PROBABLY AVERAGE VERY CLOSE TO 66.4 OR AT LEAST 6
DEGREES ABOVE NORMAL. POR BACK TO 1922.  NORMAL 59.9

PROBABLY THE 2ND WARMEST ON RECORD.
1991 67.2
2015 66.4
2012 66.1
1944 66.0

NORMAL PCPN 4.14. AS OF 2 PM TODAY ALLENTOWN SECOND DRIEST MAY ON
RECORD SO FAR WITH 0.27 INCHES.  DRIEST MAY 0.09 1964.

--

PHILADELPHIA WILL PROBABLY AVERAGE CLOSE TO 70.1 DEGREES OR AT LEAST
6 DEGREES ABOVE NORMAL.  SECOND WARMEST ON RECORD.   NORMAL 63.9

1991 70.8

NUMBER 3 WOULD BE 69.2 IN 2004.

NORMAL RAINFALL 3.71  THE 1.19 INCHES SO FAR IS 13TH DRIEST ON
RECORD.

--

ATLANTIC CITY MAY 2015 66.5 OR OVER 5 DEGREES ABOVE NORMAL AND
PROBABLE  #2 POR BACK TO 1874   NORMAL 61.1

2004 66.9
2015 66.5
1991 66.0

NORMAL PCPN 3.35  THE 0.71 INCHES SO FAR MAKES THIS AROUND THE 7TH
DRIEST MAY ON RECORD.

--

WILMINGTON DE SOLID POR BACK TO 1916 LOCKED INTO #4 WARMEST, SMALL
CHANCE EQUAL NUMBER 3 WARMEST. NORMAL 62.8

1896 70.1
1991 69.1
2004 68.2
2015  AROUND 68.1

NORMAL PCPN 3.95  THE 2.39 INCHES IS MIDDLE OF THE PACK AND NOT
ESPECIALLY OF STANDOUT DRY INTEREST FOR THIS STATION

NO AVAILABLE MONTHLY HISTORICAL DATA FOR KMPO KGED KTTN AND KRDG.


AN ADDITIONAL TIDBIT... PER TONY...

SECOND 90F OF THE MONTH OCCURRED TODAY AT BOTH KRDG AND KABE
KPNE HAS HAD 3 DAYS OF 90 SO FAR.

KPHL WITH ITS 2ND WARMEST MAY EVER...AND FINALLY THE FIRST 90 OCCURRED
TODAY... 92 AT 213PM. THE HISTORICAL RECORD DATING BACK TO 1874
FINDS PHILADELPHIA WITH ITS MEAN FIRST 90 AROUND MAY 29.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FLASH FLOOD WATCH UNTIL 2 AM EDT MONDAY FOR PAZ054-055-060>062-
     105.
NJ...FLASH FLOOD WATCH UNTIL 2 AM EDT MONDAY FOR NJZ001-007>010-012.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ430-431-
     450>453.

&&

$$
SYNOPSIS...GAINES
NEAR TERM...DRAG/GORSE 614
SHORT TERM...GORSE
LONG TERM...GAINES
AVIATION...DRAG/GAINES/GORSE
MARINE...DRAG/GAINES/GORSE 614
RIP CURRENTS...
CLIMATE...


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