Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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733
FXUS61 KPHI 020136
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
936 PM EDT SUN MAY 1 2016

.SYNOPSIS...
A WARM FRONT WILL SLOWLY LIFT NORTHWARD TOWARD THE AREA TONIGHT,
THEN ACROSS THE AREA DURING THE DAY MONDAY AS AN AREA OF LOW
PRESSURE SLIDES ACROSS THE NEW ENGLAND STATES. A COLD FRONT WILL
SAG INTO OUR AREA MONDAY, WHILE AN AREA OF LOW PRESSURE MOVES
ALONG THE BOUNDARY AND APPROACHES OUR AREA FROM WEST LATE IN THE
DAY INTO THE EVENING. THE FRONT WILL SLOWLY DRIFT OFFSHORE THROUGH
TUESDAY, WITH SEVERAL AREAS OF LOW PRESSURE MOVING ALONG THE
BOUNDARY TUESDAY AND TUESDAY NIGHT. HIGH PRESSURE WILL RIDGE
ACROSS THE AREA FROM THE NORTH WEDNESDAY. MORE LOW PRESSURE WILL
STRENGTHEN AND AFFECT OUR WEATHER FROM THURSDAY INTO THE UPCOMING
WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
A WARM FRONT LOCATED TO OUR SOUTH IS FORECAST TO SLOWLY LIFT
NORTHWARD TOWARD THE AREA OVERNIGHT TONIGHT. MEANWHILE, AN AREA OF
LOW PRESSURE IS FORECAST TO WORK ITS WAY UP THE OHIO RIVER VALLEY
TONIGHT. ANOTHER WEAK AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP
OFF OUR COAST ALONG THE WARM FRONTAL BOUNDARY AND LIFT TO OUR
NORTHEAST. AS A RESULT, THE SURFACE WIND IS ANTICIPATED REMAIN OUT
OF THE EAST TO THE NORTHEAST ON THE COASTAL PLAIN AND ON MOST OF
OUR MARINE AREA. THE WIND SHOULD BECOME LIGHT AND VARIABLE FARTHER
INLAND, BUT ANY DIRECTION WILL LIKELY BE EAST TO NORTHEAST.

THE ONSHORE FLOW NORTH OF THE WARM FRONT WILL HOLD LOW LEVEL
MOISTURE IN OUR REGION THROUGH THE NIGHT WHICH WILL KEEP PATCHY
FOG AND DRIZZLE ACROSS THE AREA. WEAK VORTICITY IMPULSES
TRAVELING IN THE WEST SOUTHWEST MID LEVEL FLOW MAY ACT TO TOUCH
OFF SCATTERED TO ISOLATED SHOWERS. THERE IS THUNDERSTORM ACTIVITY
TO OUR WEST, BUT AS THESE RIDE OVER THE FRONTAL BOUNDARY TO OUR
SOUTH AND WEST, THEY SHOULD LOSE STEAM, SO NO THUNDERSTORMS ARE
EXPECTED ACROSS THE AREA OVERNIGHT.

THE CLOUD COVER IS FORECAST TO KEEP TEMPERATURES FROM DROPPING MUCH
OVERNIGHT. LOWS SHOULD BE MOSTLY IN THE 40S IN THE NORTH AND IN THE
50S IN THE SOUTH.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
THE LOW LEVEL MOISTURE WILL REMAIN IN OUR REGION INTO MONDAY
MORNING. AS A RESULT, THE DAY SHOULD BEGIN OVERCAST WITH PATCHY
DRIZZLE AND FOG ALONG WITH A CHANCE OF SHOWERS. THE MARINE LAYER
IS EXPECTED TO ERODE GRADUALLY FROM THE SOUTH THROUGH THE DAY AS
THE WARM FRONT LIFTS NORTHWARD. HOWEVER, THE IMPROVEMENT MAY NOT
REACH PARTS OF NORTHERN NEW JERSEY AND OUR ADJACENT COUNTIES IN
EASTERN PENNSYLVANIA BY DAY`S END.

DUE TO THE VARYING AMOUNTS OF CLOUD COVER, WE ARE ANTICIPATING A
WIDE SPREAD IN MAXIMUM TEMPERATURES. HIGHS MAY NOT GET OUT OF THE
50S IN THE FAR NORTH AND PERHAPS ALONG THE NORTHERN PART OF THE
JERSEY SHORE. MEANWHILE, MAXIMUM TEMPERATURES ARE FORECAST TO
APPROACH 80 IN OUR FAR SOUTHERN COUNTIES.

THE WIND SHOULD BEGIN THE DAY FROM THE NORTHEAST AND EAST AROUND
4 TO 8 MPH. THE DIRECTION IS EXPECTED TO VEER TOWARD THE SOUTHEAST
AND SOUTH AS THE MARINE LAYER ERODES.

MADE SOME UPDATES TO THE FORECAST WITH THE EVENING UPDATE TO
INCREASE THUNDERSTORMS CHANCES ACROSS FAR SOUTHEASTERN PA, SOUTHERN
NJ AND ESPECIALLY OUR DELMARVA ZONES. THE LATEST 12Z/18Z GUIDANCE
STILL SHOWS SOME DIFFERENCES REGARDING HOW FAR NORTH INTO OUR AREA
THE WARM FRONT ADVANCES BUT SOLUTIONS ARE CONVERGING TOWARD THE WARM
FRONT BEING IN CLOSE PROXIMITY TO THE PHILA METRO BY LATE AFTERNOON.
CONVECTION MAY BE SLOW TO DEVELOP DUE TO A LACK OF ORGANIZED/DEEP
LIFT INITIALLY ON MONDAY AFTERNOON. HOWEVER, LIFT SUBSEQUENTLY
INCREASES LATE IN THE AFTERNOON AND ESPECIALLY MONDAY NIGHT AS A
WAVE OF LOW PRESSURE ALONG THE FRONTAL BOUNDARY DEEPENING OVER THE
DC AREA, LOW-LEVEL CONVERGENCE INCREASES NEAR THE WARM FRONT
BOUNDARY. ADDITIONALLY, FORCING FOR ASCENT IS FORECAST TO DEEPEN
LATER MONDAY NIGHT IN RIGHT-ENTRANCE REGION OF AN UPPER-LEVEL JET
STREAK TO OUR NORTHWEST AND AHEAD OF AN APPROACHING MID-LEVEL
SHORTWAVE TROUGH.

THERE IS ALSO GROWING CONCERN FOR STRONG TO SEVERE THUNDERSTORMS
POTENTIALLY DEVELOPING ALONG AND SOUTH OF THE WARM FRONT DURING THE
LATE AFTERNOON AND EVENING. FORECAST CONVECTIVE INDICES FROM THE
18Z NAM WAS PARTICULARLY OMINOUS WITH 2000-3000 J/KG OF SBCAPE AND
45-55 KT OF DEEP-LAYER BULK SHEAR PRESENT IN THE WARM SECTOR FROM
ABOUT ILG TO ACY SOUTHWARD AT 21Z MON AND 00Z TUE. LAST NIGHT`S 00Z
RUN OF THE HI-RES NCAR ENSEMBLES ALSO INDICATE A SIMILAR FAVORABLE
ENVIRONMENT FOR CONVECTION IN THE WARM SECTOR ALTHOUGH MEAN FORECAST
INDICES ARE NOT QUITE AS EXTREME AS THE 18Z NAM (NOT SURPRISING
SINCE AN ENSEMBLE MEAN BLENDS OUT THE EXTREMES). NONETHELESS, THE
FORECAST ENVIRONMENT INDICATES A POTENTIAL FOR DAMAGING WINDS/WET
MICROBURSTS AND LARGE HAIL ACROSS OUR SOUTHERN ZONES. WILL ADD THE
SEVERE RISK IN THE HWO. FURTHER COORDINATE WITH SPC MAY BE NEEDED.

WE ALSO MAY TRANSITION TO A HEAVY RAINFALL EVENT MONDAY NIGHT
SOMEWHERE IN THE SOUTHERN TIER OF THE CWA NEAR THE WARM FRONT. MORE
DETAILS WILL BE PROVIDED IN UPCOMING FORECAST DISCUSSIONS IF
NECESSARY.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
LITTLE CHANGE FROM THE PREVIOUS FORECAST IN THIS TIME PERIOD.
UNSETTLED WEATHER FOR MUCH OF THIS TIME FRAME WITH TEMPERATURES
RUNNING SEVERAL DEGREES COOLER THAN NORMAL.

CONSIDERABLE UNCERTAINTY WITH THE SURFACE PATTERN DETAILS LATER
THIS WEEK AS THE DEEP UPPER TROUGH SETTLES IN OVER THE REGION.

BEST CHANCES FOR PRECIPITATION ARE IN THE MONDAY NIGHT/TUESDAY
TIMEFRAME AND THEN AGAIN THURSDAY/FRIDAY.

NEXT SUNDAY IS CURRENTLY THE DRIEST DAY IN THIS FORECAST PERIOD.

PRIMARILY USED 12Z SUPERBLEND IN THIS TIME PERIOD.  BUT 12Z
SUPERBLEND STRUGGLED WITH THE WINDS FOR MUCH OF THIS TIME PERIOD.
00Z NATIONAL BLEND PROVIDED BETTER CONTINUITY FOR WINDS WITH OUR
PREVIOUS FORECAST AND WITH ADJACENT OFFICES SO THAT WAS USED.
ALSO USED WPC GUIDANCE IN LIEU OF SUPERBLEND FOR DAY 7 TO REFLECT
LATEST FORECAST THINKING.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY, AND SURROUNDING AREAS.

IFR CONDITIONS ARE FORECAST TO PREVAIL THROUGH TONIGHT AND INTO
MONDAY MORNING AT OUR TAF SITES. THERE IS A CHANCE OF SHOWERS. ALSO,
PATCHY FOG AND DRIZZLE ARE POSSIBLE OVERNIGHT INTO EARLY MONDAY
MORNING. THE WIND IS EXPECTED TO FAVOR THE EAST AND NORTHEAST AROUND
4 TO 8 KNOTS.

GRADUAL IMPROVEMENT IS EXPECTED FROM THE SOUTH FROM LATE MONDAY
MORNING INTO MONDAY AFTERNOON. HOWEVER, THE SPEED AND EXTENT OF THE
IMPROVEMENT REMAINS A LOW CONFIDENCE FORECAST AT THIS TIME. WE HAVE
KEPT THE TAFS PESSIMISTIC BASED ON THE UNCERTAINTY IN THIS TYPE OF
WEATHER PATTERN. THE WIND DIRECTION SHOULD BEGIN TO VEER TOWARD THE
SOUTHEAST AND SOUTH ON MONDAY AFTERNOON, ESPECIALLY AT KACY, KMIV
AND KILG.

ALSO MONDAY AFTERNOON INTO THE EVENING, AS A COLD FRONT MOVES
ACROSS THE AREA AND LOW PRESSURE APPROACHES FROM THE WEST, THERE
IS A CHANCE FOR SHOWERS AND POSSIBLE THUNDERSTORMS TO INCREASE
ACROSS THE SOUTHERN PORTIONS OF THE AREA. WE CURRENTLY ONLY HAVE
SHOWERS IN THE TAFS, BUT THUNDERSTORMS MAY BE NEED TO BE INCLUDED
IN THE FUTURE.


OUTLOOK...
MON NIGHT THRU TUE NIGHT...SHOWERY CONDITIONS WITH LOWER CIGS/VSBYS
AT TIMES.

WED...MOSTLY VFR.

WED NIGHT THRU FRI...MORE SHOWERY CONDITIONS WITH LOWER CONDITIONS
POSSIBLE.

&&

.MARINE...
THE ONSHORE FLOW IS EXPECTED TO CONTINUE TONIGHT INTO MONDAY MORNING
WITH WEAK LOW PRESSURE DEVELOPING OFF OUR COAST. WE ANTICIPATE THAT
WAVE HEIGHTS ON OUR OCEAN WATERS WILL BUILD TO AROUND 5 FEET AND WE
WILL CONTINUE TO CARRY A SMALL CRAFT ADVISORY FOR SEAS. WE WILL
ADJUST THE TIME OF THE ADVISORY, STARTING IT AT 800 PM THIS EVENING
AND ENDING IT AT 400 PM MONDAY BASED ON THE LATEST GUIDANCE.

WIND SPEEDS ARE FORECAST TO REMAIN BELOW 20 KNOTS WITH THE DIRECTION
FAVORING THE NORTHEAST AND EAST TONIGHT AND MONDAY MORNING, AND THE
SOUTHEAST AND SOUTH ON MONDAY AFTERNOON.

OUTLOOK...
MONDAY NIGHT THRU FRIDAY NIGHT...MOSTLY SUB SCA CONDITIONS. SCT
SHOWERS THRU MUCH OF THE TIME. LOW END SCA SEAS POSSIBLE FRIDAY INTO
FRIDAY NIGHT.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM EDT MONDAY
     FOR ANZ450>455.

&&

$$

SYNOPSIS...SZATKOWSKI/ROBERTSON
NEAR TERM...IOVINO/ROBERTSON
SHORT TERM...IOVINO/KLEIN
LONG TERM...SZATKOWSKI
AVIATION...SZATKOWSKI/IOVINO/ROBERTSON
MARINE...SZATKOWSKI/IOVINO



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