Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 260858
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
358 AM EST FRI DEC 26 2014

.SYNOPSIS...
A HIGH PRESSURE SYSTEM OVER NORTH CAROLINA WILL SLOWLY MOVE EAST
TODAY THROUGH SATURDAY AND BE WELL OFFSHORE BY SATURDAY NIGHT. A
COLD FRONT IS FORECAST TO MOVE THROUGH OUR AREA SUNDAY BEFORE
SLOWING ITS SOUTHWARD PROGRESSION AS A WAVE OF LOW PRESSURE MOVES
ALONG IT ON MONDAY. A STRONG CANADIAN HIGH PRESSURE SYSTEM WILL
SLOWLY SINK SOUTH AND REACH THE NORTHERN PLAINS ON TUESDAY AND THE
GULF COAST STATES ON THURSDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
GREAT WEATHER EXPECTED ACROSS THE MIDDLE ATLANTIC REGION TODAY. HIGH
PRESSURE ACROSS THE SOUTHEAST STATES WILL RIDGE ACROSS THE AREA AS
UPPER HEIGHTS SLOWLY BUILD. THIS WILL RESULT IN MOSTLY SUNNY SKIES
AND MORE ABOVE NORMAL TEMPS FOR THE REGION. HIGHS WILL RANGE FROM
THE UPPER 40S TO LOW 50S ACROSS MOST AREAS. WINDS WILL BE LIGHT FROM
THE W/NW THIS MORNING...THEN W/SW BY SUNSET.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
MORE FAIR WEATHER TONIGHT WITH THE SFC HIGH MOVING OFF THE COAST.
SKIES WILL REMAIN MOSTLY CLR AND TEMPS WILL CONTINUE ABOVE NORMAL.
LOWS TONIGHT WILL BE IN THE LOW/MID 30S IN MOST AREAS. WINDS WILL BE
LIGHT.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

THE LONG TERM PERIOD WILL BRING COLDER WEATHER BACK INTO OUR CWA
WITH A TRANSITIONAL PCPN EVENT SUNDAY INTO MONDAY. THE GFS
INITIALIZATION AT 500MB LOOKS BETTER THAN IT DID LAST NIGHT AND
WAS ON PAR WITH THE ECMWF AND WRF-NMMB. DOMESTICALLY THE WRF-NMMB
LOOKED BETTER AT 850MB AND BOTH MODELS COMPARABLE AT 925MB. WHILE
THE MODELS HAVE COME CLOSER, THERE ARE STILL TIMING AND INTENSITY
DIFFERENCES THAT ONLY SUBTLE CHANGES INITIATED. WHILE WE THOUGHT
WE HAD THE DIURNAL BIAS OF FLATTER SOLUTIONS NIGHT SOUNDING RUNS,
MORE ROBUST SOLUTIONS DAY SOUNDING RUNS, THE ECMWF FLIPPED ON US
TONIGHT BECAUSE ITS DECAY OF ITS SOUTHWESTERN TROF IS SLOWER.

THE ECMWF ENSEMBLES INFER A SLIGHTLY NORTHWEST AND WARMER TRACK.
GREATEST UNCERTAINTY IS SMACK AT THE BASE OF THE SHORT WAVE TROF.
THERE WERE ABOUT 5 GEFS MEMBERS THAT WERE WETTER THAN THE OP AND
THE CAN GEFS, TWO MEMBERS WERE STRONGER, TWO COMPARABLE AND ABOUT
16 WEAKER THAN THE OP MODEL.

NO WEATHER ISSUES ON SATURDAY AS THE HIGH PRESSURE SYSTEM SHOULD BE
OFF THE NORTH CAROLINA COAST AND THE APPROACHING COLD FRONT STILL
WELL TO OUR WEST. THE PREDICTED CONVECTIVE TEMPERATURES OFF THE
SOUNDINGS ARE STILL IN THE 90S AND LOW 100S AND LOW LEVEL MOISTURE
EVEN ON THE WRF-NMMB IS NOT THAT PLENTIFUL. WE ARE EXPECTING A
MOSUNNY DAY WITH MAXIMUM TEMPERATURES A COUPLE OF DEGREES HIGHER
THAN TODAY. ONCE AGAIN THE FULL SUN MACROS OFF THE WRF-NMMB MODEL
SUPPORT GFS MOS MORE THAN ITS OWN NAM MOS (WHICH WAS NOT
UTILIZED).

SATURDAY NIGHT CLOUDINESS ASSOCIATED WITH THE COLD FRONT`S
PRECIPITATION SHOULD START ARRIVING IN THE AREA. MIN TEMP CONFIDENCE
IS LOWER THAN AVERAGE BECAUSE OF THIS AND ACTUAL MINS MIGHT OCCUR
EARLIER AT NIGHT WITH A BUMP UP IN TEMPS AS CLOUDS ARRIVE. FAR
NORTHWEST CWA ONLY AREA THAT GETS PREDICTED OMEGA AND LOCATION OF
LIQUID POPS LATE.

THE CDFNT IS PREDICTED TO PASS THROUGH OUR CWA ON SUNDAY AND SUNDAY
EVENING. MODELS NOT OVERLY ENTHUSED ABOUT SHOWER/PCPN POTENTIAL. WE
DO SEE THE BEST PREDICTED MID LEVEL QVEC CONVERGENCE WITH THE PCPN
POTENTIAL OCCURRING DURING THE DAY AND HIEST RELATIVELY SPEAKING
INSTABILITY. NOT MUCH DPVA OR REFLECTED OMEGA, SO WE KEPT POPS AS
CHANCE AND MENTION OF PCPN AS SCATTERED SHOWERS. WE DID NOT SWAY
MUCH FROM STAT GUIDANCE FOR MAX TEMPS.

THERE ARE FORCING SIMILARITIES WITH THE WAVE ON THE FRONT. SINCE ITS
PREDICTED TO BE RELATIVELY WEAK WE ARE NOT SEEING MUCH MID LEVEL WAA
PAST 12Z MON AND NOT MUCH PREDICTED ISENTROPIC LIFT. BUT, OUR CWA
WILL BE IN AN EXCELLENT ENTRANCE REGION OF A 180KT 250MB JET AND THE
700MB JET ALSO IS PREDICTED TO PASS ACROSS THE SOUTHERN PART OF OUR
CWA. MID LEVEL QVEC CONVERGENCE GETS REPLACED BY MID LEVEL FGEN
FORCING AS A PCPN PROCESSOR (AGAIN LEANING SOUTH). DIFFERENCES COME
AROUND WITH TIMING AND HOW STRONG THESE PROCESSES WILL BE. THE ADDED
ELEMENT IS THAT COLDER AIR WILL BE ADVECTING INTO THIS SYSTEM AND A
CHANGE TO NON LIQUID PTYPE IS EXPECTED TO OCCUR. BUT LIKE LAST
NIGHT, THE MOST LIKELY PLACES TO SEE A TRANSITION TO SLEET (ADDED IT
PER WRF FCST SOUNDINGS) AND SNOW (GENERALLY NORTHWEST OF THE FALL
LINE/I95 CORRIDOR AND WEST OF 287 IN NJ) ARE EXPECTED TO SEE THE
LOWEST AMOUNTS OF PCPN. IN ADDITION WARM WEATHER LEADING INTO
THIS EVENT AND SUPPOSIVE LIGHT PCPN INTENSITY SHOULD REDUCE
ACCUMULATION EFFICIENCY. ON THE OTHER HAND, PCPN TRANSITION
OCCURRING AT NIGHT WILL NOT HURT. RIGHT NOW ANY ACCUMS DONT LOOK
TO BE MUCH, BUT MIGHT COINCIDE WITH THE MONDAY MORNING COMMUTE.
WE WILL ADD A MENTION IN THE HWO GIVEN THERE ARE STILL
UNCERTAINTIES TO THE STRENGTH OF THE SYSTEM AND DO NOT WANT TO
SELL IT SHORT. TIMING WE ARE CLOSEST TO THE PARALLEL GFS. THERMAL
FIELDS WITH THE GFS AND ECMWF WERE FAIRLY CLOSE AND 925S AND 850S
TEMPS WERE USED AS THE DEMARCATION OF NON-LIQUID. AS PCPN
INTENSITY DECREASES AS MONDAY CONTINUES, A BACKWARD CHANGE OR MIX
TO SOME RAIN MIGHT OCCUR.

GIVEN THE FASTER TREND, WE DECIDED TO REMOVE THE MENTION OF POPS FOR
MONDAY NIGHT. THE SHORT WAVE ON TUESDAY IS PREDICTED TO BE SO
CHANNELIZED AND RELATIVELY WEAKER, WE ONLY KEPT THE MENTION OF
FLURRIES IN NORTHWEST. WE DID ADD FLURRIES IN AS A STARTER FOR
WEDNESDAY AS A MUCH STRONGER AND MORE ORTHOGONAL SHORT WAVE TROF IS
PREDICTED TO MOVE THROUGH. BY TUESDAY AND NEW YEARS EVE
TEMPERATURES SHOULD BECOME COLDER THAN NORMAL. NO CHANGE TO THURSDAY
(NEW YEARS DAY) FORECAST WAS MADE AS 2015 IS EXPECTED TO COMMENCE
RELATIVELY QUIETLY.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

WONDERFUL FLYING CONDITIONS TODAY AND TONIGHT AS HIGH PRESSURE RULES
THE WEATHER PICTURE. SKIES WILL FEATURE JUST SOME HIGH CLOUDINESS AT
TIMES TODAY. WINDS WILL BE WRLY/NWRLY AROUND 5 KNOTS EARLY TODAY AND
THEN WINDS WILL SHIFT MORE SWRLY AT 5 TO 10 KNOTS LATER THIS
AFTERNOON. TONIGHT SKC AND CALM OR VRY LGT SW WINDS.

OUTLOOK...
SATURDAY...VFR.

SATURDAY NIGHT...SOME MVFR CIGS POSSIBLE NORTHWEST AIRPORTS, VFR CIGS
ELSEWHERE.

SUNDAY INTO MONDAY...MVFR, POSSIBLY IFR, CONDITIONS POSSIBLE AT
TIMES AS WAVES OF PRECIPITATION MOVE FROM NORTH TO SOUTH ACROSS THE
AREA. THE NORTHERN PART OF THE PRECIPITATION SHIELD COULD BE SNOW.

MONDAY NIGHT AND TUESDAY...VFR.

&&

.MARINE...
HIGH PRESSURE OFF TO THE SOUTH WILL BUILD ACROSS THE WATERS TODAY
AND THEN MOVE TO THE EAST TONIGHT. WINDS AND SEAS WILL REMAIN SUB-
SCA CONDITIONS THROUGH THE PERIOD. WINDS WILL BE W OR NW THIS
MORNING AND THEN BACK TO MORE OF A W OR SW DIRECTION TONIGHT.
SPEEDS WILL BE AROUND 10 KNOTS TODAY AND CLOSER TO 5 KNOTS
TONIGHT. SEAS ON THE OCEAN 2 TO 3 FT AND 1 TO 2 FT OVER DEL BAY.

OUTLOOK...
SATURDAY AND SATURDAY EVENING...SUB SMALL CRAFT ADVISORY CONDITIONS
EXPECTED.

SATURDAY NIGHT INTO SUNDAY MORNING...A SLIGHTLY STRONGER SOUTHWEST
FLOW PRECEDING A COLD FRONT WILL BRING WIND GUSTS CLOSER TO SMALL
CRAFT ADVISORY CRITERIA ON THE OCEAN.

SUNDAY AFTERNOON AND NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS
EXPECTED.

MONDAY AND MONDAY NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED.
LOWER CONFIDENCE AS A WAVE OF LOW PRESSURE IS PREDICTED TO FORM
SOUTH OF THE AREA WATERS ON THE MENTIONED FRONT.  ITS POSSIBLE THAT
SMALL CRAFT ADVISORY CONDITIONS MIGHT OCCUR IF THIS LOW INTENSIFIES
FASTER THAN WE ARE CURRENTLY FORECASTING.

TUESDAY...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED.

&&

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

&&

$$
SYNOPSIS...GIGI/MIKETTA
NEAR TERM...O`HARA
SHORT TERM...O`HARA
LONG TERM...GIGI
AVIATION...GIGI/MIKETTA/O`HARA
MARINE...GIGI/O`HARA






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