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Area Forecast Discussion
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000
FXUS61 KPHI 200814
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
414 AM EDT MON OCT 20 2014

.SYNOPSIS...
A HIGH PRESSURE SYSTEM NEAR NORFOLK WILL MOVE OFFSHORE TODAY.
A LOW PRESSURE SYSTEM WITH AN ASSOCIATED COLD FRONT OVER LAKE 
SUPERIOR WILL DIVE SOUTHEAST REACHING OUR REGION DURING THE DAY ON 
TUESDAY. ANOTHER LOW PRESSURE SYSTEM WILL FORM OFF THE MID ATLANTIC 
COAST LINE ON TUESDAY AND THEN DRIFT SLOWLY NORTHEAST, REACHING CAPE 
COD ON THURSDAY AND NOVA SCOTIA ON FRIDAY. HIGH PRESSURE WILL
THEN BRIEFLY MOVE IN FROM THE WEST LATE FRIDAY. A COLD FRONT
SHOULD PASS THROUGH THE NORTHEAST AROUND SATURDAY NIGHT, WITH
ANOTHER HIGH PRESSURE SYSTEM REACHING THE GREAT LAKES ON SUNDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE FROST ADVISORY AND FREEZE WARNING REMAINS IN EFFECT FOR EARLY 
THIS MORNING, AS MANY AREAS ARE WELL DOWN INTO THE 30S. THE HIGH 
LEVEL CLOUDS THOUGH MAY HAVE SLOWED THE TEMPERATURE DROP A LITTLE 
FOR SOME SPOTS.

HIGH PRESSURE WILL BE SHIFTING OFFSHORE TODAY ALLOWING A 
SOUTHWESTERLY FLOW AT THE SURFACE TO DEVELOP. THIS FLOW WILL BE MUCH 
LESS COMPARED TO THE GUSTINESS THAT WAS OBSERVED YESTERDAY. A ROBUST 
SHORT WAVE DIVING SOUTHEASTWARD FROM THE MIDWEST WILL HELP CARVE OUT 
ANOTHER UPPER-LEVEL TROUGH ACROSS THE GREAT LAKES AND OHIO VALLEY 
DURING THE COURSE OF TODAY. DOWNSTREAM FROM THIS, SOME WEAK WAA IS 
FORECAST TO OCCUR ACROSS THE MID ATLANTIC. THIS COMBINED WITH THE 
PRESENCE OF AN UPPER-LEVEL JET WILL SPREAD AREAS OF MID AND HIGH 
LEVEL CLOUDINESS ACROSS THE REGION. THE MAIN LIFT ASSOCIATED WITH 
THE AMPLIFYING UPPER-LEVEL TROUGH IS FORECAST TO REMAIN TO OUR WEST, 
THEREFORE WE MAINTAINED A DRY FORECAST TODAY. WE DID CARRY SOME 
ADDITIONAL CLOUDINESS THOUGH FOR MANY AREAS.

AS FOR HIGH TEMPERATURES, WE USED A MODEL/MOS BLEND WHICH RESULTS 
IN MILDER TEMPERATURES COMPARED TO YESTERDAY. THIS LINES UP WITH THE 
WEAK WAA THAT IS ALSO FORECAST THROUGH THE DAY ALONG WITH A 
SOUTHWESTERLY SURFACE FLOW.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
AN UPPER-LEVEL TROUGH WILL CONTINUE TO AMPLIFY ACROSS THE GREAT 
LAKES AND NORTHEAST. AS THIS OCCURS, LOW PRESSURE ORGANIZING AT THE 
SURFACE IS FORECAST TO BE IN THE GENERAL VICINITY OF THE EASTERN 
GREAT LAKES LATER TONIGHT.

THERE IS SOME WAA BEING MAINTAINED AHEAD OF THIS SYSTEM, BUT OVERALL 
THE BEST FOCUS FOR THIS IS FORECAST TO BE TO OUR SOUTH AND EAST. IN 
ADDITION, A DECENT SHOT OF LOW-LEVEL THETA-E ADVECTION IS FORECAST 
TO ARRIVE THROUGH THE NIGHT. AS THE ATMOSPHERE MOISTENS AND THE 
LARGE SCALE ASCENT BEGINS TO OVERSPREAD THE REGION LATE, SOME 
SHOWERS COULD DEVELOP. THIS LOOKS TO BE ACROSS OUR WESTERN ZONES 
WHICH IS WHERE WE HAVE THE HIGHEST /CHC/ POPS LATE. THERE MAY ALSO 
BE ANOTHER AREA OF FOCUS, WHICH IS OFFSHORE WHERE THE LEADING EDGE 
OF THE STRONGER THETA-E ADVECTION INTERACTS WITH SOME INSTABILITY 
PARTIALLY DUE TO THE GULF STREAM. OVERALL, THE CLOUDS ARE FORECAST 
TO LOWER SOME THROUGH THE NIGHT FROM WEST TO EAST AND THE POPS WERE 
GRADUALLY INCREASED AS WELL.

AS FOR LOW TEMPERATURES, WITH THE THICKENING CLOUDS AND A WEAK 
SOUTHWESTERLY FLOW IN PLACE IT WILL BE A MILDER NIGHT. OVERALL, WE 
USED A MOS BLEND WITH SOME MINOR ADJUSTMENTS.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
THE WRF-NMMB 500MB INITIALIZATION WAS BETTER THAN THE GFS OR THE 
ECMWF. THE LATTER WAS TOO AMPLIFIED FROM THE MISSISSIPPI VALLEY
WESTWARD. THIS PRESENTS THE FCST CONUNDRUM AS THE DP/DT IS SHOWING
STRONGER RIDGING IN CENTRAL NOAM VS LAST NIGHT'S SOUNDING RUN. WE
SEEM TO BE VACILLATING AROUND A LINE VS TRENDING STEADILY IN ANY
SPECIFIC, CONSISTENT DIRECTION. E.G. AT 78 HRS THE CAN
GGEM/WRF/GFS/GEFS ENSEMBLE MEAN SFC LOWS ARE STACKED ON TOP OF ONE
ANOTHER. THIS FORECAST PACKAGE IS GOING TO GO WITH THIS CONSENSUS
AS IT INCLUDES THE BETTER INITIALIZED CLUSTERING PLUS THERE IS NO
CLEAR CUT DP/DT. IN THE GRAND SCHEME, IT WILL NOT MAKE THE MIDDLE
OF THE WEEK PLEASANT, JUST A SLIGHTLY FASTER IMPROVEMENT THAN THE
ECMWF HAS FOR THE LATTER PART.

THERE IS FAIRLY GOOD MODELING AGREEMENT ON TUESDAY MORNING OF OUR 
CWA BEING IN A RELATIVE PCPN LULL BETWEEN IMPULSES. POPS INCREASE 
DURING THE AFTERNOON AS THE PRIMARY LOW PRESSURE SYSTEM APPROACHES 
OUR CWA AND IT BECOMES MORE UNSTABLE ALOFT. OTHER THAN THE WRF-NMMB, 
OTHER MODELS ARE NOT UNSTABLE ENOUGH FOR THUNDER. THE 18Z WRF WAS  
THE MOST UNSTABLE OF THE 21 SREF MEMBERS IN OUR CWA, SO SHOWERS YES, 
BUT NO THUNDER. MAX TEMPS CLOSE TO A STAT GUIDANCE BLEND.

ON TUESDAY NIGHT THERE IS STILL A CONVECTIVE LOOK TO THE SOUNDINGS 
AND INSTABILITY IS FORECAST TO BE JUST OFFSHORE. THIS GETS TRICKY 
WITH THE 2NDRY CYCLOGEN AS TO HOW QUICKLY WILL PCPN GET GENERATED
PLUS ANY LEFTOVER CONVECTIVE TRIGGERING. THE CONVECTIVE ELEMENT
TO IT HAS BEEN PRODUCING VERY LITTLE CONSISTENCY IN THE QPF FIELDS
OTHER THAN TO SUGGEST HEAVIER RAIN BECOMES A POSSIBILITY EAST. THE
SECONDARY DEVELOPMENT HAS BEEN IN A STEADY LINE TRENDING A LITTLE
BIT SLOWER. SO FOR NOW WHILE WE HAVE LIKELY POPS ACROSS MOST OF
OUR CWA, WE DO NOT HAVE MODERATE RAIN MENTIONED.

WEDNESDAY LOOKS TO BE THE MOST LIKELY FCST TIME PERIOD FOR RAIN, 
ESPECIALLY EAST AS OUR CWA WILL BE IN THE MOST DIVERGENT LOCATION OF 
THE UPPER LEVEL JET AND THE STGST FCST MID LEVEL QVEC CONVERGENCE. 
WE UPPED POPS AND ARE CARRYING SOME MODERATE INTENSITY RAIN EAST.
THE ONGOING 2NDRY CYCLOGENESIS APPEARS TO BE OCCURRING TOO CLOSE TO 
OUR CWA TO PRODUCE A LONG ENOUGH FETCH OR PERIOD OF ONSHORE WINDS 
FOR TIDAL FLOODING. IF THE LOW DOES FORM FARTHER TO THE SOUTH, THE 
CHANCES FOR TIDAL FLOODING WOULD INCREASE. WE ARE ASSISTED ALSO THAT 
THE MOON'S PERIGEE DOES NOT COINCIDE WITH THE NEW MOON AND THE 
HIGHEST SPRING TIDES WITH THIS LUNAR PHASE ARE ON THE WEEKEND, TWO 
DAYS AFTER THE NEW MOON. 

MODELS START DIVERGING COME WEDNESDAY NIGHT AS TO HOW MUCH PCPN WILL 
GET WRAPPED INTO OUR CWA. THE CONSENSUS IS A LONGER MORE CIRCUITOUS 
ROUTE FOR IT TO GET BACK INTO OUR AREA. WE LOSE THE PREDICTED HIGHER 
LEVEL MOISTURE AND LEANS MORE TOWARD SMALLER RAIN DROPS OR DRIZZLE 
AS A PREDOMINATE PTYPE. THIS DIVERGENCE IN THE MODELS CONTINUES ON 
THURSDAY AS TO HOW MUCH PCPN CAN WRAP BACK INTO OUR CWA. THE 
CONSENSUS CLUSTERING IS THAT MOST OF THIS WILL BE NORTH OF OUR CWA. 
POPS WERE KEPT AS CHANCE, BUT THE PERSISTENT NE FLOW WILL NOT MAKE 
FOR TOO NICE A DAY. BY WEDNESDAY AND ESPECIALLY THURSDAY WE ARE 
GOING BELOW STAT GUIDANCE FOR TEMPERATURES.

SLOW IMPROVEMENT THE REST OF THE WORK WEEK WITH AT LEAST A WELL 
TIMED BREAK COME THE WEEKEND. AN APPROACHING COLD FRONT IS NOT 
EXPECTED TO HAVE ANY MOISTURE TO GENERATE SHOWERS. AS PREVIOUSLY 
MENTIONED A PREDICTED TELECONNECTION SWITCH TO A POSITIVE AO/NAO AND 
NEGATIVE PNA WILL BRING A MILDER REGIME BACK INTO THE CONUS. NOT 
SURPRISING WE ARE HAVING A PCPN EVENT DURING THIS SWITCH EITHER. SO 
BY THE WEEKEND FAIR WEATHER RETURNS ALONG WITH ABOVE NORMAL 
TEMPERATURES. 

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY AND SURROUNDING AREAS.

TODAY...VFR, WITH A CEILING AT TIMES MAINLY AT OR ABOVE 15000 FEET. 
LIGHT AND VARIABLE WINDS, BECOMING SOUTHWESTERLY AND INCREASING TO 
AROUND 10 KNOTS.

TONIGHT...VFR, WITH A CEILING LOWERING TO BETWEEN 5000-8000 FEET. 
SOME SHOWERS MAY APPROACH KABE AND KRDG TOWARD DAYBREAK. 
SOUTH-SOUTHWEST WINDS DIMINISHING TO 5 KNOTS, AND EVEN BECOMING 
LIGHT AND VARIABLE AT SOME TERMINALS. 

OUTLOOK...
TUESDAY...SOME MVFR CONDITIONS MAINLY DUE TO CIGS ARE POSSIBLE 
DURING THE AFTERNOON.

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...PREVAILING MVFR CONDITIONS 
(MAINLY CIGS) WITH SOME IFR CONDITIONS (MAINLY DUE TO CIGS AGAIN) 
SHOULD OCCUR. HIGHEST POSSIBILITIES EASTERN TERMINALS AND AIRPORTS. 
GUSTIER NORTHEAST TO NORTH WINDS EXPECTED WEDNESDAY AND WEDNESDAY 
NIGHT.

THURSDAY...PREVAILING MVFR CONDITIONS. GREATEST DURATION NORTHERN 
AIRPORTS AND TERMINALS. GUSTY NORTHWEST WINDS.

THURSDAY NIGHT AND FRIDAY...BECOMING VFR THURSDAY NIGHT AND VFR 
FRIDAY. GUSTY NORTHWEST WINDS POSSIBLE.
 
 
&&

.MARINE...
TODAY AND TONIGHT...THE CONDITIONS ARE EXPECTED TO BE BELOW SMALL 
CRAFT ADVISORY CRITERIA. HIGH PRESSURE SHIFTS TO THE EAST ALLOWING A 
SOUTH-SOUTHWEST FLOW TO DEVELOP. THIS WILL BE ON THE LIGHTER SIDE 
FOR MUCH OF TODAY, HOWEVER IS IS FORECAST TO INCREASE SOME LATER 
TODAY AND TONIGHT FOR A TIME. THE OVERALL BOUNDARY LAYER FLOW SHOULD 
BE LIGHT ENOUGH THOUGH TO KEEP THE WINDS BELOW 25 KNOTS. THE SEAS 
ARE ANTICIPATED TO BE AT OR BELOW 4 FEET.

OUTLOOK...
TUESDAY AND TUESDAY NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS 
EXPECTED.

WEDNESDAY THROUGH FRIDAY...A PROTRACTED PERIOD OF SMALL CRAFT 
ADVISORY CONDITIONS IS POSSIBLE THROUGH THE PERIOD. A SECONDARY LOW 
PRESSURE SYSTEM DEVELOPMENT SHOULD INCREASE THE GRADIENT ON 
WEDNESDAY AND MORE CONFIDENTLY WEDNESDAY NIGHT. WINDS AND SEAS 
SHOULD LIKELY PEAK ON WEDNESDAY NIGHT AND THURSDAY WITH SLOW 
IMPROVEMENT THEREAFTER WITH DELAWARE BAY FIRST TO LOOSE SMALL CRAFT 
ADVISORY CONDITIONS.
 
&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FREEZE WARNING UNTIL 8 AM EDT THIS MORNING FOR PAZ054-055-061-
     062.
     FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR PAZ060-101>106.
NJ...FREEZE WARNING UNTIL 8 AM EDT THIS MORNING FOR NJZ001-007>010-
     020>022-027.
     FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR NJZ012-013-
     015>019-023.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...FRANCK/GAINES/GIGI
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...GIGI
AVIATION...GAINES/GIGI/GORSE
MARINE...GAINES/GIGI/GORSE






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