Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 161036 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 536 AM EST SUN NOV 16 2014 .SYNOPSIS... HIGH PRESSURE ALONG THE MID ATLANTIC COAST WILL SHIFT OFFSHORE TODAY AS LOW PRESSURE FORMS IN LOUISIANA. THE LOW RACES NORTHEAST THROUGH THE MID ATLANTIC STATES MONDAY. COLD HIGH PRESSURE IS FORECAST TO FOLLOW FOR TUESDAY AND WEDNESDAY, THEN A COLD FRONT IS EXPECTED TO PASS THROUGH OUR REGION LATE THURSDAY OR FRIDAY. HIGH PRESSURE SHOULD BUILD IN FOR SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... RIDGING WILL CONTINUE TO MOVE OFFSHORE TODAY WHILE A RETURN FLOW SETS UP. MID-LEVEL MOISTURE WILL CONTINUE TO ADVECT IN FROM THE SOUTH-SOUTHWEST AND WE WILL SEE AMPLE MID-LEVEL CLOUD COVER. SOUTHERLY SURFACE FLOW, INCREASING BY THE AFTERNOON, SHOULD ALLOW FOR WARMING TEMPERATURES, POSSIBLY INTO THE UPPER-40S, WITH INCREASING DEWPOINTS...THOUGH STILL DRY ENOUGH IN THE BOUNDARY LAYER TO NOT SEE PRECIPITATION. ANY AFTERNOON MIXING SHOULD ALSO HELP TO KEEP LOW-LEVEL MOISTURE LOWER. THERE IS LIKELY TO BE A LOT OF VIRGA AROUND THIS AFTERNOON AS THE FIRST NORTHERN STREAM SHORTWAVE PUSHES THROUGH LATER THIS AFTERNOON...AGAIN DRY SUB-CLOUD LAYER. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... WINTER WEATHER ADVISORY LATE TONIGHT FOR THE POCONOS AND NORTHWEST NEW JERSEY. CONDITIONS START OFF TRANQUIL BUT START TO BECOME UNSETTLED LATER THIS EVENING. WAVY WARM FRONT WITH A WEAK IMPULSE RIDING ALONG IT BEGINS TO NEAR FROM THE SOUTH-SOUTHWEST. EXPECTING PRECIPITATION TO OVERSPREAD LATER THIS EVENING FROM SOUTHWEST TO NORTHEAST. THE QUESTION THEN BECOMES HOW FAST DO THE LOW-LEVEL TEMPERATURES MODIFY AS THE WAVE MOVES BY WITH AN INITIAL SHOT OF WARM AIR ADVECTION. THE TRACK OF THE SURFACE WAVE HAS BEEN WAFFLING THE PAST SEVERAL NIGHTS AND DEPENDING ON ITS PROGRESSION WOULD MEAN A DIFFERENCE IN PTYPE...MOSTLY ACROSS OUR NORTHWEST ZONES. IT SHOULD BE NOTED THAT THE 00Z MODELS, GFS/NAM/EC INITIALIZED TOO WARM UPSTREAM AT 850MB WHILE THE GGEM/RGEM WERE TOO COLD. MOVING DOWN TO 925MB, THE GFS HAD THE BETTER INITIALIZATION, THOUGH NOT PERFECT. THAT BEING SAID DECIDED TO DELAY THE CHANGEOVER ACROSS OUR NORTHWESTERN ZONES FROM SNOW TO SLEET/RAIN/FREEZING RAIN BY A FEW HOURS. THE WESTERN BURBS COULD START OUT AS A MIX BEFORE CHANGING OVER TO ALL RAIN LATER THIS EVENING WHILE THE CITY SOUTH AND EAST ARE EXPECTED TO BE ALL LIQUID. DO NOT THINK, EVEN WITH A FEW HOURS OF LIGHT SNOWFALL, THAT WE WILL HAVE ENOUGH QPF FOR A BIGGER FRONT END EVENT IN THE POCONOS AND NORTHERN NEW JERSEY. WITH MORE MIXING OCCURRING AND WARMING LOW-LEVEL TEMPERATURES, THIS SHOULD CUT DOWN ON RATIOS. STILL THINK THAT WE WILL HAVE AT OR BELOW FREEZING TEMPERATURES EARLY TOMORROW MORNING, IF EVEN FOR A COUPLE HOURS, WHERE FREEZING RAIN WILL THE BIGGEST THREAT...JUST IN TIME FOR THE EARLY MORNING COMMUTE. AS WAS STATED ABOVE, THE TRACK OF THE WEAK LOW WILL BE KEY BUT FOR NOW THE OFFSHORE RIDGING SHOULD BE FAR ENOUGH EAST TO KEEP THE LOW FROM BEING FORCED TO THE WEST. IF WE ARE ABLE TO TAP INTO THE DEEPER MOISTURE EARLIER AND SEE MORE MODERATE TO HEAVY PRECIPITATION THE SUB-FREEZING SURFACE TEMPERATURES SHOULD BE ABLE TO MIX OUT EASIER...QUICKER TRANSITION TO PLAIN RAIN. NOT EXPECTING MUCH IN THE WAY OF RADIATIONAL COOLING TONIGHT THOUGH WE SHOULD SEE MORE EVAPORATIVE AND WEAK DYNAMICAL COOLING OCCUR. EVEN WITH ALL THE CLOUD COVER IN PLACE AND A WARMER STARTING POINT THAN ON SATURDAY TEMPERATURES WILL QUICKLY DROP...BLEND OF THE MET/MAV WAS USED WITH HEAVIER WEIGHTING ON THE MAV. && .LONG TERM /MONDAY THROUGH SATURDAY/...
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**ON GOING ELEVATION ICING ADVY NW FRINGE OF AREA FOLLOWED BY COLDEST AIR OF THE SEASON ..SO FAR.. WEDNESDAY MORNING** HAZARDS: ON GOING WXA DURING THE MORNING WHERE MOST CONFIDENT. GALE LATER MON NIGHT - TUE NIGHT. 500 MB: HIGH AMPLITUDE TROUGH CENTRAL NORTH AMERICA MONDAY ROTATES NEWD AS IT REACHES THE EAST COAST LATE TUESDAY. A STRONG SHORT WAVE FOLLOWS INTO THE GREAT LAKES REGION THURSDAY SHIFTING E-NEWD ACROSS THE NORTHEAST FRIDAY WITH CONSIDERABLE WARMING HEIGHTS TO FOLLOW HERE NEXT WEEKEND. MEANWHILE A NEW TROUGH FORMS IN THE PLAINS NEXT SUNDAY. TEMPERATURES: CALENDAR DAY AVERAGES 10 TO 15 BELOW NORMAL TUESDAY, 15 TO 18 BELOW WEDNESDAY, NEAR 10 BELOW THU - SAT AND MILDER SUNDAY BUT STILL A BIT BELOW NORMAL. NOTE: THE 00Z/16 OP EC IS MUCH COLDER AGAIN FRIDAY. SO ANY POTENTIALLY LENGTHY WARMUP SEEMS TO BE DELAYED UNTIL AT LEAST NEXT SUNDAY! FORECAST BASIS: UNLESS OTHERWISE NOTED THE LONG TERM PERIOD OF THIS FORECAST IS GENERALLY BASED ON A 50 50 BLEND OF THE 00Z/16 NAM/GFS MOS FOR THE PERIOD MONDAY - TUESDAY. THEN THE 00Z/16 GFS MOS COMPRISES TUESDAY NIGHT AND WEDNESDAY. THEREAFTER (WEDNESDAY NIGHT ONWARD) THE 0503Z/16 WPC GRIDDED GUIDANCE WHICH AT TIMES IS BLENDED 50 50 WITH THE 00Z/16 MEXMOS. ALL THIS IS EVENTUALLY CHECKED AGAINST THE 00Z/16 ECMWF TO SEE IF WE`RE IN THE BALLPARK WITH ECMWF CYCLICALLY PERSISTENT 18Z 2 METER TEMPERATURES (SEEMS LIKE A RECENT WARM BIAS IN THOSE EC 2M TEMPS). ON FRIDAY... YOU WILL SEE WE ARE CONSIDERABLY WARMER THAN THE ECMWF AND UNSURE WHICH SOLUTION WILL BE CLOSEST TO REALITY. PRECIPITATION PROBABILITY GUIDANCE IS CHECKED AGAINST THE 21Z/15 SREF 3HRLY POPS FOR .01 THROUGH 12Z WEDNESDAY AND THEREAFTER THE 00Z/16 GEFS 6HR POPS FOR 0.05. THE DAILIES BELOW... MONDAY...WE CONTINUE TO EXPECT A FREEZING RAIN EVENT LINGERING TIL ABOUT 9 OR 10 AM ACROSS THE POCONOS AND ELEVATED FAR NORTHWESTERN NEW JERSEY. THE WSW IS POSTED. QUESTIONS ARISE ON HOW MUCH SOUTHERLY FLOW WILL IMPINGE ON THE I95 CORRIDOR AND WHETHER THE 50S/60S WARM SECTOR OF THE NEWD MOVING WARM FRONTAL WAVE CAN REACH I95. MULTI MODELS SAY IT WILL WARM TO ABOUT I95 AND SO WE HAVE A WARMER FCST THAN YDY... HOWEVER...ITS NOT A CERTAINTY AND IF THE COOLER GGEM PREVAILS...TEMPS WILL BE COOLER ALONG THE I 95 CORRIDOR. I DONT SEE TEMPS WARMER THAN CURRENTLY IN OUR 330 AM FCST. THE 06Z RUN OF THE GFS IS ABOUT 5F COLDER ALONG THE I95 CORRIDOR...SO UNCERTAINTY REGARDING MAX TEMPS MONDAY. GUSTY SOUTHERLY WINDS OF 20-30 MPH COULD DEVELOP IN THE WARM SECTOR MONDAY AFTERNOON...ESPECIALLY DELAWARE AND SE NJ. THERE COULD BE A PERIOD OF EXTENSIVE FOG NEAR THE WARM FRONTAL WAVE MONDAY AFTERNOON....I95 NWWD. THE FCST QPF IS DIRECTLY FROM WPC. PWAT UP TO 1.3 INCHES WITH THE WARM FRONTAL WAVE SHOULD PERMIT BRIEF PERIODS OF HEAVY RAIN ALONG THE VORTICITY RICH 850 MB CONVERGENCE ZONE. TOTALS FOR THE EVENT ARE FORECAST BETWEEN A HALF INCH AND 1.25 INCHES. WHILE WIDESPREAD FLOODING IS NOT EXPECTED, LOCALIZED PONDING OF WATER IS LIKELY IN AREAS OF POOR DRAINAGE, ESPECIALLY WHERE LEAVES AND OTHER DEBRIS ARE BLOCKING STORM DRAINS. THE BACK EDGE OF THE RAIN WILL BEGIN PUSHING OFF THE COAST ON MONDAY EVENING, AS LOW PRESSURE MOVES TO OUR NORTHEAST PULLING A COLD FRONT OFF THE COAST. LATE MONDAY EVENING THROUGH TUESDAY NIGHT...STRONG COLD ADVECTION WITH PARTLY CLOUDY SKIES AND NORTHWEST WIND GUSTS INCREASING TO 25-30 MPH BY DAYBREAK TUESDAY AND THEN TO 35 OR 40 MPH DURING THE DAY TUESDAY AND ONLY SLOWLY DIMINISHING TUESDAY NIGHT. HIGH TEMPERATURES TUESDAY COULD OCCUR AT MIDNIGHT TUESDAY MORNING WITH ONLY A COUPLE OF DEGREES RISE FROM THE 7 AM TUESDAY READINGS. LOWS FOR THE DAY WILL OCCUR NEAR 1159 PM TUESDAY. THE LAKE EFFECT MACHINE OVER THE GREAT LAKES WILL BE SENDING STREAMERS OF MOISTURE EAST SOUTHEASTWARD ACROSS THE APPALACHIANS. THIS COMBINED WITH THE TROUGH ALOFT PASSING BY STEEPENS LAPSE RATES TO 7C/KM AND LIKELY RESULTS IN SNOW SHOWERS PRODUCING AN INCH OR 2 OF FLUFFY SNOW IN THE POCONOS AND FLURRIES FURTHER SE TO I-78 TUESDAY AFTERNOON AND NIGHT. FOR NOW WE HAVE IS AS CHANCE SNOW SHOWERS. NEAR RECORD COLD IS STILL POSSIBLE IN THE POCONOS TO NEAR READING WEDNESDAY MORNING. SEE THE CLI SECTION. WEDNESDAY...DRY WEATHER AND HIGH PRESSURE ARE FORECAST WITH LESS WIND BUT VERY COLD DAYTIME TEMPS. THURSDAY...WARMING UP AHEAD OF THE NEXT COLD FRONT. FRIDAY...WEAK LOW PRESSURE AND A COLD FRONTAL PASSAGE WITH A PERIOD OF SHOWERS SOUTH...POSSIBLY SNOW NEAR AND NORTH OF I-95. THE WEATHER THIS DAY IS NOT CONFIDENTLY DETERMINED SINCE THERE IS A LACK OF CONSENSUS BETWEEN THE RELIABLE MODELS THAT WE USE DAILY. SATURDAY...HIGH PRESSURE AND COLDER.
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&& .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THIS MORNING - TODAY...VFR. SOUTHERLY WINDS AROUND 8 TO 10 KNOTS EXPECTED. ALTOCU FIELD WILL LOWER WITH TIME...WE SHOULD REMAIN DRY TODAY. TONIGHT...MVFR/IFR EXPECTED. RAIN/SNOW WILL MOVE IN FROM THE SOUTHWEST LATER THIS EVENING. CIGS WILL BEGIN TO LOWER AND FALL INTO THE MVFR RANGE AFTER MIDNIGHT. MOSTLY RAIN, AND HEAVY AT TIMES, WILL DROP VSBYS INTO THE IFR RANGE. COULD BE SOME RAIN/SNOW MIXING AT RDG/ABE LATE TONIGHT BEFORE GOING OVER TO ALL RAIN. OUTLOOK... MONDAY...MVFR AND IFR IN RAIN. LIGHT WINDS KABE...KRDG AND KTTN. MAY BE LIGHT WIND ALL DAY VCNTY KPHL. LLWS POSSIBLE KACY IN THE AFTN ALONG WITH SOUTHERLY GUST 25 KT. MONDAY NIGHT...CONDITIONS IMPROVING FROM MVFR AND IFR TO VFR BY MIDNIGHT AS DRY AIR BUILDS INTO OUR REGION FROM THE WEST WITH GUSTS TO 25 OR 30 KT BY DAYBREAK TUESDAY. TUESDAY...MAINLY VFR WITH A GUSTY WEST WIND OF 30 TO 35 KT. TUESDAY NIGHT THROUGH THURSDAY...MAINLY VFR. GUSTY WEST WINDS TUESDAY NIGHT AND WEDNESDAY MORNING TO 25 KT.
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&& .MARINE... TODAY - TONIGHT...SUB-SCA CONDITIONS EXPECTED. WINDS WILL INCREASE OUT OF THE SOUTH LATER TODAY WITH GUSTS UPWARDS OF 20 KNOTS. SEAS WILL ALSO BEGIN TO CLIMB BACK TOWARDS THE 3-4 FEET RANGE LATE TONIGHT AS A WEAK COASTAL LOW PRESSURE MOVES THROUGH. OUTLOOK... MONDAY...WE MAY YET NEED A SOUTHERLY GALE FOR THE DE CW MONDAY AFTN. FOR NOW AN SCA IS POSTED. NO WIND DATA AT 44009 MAKES IT DIFFICULT TO DETERMINE WHAT IS OCCURRING ON SOUTHERLY FLOW OVER THE ATLC WATERS EAST OF DELAWARE. MONDAY NIGHT INTO TUESDAY NIGHT...GALE FORCE WIND GUSTS FROM THE WEST AND NORTHWEST ARE EXPECTED. WEDNESDAY INTO THURSDAY...SMALL CRAFT ADVISORY CONDITIONS ARE POSSIBLE. && .CLIMATE... VULNERABLE NEAR RECORDS WEDNESDAY MORNING LOWS (WITHIN 2F) RDG 18 -1936 MPO 10 -1933 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 9 AM EST MONDAY FOR PAZ054-055. NJ...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 9 AM EST MONDAY FOR NJZ001. DE...NONE. MD...NONE. MARINE...GALE WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON FOR ANZ450>452. SMALL CRAFT ADVISORY FROM NOON TO 6 PM EST MONDAY FOR ANZ450>455. GALE WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON FOR ANZ453>455. GALE WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON FOR ANZ430-431. && $$ SYNOPSIS...DRAG NEAR TERM...HEAVENER SHORT TERM...HEAVENER LONG TERM...DRAG 536 AVIATION...DRAG/HEAVENER MARINE...DRAG/HEAVENER CLIMATE...

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