898  
FXUS61 KPHI 180055  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
755 PM EST SAT FEB 17 2018  
   
SYNOPSIS
 
 
LOW PRESSURE RAPIDLY INTENSIFIES OFF THE MID ATLANTIC COAST  
THIS EVENING THEN RACES OUT TO SEA BY SUNDAY MORNING. HIGH  
PRESSURE BRIEFLY BUILDS ACROSS THE AREA AGAIN ON SUNDAY, THEN  
OFFSHORE SUNDAY NIGHT. A STRONG WARM FRONT LIFTS NORTHWARD  
ACROSS OUR AREA LATER MONDAY INTO EARLY TUESDAY, FOLLOWED BY A  
COLD FRONT LATE WEDNESDAY. THE COLD FRONT STALLS TO OUR SOUTH BY  
NEXT THURSDAY WITH A SERIES OF WAVES MOVING NORTH AND EAST  
ALONG IT LATE NEXT WEEK INTO EARLY NEXT WEEKEND.  
 

 
   
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
 
 
WE ARE GETTING TOTAL SNOW REPORTS UP TO 6 INCHES ACROSS PARTS OF  
EASTERN PA AND NORTHERN NJ (SEE LATEST PNSPHI PRODUCT) AND SNOW  
CONTINUES TO FALL OVER THOSE AREAS. THEREFORE WE HAVE UPGRADED  
TO A WINTER STORM WARNING THERE. RADAR MOSAIC LOOP INDICATES  
SNOW STARTING TO TAPER OFF FOR BERKS CO AND VICINITY, BUT  
MODERATE TO HEAVY SNOW SHOULD CONTINUE FARTHER EAST FOR A COUPLE  
MORE HOURS.  
 
PREVIOUS DISCUSSION BELOW:  
CLOUDS WILL CONTINUE TO THICKEN AND LOWER AND PRECIPITATION  
WILL OVERSPREAD OUR REGION FROM THE WEST AND SOUTHWEST DURING  
THE LATE AFTERNOON AND EARLY EVENING HOURS. TEMPERATURES ARE  
SUCH THAT THE PRECIPITATION SHOULD BEGIN AS SNOW IN THE POCONOS  
AND IN FAR NORTHERN NEW JERSEY. IT IS EXPECTED TO BEGIN AS A  
BRIEF PERIOD OF RAIN IN EXTREME NORTHEASTERN MARYLAND, NORTHERN  
DELAWARE, SOUTHEASTERN PENNSYLVANIA, AND MUCH OF NORTHERN AND  
CENTRAL NEW JERSEY BEFORE CHANGING TO SNOW. AN ALL RAIN EVENT IS  
ANTICIPATED FOR SOUTHEASTERN MARYLAND, SOUTHERN DELAWARE AND  
MUCH OF SOUTHERN NEW JERSEY.  
 
MID LEVEL SHORT WAVE ENERGY MOVING UP THE OHIO RIVER VALLEY  
THIS AFTERNOON WILL ENHANCE PRECIPITATION RATES THIS EVENING. A  
RELATIVELY BRIEF PERIOD OF MODERATE TO HEAVY SNOW IS EXPECTED  
WITH AMOUNTS IN MUCH OF EASTERN PENNSYLVANIA, FAR NORTHEASTERN  
MARYLAND, NORTHERN DELAWARE AND CENTRAL AND NORTHERN NEW JERSEY  
RANGING FROM 2 TO 5 INCHES. THE FAR UPPER DELMARVA, EXTREME  
SOUTHEASTERN PENNSYLVANIA AND THE SOUTHERN PART OF CENTRAL NEW  
JERSEY SHOULD FAVOR THE LOW END OF THOSE VALUES.  
 
THE GUIDANCE HAS TRENDED A BIT WARMER WITH THE SYSTEM THAN IN  
PREVIOUS RUNS. AS WE GET INTO THE LATE EVENING HOURS, THE  
RAIN/SNOW LINE MAY ADVANCE WELL INTO THE PHILADELPHIA  
METROPOLITAN AREA AND CENTRAL NEW JERSEY. WE WILL INDICATE A  
CHANGE TO RAIN BEFORE THE PRECIPITATION ENDS. THE RAIN WILL CUT  
INTO SNOWFALL AMOUNTS IN PARTS OF THOSE AREAS.  
 
DUE TO THE EXPECTED LOCATION OF THE RAIN/SNOW LINE, OUR LOWEST  
AREA OF CONFIDENCE IN OUR SNOWFALL FORECAST EXTENDS FROM THE  
UPPER DELMARVA AND EXTREME SOUTHEASTERN PENNSYLVANIA INTO PARTS  
OF SOUTHERN AND CENTRAL NEW JERSEY.  
 
A MID LEVEL SHORT WAVE TROUGH LOCATED OVER IOWA AND VICINITY  
THIS AFTERNOON WILL PROGRESS TO THE EAST AND IT SHOULD PASS  
OVERHEAD LATE TONIGHT. THE FEATURE WILL KICK THE LAST OF THE  
PRECIPITATION OUT TO SEA. IT APPEARS AS THOUGH MOST OF THE RAIN  
AND SNOW IN OUR REGION WILL END BY 2 OR 3 O'CLOCK IN THE  
MORNING.  
 
THE WIND IS FORECAST TO BE FROM VARYING DIRECTIONS AT LESS THAN  
10 MPH FOR MUCH OF THE NIGHT, BECOMING NORTHWEST AT 10 TO 15  
MPH TOWARD MORNING. LOW TEMPERATURES ARE ANTICIPATED TO RANGE  
FROM THE MIDDLE 20S IN THE POCONOS TO THE MIDDLE 30S IN SOUTHERN  
DELAWARE.  
 

 
   
SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/
 
 
HIGH PRESSURE IS FORECAST TO BUILD INTO OUR REGION FROM THE  
WEST FOR SUNDAY. WE ARE ANTICIPATING A MOSTLY SUNNY DAY WITH A  
NORTHWEST TO WEST WIND AROUND 10 MPH.  
 
SUNDAY AFTERNOON IS EXPECTED TO BECOME RELATIVELY MILD. HIGHS  
ARE FORECAST TO BE IN THE LOWER AND MIDDLE 40S IN THE POCONOS,  
THE LEHIGH VALLEY AND NORTHERN NEW JERSEY. READINGS SHOULD GET  
INTO THE UPPER 40S AND LOWER 50S IN NORTHEASTERN MARYLAND,  
DELAWARE, SOUTHEASTERN PENNSYLVANIA, AND SOUTHERN AND CENTRAL  
NEW JERSEY. MUCH OF THE NEW SNOW COVER SHOULD MELT BY DAY'S END.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/
 
 
**RECORD WARMTH POSSIBLE TUE AND EXPECTED WED**  
 
SUNDAY NIGHT THROUGH WEDNESDAY....  
 
TO START THE PERIOD SUNDAY EVENING, HIGH PRESSURE CRESTS OVER  
THE AREA IN THE EVENING BEFORE SLOWLY MOVING EAST OVERNIGHT.  
THIS WILL SET UP GOOD CONDITIONS FOR RADIATIONAL COOLING DUE TO  
LIGHT WINDS AND MAINLY CLEAR SKIES DESPITE THE AIRMASS NOT BEING  
ALL THAT COLD. LOWS BY MONDAY MORNING SHOULD GENERALLY BE IN  
THE 20S TO LOW 30S.  
 
FOR MONDAY, THE HIGH CONTINUES TO PUSH OFF TO THE EAST THROUGH  
THE DAY WITH A WARM FRONT APPROACHING FROM THE SOUTH AND WEST  
AHEAD OF THE NEXT SYSTEM. THIS WILL BRING INCREASING CLOUDS WITH  
SOME SHOWERS LIKELY BY AFTERNOON...MAINLY OVER EASTERN PA.  
HIGHS WILL GENERALLY RANGE FROM THE MID 40S NORTH TO THE 50S  
ACROSS THE DELMARVA AND SOUTHERN NJ.  
 
SOME SHOWERS MAY CONTINUE INTO MONDAY EVENING BEFORE LIFTING  
OUT OVERNIGHT AS THE FRONT MOVES THROUGH. TEMPERATURES WILL BE  
QUITE MILD WITH LOWS ONLY DROPPING TO THE 40S TO LOW 50S. THIS  
WILL BE FOLLOWED BY NEAR RECORD WARMTH ON TUESDAY AS A STRONG SW  
FLOW TAKES HOLD. WE CONTINUE TO FORECAST TEMPERATURES ABOVE THE  
MODEL CONSENSUS AND ARE GENERALLY LOOKING AT HIGHS RANGING FROM  
THE 60S IN THE NORTH TO THE LOW 70S ACROSS SE PA AS WELL AS  
MUCH OF THE DELMARVA AND SOUTHERN NJ. AREAS RIGHT NEAR THE COAST  
WILL LIKELY BE COOLER THOUGH.  
 
FOR TUESDAY NIGHT INTO WEDNESDAY, TEMPERATURES CONTINUE TO WARM  
WITH RECORD WARMTH FORECAST BY WEDNESDAY...HIGHS CURRENTLY  
FORECAST TO REACH THE LOW TO MID 70S OVER SE PA AS WELL AS MUCH  
OF THE DELMARVA AND NJ. CONDITIONS SHOULD BE DRY FOR THE MOST  
PART THOUGH BY LATE WEDNESDAY A COLD FRONT COULD BRING SOME  
SHOWERS IN FROM THE WEST...MAINLY FOR EASTERN PA.  
 
WEDNESDAY NIGHT THROUGH SATURDAY...  
 
IN THE BIG PICTURE, THIS PERIOD WILL BE DOMINATED BY SOMEWHAT  
COOLER, THOUGH STILL WELL ABOVE AVERAGE TEMPERATURES AS A LONG  
WAVE TROUGH PERSISTS OVER THE ROCKY MOUNTAINS WITH THE AREA IN A  
SW FLOW. CONDITIONS WILL ALSO TREND MORE UNSETTLED AS A SERIES  
OF WAVES MOVE NORTH AND EAST ALONG A WAVERING FRONT THAT WILL  
LINGER IN THE REGION.  
 
FOR WEDNESDAY NIGHT INTO THURSDAY, THE AFORMENTIONED COLD FRONT  
WITH SOME ASSOCIATED RAIN SHOWERS PUSHES SOUTH THROUGH THE AREA  
BEFORE STALLING OVER THE MID ATLANTIC. FORECAST GUIDANCE THEN  
INDICATES A WAVE TRYING TO MOVE NORTH ALONG THE FRONT THOUGH  
THERE IS UNCERTAINTY IN HOW THIS ALL EVOLVES AS HIGH PRESSURE  
WILL ALSO BE BUILDING IN TO OUR NORTH. THE HIGH COULD SUPPRESS  
PRECIP MAINLY TO OUR SOUTH INTO THURSDAY BUT AGAIN, THESE  
DETAILS ARE UNCERTAIN SO WE KEEP CHANCES FOR SHOWERS IN THE  
FORECAST THROUGH THURSDAY. BEYOND THIS TIME THERE MAY BE A BRIEF  
BREAK BEFORE A STRONGER LOW PRESSURE SYSTEM MOVES NORTH ALONG  
THE FRONT BY LATER FRIDAY INTO NEXT SATURDAY. HIGHS THURSDAY AND  
FRIDAY WILL GENERALLY BE IN THE 40S AND 50S WITH 60S POSSIBLE  
AGAIN BY NEXT SATURDAY.  
 

 
   
AVIATION /01Z SUNDAY THROUGH THURSDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
THROUGH 0600Z...CONDITIONS BECOMING IFR EARLY THIS EVENING IN  
SNOW AT KRDG, KABE, KTTN, KPNE, KPHL AND KILG. ACCUMULATING SNOW  
IS EXPECTED AT THE AIRFIELDS (UP AROUND 4 INCHES AT KRDG, KABE  
AND KTTN, AND UP AROUND 2 OR 3 INCHES AT KILG, KPHL AND KPNE). A  
MIX OR CHANGE TO RAIN IS EXPECTED AT KILG, KPHL AND KPNE LATE  
THIS EVENING BEFORE THE PRECIPITATION ENDS. CONDITIONS LOWERING  
TO IFR IN RAIN AT KMIV AND KACY THIS EVENING. EAST TO SOUTHEAST  
WIND AROUND 5 TO 10 KNOTS.  
 
LATE TONIGHT (0600Z-1200Z)...PRECIPITATION ENDING FROM  
SOUTHWEST TO NORTHEAST WITH CONDITIONS GRADUALLY IMPROVING TO  
VFR. WIND BECOME NORTHWEST 10 TO 15 KNOTS WITH GUSTS AROUND 20  
KNOTS.  
 
SUNDAY...VFR. MOSTLY CLEAR WITH A NORTHWEST WIND AROUND 10  
KNOTS.  
 
OUTLOOK...  
SUNDAY NIGHT...VFR. CONFIDENCE: WELL ABOVE AVERAGE.  
 
MONDAY...VFR EARLY, LOWERING TO MVFR OR IFR DURING THE  
AFTERNOON OR EVENING WITH RAIN. SOUTH TO SOUTHWEST WIND.  
CONFIDENCE: ABOVE AVERAGE.  
 
MONDAY NIGHT...MVFR/IFR CONDITIONS CONTINUE WITH RAIN POSSIBLE  
IN THE EVENING, AND LOW CLOUDS/DENSE FOG POSSIBLE OVERNIGHT.  
CONFIDENCE: ABOVE AVERAGE.  
 
TUESDAY...MVFR/IFR CONDITIONS POSSIBLE THROUGH MIDDAY IN LOW  
CLOUDS/FOG. CONDITIONS IMPROVING TO VFR DURING THE AFTERNOON.  
SOUTHWEST WINDS MAY GUST AROUND 20-25 KNOTS IN THE AFTERNOON.  
CONFIDENCE: AVERAGE.  
 
TUESDAY NIGHT...VFR EARLY, THEN POSSIBLY LOWERING TO MVFR/IFR  
AS LOW CLOUDS/FOG MAY DEVELOP OVERNIGHT. CONFIDENCE: AVERAGE.  
 
WEDNESDAY...MVFR/IFR CONDITIONS POSSIBLE EARLY WITH LOW  
CLOUDS/FOG. CONDITIONS IMPROVING TO VFR DURING THE DAY. CHANCE  
OF SHOWERS LATE IN THE DAY. SOUTHWEST WINDS MAY GUST AROUND  
20-25 KNOTS. CONFIDENCE: AVERAGE.  
 
WEDNESDAY NIGHT THROUGH THURSDAY...CHANCE OF SHOWERS WITH  
ASSOCIATED RESTRICTIONS. CONFIDENCE: BELOW AVERAGE.  
 

 
   
MARINE
 
 
LOW PRESSURE WILL PASS OFF THE VIRGINIA CAPES THIS EVENING  
BEFORE MOVING QUICKLY OUT TO SEA. A GUSTY NORTHWEST WIND IS  
EXPECTED TO DEVELOP ON THE COASTAL WATERS OF NEW JERSEY AND  
DELAWARE IN THE WAKE OF THE LOW. AS A RESULT, WE WILL ISSUE A  
SMALL CRAFT ADVISORY FOR OUR OCEAN WATERS AND FOR DELAWARE BAY.  
IT WILL BE IN EFFECT FROM 4:00 AM UNTIL 11:00 AM SUNDAY. THE  
WIND IS FORECAST TO DIMINISH GRADUALLY ON SUNDAY AFTERNOON.  
 
OUTLOOK...  
SUNDAY NIGHT THROUGH MONDAY...SUB SMALL CRAFT ADVISORY SOUTH  
WINDS. CONFIDENCE: WELL ABOVE AVERAGE.  
 
MONDAY NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED,  
ALTHOUGH SOUTHWEST WINDS MAY GUST AROUND 20 KNOTS. CONFIDENCE:  
ABOVE AVERAGE.  
 
TUESDAY-WEDNESDAY...WINDS SHOULD STAY BELOW ADVISORY LEVELS,  
BUT SEAS MAY INCREASE TO NEAR 5 FEET. CONFIDENCE: AVERAGE.  
 
WEDNESDAY NIGHT - THURSDAY...WINDS SHOULD STAY BELOW SCA LEVELS  
WITH SEAS PERSISTING IN THE 3 TO 5 FOOT RANGE.  
 

 
   
CLIMATE
 
 
RECORD HIGH TEMPERATURES COULD BE CHALLENGED ON TUESDAY,  
FEBRUARY 20TH AND PROBABLY WILL BE EQUALED OR EXCEEDED WEDNESDAY  
FEBRUARY 21ST. THESE RECORDS ARE LISTED BELOW.  
 
FEBRUARY 20:  
 
ATLANTIC CITY...70 IN 1930  
 
PHILADELPHIA....70 IN 1939  
 
WILMINGTON......71 IN 1930  
 
ALLENTOWN.......68 IN 1930  
 
TRENTON.........70 IN 1930  
 
GEORGETOWN......68 IN 2002  
 
MOUNT POCONO....59 IN 1930  
 
READING.........72 IN 1930  
 
FEBRUARY 21:  
 
ATLANTIC CITY...74 IN 1930  
 
PHILADELPHIA....72 IN 1930  
 
WILMINGTON......70 IN 1953  
 
ALLENTOWN.......67 IN 1953  
 
TRENTON.........70 IN 1930  
 
GEORGETOWN......71 IN 2014  
 
MOUNT POCONO....60 IN 1930  
 
READING.........71 IN 1930  
 
WE ARE NOT POSTING THE MONTHLY RECORDS AT THIS TIME SINCE OUR  
FORECAST IS 3 TO 7 DEGREES BELOW THE MONTHLY RECORD. WE'LL CHECK  
AGAIN SUNDAY AND MONDAY TO SEE IF OUR FORECAST EDGES WARMER.  
 
THE FOLLOWING ARE THE RECORD WARM MINS FOR WEDNESDAY FEB 21.  
BARRING A SUDDEN IMMEDIATE COOL DOWN BEHIND THE COOL FRONT AT  
1159PM WEDNESDAY, THERE IS A GOOD CHANCE OF RECORD WARM DAILY  
MINIMUM TEMPERATURES AS WELL THE PREVIOUSLY REFERENCED RECORD  
HIGHS.  
 
RECORD HIGH MINS FOR 2/21  
 
ABE 46-1981  
ACY 49-1954  
PHL 49-2002  
ILG 47-2002  
RDG 48-1930  
TTN 48-2002  
 
ATLANTIC CITY RAINFALL ALREADY RANKS 11TH WETTEST IN FEBRUARY  
HISTORY WITH 6.50" IN 2010 THE WETTEST. BY SUNRISE SUNDAY,  
ATLANTIC CITY SHOULD RANK ABOUT 8TH WETTEST IN ITS HISTORICAL  
DATABASE.  
 
THE FEBRUARY AVERAGE TEMP FOR PHL PROJECTS 41.0 OR 5.3F ABOVE  
NORMAL OR 8TH WARMEST ON RECORD. THIS PLACEMENT CAN CHANGE  
ANYWHERE FROM 3RD TO 12TH DEPENDING ON A 1 DEGREE CHANGE IN THE  
EVENTUAL AVERAGE. BOTTOM LINE...WE'RE LIKELY ON OUR WAY TO A TOP  
10 WARMEST FEBRUARY ON RECORD. THE WARMEST WAS LAST YEAR WITH A  
44.2F AVERAGE. YEARS 2002 AND 2012 FLANK OUR CURRENTLY  
PROJECTED 8TH WARMEST.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...WINTER STORM WARNING UNTIL 4 AM EST SUNDAY FOR PAZ054-055-  
060>062-103-105.  
WINTER WEATHER ADVISORY UNTIL 4 AM EST SUNDAY FOR PAZ070-071-  
101-102-104-106.  
NJ...WINTER STORM WARNING UNTIL 4 AM EST SUNDAY FOR NJZ001-007>010.  
WINTER WEATHER ADVISORY UNTIL 4 AM EST SUNDAY FOR NJZ012-013-  
015>019.  
DE...WINTER WEATHER ADVISORY UNTIL 4 AM EST SUNDAY FOR DEZ001.  
MD...WINTER WEATHER ADVISORY UNTIL 4 AM EST SUNDAY FOR MDZ008.  
MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 11 AM EST SUNDAY FOR ANZ430-  
431-450>455.  
 

 
 

 
SYNOPSIS...FITZSIMMONS  
NEAR TERM...AMC/IOVINO  
SHORT TERM...IOVINO  
LONG TERM...FITZSIMMONS  
AVIATION...FITZSIMMONS/IOVINO  
MARINE...FITZSIMMONS/IOVINO  
CLIMATE...  
 
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