327  
FXUS61 KPHI 300930  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
430 AM EST FRI JAN 30 2015  
   
SYNOPSIS
 
 
LOW PRESSURE WILL MOVE OUT OVER THE NEW ENGLAND WATERS TODAY AND A  
COLD FRONT WILL CROSS THE AREA THIS MORNING. MUCH COLDER AND WINDY  
CONDITIONS WILL ARRIVE BEHIND THE FRONT. HIGH PRESSURE WILL BUILD  
ACROSS THE AREA FOR TONIGHT THROUGH EARLY SUNDAY. A LOW PRESSURE  
SYSTEM WILL AFFECT THE AREA SUNDAY NIGHT THROUGH MONDAY. ANOTHER  
HIGH WILL MOVE IN FOR TUESDAY AND WEDNESDAY. A COASTAL DISTURBANCE  
MAY AFFECT THE AREA NEXT THURSDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
08Z SURFACE ANALYSIS SHOWS AN AREA OF LOW PRESSURE LOCATED JUST  
NORTHEAST OF LAKE ONTARIO. A COLD FRONT EXTENDS SOUTHWARD FROM THE  
LOW DOWN THE LEE SIDE OF THE APPALACHIANS. A STRONGER ARCTIC COLD  
FRONT WAS POSITIONED OVER THE MIDWEST.  
 
THREE AREAS OF PRECIP WERE NOTED ON THE REGIONAL MOSAIC RADAR AT 430  
AM, EACH ASSOCIATED WITH SEPARATE MID-LEVEL SHORTWAVE TROUGHS. THERE  
WAS VERY LIGHT SNOW AND FLURRIES THAT HAS LINGERED ALONG AND NORTH  
OF I-80 FOR MUCH OF THE NIGHT. THE SECOND AREA TO NOTE WAS A BAND OF  
RAIN/SNOW SHOWERS THAT HAS STARTED TO DEVELOP OVER THE PAST HOUR OR  
SO TO THE EAST OF I-95. HIRES MODELS HAVE THIS AREA OF PRECIP SHIELD  
BLOSSOMING EARLY THIS MORNING. ADDITIONALLY THERE WAS AN AREA OF  
SNOW BACK TO THE WEST OVER STATE COLLEGE AND PITTSBURGH. THEREFORE,  
EXPECT PERIODS OF SNOW (MIXING WITH RAIN TOWARD THE COAST) THROUGH A  
GOOD PART OF THE MORNING. MOST LOCATIONS WILL NOT PICK UP MUCH MORE  
THAN A HALF INCH OF SNOWFALL (AND NOT EVERYONE WILL SEE MEASURABLE  
SNOW). THE POCONOS AND FAR NORTHWEST NJ MAY GET AN ADDITIONAL INCH  
WITH THIS ACTIVITY WHERE THE SNOW WILL BE THE MOST PERSISTENT DURING  
THE MORNING.  
 
THE OTHER STORY TODAY WILL BE THE GUSTY NORTHWEST WINDS THAT DEVELOP  
BEHIND THE FIRST COLD FRONT THIS AFTERNOON. WIND GUSTS UP TO 35 MPH  
ARE EXPECTED THROUGH EARLY THIS AFTERNOON. A SECOND COLD FRONT WILL  
MOVE THRU THE AREA LATE IN THE DAY, MARKING THE ARRIVAL OF ARCTIC  
AIR. WINDS WILL STRENGTHEN FURTHER BEHIND THIS FRONT AS LAPSE RATES  
BECOME VERY STEEP AND THE PRESSURE GRADIENT TIGHTENS. A WIND  
ADVISORY WAS ISSUED FOR THE ENTIRE FORECAST AREA STARTING AT 4 PM  
TODAY. THE HIGHER ELEVATIONS IN EASTERN PA AND NORTHWEST NJ ARE MOST  
LIKELY TO GET WIND GUSTS NEAR 45 MPH INITIALLY.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/
 
 
LOW PRESSURE WILL RAPIDLY DEEPENS OFF THE NEW ENGLAND COAST THIS  
EVENING. MEANWHILE, HIGH PRESSURE OVER THE MIDWEST WILL BUILD  
EASTWARD. A TIGHTENING PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS  
WILL PRODUCE WINDY CONDITIONS ACROSS THE MID ATLANTIC. AS MENTIONED  
IN THE NEAR TERM, A WINDY ADVISORY WAS ISSUED FOR THE ENTIRE AREA  
AND GOES THROUGH TONIGHT. MOMENTUM TRANSFER ALGORITHMS ON GFS BUFKIT  
SOUNDINGS SUPPORT MIXING OF 40 KT WINDS DOWN TO THE SURFACE WHILE THE  
WIND PROFILE FROM THE NAM ARE SLIGHTLY WEAKER. VERY STEEP LAPSE  
RATES WILL BE PRESENT IN THE BOUNDARY LAYER UNDER STRONG CAA AS THE  
ARCTIC AIRMASS MOVES IN. THE DEEPER MIXING ADVERTISED BY THE GFS AND  
SEVERAL SREF MEMBERS WAS FAVORED IN THIS SETUP, WHICH SUPPORTED A  
WIND ADVISORY.  
 
LOW TEMPS TONIGHT RANGE FROM NEAR ZERO IN THE POCONOS TO MID TEENS  
IN THE DELMARVA. COMBINED WITH THE WINDS, WIND CHILLS ARE FORECAST  
TO BE AT OR BELOW ZERO ACROSS JUST ABOUT THE ENTIRE AREA BY EARLY  
SATURDAY MORNING. THE WIND CHILL ADVISORY THAT WAS ALREADY IN EFFECT  
FOR THE POCONOS WAS EXPANDED TO SUSSEX COUNTY, NJ FOR WIND CHILL  
VALUES OF -10F TO -20F.  
 

 
   
LONG TERM /SATURDAY THROUGH THURSDAY/
 
 
SATURDAY THRU SUNDAY AFTERNOON...  
HIGH PRESSURE TO THE WEST WILL CONTINUE TO USHER COLD AND WINDY  
CONDITIONS SATURDAY WITH TEMPERATURES SOME 20 DEGREES BELOW NORMAL.  
WIND ADVISORIES WILL BE IN EFFECT FOR THE CWA FOR THE MORNING  
SATURDAY. WINDS WILL SUBSIDE BY LATE IN THE DAY SAT AS THE HIGH  
CRESTS OVER THE AREA. DRY WEATHER IS FORECAST THROUGH SUNDAY  
MORNING. SKY COVER...PARTLY TO MOSTLY SUNNY SAT AND MOSTLY CLOUDY  
SKIES SUNDAY.  
 
SUNDAY EVENING THROUGH MONDAY...  
THE NEXT SIGNIFICANT WEATHER PRODUCER FOR OUR AREA WILL ARRIVE FROM  
THE OHIO VALLEY SUNDAY AND THE CENTER OF THE LOW WILL MOVE ACROSS  
THE DELMARVA MONDAY MORNING. THE MOST RECENT MODELS ARE OFFERING A  
MORE NORTHWARD TREND WITH THE SYSTEM WHEN COMPARED TO THU'S MODEL  
RUNS. CLOUDS WILL THICKEN SUNDAY AND SNOW WILL ARRIVE OVER THE  
DELMARVA AND SE PA LATE IN THE AFTERNOON. THE PRECIPITATION WILL  
OVERSPREAD THE WHOLE AREA SUNDAY NIGHT AND CONTINUE INTO MONDAY.  
WHILE SNOW WILL BE THE PREDOMINANT P-TYPE...SOME SLEET WILL OCCUR  
OVER THE DELMARVA AND SRN NJ LATER SUN NIGHT AND INTO MONDAY.  
PRELIMINARY SNOWFALL ACCUMS LOOK TO BE 4 TO 5 INCHES ACROSS THE SE  
PA BERKS COUNTY--LEHIGH VALLEY--NRN NJ REGION WITH LIGHTER AMOUNTS  
BOTH NORTH AND SOUTH. SLEET AND RAIN (FAR SOUTH DEL) WILL REDUCE  
THE ACCUMS OVER THE DELMARVA AND SRN NJ AREAS. IF THE TRACK  
CONTINUES A NORTHWARD TREND...THEN MORE RAIN WILL MIX IN OVER THE  
SRN FORECAST AREA. THE PRECIP WILL END AS SNOW ONCE THE LOW SWEEPS  
BY MONDAY AFTERNOON BRINGING IN COLDER AIR BEHIND IT. HWO PRODUCT  
WILL HIGHLIGHT THE POTENTIAL FOR A SUNDAY NIGHT/MONDAY WINTRY  
WEATHER EVENT. FUTURE FCSTS WILL OFFER BETTER SNOWFALL FCST AND  
POSSIBLE HEADLINES...SO CHECK BACK LATER TODAY AND SAT/SUN FOR  
UPDATES.  
 
MONDAY NIGHT THRU WEDNESDAY...  
ANOTHER HIGH PRESSURE SYSTEM WITH COLD AIR WILL AFFECT THE AREA.  
HIGH TEMPERATURES TUE WILL BE IN THE TEENS AND LOW 20S...SO READINGS  
AGAIN WILL BE 15 TO 20 DEGREES BELOW NORMAL. MORE WIND CHILL  
HEADLINES POSSIBLE ACROSS THE FAR NORTH. MODERATING TEMPS WED WITH  
HIGHS IN THE UPPER 20S TO MID 30S OVER THE REGION.  
 
WEDNESDAY NIGHT THRU THURSDAY...  
THE 00Z GFS AND OLDER 12Z EC MODELS BOTH SHOW ANOTHER H5 TROUGH  
SWINGING ACROSS THE GREAT LAKES WITH A SFC LOW PRESSURE DEVELOPING  
AHEAD OF IT. BOTH OF THESE MODELS ALSO SHOW THE LOW PRESSURE SYSTEM  
DEVELOPING ACROSS THE DEEP SOUTH AND MOVING UP THE EAST COAST. THE  
LATEST 00Z EC SHOWED THE LOW ALSO...BUT PUSHED IT OFFSHORE THU NGT  
INTO FRIDAY WITH HIGHER QPF ONLY NEAR THE COAST. WE HAVE GONE ALONG  
WITH THE WPC AND RAISED POPS UP A BIT FOR THESE PERIODS. THEY ARE  
STILL ONLY IN THE CHC RANGE HOWEVER.  
 

 
   
AVIATION /09Z FRIDAY THROUGH TUESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
MAJORITY OF THE TERMINALS WILL HAVE VFR FOR MOST OF THE DAY.  
HOWEVER, THERE ARE SEVERAL AREAS OF LIGHT SNOW THAT WILL MOVE INTO  
THE AREA THRU ABOUT 15Z. A BRIEF PERIOD OF REDUCED VSBY TO MVFR MAY  
OCCUR AT JUST ABOUT ANY OF THE AIRPORTS. THERE WILL ALSO BE A  
STRATOCU DECK THAT DEVELOPS BETWEEN 2500-4000 KFT. THE LOWER END OF  
THAT RANGE WOULD YIELD MVFR CIGS. LOW CLOUDS WILL START TO SCT OUT  
TOWARD SUNSET.  
 
NW WINDS WILL INCREASE THRUOUT THE DAY. EXPECT WINDS SUSTAINED NEAR  
20 KT THIS AFTN AND TNGT. GUSTS WILL GENERALLY BE AOB 30 KT THRU  
ABOUT MID AFTN BUT THEN INCREASE TO 35-40 KT LATE IN THE DAY AND  
TNGT.  
 
OUTLOOK...  
SATURDAY...VFR WITH WINDY CONDITIONS.  
SATURDAY NIGHT THRU SUN AFTERNOON...VFR. INCREASING CLOUDS SUNDAY.  
SUN NIGHT THRU MONDAY...WIDESPREAD IFR/LIFR. SNOW AND MIXED PRECIP.  
ACCUMULATING SNOW AT PHL.  
MONDAY NIGHT THRU TUE...IMPROVING CONDITION MON EVE. VFR MON NGT  
THRU TUE.  
 

 
   
MARINE
 
 
NO CHANGES TO THE MARINE HEADLINES. GALE WARNING GOES INTO EFFECT AT  
9 AM THIS MORNING. GUSTS WILL GENERALLY BE 25-30 KT THIS MORNING,  
INCREASING TO 35-40 KT LATE THIS AFTERNOON INTO TONIGHT. SEAS WILL  
ALSO BUILD TO 5-8 FT BY TONIGHT. WENT SLIGHTLY ABOVE WAVEWATCH  
GUIDANCE FOR WAVE HEIGHTS.  
 
OUTLOOK...  
SAT AND SAT NIGHT...GALES DIMINISH SAT. SCA CONDITIONS EARLY SAT NIGHT.  
SUN AND SUN NIGHT...SUB-SCA CONDITIONS. SNOW AND SLEET LATE SUN NIGHT.  
MON AND MON NIGHT...SCA CONDITIONS EXPECTED.  
TUE...SCA SEAS ON THE OCEAN EARLY THEN SUB-SCA CONDITIONS.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST SATURDAY  
FOR PAZ054-055-060>062-070-071-101>106.  
WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM EST  
SATURDAY FOR PAZ054-055.  
NJ...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST SATURDAY  
FOR NJZ001-007>010-012>027.  
WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM EST  
SATURDAY FOR NJZ001.  
DE...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST SATURDAY  
FOR DEZ001>004.  
MD...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST SATURDAY  
FOR MDZ008-012-015-019-020.  
MARINE...FREEZING SPRAY ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EST  
SATURDAY FOR ANZ430-431-450>455.  
GALE WARNING FROM 9 AM THIS MORNING TO 6 PM EST SATURDAY FOR  
ANZ430-431-450>455.  
 

 
 

 
SYNOPSIS...O'HARA  
NEAR TERM...KLEIN  
SHORT TERM...KLEIN  
LONG TERM...O'HARA  
AVIATION...KLEIN/O'HARA  
MARINE...KLEIN/O'HARA  
 
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