941  
FXUS61 KPHI 070235  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
935 PM EST SAT FEB 6 2016  
   
SYNOPSIS
 
 
LOW PRESSURE IS FORECAST TO DEVELOP OFF THE SOUTHEAST COAST THIS  
WEEKEND AND TRACK NORTHEASTWARD LATE SUNDAY INTO MONDAY. ANOTHER  
LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP IN ITS WAKE NEAR THE  
MID- ATLANTIC COAST MONDAY NIGHT INTO TUESDAY. ARCTIC HIGH  
PRESSURE IS THEN EXPECTED TO BUILD IN FROM THE NORTH AND WEST  
DURING THE LATTER PART OF THE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
 
 
VERY FEW CHANGES WERE NEEDED FOR THE EVENING FCST. MOSTLY CLR  
SKIES ARE ACROSS THE AREA. OCCASIONAL CI/CS CLOUDS ACROSS THE DEL  
VALLEY AREAS. TEMPERATURES BEHAVING AS EXPECTED WITH MOSTLY UPPER  
20S/LOW 30S ATTM WITH READINGS EXPECTED TO BE IN THE LOW/MID 20S  
BY MORNING...EXCEPT UPPER 20S IN THE METRO AREAS. WINDS WILL  
REMAIN LIGHT.  
 

 
   
SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/
 
 
AFTER ANOTHER FROSTY START, TEMPERATURES WILL RISE SEVERAL DEGREES  
WARMER THAN SATURDAY AND END UP A FEW DEGREES ABOVE NORMAL. CLOUDS  
WILL BEGIN TO THICKEN AND LOWER DURING THE AFTERNOON FROM SOUTH TO  
NORTH AS A SYSTEM APPROACHES FROM THE SOUTH. HOWEVER, WE EXPECT THE  
FORECAST TO REMAIN PRECIPITATION FREE THROUGH THE DAYTIME HOURS.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/
 
 
THERE ARE 2 SYSTEMS TO WATCH DURG THE EXTENDD PD. THE FIRST IS A  
STRONG CSTL LOW THAT EMERGES OFF THE SERN CST ON SUN. THE VAST  
MAJORITY OF THE MDL GUID KEEPS THIS LOW OFF THE ATLC CST, WITH  
MINIMAL IMPACT ON OUR AREA. THIS IS A VERY STRONG LOW AND BEARS  
WATCHING AS IT MAKES ITS CLOSEST APPROACH ON MON. THE NAM AND CMC IS  
IMPLYING A MORE WWD TRACK THAT WOULD HAVE AT LEAST SOME IMPACTS ON  
CSTL AREAS OF NJ. THE MORE WWD SOLN HAS SEEMINGLY WON OUT THIS  
SEASON, WITH THE JAN BLIZZARD AND EVEN THE SYS EARLIER THIS WEEK,  
SO THIS SOLN IS NOT TERRIBLY FAR FETCHED. HOWEVER, THE  
PREPONDERANCE OF THE MDL GUID CONTINUES TO BE AGAINST IT. IF IT  
WERE TO PRECIP MON AFTN, IT WOULD BE TOO WARM IN MANY AREAS FOR  
SNOW.  
 
THE NEXT SYS WILL THEN DEVELOP SOMEWHERE OFF THE MID-ATLC CST MON  
NIGHT. MDL GUID CONTINUES TO STRUGGLE TO RESOLVE THE DETAILS OF  
THIS SYS AND CONFIDENCE REMAINS MUCH BELOW AVERAGE. THIS LOW WILL  
MOVE NEWD THRU TUE. THE ECMWF MADE A PRONOUNCED EWD SHIFT THIS  
CYCLE AND IS MUCH DRIER AS A RESULT ON TUE. THE GFS SHIFTED  
SLIGHTLY FURTHER E, BUT REMAINS WETTER. THE CMC IS THE WETTEST  
SOLN OF ALL. ANOTHER FACTOR TO CONSIDER IS TEMPS. THE GFS HAS HAD  
A WARM BIAS WITH BOTH THE JANUARY BLIZZARD AND THE SYSTEM EARLIER  
THIS WEEK, BUT ITS TEMPS ARE FAIRLY CLOSE TO THE ECMWF. THAT WOULD  
SUGGEST FOR AREAS FROM THE I-95 CORRIDOR S AND EWD SFC TEMPS  
WOULD BE ABV FREEZING ON TUE. WHILE THERE COULD BE SOME DIABATIC  
COOLING, IF THINGS GET WARM ENOUGH THERE COULD BE MIXING OR EVEN A  
CHANGE OVER OR SNOW THAT FALLS AND DOESN'T ACCUMULATE, ESPECIALLY  
DUG THE DAYLIGHT HOURS.  
 
BASED ON ALL THIS UNCERTAINTY, ESPECIALLY THE EWD SHIFT OF THE  
ECMWF (DESPITE ITS LESS THAN STELLAR PERFORMANCE THIS WINTER),  
SEE NO REASON TO INCREASE SNOW AMTS AT THIS TIME AND WILL ONLY  
MAKE SOME MINOR TWEAKS.  
 
KEY TAKEAWAYS HERE, WHILE THERE IS STILL ALOT OF UNCERTAINTY WITH  
THIS STORM, JANUARY 23RD THIS IS NOT. A COUPLE OF INCHES IS PSBL.  
SOME PLACES CUD GET MORE, SOME LESS.  
 
AS THIS LOW PULLS AWAY, CANADIAN HIGH PRES WILL BUILD INTO THE  
MID-SECTION OF THE COUNTRY AND EVENTUALLY BUILD EWD. TEMPS WILL  
STRUGGLE TO CLIMB OUT OF THE 30S BY THE END OF THE WEEK.  
 

 
   
AVIATION /03Z SUNDAY THROUGH THURSDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
MINOR CHANGES FOR THE 00Z TAFS. VFR THRU THE PERIOD WITH LIGHT  
AND VARIABLE WINDS OVERNIGHT AND THEN A FRESHENING E/NE WIND SUN  
AFTERNOON. CI/CS THIS EVENING...DECREASING OVERNIGHT. MORE CI/CS  
LATER SUNDAY.  
 
OUTLOOK...  
SUN NIGHT...VIRTUALLY ALL OF THE GUID CONTINUES TO KEEP THE  
STRONG STORM OFFSHORE. HOWEVER, ANY WESTWARD SHIFT IN THE TRACK  
MAY BRING A PERIOD OF LIGHT RAIN AND/OR SNOW TO EASTERN TERMINALS.  
OTHERWISE, VFR CONDS ARE EXPECTED. MDT CONFIDENCE.  
 
MON AND TUE...LOWER THAN AVERAGE CONFIDENCE THIS PD, AS A STORM  
SYS MAY DEVELOP NR THE MID-ATLC CST AND PRECIP MAY OVERSPREAD THE  
AREA MONDAY AFTERNOON AND EVENING. THERE ARE UNCERTAINTIES WRT  
THE TRACK OF THIS SYS AS WELL AS TEMPS ON TUE. PRECIP SHUD BEGIN  
AS RAIN LATER MON AND SHUD CHANGE OVER TO SNOW MON NIGHT. ON TUE,  
PRECIP COULD CHANGE BACK OVER TO RAIN ESPECIALLY FROM THE I-95  
CORRIDOR SE, BUT HERE IS WHERE THE GREATEST UNCERTAINTY LIES.  
POTENTIAL FOR IFR RESTRICTIONS ESPECIALLY ONCE IT CHANGES OVER TO  
SNOW. HIGH UNCERTAINTY EXISTS ALSO FOR SNOW AMTS.  
 
WED...IMPROVING CONDITIONS. MAINLY VFR ALTHOUGH THERE IS A SMALL  
RISK FOR A BRIEF RESTRICTION WITH A PASSING SNOW SHOWER. MDT  
CONFIDENCE.  
 
THURSDAY...VFR. HIGH CONFIDENCE.  
 

 
   
MARINE
 
 
SUB-ADVISORY CONDITIONS WILL PREVAIL ACROSS THE WATERS TONIGHT AS  
HIGH PRESSURE CONTINUES TO AFFECT THE AREA. WINDS WILL BEGIN TO  
INCREASE FROM THE SOUTH TO THE NORTH DURING THE AFTERNOON SUNDAY AS  
THE PRESSURE GRADIENT BEGINS TO TIGHTEN AHEAD OF THE APPROACHING  
SYSTEM FROM THE SOUTH. A SMALL CRAFT ADVISORY IS NOW IN EFFECT  
STARTING AT 1 PM SUNDAY, THOUGH THE WINDS WILL LAG A COUPLE OF HOURS  
ACROSS THE FAR NORTHERN WATERS.  
 
OUTLOOK...  
SUN NIGHT AND MONDAY...THE GALE WATCH WILL REMAIN IN EFFECT. THERE  
IS A LOT OF UNCERTAINTY WITH RESPECT TO THE TRACK OF THE LOW AND,  
THEREFORE WE DID NOT OPT TO RAISE TO A GLW ATTM. IT WILL EITHER BE  
A VERY STRONG SCA OR MARGINAL GLW.  
 
MON NIGHT THROUGH THU...ANOTHER AREA OF LOW PRESSURE WILL DEVELOP  
OFF THE MID-ATLANTIC COAST. AN EXTENDED PERIOD OF SCA CONDITIONS  
LIKELY DURING THIS TIME. IT COULD POTENTIAL REACH GALE FORCE LATE  
WED INTO THU BUT UNCERTAINTY IS VERY HIGH REGARDING THE STRENGTH  
OF THE WINDS.  
 

 
   
TIDES/COASTAL FLOODING
 
 
***WE ARE WATCHING TWO POTENTIAL COASTAL FLOOD EVENTS NEAR THE  
MONDAY MORNING HIGH TIDE AND TUESDAY MORNING HIGH TIDE***  
 
THE FLOW WILL BECOME ONSHORE SUNDAY AFTERNOON AS HIGH PRESSURE  
ANCHORS OVER SOUTHEAST CANADA AND LOW PRESSURE DEVELOPS OFF THE  
CAROLINAS. THIS AREA OF LOW PRESSURE IS EXPECTED TO PASS WELL  
SOUTHEAST OF OUR REGION. WITH THE AFOREMENTIONED HIGH REMAINING  
TO OUR NORTH, ANOTHER AREA OF LOW PRESSURE WILL DEVELOP OFF THE  
OUTERBANKS OF NORTH CAROLINA MONDAY NIGHT AND PASS SOUTHEAST OF  
OUR REGION DURING THE DAY TUESDAY.  
 
THESE TWO SYSTEMS WILL MAINTAIN AN ONSHORE FLOW ALONG THE COAST  
TO VARYING DEGREES SUNDAY THRU TUESDAY. ASTRONOMICAL TIDES WILL  
BE HIGH TO BEGIN WITH, GIVEN THE NEW MOON ON MONDAY, REACHING  
THEIR PEAKS DURING THE MONDAY AND TUESDAY MORNING HIGH TIDES.  
 
FOR THE MONDAY MORNING HIGH TIDE, THE THREAT OF COASTAL FLOODING  
WILL BE HIGHEST ALONG THE NORTHERN NJ COAST, WHERE THE GREATEST  
COMPONENT OF ONSHORE FLOW WILL BE PRESENT. GIVEN THE SHORT  
DURATION OF STRONGER ONSHORE FLOW, THE WIND BACKING FROM THE  
NORTHEAST TO NORTH /MORE OFFSHORE/ AS WE APPROACH HIGH TIDE,  
AND CONTINUED UNCERTAINTY REGARDING THE STORM TRACK, CONFIDENCE  
REGARDING IMPACTS IS LOW. AT THIS TIME, THERE IS THE POTENTIAL  
FOR AT LEAST MINOR COASTAL FLOODING, PARTICULARLY THE NORTHERN  
NJ COAST.  
 
REGARDING THE TUESDAY MORNING HIGH TIDE, A MORE ROBUST AREA OF  
LOW PRESSURE IS EXPECTED TO TRACK CLOSER TO THE COAST, WITH A  
STRONGER ONSHORE FLOW. ASIDE FROM A BRIEF LULL IN THIS FLOW LATE  
MONDAY, WE'LL HAVE HAD NEARLY 48 HOURS DURATION OF ONSHORE FLOW,  
WHICH WILL MAKE FOR POSITIVE TIDAL DEPARTURES TO BEGIN WITH.  
IN ADDITION, A MORE EASTERLY WIND WILL MAKE FOR A LONGER FETCH  
IN TERMS OF BUILDING WAVE ACTION. BUT THERE IS CONSIDERABLE  
UNCERTAINTY REGARDING THE EVOLUTION OF THIS LOW AND ASSOCIATED  
LOW-LEVEL JET, SO AGAIN OUR CONFIDENCE REGARDING IMPACTS IS  
LOW. AT THIS TIME, THERE IS THE POTENTIAL FOR MORE WIDESPREAD  
MINOR COASTAL FLOODING.  
 
PLEASE STAY TUNED TO LATER FORECASTS AND POSSIBLE HEADLINES.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...GALE WATCH FROM SUNDAY EVENING THROUGH MONDAY MORNING FOR  
ANZ450>455.  
SMALL CRAFT ADVISORY FROM 1 PM TO 8 PM EST SUNDAY FOR  
ANZ450>455.  
SMALL CRAFT ADVISORY FROM 8 PM SUNDAY TO 6 AM EST MONDAY FOR  
ANZ430-431.  
 

 
 

 
SYNOPSIS...NIERENBERG  
NEAR TERM...ROBERTSON/O'HARA  
SHORT TERM...ROBERTSON  
LONG TERM...NIERENBERG  
AVIATION...NIERENBERG/ROBERTSON/O'HARA  
MARINE...NIERENBERG/ROBERTSON  
TIDES/COASTAL FLOODING...  
 
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