Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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001 FXUS61 KPHI 240100 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 900 PM EDT Sat Sep 23 2017 .SYNOPSIS... High pressure remains entrenched over the Northeast before weakening by the middle of the week. Hurricane Maria will track northward over the Atlantic waters, approaching the Coastal Carolinas on Wednesday, then curving out to sea on Thursday as a cold front passes through the region. High pressure builds east to close out the week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... No changes to the forecast tonight other than hourly temperature and dewpoint adjustments. This will be the main challenge into the evening hours as temperatures will rapidly drop in some areas as the sun sets, and not as quickly in others. Under clear skies, temperatures will drop into the low/mid 60s in most areas. Otherwise, high pressure will remain nearby tonight and fair weather is expected tonight. There could be a few patches of ground fog overnight, confid in this is low however. Winds will become light and variable through the night. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... The surface high will remain just west of the region Sunday while the upper high remain overhead. A continuation of fair weather along with very warm temperatures is expected. We expect high temperatures to be around 90 degrees in many areas, a bit cooler at the shore and in the Poconos. Humidity levels will be a little higher, but overall not too uncomfortable. Winds will be light from the NE during the morning then E or SE during the afternoon. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... Monday...Surface high remains over the region. As a result expect continued dry and very warm weather. We could get close to record highs at inland locations (see climate section for the current record highs for those days). Forecast is a few degrees above most guidance as the increasing thicknesses and abundant sunshine should win out over the light northerly flow. Closer to the coast however, a light onshore flow could temper the warming trend. Tuesday...Surface high weakens. As it does so, we could have some showers develop, primarily diurnally driven (rain associated with the low over eastern Canada will stay well to our northwest. Wednesday...depending on how close Hurricane Maria gets to the Outer Banks during this period, we may see some outer rain bands reach the Coastal Plains in our area. The center of Maria is expected to stay well to our south (by a few hundred miles) through this period. Please see the forecast discussion from the National Hurricane Center for the latest information on the track. Thursday...There are two things to watch through this period. First, the cold front still looks on track to propagate through our region late Wednesday night into Thursday. That will bring us back to near normal temperatures (although depending on how quickly it moves through, we may not notice it until Friday). The other thing we will be watching is the eventual track of Maria. Nearly all guidance continues to show the storm taking a hard turn to the right during this period in response to the cold front moving off shore. If this trend continues, even tropical storm force winds should stay well south of our region. Friday and Saturday...Cooler and drier air should settle in over the region. Temperatures through this period are likely to be near or slightly below normal (in stark contrast to the beginning of the week). && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. High pressure across the area will ensure a continuation of VFR conditions with few clouds through Sunday. Winds will become light and variable/calm for most areas this evening and overnight. Any direction will vary between NW and NE. Winds on Sunday may become NE or E by afternoon, but remain under 10 knots. It appears to be too dry to support anything more than patchy fog overnight. We will keep it out of the tafs at this time. Outlook... Monday...mostly VFR conditions are expected. Tuesday and Wedensday...mostly VFR conditions expected. There is a chance for showers both days (if any showers move over a TAF site, MVFR or lower conditions are possible). Northeasterly wind up to 10 KT possible. Thursday...A cold front will bring a shift to northwesterly winds and a slight chance for showers. Otherwise, mostly VFR conditions are expected. && .MARINE... We will continue with the SCA for hazardous seas across the southern waters and drop it further north. The wave heights continue to slowly decrease and are mostly around 3-4 ft north and around 5 ft south attm. Guidance shows that this decreasing trend will continue into the evening and then slowly reverse Sunday. Eventually, the SCA flag will return to the northern waters later Sunday when seas could reach 5 to 6 ft again. Overall, a long period swell with the offshore tropical systems and some minor winds waves too. Fair weather tonight and Sunday. Outlook... Monday through Wednesday...An SCA will likely be needed for the entire period on the ocean waters as elevated seas due to swells associated Hurricane Maria will be observed through this time. Seas will gradually build to 8-12 feet by Wednesday. Gusts up to 25 KT will be possible especially on the Delaware Coastal waters Tuesday and Wednesday. Elevated waves will be possible at the mouth of the Delaware Bay. Otherwise, winds and waves should stay below SCA criteria on the Bay. Thursday...A cold front will bring a shift to northwesterly winds and gusts above 25 KT likely on the Atlantic Coastal waters. In addition, seas will likely still be elevated due to swells from Maria. Rip Currents... Sunday...A MODERATE risk for dangerous rip currents is expected for Sunday. Monday...a 5 or 6 foot SE swell of 15 seconds is expected to be dominant and could result in a high risk. 8 foot 15 second swell should be dominant by that time. If this trend continues, this would result in a high risk. Wednesday...around an 11 to 13 foot SE swell at 15 seconds. This would mean a high risk. Thursday the 28th...still a 10 foot SE swell at 14 seconds. This would mean a high risk. Friday...maybe down to 5 or 6 feet and a moderate or high risk. && .CLIMATE... Todays high temp of 89 at ABE is the warmest there since August 22...when it reached 91. So far nothing higher than ydy at PHL/ILG. With high temperatures making a run at 90 Sunday and Monday across portions of the region, some record high temperatures may be tied or broken. The highest chances are for inland locations as onshore flow may slightly temper the warming trend at ACY and GED. Here are the records for both days. Sunday ACY-92(2010) PHL 95(1970) ILG-92(2010) ABE-92(1970) TTN-92(1970) GED-97(2010) RDG-95(1970) MPO-85(2010) Monday ACY-91(1970) PHL-92(1970) ILG-93(1970) ABE-92(1970) TTN-92(1970) GED-92(2010 and 1970) RDG-92(1970) MPO-85(1970) && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory for hazardous seas until 6 PM EDT Sunday for ANZ452>455. && $$ Synopsis...Johnson Near Term...Robertson/O`Hara Short Term...O`Hara Long Term...Johnson Aviation...Johnson/Robertson/O`Hara Marine...Johnson/O`Hara Climate... is the U.S. government's official web portal to all federal, state and local government web resources and services.