Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 230152 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 952 PM EDT Fri Sep 22 2017 .SYNOPSIS... Post-Tropical Cyclone Jose will continue to weaken and drift southeast of New England before dissipating late this weekend. High pressure stretched from New England to the central Appalachians will hold firm into early next week. Hurricane Maria will be moving northward in the offshore Atlantic waters, off the east coast next week. A cold front passing through the mid Atlantic states should turn Maria eastward and far out to sea later Thursday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 930 PM: some small adjustments for sky and temps overnight as patches of AC/SC develop swwd. 840 PM update is to cancel the rp.s for now. It may need to be invoked again at 6 am, pending further information on the incoming swells in the surf zone. 630 PM ESTF: adjusted some temps and dews. The respite from the drier air that arrived earlier today may be short lived. Have also added Maria to the synopsis as possible (for now small chance) player in our weather...mainly via substantial se swell, but possibly contributing moisture to a cold frontal passage and need showers on Thu. Patchy fog is in a few countryside locations between 9-11z/23, Post-Tropical Cyclone Jose, which has been around a long time, will finally drift to the southeast tonight and weaken as it does so. TPC began issuing advisories on Jose on September 5, 18 days ago. The 70th advisory will be issued by the TPC this afternoon. The large mid-level ridge over the eastern half of the U.S. will expand to the eastern seaboard tonight. H5 heights are an impressive 590 dm over the Ohio Valley. Other than some wrap around moisture from Jose across our far outer coastal waters into the early evening hours, the forecast area will remain dry tonight under the influence of the summertime ridge. An increase in clouds across the coastal plain this evening is expected before Jose makes its move out to sea. North winds will slacken and go calm in spots. Temperatures will drop back to mid 50s north and west and into the lower to mid 60s across the I-95 corridor and coastal plain. Overnight lows will run above normal. Dewpoints are lower compared to 24 hours ago. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... The mid-level ridge continues to drift eastward tomorrow. H5 heights climb to at least 588 dm. H8 temps climb to about 30 deg C. As a result, another warm day is in store for the Delaware valley and adjacent locales. Just about everyone should hit at least 80. The exceptions could be the higher terrain in the Poconos and NW NJ and at the beaches. No rain is forecast. Expect lots of blue sky, especially by late morning. Winds will be out of the north and slacken during the afternoon hours. With the gradient weakening, a seabreeze should develop. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Sunday through Monday...Surface high settles in over the region. As a result expect continued dry and very warm weather. We could get close to record highs both days at inland locations (see climate section for the current record highs for those days). A light onshore flow could temper the warming trend at coastal locations. Tuesday and Wednesday...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, and at this point it doesn`t look like Maria will get close enough that we will see any of the outer rain bands). As for Maria, it 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. This is beyond the 5 days of the official hurricane track forecast, so there is considerable uncertainty, but at this point, almost all guidance shows the storm taking a right turn, further out to sea, through this period. If this does occur, we will see very little in the way of impacts aside from the swells and high surf. Friday...Cooler and drier air should settle in over the region. It will be quite a bit cooler than the early week periods, but only near normal for late September. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR with patches of cloud aoa 6000 ft, mainly vcnty KACY/KMIV/KPHL/KILG. No issues with visibility expected overnight, except maybe some ground fog in the most prone areas around 09z-10z but not in the TAF. Winds will be light out of the NW-N. Saturday...VFR. Light northwest winds. Lots of blue sky. Outlook... Sunday and Monday...mostly VFR conditions are expected. Tuesday and Wedensday...mostly VFR conditions expected. There is a slight chance for showers both days. Northeasterly wind up to 10 KT possible. && .MARINE... Tonight... SCA seas continues. The north winds are expected to continue through the period. Speeds will mainly be in the 10 to 15 kt range on the ocean. The dominant long period easterly swell will continue. Seas will range in the 4 to 7 foot range on the ocean overnight; mainly in the 1 to 2 foot range on Delaware bay. Saturday...The SCA advisory will remain posted on the Atlantic waters. Saturday conditions will be very much like tonight with northerly winds occasionally gusting up to 20 kt, a large easterly swell, and seas in the 4 to 6 foot range. Outlook... Saturday night and Sunday...elevated seas on the Atlantic Coastal waters are expected to continue through at least part of the night Saturday night. However, we are expecting a lull in elevated seas before the swells from Hurricane Maria arrive. Some guidance has seas increasing by mid day, but trends with recent storms have guidance showing swells arriving too quickly. If this trend continues, we may see a lull in elevated seas for much of the day. Monday through Wednesday...Swells from Hurricane Maria are expected to result in a prolonged period of hazardous seas on the Atlantic Coastal Waters. A few gusts near 25 KT are possible especially Wednesday, but in general, winds should stay below SCA criteria through this period. Rip Currents... Saturday...looks to be somewhat of a transition day as the beaches see leftover NE swells of around 4 or 5 feet from Jose at 9 second intervals and the introduction of 2-3 foot se swells of 15 second intervals from Maria. Maria`s swells will grow with time next week. More about that in the outlook. The surf zone may be a bit chaotic as swells from differing directions and energy collide. So while the surf height will be less, it still looks troublingly difficult to safely enjoy the surf zone swimming. For now we`ve issued a moderate risk but that may need to be raised to a high risk pending overnight swell trends from decaying Jose. Outlook... Sunday...There may be a brief lull in the larger swells but for now...a se swell of 4-5 feet is modeled at 15 second intervals from Maria. Thats a strong moderate risk if not a high risk for the formation of dangerous rip currents. Monday...a 5 or 6 foot se swell of 15 seconds is expected to be dominant and result in a high risk. 8 foot 15 second swell should be dominant by that time...lots of energy and a solid high risk. Wednesday...around an 11 to 13 foot se swell at 15 seconds. Even higher risk and if this materializes as constantly modeled...we`d need a high surf advisory as well, allowing 70 percent for breaking waves at the beach (8 to 9 foot). Thursday the 28th...still a 10 foot se swell at 14 seconds. High risk. Friday...maybe down to 5 or 6 feet and a mdt or high risk. && .TIDES/COASTAL FLOODING... We are still feeling the effects from Post-Tropical Cyclone Jose and the new moon. The Coastal Flood Advisory expired at 3 pm. Minor flooding occurred up and down the DE/NJ coasts...more spotty across northern NJ and more widespread across southern NJ and Sussex county DE. For this evening`s high tide, spotty minor flooding is expected along the NJ and DE coasts. This evening`s high tide is the lower of the two today by about 1/2 foot. As a result, we don`t think the flooding will be widespread enough to issue another advisory. && .CLIMATE... With high temperatures making a run at 90 Sunday and Monday across the region, some record high temperatures may be tied or broken. The highest chances are on Monday where all locations but Georgetown are expected to be within three degrees of a record. 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) Monthly climate: Depending on whether there is any rain at KILG, if none for the remainder of the month, the current monthly total of 1.12 inches would rank 12th driest in the period of record. September temps: PHL is projecting a 71.7 average or 2.6 degrees above average, which would make it the 13th warmest September in the PHL period of record. ABE is projecting a 68 degree avg or 4.1 degrees above normal which would be 9th warmest September in the ABE period of record. These projections took into account todays high/low, the PHI 330 PM forecast through the 29th and a normal high/low for the 30th. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Sunday for ANZ450>455. && $$ Synopsis...Drag/Johnson Near Term...Drag 952 Short Term...Kruzdlo Long Term...Johnson Aviation...Drag/Johnson 952 Marine...Drag/Johnson 952 Tides/Coastal Flooding...952 Climate... is the U.S. government's official web portal to all federal, state and local government web resources and services.