Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 210152 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 952 PM EDT Thu Oct 20 2016 .SYNOPSIS... A warm front Will move north across our area through Friday. Meanwhile, low pressure will strengthen across the Ohio Valley and move north of the region into Friday. A strong front associated with the low will cross the area Friday evening, while the low remains over New England into the weekend. Gradually, high pressure will build across our area into the middle of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... The warm front appeared to extend across southeastern Pennsylvania and southern New Jersey this evening with mainly east winds to its north and southeast winds to its south. Also, stratus has become established to the north of the boundary. We are fairly confident that the low clouds will hold through the night across much of northern and central New Jersey and into the Poconos, the Lehigh Valley, upper Bucks County and Berks County. Our thinking is that the inflow of low level moisture on the southeasterly flow will cause the low clouds to expand southward. However, our confidence in the amount of low clouds over the Philadelphia metropolitan area, southern New Jersey and the upper Delmarva is not particularly high. Where low clouds exist there is the potential for areas of drizzle and fog, as well. The moderate to heavy showers over parts of western and central Pennsylvania into western New York this evening should remain to our west and northwest. However, scattered showers did begin to develop over our northwestern counties this evening and that may continue to be the case overnight in the upslope flow. Temperatures should drop only into the upper 50s and lower 60s which is near the normal maximum readings for this time of the year. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... There are 2 areas of low pressure that will impact the region on Friday. The first is the primary low over western NY/PA that will track to the north and east, dragging a strong cold front with it. Based on latest model QPF fields, not expecting much precip to spread into the local CWA until the afternoon. Will carry likely PoPs for NW zones early, but think the bulk of the showers will hold off until late afternoon, possibly even Friday evening. There may even be enough upper level energy to support some scattered thunderstorms in the afternoon, so will mention that in the forecast. The second wave of low pressure that could impact the region will spin off of low pressure over the western Atlantic Ocean waters. Looks like some rain will spread to the north along the Jersey Shore. High chance to low end likely PoPs will cover this possibility. With strong southerly flow ahead of the approaching cold front, looks like there will be another day of unseasonably warm temps, especially if enough sun can break through the clouds. Used a blend of MOS guidance for highs in the mid to upper 70s for most areas. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... Friday night and Saturday...500 hPa closed low traverses the region during this time frame. A strong cold/occluded frontal passage Friday night will lead to gusty northwest winds thru Saturday. Given the strong cold air advection, in concert with a tight pressure gradient, mixing to 850 hPa yields gusts close to advisory criteria (46 mph) Saturday afternoon and evening, especially in the coastal plain. Therefore, a wind advisory may be needed in future forecast packages. There will be considerable cloud cover on Saturday, especially north of Delmarva. Given the strong PVA aloft and abundant low-level moisture, expect scattered rain showers, especially over the higher terrain (less downsloping). Saturday night and Sunday...Northwest flow continues, albeit lighter, with gusts 30 to 35 mph still possible into Sunday afternoon. Otherwise, clear to partly cloudy and dry. Sunday night thru Tuesday...A quick moving disturbance in the northwest flow aloft will lead to an increase in cloudiness by Sunday night. Cannot rule out a light shower over the higher terrain, but the stronger dynamics and deeper moisture are not in concert, in addition to the downsloping flow. During Tuesday, another disturbance, very similar to the previous one, moves just northeast of the region. Given the disjointed moisture and dynamics, forecast was kept dry at this time. Wednesday and Thursday...A storm system moving through the Great Lakes sends a warm front toward the region Wednesday with an increase in cloudiness. At this time, any appreciable precip looks to hold off until Thursday. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. IFR conditions are expected through the night and into Friday morning at KABE and KTTN. MVFR ceilings are forecast to lower to IFR at KRDG. We expect the low clouds to expand southward during the night and they should impact KPNE, KPHL and KILG. While we are anticipating that low clouds may reach KMIV and KACY, our overall forecast confidence for those two locations is rather low. The low clouds and fog should be slow to lift and dissipate on Friday morning due to the lowering autumn sun angle. We expect conditions to improve into the VFR category for the afternoon even with the increasing potential for showers. The wind direction will favor the southeast overnight and on Friday morning, and the southwest on Friday afternoon. Speeds should be mostly in the 6 to 12 knot range. A strong cold front is forecast to arrive late in the day bringing a shift to a northwesterly wind. OUTLOOK... Fri night...-SHRA likely with MVFR restrictions possible. Northwest wind gusts to 25 knots possible late. Sat through Sun...Predominantly VFR conditions anticipated. Northwest wind gusts up to around 35 to 40 knots possible Saturday, dropping of to around 25 to 30 knots Sunday. Mon and Tuesday...Predominantly VFR conditions anticipated. && .MARINE... Sub-SCA conditions expected on the waters tonight through Friday. There may be VSBY restrictions tonight over the waters due to fog and low clouds. Those restrictions should lift Friday morning. OUTLOOK... Fri night thru Sun...A Gale Watch remains in effect Fri night thru Sunday morning, but may eventually need to be extended thru Sunday. Strong gusts and rough seas are expected. Sun night thru Tue...SCA conditions anticipated in a continued northwest flow. && .TIDES/COASTAL FLOODING... Water levels remained a bit elevated along the coasts of New Jersey and Delaware today and there was some isolated minor flooding around the midday high tide. The onshore flow is expected to weaken tonight and the flow should veer toward the south on Friday. As we get further away in time from the recent full moon astronomical tides will be a few tenths of a foot lower on Friday than they were today. As a result, we are not expecting any coastal flooding issues on Friday. && .CLIMATE... The following sites set new record daily high temperatures today (Thursday, 10/20). New RecordOld Record Philadelphia, PA 81 80 (1916/1938) Georgetown, DE 84 83 (1953) && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Watch from Friday evening through late Saturday night for ANZ430-431-450>455. && $$ Synopsis...Franck/O`Hara Near Term...Iovino Short Term...MPS Long Term...Franck Aviation...Franck/Iovino Marine...Franck/MPS Tides/Coastal Flooding...Iovino Climate...Franck is the U.S. government's official web portal to all federal, state and local government web resources and services.