Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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029 FXUS61 KPHI 202100 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 500 PM EDT Thu Oct 20 2016 .SYNOPSIS... A warm front just south of our region will move north across our area on 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/... Warm front lifting north of I-78. South of the front, temps have risen well into the mid and upper 70s, and even into the low 80s across MD/DE. North of the front, temps are in the upper 60s to low 70s. As the front lifts to the north, those warmer temps should continue to lift to the north, but there is not much daytime left for temps to reach 80 across northern zones. Abundant stratus just offshore has spread westward, and cloudy skies in place for much of NJ. That warm front has scattered out some of the clouds in southern and western NJ, but after sunset, expecting those clouds to spread back to the west, and widespread low clouds and fog will develop across the region. MOS guidance indicating the potential for dense fog, and do think that some spots may have visibilities less than 1/2 mile, but at this time, not confident enough to issue a Dense Fog Advisory. Think best chances will be along coastal NJ, as well as across the Lehigh Valley, as sfc dewpoints continue to rise into the 60s, and air temps drop back into the 60s. With a saturated airmass, will include areas of fog and drizzle in the forecast, from mainly after midnight tonight. Low pressure over the OH valley will track to the north and east through western NY and PA, and the bulk of the rainfall should stay well to the west. Some rain may spread out ahead of that low, and will therefore carry low chance PoPs, mainly for northern zones, tonight. Not expecting much, if any, actual rainfall aside from some drizzle across central and southern areas. && .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 /21Z THURSDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Stratus and fog over the western Atlantic has spread into eastern NJ with MVFR to IFR CIGs. Some of the clouds scattered out over SE PA and SW NJ. Going into tonight, with a saturated airmass over the area, expecting CIGs and VSBYs to lower to LIFR, with RDG/ABE and possibly ACY having the potential to drop to VLIFR. Conditions will gradually improve to VFR late Friday morning. Showers and scattered thunderstorms approach in the afternoon. 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...
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Preliminary update as of 4:45 PM...The following sites set new record daily high temperatures today (Thursday, 10/20). The final climate report will be issued at 5:30 PM. New RecordOld Record Philadelphia, PA 81 80 (1916/1938) Georgetown, DE 84 83 (1953)
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&& .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...MPS Short Term...MPS Long Term...Franck Aviation...Franck/MPS Marine...Franck/MPS Tides/Coastal Flooding... Climate... is the U.S. government's official web portal to all federal, state and local government web resources and services.