Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 161553 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1153 AM EDT Sat Sep 16 2017 .SYNOPSIS... Weak high pressure will build over our region through Sunday. Hurricane Jose is forecast to move northward off the mid- Atlantic coast through mid week, passing near our region Tuesday into Wednesday. High pressure is expected to once again build over our region late in the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The latest visible satellite imagery and surface observations show the pockets of fog/stratus continue to lift. A noted increase in cumulus development has occurred over the last hour, with a few areas of more pronounced development. One of these is from Mercer County southeastward with another area across portions of northeastern Pennsylvania (especially higher elevations). There is still some stratus, which looks to be lifting some while moving into portions of Monmouth and northern Ocean counties. The idea is with additional surface heating this should erode/lift as it tries to advect southwestward. Our area will remain within a weakening trough aloft and its associated strung out short wave energy. This along with local areas of surface convergence may lead to some showers (especially across eastern Pennsylvania and northern New Jersey). There is some instability across the area late this morning and this will continue during the afternoon. While this might be enough for some thunder, the lack of flow and organized lift should keep this potential rather low. Any activity may end up being low-topped, especially if the inversion near 700 mb on the 12z Sterling, VA raob remains. The hourly temperature, dew point and wind grids were adjusted based on the latest observations, then the LAMP guidance was blended in for the next few hours.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... The showers that develop during the day are expected to dissipate around or after sunset as daytime instability wanes. Once the sun goes down and the surface temperatures cool, areas of fog and/or stratus should begin to develop across the area. How thick the fog becomes is still uncertain at this time, but areas that receive rainfall today have the greatest threat for the fog to develop. && .LONG TERM /SUNDAY THROUGH FRIDAY/... The main story remains Hurricane Jose and its pass off our coast next week. First on Sunday, we could once again see some isolated to scattered shower coverage in the afternoon under a weak mid and upper level low. Temperatures should be similar to what we have seen the last several days with highs ranging from the lower 70s to lower 80s. Monday through Wednesday...Please see the forecast discussion from the National Hurricane Center for the latest details on the forecast track of Hurricane Jose. For our area, we are still looking at a track with the center passing several miles off shore, though still close enough for impacts to our region. At this point, we are expecting most of the impacts on Tuesday, though it should be noted there are still large timing differences between the models. As for the impacts for our region: Wind: With the latest track, it appears unlikely, though not impossible, that our land areas will see winds of tropical storm force. That being said, Tuesday into Wednesday will be quite breezy at the shore. Coastal Flooding: Please see the section below on the potential for coastal flooding Monday into Tuesday night. Heavy Rain: Current track keeps the heavy rain off shore on Tuesday, with our area only seeing the outer rain bands. However, any additional rain at the shore near or shortly before a high tide could exacerbate coastal flooding. Rip currents: Please see the discussion under the marine section for details on the rip current risk. Thursday and Friday...Most of the operational models depict a high amplitude ridge beginning to build over the region through this period, but it remains uncertain how quickly this will build. In addition, if it develops far enough north, we could be in a on shore low level flow regime for our area, tempering any warming trend due to the increasing thicknesses. && .AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. This afternoon...Cloud bases in the 3,500-4,500 feet range, however these could lower to around 2,500 feet for a period of time especially at KABE and KRDG. Some showers (perhaps an isolated thunderstorm) should develop this afternoon, however widespread coverage is not expected. Winds light and variable, becoming locally light from the east to southeast. Tonight...Any showers end earlier, then some fog and/or stratus should develop especially initially at KACY and KMIV. There is less certainty how far inland the stratus gets as it may be more fog. If less stratus develops, then fog may end up becoming more widespread with significant visibility restrictions. Winds light and variable. Outlook... Sunday...Once the fog dissipates, should have VFR conditions through the day. Another round of fog with visibilities of MVFR or lower is possible Sunday night, but details are uncertain at this time. Monday-Tuesday...Expect conditions to deteriorate to MVFR or lower across most of the region especially Monday night into Tuesday as Jose passes near our coast. KABE and KRDG may stay VFR for much of the period as they may be west of the main rain shield. Breezy easterly winds are possible for much of the region, with KACY having the highest risk of gusts above 30 KT. Wednesday...Becoming VFR with decreasing northwest winds.
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&& .MARINE... Sub-Small Craft Advisory criteria today as seas are forecast to be 3- 4 feet. However, seas are expected to build to 5-6 feet this evening and remain through the overnight hours. Winds are expected to remain 5-10 knots through tonight. Some fog mainly nearshore should dissipate today, however then probably redevelop tonight. Outlook... Sunday...SCA conditions are expected primarily for seas above 5 feet and primarily for the coastal waters and lower Delaware Bay. Monday through Wednesday...Tropical storm conditions will be possible Tuesday. However, even by Monday morning, winds will be above SCA criteria in advance of Hurricane Jose approaching from the south. Although winds will begin to diminish Wednesday, it will take time for seas to subside. Rip Currents... With 3-4 foot swells of 12-13 seconds today, along with a developing easterly wind of 5-10 knots, there is a moderate risk for the development of dangerous rip currents. A moderate or even high risk is expected through at least mid week as we continue to see the swells from Hurricane Jose reach our shores. && .TIDES/COASTAL FLOODING... Coastal flooding is possible with the high tide cycles Monday through Tuesday night due to the passage of Hurricane Jose. A prolonged period of east to northeast winds will allow water to pile up along the shores. In addition, there is a new moon on Wednesday, September 20, so astronomical tide levels will be running high. Depending on how close Jose tracks to the coast changes how significant the coastal flooding will be. As of now, minor coastal flooding is likely with the high tide cycles from Monday afternoon through Tuesday night. If Jose tracks closer to the coast, then widespread moderate coastal flooding will become more likely. If the timing of Jose slows down, then high tide cycles on Wednesday may be affected as well. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory for hazardous seas from 6 PM this evening to 6 PM EDT Sunday for ANZ450>455. && $$ Synopsis...Johnson Near Term...Gorse Short Term...Robertson Long Term...Johnson Aviation...Gorse/Johnson Marine...Gorse/Johnson/Robertson Tides/Coastal Flooding...

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