Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 170746 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 346 AM EDT Sun Sep 17 2017 .SYNOPSIS... High pressure gradually builds to our north and east into Monday. All interests in coastal areas of New Jersey and Delaware should follow the forecast of Hurricane Jose as it moves northward off the mid-Atlantic coast, probably passing well east of New Jersey Tuesday into Wednesday. High pressure is expected to settle back down into our area late in the week, behind the departing Jose. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Stratus and fog has spread across much of the area overnight and will continue to spread farther inland through the early morning hours. Some locally patchy dense fog will occur, but it is not expected to be widespread. The fog and stratus is expected to dissipate and lift through the morning hours after sunrise. Similar conditions as Saturday will occur today as our area will remain under the influence of a mid level low/trough and its associated vorticity. It`s hard to find any surface reflection, but with the trough and vorticity aloft, there will be some enhanced lift across the area. So there will be a chance for isolated/scattered showers to develop again today. Similar to Saturday, PW values are around 1.25-1.50 inches, so there could be some locally moderate to heavy downpours with any showers.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
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The showers that develop during the day are expected to dissipate around or after sunset as daytime heating wanes. Once the sun goes down and the surface temperatures cool, areas of fog and/or stratus should begin to develop and spread across the area from east to west. Overall fog is not expected to be widespread dense, but a some locally patchy dense fog will be possible.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/...
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As has been the case the last several days, all of the focus in the long term is on Hurricane Jose and its track a few hundred miles off our shore. Please see the forecast discussion from the National Hurricane Center for the latest details on the forecast track of Jose. Not many changes with this forecast issuance in the expected impacts. Here is a summary of the impacts from most likely to less likely: 1. High Surf resulting in beach erosion and a high risk of rip currents: Though we are seeing a brief lull in the wave heights, that is expected to be increasing over the next two days, with the highest wave heights coming Monday night and Tuesday. We have high confidence of this occuring. 2. Tidal flooding: We have high confidence that tidal coastal flooding will occur, though there is still some uncertainty with the severity of the coastal flooding. See the coastal flooding section below for more details. 3. Tropical Storm force winds (sustained of 34 KT or higher): this appears very unlikely on our land zones. However, a period of wind gusts up to 40 mph is possible right along the coast generally on Tuesday night. 4. 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. As for temperatures, stayed close to guidance from WPC given the dependence on the track of Jose. One thing of note that I have not yet included in the forecast, the GFS MOS (MEX) shows a dramatic warming trend on Wednesday even though we should still be under the northwesterly flow behind departing Jose. This is unusual for such a pattern, but will be watching if this trend continues or if other models and MOS guidance jump on to this trend as well. Thursday through Saturday...A high amplitude ridge should begin to build over our region. However, as mentioned by the previous shift, the center of the high will likely be far enough north that our region will see weak onshore flow, tempering any warming trend due to the building high.
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&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Stratus and fog has pushed inland and covers most of central/southern New Jersey, portions of eastern Pennsylvania, as well as central/southern Delaware and eastern Maryland. The stratus and fog is expected to continue to push inland and cover all areas during the early morning hours. CIGS/VSBYS will be IFR as the stratus builds over, with some areas lifting to MVFR at times. The fog and stratus will lift through the morning hours after sunrise, and VFR conditions should return by late morning into the afternoon. There will be another chance of isolated/scattered showers this afternoon, so a PROB30 was included. The showers will dissipate around or shortly after sunset. Then another round of stratus and fog is expected to spread back across the area overnight again. Winds will continue to be light, with any direction from the east around 5-10 knots or less. Outlook... Monday...starting out MVFR or IFR with low clouds and fog. Visibilities should improve early. Ceilings may raise to 4000 ft AGL by 18Z. However, expect ceilings to lower once again Monday night to MVFR or even IFR along the coast. Western TAF sites like KRDG and KABE are likely to stay VFR. Tuesday...VFR conditions are expected at KRDG and KABE. For the Delaware Valley TAF sites (KPHL, KILG, KPNE, and KTTN) and coastal sites (KMIV and KACY) MVFR or lower ceilings are possible. Northeasterly winds 10 to 20 KT with gusts to 30 KT will be possible for the coastal sites. Wednesday...Becoming VFR with decreasing northwest winds...gusting 15 to 20 KT. Thursday...Mostly VFR conditions are expected. Light winds shifting from northerly to northeasterly
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&& .MARINE...
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With seas 4-6 feet across the waters today, we will continue with the Small Craft Advisory for Hazardous seas. Winds today will remain generally out of the east to northeast around 5-10 knots, then increase to 10-15 knots through this afternoon and tonight. Outlook... Monday through Wednesday...Tropical storm conditions will be possible Tuesday. However, even Monday, winds may be above 25 KT in advance of Hurricane Jose approaching from the south. Although winds will begin to diminish Wednesday, it will take time for seas to subside. A tropical storm or gale related marine hazard may be issued later today...all dependent on internal assessment of the wind fields. Wednesday night and Thursday...once seas subside below 5 ft Wednesday night, winds and seas should stay below SCA criteria for the remainder of the period. Rip Currents... With swells of 12-13 seconds forecast to build to 5-6 feet today, along with an easterly wind of 5-10 knots, we will continue with a high risk for the development of dangerous rip currents today. The high risk will likely continue through mid week. Swimming at the beaches is not recommended the next few days.
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&& .TIDES/COASTAL FLOODING...
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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 morning. The high tide cycle of greatest concern at this point is the Tuesday evening high tide, when moderate coastal flooding will be possible especially along the New Jersey Shore and adjacent back bays.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...High Rip Current Risk from 8 AM EDT this morning through this evening for NJZ014-024>026. DE...High Rip Current Risk from 8 AM EDT this morning through this evening for DEZ004. MD...None. MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Monday for ANZ450>455.
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&& $$ Synopsis...Drag Near Term...Robertson Short Term...Robertson Long Term...Johnson Aviation...Johnson/Robertson Marine...Johnson/Robertson Tides/Coastal Flooding...

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