Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 170023 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 823 PM EDT Wed Aug 16 2017 .SYNOPSIS... Weak high pressure will shift offshore tonight and Thursday. A warm front will lift northward towards the area late Thursday and move through the area Thursday night. At the same time, a cold front will approach the mid-atlantic region from the west. This front will track off the coast Friday night into Saturday. Surface high pressure will return for Sunday and persist into Tuesday. The affects of the next cold are expected to arrive late Tuesday into Wednesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Showers have stubbornly persisted in portions of Talbot and Caroline Counties in Maryland and in coastal Ocean County in New Jersey as the continued small-scale lift provided by associated sea/bay breezes supports their development. Should see a downward trend in the next couple of hours, but needed to extend PoPs a little longer in these areas. Though coverage is quite isolated, locally heavy downpours may occur, especially in Maryland. Main question tonight is fog formation. Conditions are not nearly as favorable for widespread fog versus last night given that most of the area was dry today and dew points are several degrees lower. Nevertheless, with light winds and sufficient residual near-surface moisture in play, patchy fog is likely, especially in the favored valley/rural locations (e.g., KPTW, K22N, KMIV, and KFWN). Will be making some tweaks to the Wx grids to fine-tune timing/location of expected fog formation. Lows tonight will be in the upper 50s in the Poconos and in the mountains of northwest NJ, and otherwise in the low to mid 60s. The urban heat island effect will keep the Philly metro area in the low 70s.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Made some adjustments to cloud cover and wind forecast on Thursday, as latest short-range model simulations are a little slower in bringing increased clouds to the region through the day. Will reevaluate the PoPs/Wx forecast later this evening, but first impression is that may need to slow the onset of precipitation (chances) from what is currently in the forecast. Previous discussion below remains relevant... Warm front continues to lift north through the region on Thursday, but may not clear northern zones until late. This results in surface dewpoints in the low 60s north and west of the Fall Line, and in the mid to upper 60s across much of southern NJ and the Delaware Valley. Extreme southern NJ and the Delmarva should have dewpoints in the low 70s. Meanwhile, low pressure currently over the Midwest will track to the north and east, and will move into the upper Great Lakes by Thursday afternoon. Upper level ridging builds into western and central NY/PA during the day, and despite several shortwaves spinning out ahead of the storm system, think most of the precip should hold off until late in the afternoon. Best chances will be across southwest zones, where the dewpoints are the highest. Highs will generally top off in the low to mid 80s, except for the mid to upper 80s in the Delmarva and in the upper 70s along the coasts and in the mountains. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Overview...The period starts with a warm front to our north and cold front across the Ohio Valley. The cold front will cross the region later Friday night into Saturday. By Sunday morning, the front is expected to be well offshore with high pressure building in. The center of the high will move across the region on Monday and then move offshore on Tuesday. A pre-frontal trof is likely to set up on Wednesday as a cold front moves through the eastern Great Lakes. Temperatures...Normals at KPHL will run in the mid 80s and upper 60s through the period. Friday will run near normal with clouds and precipitation present. Saturday will run above normal. Sunday and Monday will run normal. Tuesday and Wednesday will run above normal. No major extremes are in the forecast. Precipitation...PoPs will increase Thursday night into Friday. Calendar day Friday appears to be the most unsettled during the period. We`ll run with likely PoPs most everywhere. PoPs will decrease on Saturday. Small PoPs will be included for Saturday night as a mid-level feature tracks through the region. Sunday and Monday look dry. PoPs will be reinserted into the grids starting Tuesday afternoon. We are included in general t-storms on the day 3 SPC outlook. PW`s will be between 2.0 and 2.5 inches Thursday night into Friday. As such, WPC has our area in a marginal risk for excessive rain. Winds...Winds are forecast to be mainly 15 mph or less through much of the period. Southerly winds will increase on Friday ahead of the cold front. Gusts in the 20 to 25 mph range can`t be ruled out on Friday...especially as one approaches the coast. Winds could also gust in and near thunderstorms. Impacts...Limited through the extended, minus Thursday night through Friday night. Although the SPC Day 3 Convective Outlook has us in general, we`re lying just outside of marginal. We`ll need to keep on eye on the threat for some strong to severe thunderstorms as well as isolated high-rate rainfall. WPC has us in a marginal risk for excessive rainfall. Localized flooding is possible. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. For the 00Z TAFs...Main concern is patchy fog tonight. Decided to add at least a mention of slightly lowered visibilities at KRDG, KABE, and KILG and maintained sub-VFR VSBYs at KMIV after midnight. However, not confident that KACY will see prolonged lower VSBYs based on latest guidance. Fog should quickly dissipate after 12Z. Winds will become southeast or south 5-10 kts tomorrow, with increasing mid and high clouds through the day. OUTLOOK... Thursday night...Mainly VFR. MVFR conditions possible in showers and thunderstorms. Fog possible late reducing vsbys. Friday...Fog possible early morning. Additional MVFR conditions likely in showers and thunderstorms. Saturday...Some MVFR conditions expected the first half of the day in isolated showers and thunderstorms. MVFR conditions improving to VFR during the afternoon. Sunday and Monday...VFR conditions expected.
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&& .MARINE...
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Seas remain well below 5 feet this evening, with winds generally light southerly at this time. Expect winds to veer to northerly late tonight and tomorrow morning before returning to southeasterly by afternoon. Speeds should generally remain at or below 10 kts. Seas should hover around 3 feet through the period (lower in Delaware Bay). OUTLOOK... Thursday night through Saturday morning...Sub-SCA conditions expected, although gusts could approach 25 knots on Friday afternoon and evening. Showers and thunderstorms becoming likely late Thursday through Saturday. Locally higher seas and winds in heavier showers and stronger thunderstorms. Sunday into Monday...Sub-SCA conditions with no precipitation expected. RIP CURRENTS... Buoy observations indicate that the longer-period swells generated by Hurricane Gert are beginning to diminish (or at least becoming less frequent). Observations from the beach (via patrols and webcams) suggest rip currents were prevalent today, but conditions are expected to improve tonight and tomorrow. As such, the risk for dangerous rip currents is downgraded to moderate for tomorrow. The rip current statement will be allowed to expire at 9 pm this evening. Swim only in the presence of lifeguards where safety prevails and if beaches are closed...respect the decisions of the local officials. Do we need a reminder? There have been numerous drowning fatalities this year along the NJ coast, and most of those at unguarded beaches.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...High Rip Current Risk until 9 PM EDT this evening for NJZ014- 024>026. DE...High Rip Current Risk until 9 PM EDT this evening for DEZ004. MD...None. MARINE...None. && $$ Synopsis...Kruzdlo Near Term...CMS/MPS Short Term...CMS/MPS Long Term...Kruzdlo Aviation...CMS/Kruzdlo Marine...CMS/Kruzdlo/MPS

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