Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 252211 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 611 PM EDT Wed Apr 25 2018 .SYNOPSIS... An area of low pressure will move across our area this evening, then move toward New England tonight as it combines with another low pressure. Very weak high pressure tries to build into the region late Thursday, before another low pressure moves northward across the Mid Atlantic region Friday. This low will combine with another low as it moves across New England Saturday before moving into eastern Canada. A cold front is expected Saturday, with additional surface troughs Sunday into Monday. High pressure across the Great Lakes and Ohio Valley Sunday will build to our south Monday, and remain to our south through Wednesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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6 PM Update...Based on current web cams and satellite, we have extended the dense fog advisory along coastal NJ until midnight after which time conditions should improve as a cold front moves through. Otherwise, just some mostly minor adjustments to POP, T/Td, and sky grids based on current conditions and trends. Previous Discussion...Low pressure is currently located over Delmarva and will continue to move to the north and east through our area tonight. The associated upper trough will rotate through the area through the overnight hours. A good amount of energy associated with the upper trough will allow for the continuation of showers late tonight with majority of the rain ending between midnight and 2 AM. Even though the system will move off to the north of the area overnight, low clouds and fog will be slower to clear as plenty are likely to remain through the early morning hours, especially across the northern parts of our area. Precipitation is spotty this afternoon. Some isolated heavier showers, with embedded thunderstorms, remain possible across southern Delaware and into southern New Jersey as the sun has broken out across those areas this afternoon. We should lose the convective potential as we continue to head towards sunset. Some light rain was moving northward across northern New Jersey with just some spotty showers or drizzle remaining. Areas to the north and west of Philadelphia continue to see areas of fog with varying visibilities. We have taken down the Dense Fog Advisory for the Delaware coast as the web cams show that things have cleared up nicely there this afternoon. Dense Fog Advisory remains in place along the New Jersey coast through 7PM. Areas along the New Jersey coast show considerable fog this afternoon on area web cams. Overnight lows will be mild and in the 40s to around 50 across the region.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Thursday brings a brief return to high pressure and fair weather across our area. The day may start off a little cloudy, especially across northern areas, but we should see plenty of sunshine through the day. Winds will be out of the west to northwest around 10 to 15 mph. Temperatures are expected to rise into the mid to upper 60s across the majority of the area with upper 50s across the higher terrain of the Poconos and lower 70s across southern New Jersey and southern Delaware. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... After a brief period of possible unsettled weather at the beginning of the period, dry weather takes hold of the forecast for the rest of the long term forecast. On Thursday night, an area of low pressure will be approaching the area from the southwest, before moving across the area during the day Friday. There remains some timing and locations differences with the low between the guidance, however, there is better agreement than there was yesterday. They all indicate an increase in moisture while several short wave/vorticity impulses slide across the area as well, especially during the day Friday, which has the best chance of rainfall. Once this low lifts to our northeast, it will combine with another low pressure that will be moving out of the Great Lakes region and across eastern Canada and northern New England. This will pull a cold front across the area during the day Saturday. Low-mid level lapse rates increase ahead of the front while there will be an increase in low-mid level moisture. This could bring another chance of showers during the day as the front moves across the area. Not much in the way of instability is forecast, so we are not including thunderstorms at this time. Behind this front, drier conditions return to the forecast. The low pressure across eastern Canada will stay near the Canadian Maritimes through Monday, while high pressure across the Great Lakes and Ohio Valley Sunday will build to our south Monday. A couple of surface troughs will cross the area during this time period, but are expected to remain dry. For Sunday and Monday, there will be a pressure gradient in place between the high to the south and low to the north, so a steady breeze with gusts likely in the 20s is expected, with Sunday having the strongest winds. The high will remain to our south Tuesday into Wednesday, keeping dry conditions in the forecast. Winds will remain out of the west, and although a steady breeze is expected and slightly gusty at times, winds are not forecast to be as gusty as Sunday or Monday. && .AVIATION /22Z WEDNESDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Mainly IFR conditions in low clouds and fog across the terminals. Periods of MVFR and/or VFR are possible through this afternoon but are not expected to last very long. Conditions are expected to deteriorate once again this evening as winds start to go light. Scattered showers may briefly lower conditions but primary concern is low clouds and fog through tonight. Ceilings will lift between 06-09Z and start to become VFR. An isolated thunderstorm is possible this afternoon/evening, mainly towards KACY, but confidence is too low to include in the current TAF. Easterly winds tonight will lighten before turning to the northwest overnight. Thursday...Mainly VFR conditions expected. Some lingering MVFR, a little IFR possible, early in the day but clearing should be quick as west to northwest winds pick up around 10-14Z. Winds will be around 10 to 12 knots with a few higher gusts through the afternoon. OUTLOOK... Thursday night...Generally VFR, although MVFR conditions may begin late in the night across the southern areas as rain approaches. Friday...MVFR, possible IFR, with a chance of scattered showers. Friday night...MVFR conditions possible early with scattered showers, becoming VFR during the evening and overnight. Saturday...Mostly VFR. A chance of showers which may temporarily lower conditions. Saturday night-Monday...VFR. Gusty west to northwest winds 20-25 knots Sunday and Monday. && .MARINE...
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6 PM Update...Dense fog advisory has been extended until midnight based on beach cams and satellite imagery. Previous Discussion...Dense fog on the waters is slowly eroding from south to north. However, beach cams continue to show fog up and down the coastline, although there are some breaks occurring at this time. Therefore, we will leave the Dense Fog Advisory in place. The Dense Fog Advisory runs through 7pm. Otherwise, the Delaware Bay looks fairly quiet through Thursday. Winds may near 25 knots Thursday morning but are currently forecast to remain below SCa criteria. The SCA on the ocean will remain in place, mainly for seas, through Thursday. Winds may gust to around 25 knots early on Thursday. OUTLOOK... Thursday night...Small Craft Advisory continues due to elevated seas. Friday-Friday night...Elevated seas may linger into Friday and Friday night. Saturday night...Conditions expected to remain below advisory levels. Sunday-Monday...Winds may approach Small Craft Advisory levels on Sunday.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...Dense Fog Advisory until midnight EDT tonight for NJZ014- 024>026. DE...None. MD...None. MARINE...Dense Fog Advisory until midnight EDT tonight for ANZ450>455. Small Craft Advisory until 6 AM EDT Friday for ANZ450>455.
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&& $$ Synopsis...Robertson Near Term...Fitzsimmons/Meola Short Term...Meola Long Term...Robertson Aviation...Robertson/Meola Marine...Robertson/Meola/Fitzsimmons

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