Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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100 FXUS61 KPHI 312007 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 407 PM EDT TUE MAY 31 2016 .SYNOPSIS...
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A cold front has weakened and pushed offshore today, and a secondary backdoor front will push southward across the area tonight into Wednesday morning. Our area will be on the southern edge of high pressure located across eastern Canada through early Thursday. A cold front will move across the area Friday. An area of low pressure and associated frontal boundaries will move across the Great Lakes region Saturday into Sunday, and across the Northeast Monday into Tuesday, bringing unsettled weather to our area early next week.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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A few sct showers have developed across srn Delaware over the past hour. The op models from earlier had this development fcst and we will keep the slgt chc mention in the grids for the early evening. Skies are partly to mostly sunny elsewhere and temperatures are a little above normal for late May. Highs have reached the low/mid 80s in most areas...cooler at the shore. A sea breeze has developed and will push inland through the afternoon. It may reach the Delaware valley before mixing out around dusk.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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The high pressure to the north of the area Wednesday morning will move into eastern Canada. The will place our region in the erly flow on the south side of the high. This should provide some fair weather for Wednesday with cooler temperatures (compared to Tuesday). Highs will be in the upper 70s to low 80s in most areas. Sky cover will be mostly sunny early with some clouds developing late across the srn/wrn areas. We have included a small chc for a shower across the Delmarva and se PA areas. Some of the operational models show some qpf output.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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Our area will continue to be on the far southern edge of an area of high pressure that will be residing across central and eastern Canada Wednesday night through Thursday. Mostly dry conditions are expected, although an isolated shower could be possible overnight Wednesday into early Thursday as a weak vorticity impulse slides across the area and could interact with some increased moisture within the return flow at the surface. Another vorticity impulse is forecast to approach the area late in the day and overnight, which could bring additional isolated showers by the afternoon. However, there will be a greater potential for showers overnight as this short wave/vorticity impulse moves across the area. On Friday, we expect a cold front to move across the area from west to east as an area of low pressure moves across eastern Canada. there will be an increase in instability, along with PW values reaching 1.75 inches. Therefore, we can expect scattered showers and thunderstorms to develop ahead of and along the frontal boundary during the day. The flow is not very strong, so any slow moving storms could produce some high amounts. But the front should still be fairly progressive, so no widespread flooding is expected at this time. The front will slowly make its way offshore Friday night, so there could still be some lingering showers and thunderstorms during the evening and early in the night Friday. All showers should be ending overnight. There could be a dry period Saturday as high pressure across central Canada tries to nose its way down across the area. It would not be surprising if an isolated shower were to occur, but we`ll keep this out of the forecast for now as the chances are small at this time. Unsettled weather returns for Sunday through Monday as an area of low pressure will be moving through the Great Lakes region and into the northeast. A warm front should be lifting across the area late Sunday into Sunday night, then a cold front will move across the area late Sunday night into early Monday. A period of showers and isolated thunderstorms should move across the area through this time period. PW values approach 2 inches during this time, so there could be some periods of heavy rainfall possible. There will continue to be a chance of showers Monday night into Tuesday as the low slowly pinwheels to our north through New England, especially during the afternoon Tuesday as a secondary surface trough/frontal boundary crosses the area.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,KMIV, KACY AND SURROUNDING AREAS. VFR conditions have returned to all of the terminals as of the mid- afternoon. The CIGS at KILG/KMIV and KACY were the last sites to mix out due to the abundance of the low level moisture and the former front dissipating over the area. VFR conditions will last into the evening before more fog develops overnight. I have kept the mention of fog across KRDG/KABE a little more uncertain with only tempo groups and more certain at the other sites with an attempt at categories and timing. Could be some low conditions where the dew points were higher today (KMIV/KACY). Winds have been challenging with NE winds early this afternoon and trending more light and variable lately. A sea breeze will probably bring some E/SE winds to KACY/KMIV/KILG shortly. The sea breeze may make it to KPHL/KPNE towards dusk. Light winds tonight and E/SE winds 5 to 10 knots Wed morning. OUTLOOK... Wednesday night-Thursday...Generally VFR inland. Lower clouds and/or fog possible near the coast may push inland. Mostly light east to southeast flow. Thursday night...MVFR ceilings may develop across the area, with showers possibly developing from west to east. Friday-Friday night...MVFR and/or IFR ceilings possible. Showers and thunderstorms possible, especially later in the day. Improving conditions later in the evening and overnight. Saturday...Generally VFR. Saturday night-Sunday...Diminishing conditions, possible becoming IFR by Sunday morning. Rainfall becoming more widespread Sunday. Gusty southeast winds possible Sunday.
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&& .MARINE...
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We have dropped the dense fog advisory with the latest vis satellite pics showing that the fog has diminished for now. There could be more later tonight...so areas of fog (not dense) was placed in the grids for overnight. Winds will be mostly onshore with erly or serly up Delaware Bay. Winds speeds mostly in the 10 knot range for most areas. some gusts up to 20 knots possible across the Delaware bay late this afternoon and into the evening. Sct showers possible over the Delaware and Srn NJ Coastal waters and Del bay into the evening. OUTLOOK... Wednesday-Sunday...Conditions forecast to be below Small Craft Advisory levels through the period. Winds could gust around 20 knots at times. Generally east to southeasterly winds, except west to northwest briefly behind frontal boundary passage Friday night.
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&& .TIDES/COASTAL FLOODING... Onshore flow is expected to develop on Wednesday and continue into Friday. We will need to monitor the possibility of minor tidal flooding at times of high tide along the coast late this week owing to the persistent onshore flow and the approaching new moon this Saturday. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Robertson Near Term...O`Hara Short Term...O`Hara Long Term...Robertson/Borowski Aviation...Robertson/O`Hara Marine...Robertson/O`Hara Tides/Coastal Flooding...

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