Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 220034 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 834 PM EDT WED SEP 21 2016 .SYNOPSIS... High pressure will continue to build southeastward over the region tonight and become established over our area through Friday with the remnants of Julia well offshore. A backdoor cold front will then move through the region on Saturday and be followed by another high pressure system building in from the northwest early next week. By the middle of next week, a cold frontal boundary will move toward the region from the west. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Thick cirrus remains over much of the area this afternoon but a gradual thinning of these clouds will occur through this evening and especially overnight. Areas to the south and east may continue to see continual cloud cover overnight with thinning occuring more towards tomorrow morning. Aside from the clouds, tonight looks to be a fairly nice night. The airmass continues to dry out, with the exception of the far southeastern areas, and fog should be less of an issue overnight but we may still see some patchy fog occur. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Thursday will be similar to today but with an easterly flow, it might end up a degree or two cooler but areas along the coast will be closer to 5 degrees cooler today. Temperatures across the region will generally be around 80 to 85 with mid to upper 70s along the coast. The remnants of Julia may keep the clouds around our southern areas for a bit longer into Thursday but it looks like the bulk of the showers will remain to the south and east of the area. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Thursday night through Friday night: High pressure will continue to build into the region Thursday night and become established across the region on Friday. Favorable conditions for radiational cooling are expected Thursday night with lows in the 50`s and low 60`s. Some cloudcover ahead of an approaching frontal boundary may keep low temperatures slightly higher Friday night. Friday looks like the last of the anomalous early fall heat for at least a little while with temperatures well into the 80`s. Modeled boundary layer temperatures indicators of surface temperatures match well with MET/MAV and ECMWF statistical guidance. Saturday through Monday night: A cold front will move from northeast to southwest across our region. Our coolest airmass of the season will advect in as another high pressure system dives southeast from Canada. Enough lift and moisture may be present for a temporary increase in cloud cover and isolated showers on Saturday otherwise continued dry conditions. temperatures will be much cooler for the weekend. Some indications in ensemble guidance have a slightly delayed frontal passage which may allow for Saturday to get into the 80`s. However, we will stick with the mean timing of early Saturday with the operational and ensemble guidance for the frontal passage. Much cooler air, a first real taste of fall with lows in the 40`s and 50`s with highs in the 60`s and 70`s. Less spread with temperatures Sunday and Monday with the ensemble guidance. Tuesday through Wednesday: The backdoor frontal boundary coupled with a mid-level ridge to our west look to setup an omega block which will likely slow the approach of the next cold frontal boundary or weaken as it moves east. As is usually the case in the 5-7 day time period uncertainty is present on the exact timing of this feature. The UKMET, CMC and some ensemble data weaken the front before it approaches our area. On the other spectrum, the GFS and GEFS are much faster bringing it through around Tuesday. Given this spread and questions if the front makes it to our area, will keep a dry forecast. Low and high temperatures should slightly warm each day unless the high pressure system sets-up just to our north. In that case an easterly flow could slow the approach of a warmer airmass expected ahead of the next front. && .AVIATION /01Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR conditions expected. Patchy MVFR fog is possible after 06Z but with a drying airmass it seems unlikely to occur. Winds will be light and variable for most of tonight, but should eventually settle out of the ENE by sunrise. Thursday...VFR conditions expected. Any early morning fog should dissipate fairly quickly. Northeast to east winds around 10 knots or less are expected with a slight shift towards the southeast late. OUTLOOK... Thursday night through Friday night: VFR.Varibale winds becoming west-southwest but staying under 10 knots. Saturday through Monday: VFR. An isolated shower possibile on Saturday. Northerly winds around 10 knots Saturday afternoon with gusts up to 20 knots then staying under 10 knots Sunday and Monday.
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&& .MARINE...
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A Small Craft Advisory is in effect from 14z Thursday through 18Z Friday. Tonight...Sub-advisory conditions are expected to continue on the area waters tonight. Seas may near 4 feet by late tonight. Winds will remain around 15 to 20 knot through early evening before starting to subside a bit overnight. Thursday...An east to northeast wind will increase through Thursday afternoon with gusts around 20 knots. However, seas will build in the easterly flow and are expected to exceed 5 feet along the Delaware and southern New Jersey coast around late morning and continue into Thursday night. As a result, we have issued a Small Craft Advisory. OUTLOOK... Waveheights will start in the four to five feet range and should slowly decrease on Friday. GWES guidance indicates a fairly high confidence for seas to reach five feet Thursday night and early Friday. So have issued an SCA which goes through 18z Friday. This ending time may be slightly long but allows for wiggle room if waveheights respond slower, typical of easterly flow. For the weekend into early next week seas and winds are expected to remain below SCA criteria. RIP CURRENTS... There is a moderate risk for the formation of dangerous rip currents along the NJ shore and Delaware Beaches on Thursday. Onshore flow will continue, wave heights of 3 to 5 feet are expected, and the dominant period will either be 7-8 seconds if the wind wave becomes more dominant (in which case wave heights should be on the higher end of the 3-5` range) or 11-12 seconds if the swell remains dominant (as it is Wednesday evening). Friday...A generally low or low enhanced risk is forecast. Weekend...There is a pretty good chance of a moderate risk for the formation of dangerous rip currents on at least one of the weekend days as a 4 to 5 foot ESE swell from Tropical Cyclone Karl arrives along with a gusty northeast wind.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 10 AM Thursday to 2 PM EDT Friday for ANZ452>455. && $$ Synopsis...Gorse Near Term...Meola Short Term...Meola Long Term...Gaines Aviation...Gaines/Johnson/Meola Marine...Gaines/Johnson/Meola

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