Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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277 FXUS61 KPHI 221008 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 608 AM EDT Thu Jun 22 2017 .SYNOPSIS... Weak high pressure will be across the Middle Atlantic region today and tonight. Low pressure will cross north of the area Friday and Saturday. Its associated front will slowly cross the area Saturday. More high pressure will be over the area Sunday. Another disturbance will bring some showers to the area early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Weak frontal boundary, mainly as evidenced by surface dewpoints generally in the 50s north of the front and in the 60s south of the front, lies across central PA and northern NJ. This boundary washes out as it lifts north through the morning, and then winds become more southerly this afternoon, allowing that higher dewpoint airmass to spread northward. Meanwhile, broad high pressure over the East Coast moves nearly overhead by midday, and then offshore by this evening. A weak surface trough along with some weak upper level shortwave energy develops across western PA and tracks east through the day. This may touch off a few late day showers and thunderstorms across the Lehigh Valley and Poconos. Will cap PoPs at slight chance, as confidence and coverage is low. A warm day on tap today with increasing humidity levels through the afternoon. Highs today will generally top off in the upper 70s to low 80s across the Poconos and NW NJ, and in the mid to upper 80s across the Lehigh Valley and much of NJ. Highs will be around 90 in the Delmarva. Highs will be several degrees cooler, generally in the upper 70s to low 80s, right along the shores.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... ny lingering showers and thunderstorms, mainly to the north of I- 76, will taper off this evening. High pressure continues to drift offshore tonight. Return flow setting up behind the departing high will usher an increasingly humid airmass into the Mid-Atlantic and Northeast. Surface dewpoints will climb into the upper 60s and low 70s, and PWATs will climb to around 2". Meanwhile, moisture and some shortwave energy associated with what is currently Tropical Storm Cindy over the TN Valley lifts into the Appalachians tonight, and then towards the Northeast after midnight. With ML MUCAPE values approaching 1000 J/kg across northern NJ and the Poconos, there is the potential for some thunderstorms in the pre-dawn hours. Latest model guidance holds bulk of precip off until after 12Z Friday, so will cap PoPs at chance across the region. However, given the tropical nature of the airmass, can expect locally heavy rain. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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There will be some unsettled conditions across the region during the beginning of the long term. A low pressure system will move across the Great Lakes and southern Canada Friday through Saturday. A slow moving front, an upper level trough and moisture from Cindy will all reach the area by Saturday. This will bring chcs for showers and a few tstms Friday and a better chc for rains Saturday. We now have likely pops for most areas Saturday. There is still some differences with regards to if the best moisture arrives over our area, or gets shunted off to the east. Temperatures will be a bit above normal Friday and closer to normal for Saturday, with more clouds expected. Behind the departing system on Sunday, most areas will have fair weather with partly to mostly sunny skies. Temperatures will be mostly in the low/mid 80s over the region. The weakening upper trough will move across the Northeast and Middle atlantic region Monday night and Tuesday. we have included some small chc or slgt chc pops for these periods. Temperatures will be a little below normal with highs in the upper 70s north and low 80s across srn NJ and Delmarva.
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&& .AVIATION /10Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Any lingering patchy fog will dissipate through around 12Z, and widespread VFR conditions on tap. LGT/VRB winds. Otherwise, VFR today. Isolated SHRA/TSRA, mainly at KRDG/KABE from late this afternoon through this evening. SW winds increase to 5-10 KT with gusts up to 17-18 KT this afternoon. Afternoon sea breezes possible at KACY/KMIV. Tonight...Any lingering SHRA/TSRA at KRDG/KABE will taper off this evening. LGT/VRB winds. MVFR/IFR conditions possible, mainly after 06Z. Scattered SHRA/TSRA possible after 09Z. OUTLOOK... Fri and Fri night...Mostly VFR. Sct showers and a few tstms. Sat...A period of MVFR or IFR expected. Showers. Sat night thru Monday...Mostly VFR. Sct showers Monday.
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&& .MARINE...
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Light winds this morning become S 8-12 KT this afternoon and tonight. Ocnl gusts up to 20 KT possible this afternoon. Seas will average 3-4` on the ocean and waves will average 1-2` on DE Bay. OUTLOOK... Fri...Sub-SCA with a chance of showers and tstms. Fri night thru Sat night...SCA on the ocean and sub-SCA on Del Bay. Showers with a chance for tstms. Sun thru Mon...Sub-SCA with sct showers Monday. RIP CURRENTS... We are forecasting a low or low enhanced risk for the formation of dangerous rip currents today. The southerly short period swell and long period southeasterly swell are both forecast to slowly subside this morning. A light offshore wind will shift southeast today. Even with a low risk...the bigger diurnal difference in the tide cycle as we approach the date of this months new moon could mean some rapidly changing conditions. IF you`re a poor swimmer (dont overrate your swimming skill please), you should absolutely swim within sight of the life guards. AND... if you get caught in a rip current or the backwash of the incoming waves is tiring, relax and remain calm! It`s much easier to think about escape and for the lifeguards to rescue.
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&& .TIDES/COASTAL FLOODING... High astronomical tide levels are expected in association with the new moon on Friday. That, combined with increasing southerly flow, looks to result in minor coastal flooding with the afternoon and evening high tide primarily for the Atlantic coastal areas and the shores of the Delaware Bay. Will go ahead and issue a Coastal Flood Advisory for those areas this evening, as departures will range from around 1 foot to 1.5 feet. This is enough to hit minor coastal flood advisory thresholds. Minor coastal flooding may continue with the Friday afternoon and evening high tide. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...Coastal Flood Advisory from 5 PM this afternoon to 9 PM EDT this evening for NJZ012>014-020-022>027. DE...Coastal Flood Advisory from 5 PM this afternoon to 9 PM EDT this evening for DEZ003-004. MD...None. MARINE...None. && $$ Synopsis...O`Hara Near Term...MPS Short Term...MPS Long Term...O`Hara Aviation...MPS/O`Hara Marine...Johnson/MPS/O`Hara Tides/Coastal Flooding...

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