Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231357 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 957 AM EDT Fri Jun 23 2017 .SYNOPSIS... Low pressure will track well north of our area Friday and Saturday. An associated cold front will cross our region during Saturday as some tropical moisture moves ahead of and along it. High pressure will then build well to our southwest Sunday into Monday. A weak cold front will move through our area later Monday. High pressure will then build across the Mid Atlantic Tuesday and Wednesday, before shifting offshore Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Round one of three is moving through the region now. So far, no embedded thunderstorms have developed, and surface temperatures are running a bit lower than previously expected. It appears that we remain capped with this first round. The associated shortwave trough with this round should clear the area by mid day. Upstream, there are some pockets of clearing apparent on satellite. It still remains to be seen when and how long we will clear out this afternoon. Thus, it also remains uncertain how much instability we will have by this afternoon when the next shortwave trough approaches our region. However, north and west of the fall line, if we get some clearing, we will have modest CAPE values and 0-6km shear values near or above 40 kt (considerably higher than what models were depicting with yesterday`s runs). Thus, could see some storms organize with a severe wind, and possibly hail threat. At this point it looks like a stronger cap will be in place over our Coastal Plains, so not expecting any convection to initiate there, but if storms become organized over the higher terrain, they could move into the Coastal Plains late in the day. With SW flow tapping into a subtropical airmass, highs today should top off in the upper 70s to low 80s north and west of I-76, and in the mid to upper 80s across most of southern and eastern NJ, southeast PA, and the Delmarva. With dewpoints in the low 70s, the heat index will be in the low to mid 90s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... Any showers and thunderstorms early will taper off in the evening. Warm and humid conditions remain in place as the subtropical airmass remains over the region. Overnight lows will be in the low to mid 70s, and dewpoints will be in the upper 60s to low 70s. The remnant low of Cindy moves towards the Appalachians this evening, and then towards the Delmarva prior to daybreak Saturday. Showers and scattered thunderstorms will move into far western zones after midnight, and then the heaviest precip will hold off until the pre-dawn hours. Given the abundant moisture across the region, rain may be heavy at times, and cannot rule out localized flooding. && .LONG TERM /SATURDAY THROUGH THURSDAY/... A ridge of high pressure will be across the Middle Atlantic region Sunday. A fair weather day is expected with temperatures right around seasonal norms. The airmass will be much drier than both Friday and Saturday, so it will be a good day for outdoor activities. A surface cold front and a slow moving upper trough will affect the weather from Monday afternoon into Tuesday. The system will not have a great deal of moisture to work with, but the colder temperatures aloft will help develop showers and a few tstms during the period. Pops are only in the slight chc or low chc range attm. Temperatures thru the period will mostly be around 5 degrees below normal for late June. Highs will be in the mid/upper 70s across the north and close to 80 near metro Philadelphia and over Delmarva. The rest of the long term looks dry with slowly moderating temperatures and rising humidity levels. Highs will remain below normal Wednesday and then rise to near normal for Thu/Fri. Most of the models are showing high pressure across the area, slowly moving offshore by Friday. A few showers Fri afternoon far N/W are possible according to the 00Z EC. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. The fist round of showers, with brief MVFR conditions possible, will move over the TAF sites through 16Z. After that, expect a return to VFR conditions for several hours. Another round of SHRA/TSRA possible in the late afternoon and early evening, and some storms could be strong to possibly severe. Heavy rain is possible, and MVFR/IFR conditions possible. Conditions dry out in the evening, and then heavy rain, scattered thunderstorms, and IFR and lower conditions possible in the pre-dawn hours Saturday morning. SW flow 5-10 KT today through tonight. Gusts to 20 KT possible this afternoon. OUTLOOK... Saturday/Saturday night...Lower CIGS/VSBYS with showers and tstms mostly in the morning. Conditions improving late. Sunday/Monday morning...VFR expected. Monday afternoon thru Tue...Mostly VFR. Sct showers/tstms.
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&& .MARINE...
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Mostly Sub-SCA conditions through this morning. SCA conditions develop this afternoon on the ocean with 25-30 KT gusts and 4-6 ft seas. Will also hoist a SCA for DE Bay, as 25 KT gusts likely, but that would be for this afternoon and early evening. One round of showers and scattered thunderstorms will impact the waters this morning through midday, and then another round of showers and potentially strong thunderstorms possible late this afternoon and early this evening. With both rounds, gusty winds will be possible in the vicinity of any showers and thunderstorms. SCA conditions on the ocean through tonight. The remnant low of Cindy will approach late tonight, and showers and scattered thunderstorms with heavy rain will move into the waters after midnight tonight and into the pre-dawn hours on Saturday. OUTLOOK... Saturday/Saturday night...SCA conditions. Showers/tstms Saturday and Saturday evening. Sunday/Sunday night...sub-SCA conditions. Fair. Monday/Tue...Sub-SCA with sct showers late. Few tstms Tue. RIP CURRENTS... There is a moderate risk for the development of dangerous rip currents at NJ ocean beaches and a low risk for the development of dangerous rip currents at DE ocean today. However, 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.
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&& .TIDES/COASTAL FLOODING... High astronomical tide levels are expected in association with the new moon today. Based on the latest guidance, not expecting widespread minor coastal flooding with the high tide cycle this afternoon and evening. Will hold off on issuing a Coastal Flood Advisory, as tide levels should fall just short of minor flooding thresholds. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ450>455. Small Craft Advisory until 9 PM EDT this evening for ANZ430- 431.
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&& $$ Synopsis...O`Hara Near Term...Johnson/MPS Short Term...MPS Long Term...O`Hara Aviation...Johnson/MPS/O`Hara Marine...Johnson/MPS/O`Hara Tides/Coastal Flooding...

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