Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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048 FXUS61 KPHI 150739 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 339 AM EDT Tue Aug 15 2017 .SYNOPSIS... A weak front will affect the weather across our region today and tonight. High pressure will build in for Wednesday and remain into early Thursday. Another low and its associated fronts will affect our weather Thursday and into Saturday. More high pressure arrives for Sunday and persists into early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A moist southwest flow aloft combines with weak short waves to produce bands of showers. Isolated thunder is possible this afternoon. The 1230 AM fcst already had a 50 50 blend of the 00z/15 GFS/NAM MOS guidance for temps/winds and the SREF was blended with the inherited fcst for POPS which may still be too low as compared to blended GFS/NAM 00z/15 operational MOS. That leaves forecast daytime max temps generally about 5F below normal. A light and mostly southerly wind. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... Any showers should dissipate or end by around 8 PM with best chance for lingering showers, the Delmarva Peninsula. Thereafter, skies clear from west to east. With light wind, clearing skies and a moist boundary layer...foresee as previously forecast... considerable fog, at least in the countryside. We may need a dense fog advisory for some areas but probably wont be able to be sure of dense fog and where to advise, until sometime late today or this evening. Definitely see this as SPS material and will insert into the HWO. The wind will eventually trend light northwest during the night. This forecast is a 50 50 blend of the 00z/15 GFS/NAM MOS. Min temps are forecast 1 to 5F above normal. && .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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High pressure, both at the sfc and aloft, will be building across the Middle Atlantic region Wednesday and Wednesday night. This should bring fair weather for the period, with a warm day expected with highs in the mid to upper 80s over the area. Lows Wednesday night will be a summer-like across the southern areas with readings only dropping into the upper 60s to low 70s. Across the north, lows on Wednesday night will range from the upper 50s to mid 60s. A slow moving low pressure system will begin to affect the water with increasing clouds and higher chc for showers/tstms beginning Thu and persisting into the early part of the weekend. It will not be a total washout thru this period, but mostly just showery conditions. The best chcs for precip will be Thu night and Friday, mostly for the N/W areas. Temperatures for this period will be normal or a little above normal (Friday). A cold front will bring slightly cooler and drier air back to the region Saturday. Some of the models are showing that a weak wave of low pressure will move along the front Sunday and this may bring some clouds and slightly better chc for a few showers across Delmarva early Sunday. The norther parts of the fcst areas will remain dry. High pressure will gradually build in later Sunday and it should remain into early next week. Temperatures for Sunday and Monday will be mostly near normal.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through today...VFR cigs with patches of MVFR and IFR conds in or near bands of showers as has recently developed near KTTN and KABE. Small chance of an aftn tstm but not enough confidence to put thunder in the TAF. Light wind. Tonight...Generally VFR CIGS to start, which clear...then patches of IFR or LIFR conditions in st/fog develop during the night. Light wind trending northwest late. OUTLOOK... Wednesday through Wednesday night...Mainly VFR. MVFR possible in late night and early morning low clouds and fog. Thursday through Friday...Mainly VFR, but MVFR possible in showers and thunderstorms. Late night and early morning low clouds and fog possible. Saturday...Some morning MVFR possible, then VFR behind an exiting cold front.
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&& .MARINE...
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Seas will be slowly building during the next 12 hours as Hurricane Gert makes its closest, yet distant, approach to our area. It will remain well offshore, but longer-period swells should continue to increase during the period. We continue the Small Craft Advisory for hazardous seas on our ocean waters from late this afternoon until noon Wednesday. Scattered showers through today, with a small chance of lightning this afternoon. Winds/seas may be erratic near any thunderstorms that occur. Additionally, there may be some visibility restrictions in showers, though widespread/dense fog is not anticipated. Winds should generally be from the southeast around or under 10 kts today turning light northwest later this coming Tuesday night. OUTLOOK... Wednesday thru Saturday...Low end SCA seas possible Wednesday morning due to offshore Hurricane Gert. Otherwise sub-SCA conditions expected through this week and into the early part of the weekend. Sct tstm may bring locally higher winds and seas. RIP CURRENTS... Gert is forecast to pass well to our southeast later today. Swells from the Hurricane will likely bring at least a moderate risk for the development of dangerous rip currents today into Wednesday. Swim only in the presence of lifeguards where safety prevails. Otherwise, you`re on your own with any rescue potentially critically delayed. There have been numerous drowning fatalities this year along the NJ coast.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory for hazardous seas from 4 PM this afternoon to noon EDT Wednesday for ANZ451>455. Small Craft Advisory for hazardous seas from 10 PM this evening to noon EDT Wednesday for ANZ450. && $$ Synopsis...O`Hara Near Term...Drag Short Term...Drag Long Term...O`Hara Aviation...Drag/O`Hara Marine...Drag/O`Hara

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