Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 150641 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 241 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 /THROUGH TODAY/... 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 /TONIGHT/... 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/... Overview...The period starts with a stationary front draped across the western Atlantic and Carolinas, a cold front across the Great Lakes and TC Gert well east of Cape Hatteras. The cold front will work to the south and east and arrive in our region Wednesday night. It will pause across the CWA on Thursday. Confidence is low as to how far south this front will get, but right now it looks like a Reading to Trenton to Belmar line. The front will retreat north on Friday as another cold front works through the Great Lakes and Ohio Valley. Confidence is once again low on how far north the front retreats. The cold front to our west will work through the region Friday night or Saturday. Surface high pressure behind this front will cross into the region on Sunday and anchor up into Monday. Temperatures....For reference, KPHL normals are mid 80s and upper 60s. Temperatures will be above normal on Wednesday, about normal on Thursday, above normal on Friday, about normal on Saturday, Sunday, and Monday. The warmest and most humid day of the week appears to be Friday just ahead of the cold frontal passage. No extreme temperatures are expected through the period with mainly just slightly above or slightly below if not normal. Precipitation...POP confidence is low into Saturday and depends on how far the coastal warm front edges up into our area from the south Tuesday night, how far south the cold front drops into the area on Wednesday night and how far the same front retreats northward Thursday into Friday. The closer the proximity and duration of these boundaries, the more unsettled it will be. For now, we`ll paint small POPS Tuesday evening into Wednesday night across portions of the CWA. Coverage should be more widespread on Thursday into Friday night. Rainfall rates will also increase Thursday night into Friday as PWs exceed 2 inches. Small POPS will continue on Saturday and Sunday, then nil POPS Monday. Winds...Benign through the period, mainly 15 mph or less. Highest speeds right along the coast. Impacts...TC Gert is forecast to pass well to our south and east on Tuesday and Tuesday night. Swells from the system will likely bring at least a moderate risk for the development of dangerous rip currents Tuesday into Wednesday as well as the possibility of SCA conditions on the ocean. These concerns are addressed below. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... 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. Small chance of a late afternoon or evening Thunderstorm across southern NJ and the Delmarva both nights. 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. && .MARINE... 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...SCA seas possible due to Gert, Wednesday morning. Otherwise sub-SCA conditions expected through this week. 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. && .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...Kruzdlo/OHara 241A Near Term...Drag 241A Short Term...Drag 241A Long Term...Kruzdlo Aviation...Drag/Kruzdlo 241A Marine...Drag/Kruzdlo 241A is the U.S. government's official web portal to all federal, state and local government web resources and services.