Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 172216 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 616 PM EDT Mon Jul 17 2017 .SYNOPSIS... An upper level trough will slowly move through the region through Tuesday. Weak high pressure will build into the region for Wednesday. A cold front will drop down from the north and slowly move through our area late Thursday through Friday before stalling to our south. The front will then move north as a warm front on Sunday followed by another cold front on Monday. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Convection coverage is waning as of 6 PM and should continue to do so. Due to the slow storm motions, the main concern remains locally heavy rain leading to flooding. We have also seen some hail and downburst signatures with earlier convection, but expect that threat to be limited for the rest of the evening as the earlier convection has led to a cooler boundary layer mostly west of the I95 corridor, and shear remains very meager mostly east of the I95 corridor. Isolated showers and thunderstorms are possible through the night, but most places should see partly cloudy skies. It will remain mild and humid. Low will only drop into the low 70s in the metro areas and mid/upper 60s elsewhere. A little light fog may develop near the areas where storms occurred earlier. Especially in areas where there is still standing water. Winds will be light from the S/SE tonight.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... The overall pattern will not change much Tuesday. The upper trough will be weaker and will be crossing our area during the day. We do expect sct showers and tstms again Tue, but overall the coverage will be less than on Monday. We will have chc pops for the N/W areas and slgt chc elsewhere. High temperatures Tue will be in the mid to upper 80s across the area. Humidity levels, much like today or perhaps a bit more humid. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Tuesday night...convection will be winding down across the region, especially after sunset. A shortwave may cross the region overnight which would allow for some showers/thunderstorms to develop so keep a mention of a slight chance through Tuesday night. For the most part, we should be mainly dry across the region overnight. Some patchy fog may develop as low level moisture remains and we should see some breaks developing in the clouds. Wednesday through Thursday...High pressure will build into the area for Wednesday. The upper trough slides to the east during this time. A cold front will start to drop down from the north on Thursday. As the high builds in, we will see a return to more of a west to southwest flow, ushering in some hotter, moister air to the region. With 850mb temperatures back into the 18-19C rang, we will see highs creep back up into the upper 80s to lower 90s by Wednesday and then into the low to mid 90s for Thursday. Increasing moisture will also mean increased humidity across the area. Seems reasonable that some showers and thunderstorms may develop during the afternoon and evening on both days but location of activity is too difficult to pinpoint this far out. Additionally, with not much flow at the surface, storms may be slow movers and efficient rain producers, leading to flash flooding. Again, too hard to pinpoint any exact locations at this juncture. Heat index values look to fall below 100F through the midweek period but may get close. Friday...Friday may still be pretty hot out but with a cold front dropping down through the region, we should start to feel some relief from the humidity, especially to the north and west of the I-95 corridor. Areas to the south and east of I-95 may still have a hot and humid day to contend with but relief will come later in the day for those areas. Temperatures on Friday will be in the upper 80s to lower 90s across the forecast area with some low to mid 80s across the Poconos and parts of northwestern New Jersey. Saturday through Monday...Another stretch of unsettled weather as several fronts move through the region during the weekend. A chance for some showers and thunderstorms seems likely each day. && .AVIATION /22Z MONDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. The coverage of tsra is expected to decrease considerably by 03Z. There will probably be some fog across the areas that receive showers today, so some of the TAFS include this possibility. Also, the onshore flow continues and its possible that some low clouds may arrive from the S/E overnight. Most of the TAFS include a period of low clouds late tonight and past dawn Tuesday. Continue to go slightly above guidance with the ceiling heights, due to uncertainty as to when they will move in. Tue...Low clouds should mix out 13Z-15Z then becoming mostly sunny again. Light south to southeast winds expected. OUTLOOK... Tuesday night through Thursday...Mainly VFR conditions expected. Afternoon showers and thunderstorms with MVFR or lower conditions possible. Southerly winds around 10 knots or less...becoming westerly on Thursday. Friday...Mainly VFR conditions expected. West to northwest winds around 10 knots or less. Saturday...Mainly VFR conditions expected. Afternoon showers and thunderstorms with MVFR or lower conditions possible.
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&& .MARINE... Low pressure inland and high pressure offshore will continue to produce a generally S to SE flow over the waters tonight and Tuesday. Wind speeds will increase somewhat through the evening, but should remain sub-SCA conditions thru the period. Seas will be mostly 2-3 ft on the ocean. Widely sct showers and tstms are possible tonight and Tuesday. OUTLOOK... Tuesday night through Saturday...Sub-Small Craft Advisory conditions are expected on the area waters through Saturday. Locally strong winds will be possible in the vicinity of any thunderstorms. RIP CURRENTS...Overall conditions that favor rip currents are becoming a bit more favorable this afternoon. A medium period swell is beginning to be observed along the coast. Overall, low risk will probably be OK for the rest of the evening. Conditions could be more towards moderate risk for Tuesday. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Meola Near Term...Johnson/O`Hara Short Term...O`Hara Long Term...Meola Aviation...Johnson/Meola/O`Hara Marine...Meola/O`Hara is the U.S. government's official web portal to all federal, state and local government web resources and services.