Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 202000 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 400 PM EDT Tue Jun 20 2017 .SYNOPSIS...
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High pressure will gradually build east towards the region through Thursday. That high will shift off shore by the end of the week. A pair of cold fronts are expected this weekend or early next week.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Westerly winds gusting to around 20 mph late Tuesday afternoon will gradually shift to the southwest during the evening hours and subside to under 10 mph before midnight. Clouds which developed over interior sections on Tuesday will quickly dissipate toward evening, with mainly clear skies expected for most of the overnight hours. Closer to the coast...clouds associated with a stalled front may persist through the overnight hours. The GFS is suggesting a chance of rain showers with these clouds...but have decided to follow ECMWF guidance and keep the mention of showers out of the forecast. Minimum temperatures tonight expected in the mid 50s in the far north to the upper 60s in the far south.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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A weak boundary settling across the CWA during the late morning and early afternoon hours will bring some additional cloudiness and slight chance of showers and scattered thunderstorms, but widespread showers are not expected. Southwesterly winds are expected to pick up from late morning through the afternoon hours with gusts around or over 20 mph possible at times. High temps in the mid 70s are expected in the far north, and in the mid 80s in the south.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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Wednesday night and Thursday...Surface high slowly builds east towards our region before shifting off shore. As a result, expect mostly dry conditions unless the high weakens or moves off shore faster than currently anticipated. Friday...southwesterly flow over our region, thanks in large part to the Bermuda high once again develops. The biggest impact will be increasing dew point temperatures. Though temperatures won`t be appreciably higher than what we will see through mid week, expect heat index values to be increasing. Saturday through Monday...A pair of cold fronts are expected through this period. There is considerable model disagreement as to both the timing of the fronts and if the first or second cold front will be the stronger front. Looking at the larger picture, it looks like the pattern will tend to be less progressive through this period (3 or 4 Rossby waves depending on the model and time period you look at). Therefore, the forecast favors a solution closer to the ECMWF with the initial front arriving Saturday, but likely only resulting in a modest temperature gradient. The second, and likely stronger, cold front should arrive Monday night. Have kept precip chances through much of this period, given the uncertainty of the timing of the fronts. However, I do not expect the weekend to be a complete washout as the highest chances for showers and thunderstorms will likely be with and just ahead of the first cold front. Tuesday...Assuming the cold front arrives Monday night, temperatures by Tuesday should be 5 to 10 degrees below normal, with highs ranging from the upper 60s to mid 70s.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Expect VFR conditions at all TAF locations tonight with southwesterly winds below 10 KT. Generally VFR conditions are expected again on Wednesday, but an isolated shower or even a thunderstorm cannot be completely ruled out. Wind gusts around 20 KT are expected from late morning through the afternoon hours. Outlook... Thursday...mostly VFR conditions are expected. Friday through Sunday...Increasing chances for showers and thunderstorms through this period. MVFR or lower conditions are possible with any showers or thunderstorms. Otherwise, expect mostly VFR conditions.
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&& .MARINE...
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The SCA for seas now only covers the coastal waters from Sandy Hook NJ south to Little Egg Inlet, and only until midnight. After seas drop below 5 feet in this area this evening, sub-SCA conditions are expected for the remainder of the overnight hours, and on Wednesday, although there could be so gusts in the 20 KT range during the afternoon. Outlook... Thursday...winds and seas are expected to remain below SCA criteria. Friday...winds and seas will begin to build and may be at or just below SCA criteria by late in the day. Saturday and Sunday...SCA conditions are possible, especially for seas on the ocean waters. RIP CURRENTS... A moderate risk for the development of dangerous rip currents will persist through Wednesday and possibly into Thursday along the coast of Delaware and New Jersey due to a long period southeasterly swell.
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&& .TIDES/COASTAL FLOODING...
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Very high astronomical tides are expected in association with the new moon on Friday. That, combined with a brief period of on shore flow on Thursday could result in minor coastal flooding with the Thursday afternoon and evening high tide primarily for the Atlantic coastal areas and the shores of the Delaware Bay. Minor coastal flooding may continue with the Friday afternoon and evening high tide.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until midnight EDT tonight for ANZ450-451.
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&& $$ Synopsis...Johnson Near Term...Miketta Short Term...Miketta Long Term...Johnson Aviation...Johnson/Miketta Marine...Johnson/Miketta Tides/Coastal Flooding...Johnson

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