Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 150808 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 408 AM EDT Fri Sep 15 2017 .SYNOPSIS...
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A weak surface trough will linger across the area today before weakening tonight. High pressure will briefly build to our northwest Saturday, before weakening on Sunday and retreating northward through Monday. A weakening frontal boundary will approach the area Tuesday, before the southern end dissipates to our west. Tropical Storm Jose is forecast to move northward offshore of the east coast, but could still have an impact on our weather late Monday through Wednesday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Similar conditions to what we saw yesterday are expected today. Showers and thunderstorms could develop under the mid and upper level trough axis. The one difference is that the surface trough axis is not expected to be as distinct as it was yesterday. Thus, it may not be as much of a focus for convective initiation. Thus, stayed close to the previous forecast with higher PoPs across the higher terrain of east central PA and NW NJ where orographic lift could further enhance convective initiation. Instability remains quite limited, so expect mostly showers, though a few thunderstorms are possible. Temperatures should be close to yesterdays temperatures, with highs ranging from the lower 70s to lower 80s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
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With dew points still expecting to be near 60, we could see a third straight night of patchy fog developing, especially with the mid level cloud deck expected to be less extensive tonight. Temperatures will be 5 to 10 degrees above normal, with lows generally in the 60s.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/...
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High pressure is forecast to build to our northwest on Saturday, then weaken on Sunday before retreating northward through Monday. However, there will remain a chance of mainly daytime showers this weekend as a weak trough aloft and associated vorticity could linger across the east coast through the weekend. Also, a weak surface trough may linger as well. This will lead to enhanced lift across the area each day, mainly in the afternoon, which could lead to a chance for scattered showers each day. These may be more diurnally driven and diminish around/after sunset. Our attention then turns to the track of Tropical Storm Jose. The official track from the NHC keeps the storm off the coast through Tuesday evening. The long range guidance continues to keep the storm offshore of the Mid Atlantic region as it lifts northward into Wednesday. The 00z GFS and ECMWF have both shifted farther west with their tracks, although the GFS is farther west and faster than the ECMWF. The track of the storm will be depended on how strong ridging to our west takes place, and how quickly a front to our north will get to the east coast before watching out and help pull Jose away from the area. Based on the current forecast track from NHC and WPC which are farther east of the latest operations GFS and closer to the ECMWF, we can expect some impacts from Jose late Monday night/early Tuesday into late Tuesday night/early Wednesday. Rain chances are expected to begin increasing late Monday night, through Tuesday night. We can also expect an increase in winds during this time period as well. Depending on how close Jose passes to the coast will determine how strong these effects area. Coastal areas of Delaware and New Jersey have the greatest threat for impacts. Please stay tuned to the National Hurricane Center for the latest official track and forecast regarding Tropical Storm Jose. Remember, we are at the peak of hurricane season for the Atlantic Basin, so it is important to have a hurricane plan in place. For tips as to what to have in your hurricane plan, please check http:/www.nws.noaa.gov/om/hurricane/plan.shtml
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Patchy fog may lower visibilities to MVFR at times through 12Z. After that, expect mostly VFR conditions through 00Z. There is a chance for showers, and a smaller chance for thunderstorms, but coverage (which will be even lower than yesterday) is too low to mention in the TAFs at this time. Another round of patchy fog will be possible after 06Z. Winds are expected to be mostly light and variable through the TAF period. OUTLOOK... Saturday-Sunday night...MVFR CIGS possible for ABE/RDG, VFR elsewhere. Patchy fog/stratus during the late night/early morning hours. Scattered showers also possible during the day. Monday-Tuesday...MVFR CIGS developing as Tropical Storm Jose approaches the area. Rainfall chances increasing later Monday through Tuesday, which will likely lower conditions further. Depending on the track of Jose, winds could increase across the area as well.
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&& .MARINE...
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Winds and seas should stay below small craft advisory criteria today and tonight. Outlook... Saturday-Sunday night...Conditions may reach Small Craft Advisory levels as seas build to 5-7 feet. Monday-Monday night...Winds forecast to increase through the day and into the night with gusts 25-30 knots possible. Seas continue to increase to 6-10 feet. Tuesday...Depending on the track of Tropical Storm Jose, winds could continue to increase to gale force with gusts of 35-40 knots, and seas could increase to 10-15 feet. Rip Currents... For today, we are forecasting a moderate risk for the formation of dangerous rip currents. Long period (10-14 sec) southeasterly swells from Tropical Storm Jose continue. A prolonged period of moderate or high risk of rip currents is expected to continue through at least the first half of next week due to swells from TS Jose. A long duration of a moderate to potentially high risk of rip currents is expected this coming weekend through early next week (16th through possibly the 19th) as long period and larger swells from Tropical Storm Jose becomes more pronounced along our shores, especially as it passes to our east mid week.
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&& .TIDES/COASTAL FLOODING...
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Tropical Storm Jose is forecast to pass offshore of the Mid Atlantic coast Monday night through Wednesday. Astronomical tides are expected to be increasing during this time and peak on Wednesday as the new moon occurs Wednesday. With east-northeast winds and fetch increasing during this period, coastal waters levels will likely increase as well. There is the potential for coastal flooding along the Delaware and New Jersey coasts, and possibly Delaware Bay. The extent of the flooding will be dependent of the track of Jose and the strength of the winds. At this time, the greatest threat is with the Monday evening and Tuesday evening high tides.
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&& .EQUIPMENT... The Millville (MIV) observation is unavailable due to an FAA outage, while the Somerville (SMQ) observation is unavailable due to a web issue. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Robertson Near Term...Johnson Short Term...Johnson Long Term...Robertson Aviation...Johnson/Robertson Marine...Johnson/Robertson Tides/Coastal Flooding...Robertson Equipment...

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