Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 291946 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 346 PM EDT SUN MAY 29 2016 .SYNOPSIS...
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Moisture associated with tropical depression Bonnie...over the southeast United States...will remain over our region through early Tuesday. A cold front will cross the area Tuesday followed by high pressure for the middle of the upcoming week. A cold front...attached to low pressure moving through Canada...will move across the Middle Atlantic region and Northeast states early next weekend.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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High pres will continue to move away from the area. As it does, moisture assocd with TD Bonnie will move nwd and ewd. This moisture was already bringing rain to extreme srn portions of the Delmarva. Rain is expected to increase in areal coverage later this evening and overnight. However, once again, it seems as if the timing has slowed a bit. Additionally, model guid seems to indicate a lull for at least some areas overnight before precip picks up again on Monday. There is some divergence in the guid as to exactly where that lull will occur. A change in 20 miles can make a big difference in qpf amts. Rain is still expected to be hvy at times. The other noticeable trend this mdl cycle with a weaker Bonnie is that overall qpf amts have come down. Genly amts of 1 to 1.5 inches are expected with psbly as much as 2 in in sern NJ, with locally higher amounts.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
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With the slower timing, it now appears that there will be more precip on Monday, than earlier fcst. Periods of rain now look to continue for a good portion of the day, especially for srn and ern areas. Nrn and wrn areas cud see precip end durg the aftn, with srn and ern sections most likely holding onto rain thru at least sunset.
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&& .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
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The remaining showers from the back edge of the system affecting the area during the short term will be moving offshore Monday evening. Pops will then decrease below slight chc by dawn Tuesday. Except for some fog overnight...fair weather is expected. Low temperatures will be in the low to mid 60s. High pressure will build in from the north Tuesday and remain into Wednesday night. Dry weather is expected much of the time with above normal temperatures in most areas. Highs both days will be in the low/mid 80s in most areas with some 70s for highs along the shore and the higher elevations well to the north. A few scattered showers may creep into the Delmarva areas later Wed as the edge of moisture associated with what will be left of Tropical Depression Bonnie will be moving south/east of the area. The pops across srn Delaware at these times will only be 20-25 pct at most. The tropical moisture and an advancing h5 trough will be setting up across our area towards the end of next week. This will bring some unsettled conditions with typical late spring/early summer showers/tstms to the area. Pops will be mostly in the chc range for now with details yet to be specific with regards to timing and locations. Temperatures during this period will be close to normal.
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&& .AVIATION /20Z SUNDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conds durg the remainder of the aftn and erly eve will quickly deteriorate from s to n as rain moves in assocd with moisture from Tropical Depression Bonnie. Widespread MVFR and then IFR conds are then expected for the remainder of the TAF pd, for most TAF sites. Guid suggests there cud be some LIFR on Monday, mainly for the I-95 airports s and e. However, there is some disagreement in the mdls as to where and when the heaviest rain will fall. So have not fcst these conds yet, but they are psbl. There may be some improvement back to MVFR for KABE and KRDG twd the end of the TAF pd. Wind is expected to be light acrs the region. OUTLOOK... Monday night...Showers end from w to E, VFR conditions return. Patchy fog possible late however. Tue-Wed night...Mostly VFR. Few showers psbl far South Wed. Thu- Fri...Mostly vfr but lower conditions psbl in sct showers/tstms.
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&& .MARINE...
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Wind may gust in the 15 to 20 kt range overnight before decreasing to around 10 kts Monday aftn. Seas are expected to increase and could reach nr 5 ft on the srn waters. Due to confidence being lower than average, wind below criteria and ww possibly being overdone, will not issue sca attm. There is some lcl dense fog in the nr shore waters. If the rain does not improve the visibilities then a dense fog advisory for a portion of the marine area may be needed. OUTLOOK... Sub-sca conditions expected most of the period. Seas on the ocean may reach close to 5 ft Thu night...but low confid in this attm. Sct tstms with higher winds/seas possible Fri. RIP CURRENTS: low risk the rest of today. We are moving into the high tide cycle so that appears favorable for reducing the frequency and coverage of rip current formation. Relatively cold water temperatures along the north and central NJ coast probably also minimizes risk taking. Swimming within the watchful eyes of life guards ensures a safe and fun beach experience.
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&& .HYDROLOGY...
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There is potential for heavy rain and localized flooding from tonight through Monday. This is due to an influx of tropical moisture from Tropical Storm Bonnie. PWATs are forecast to be near 2 inches, well above normal, especially for late May. Depending on how the heavier showers and t-storms set up, isolated locations may possibly see a 3 inch amt. This may result in localized flooding. The potential for heavy rain was added to the forecast.
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&& .CLIMATE...
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Daily record rainfalls that have a chance of exceedance, if heavy showers can persist for 1 to 2 hours. Note, splitting amounts between two days lowers the chance of a single day record event occurrence. There is a good chance several long term climate sites will increase to a top 10 ranking for the month of May in our CWA. PHL ACY AND ILG only need an inch of rain these last 3 days of the month to rank as a top 10 wettest month of May. Today KGED 1.62 in 1990 por 1948 Monday ACY 3.07 1984 por 1874 PHL 1.74 1908 por 1872 ILG 1.10 1983 por 1894 ABE 1.68 1968 por 1922 TTN 1.62 1912 por 1865 GED 2.04 1984 por 1948 RDG 2.92 1904 por 1869 (highly unlikely to approach a record daily rainfall) MPO 1.86 1990 POR 1901 You probably saw the near records yesterday at KMPO (-1), KABE (-1), KRDG (-2). Daytime max temp guidance continues to be significantly under forecast across PA/NJ for the past 3 days, especially by Super and National blends. We are better off in these sunny non-marine influenced summer-like regimes using the latest operational guidance as a starting point and modifying this upward by adding 4F to the 18z ECMWF 2m temps. The GFS 2m temperature fcsts have also been biased low, in part because of too much low lvl moisture. Also a note about heat waves: here in the northeast USA, we tend to stay close to the AMS glossary of Meteorology definition of a heat wave and as follows: In 1900, A.T Burrows more rigidly defined a `hot wave` as a spell of three or more days on each of which the maximum shade temperature reaches or exceeds 90F. May continues to project about 1 degree below normal, the warm spell beginning the 24th having put a big dent in the well below normal averages. In fact monthly average temp may be at or above normal at KABE, KRDG and KTTN.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...O`Hara Near Term...Nierenberg Short Term...Nierenberg Long Term...O`Hara Aviation...Nierenberg/O`Hara Marine...Nierenberg/O`Hara Hydrology...Staff Climate...Staff

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