Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 302347 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 747 PM EDT THU JUN 30 2016 .SYNOPSIS... Weak high pressure will continue to move offshore overnight. A cold front, attached to low pressure over Canada, will cross the area later Friday and Friday night. High pressure will build in for the weekend and persist into the holiday. A warm front may begin to push into the region next Monday night and into Tuesday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Tonight...Isolated showers and thunderstorms should begin to move into the southeast portion of our region after midnight. 88D reflectivity images were already showing shower activity over the coast waters just to our south at 730 PM. Weak instability burst. Pwat increases to 1.6" by 12z Fri PHL south (up from the near 1 inch of today). Fog or stratus may develop toward dawn Friday. Light south wind. FCST Basis: 50 50 blend of 12z/30 gfs/nam MOS but POPS raised se of the NJT and DE tonight for an instability burst shower or garden variety thunderstorm in the 03z-09z time frame. Confidence: average. doubts about how much fog tonight and whether it can rain tonight.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... Friday...mixed clouds and sun, warm and more humid. Chance of showers/isolated thunderstorms during the morning. The primary thunderstorm event should develop eastward near and south of the Mason-Dixon line late in the afternoon with what I think is decent potential for scattered severe thunderstorms arriving Delmarva sometime after 5PM. That is where modeled MLCape is 1400+J, multi-model TT50, KI pooled 34+ and 0-6Km Bulk shear is 35-45 kt. South to southwest wind. Potential exists for svr further n through our CWA as per SWODY2. 12z/30 UK/GGEM and EC override on the almost non existent afternoon NAM QPF, even though the NAM instability pooling looks correct. Mid 80s continues to look good for max temps much of the area Friday. its possible we`ll see some 88`s Philadelphia southwestward since 850MB warms to 15C by 12z. Guidance max temps may be biased low by modeled morning qpf. FCST Basis: 50 50 blend of 12z/30 gfs/nam MOS but POPS raised to likely Delmarva because of EC/GGEM?UK qpf and modeled instability fields. Confidence: above average. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... The last of the showers and thunderstorms associated with the eastward moving cold front will be across the region Friday evening. The arrival of the cooler and drier air will cause pops to decrease from west to east overnight. The upcoming holiday weekend looks great with high pressure building in sat and remaining in control of the weather thru monday. We will begin to show some increase in pops Monday, with some slgt chcs or small chc pops across the Delmarva and se PA by mon afternoon. It shouldn`t be enough to hinder any outdoor activities for that day. The air will be pleasantly dry on sat, then some increase in humidity by the 4th. Temperatures will be near normal with highs in the low/mid 80s in most areas. The operational models are indicating a disturbance approaching from the south/southwest Monday night and lasting into Tue. It appears that a warm front and humid air will crease a round of showers/tstms for (mostly) the srn parts of the fcst areas. we will carry chc pops in the fcst attm. Details will be sorted out as the time frame draws nearer. Temperatures again near normal, or maybe a degree or two above. It will likely be rather humid as well. We will continue with a dry and seasonably mild fcst for Wed-Thu next week. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR under mostly clear skies to start but MVFR or IFR conditions in st/fog/haze possible after 06z/01. Isolated showers or thunderstorms possible 03z-09z se of the NJT and DE. Light southerly wind. Confidence: Average since there is uncertainty regarding extent of any showers and st/fog development late tonight. Friday...becoming VFR sct-bkn aoa 4000 ft after any early morning IFR/MVFR lifts by 15z. Brief MVFR or IFR conditions possible in showers and thunderstorms, especially late day. Thinking that scattered severe thunderstorms will be developing eastward across the Delmarva into southern NJ sometime after 21z/01. a prob30 group was added to all taf sites after 18z to account for the chance of convective activity. SPC keeps almost the entire CWA under marginal risk on Friday. South to southwest wind. Confidence: above average due to multi-model consensus overriding the dry 12z/30 NAM afternoon qpf. OUTLOOK... Friday night...VFR sct-bkn aoa 4000 ft with sct showers and thunderstorms ending by 06z/02 with possible MVFR fog where it rains late Friday afternoon/evening. Saturday...Mainly VFR conditions expected. West to northwest wind around 10 knots or less. Sunday...Mainly VFR conditions expected. North to northwest winds becoming west to southwest. Monday...Mainly VFR conditions expected. Showers and thunderstorms possible. Monday night and Tue...Sct Showers and thunderstorms especially S/SW.
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&& .MARINE... Winds and seas should remain below SCA criteria tonight through Friday. A few gusts to 22 kt are possible on the coastal waters late this afternoon as the sea breeze ramps up, but should stay below 25 kt. RIP CURRENTS...remainder of today. LOW risk may border on low end of moderate during late afternoon if a strong and more onshore wind develops along Ocean and Monmouth county shores. Water temperatures were around 4 to 5 degrees above normal for late June...mid 60s to lower 70s throughout the DE and NJ beaches with exceptions. The 1130z/30 (730am EDT) satellite interpretation of water temps found a cooler pocket of water at the outermost oceanside entrance to DE Bay (lower 60s) midway between Cape May and Lewes and possibly also near Barnegat. From this time forward through September 30 we will be issuing a day 2 SRF 1 line outlook for the media by 330 PM in the marine section of this AFD as per next pgh below. This will better support media early evening broadcasts while permitting our SRF to run our day 1 forecast through sunset. We have an overwhelming number of rip current related fatalities occurring near the evening dinner hour, after beach patrols depart and its still quite warm. For safety awareness purposes our Day2 will continue issuing after sunset when presumably more beachgoers are out of the water. Rip Current Outlook for Friday...The probable risk for the formation of dangerous rip currents tomorrow is low. (Friday may yet border on moderate risk during the afternoon depending on the strength of any onshore flow during the afternoon, especially NJ.) OUTLOOK... Friday night through Tuesday...Sub-SCA conditions most of the time. Sct TSTMS with higher winds and seas Fri evening and again Monday night/Tue. RIP CURRENTS...Projecting a solid LOW for Saturday with a 3 ft 7sec se swell but an offshore wind. Sunday-Monday-Tuesday projecting a LOW ENHANCED or possibly LOW end of a MODERATE risk where the new moon tends to accentuate tidal fluctuations and thereby increases current strength. The Sunday-Tuesday confidence projection is average. In other words, caution is advised when using a projection this far in advance, since a 1 foot difference in wave height expectation and/or a significant change in onshore wind can easily change the potential for dangerous rip current formation. The Atlantic Basin continues quiet for awhile so that bodes well for continuing the low risk, or possibly moderate risk for the formation of dangerous rip currents. Most fatalities from rip currents occur at unguarded beaches. The vast majority of fatalities are on low-moderate risk days which means there is a lack of awareness of the dangers of swimming at unguarded areas, or near jetties and piers. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...O`Hara Near Term...Miketta Short Term...Drag Long Term...O`Hara Aviation...Miketta/O`Hara Marine...Drag/O`Hara

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