Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 021756 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 156 PM EDT Fri Jun 2 2023 .SYNOPSIS... A strong cold front will slide southward across our region later tonight into Saturday. High pressure builds in from the north Sunday into Monday, then another cold front arrives Monday night into Tuesday. High pressure then builds from the Great Lakes Wednesday to the Tennessee Valley Thursday. && .NEAR TERM /THROUGH TONIGHT/...
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Overall, the near term forecast remains on track. A couple isolated showers/thunderstorms have initiated across the Lehigh Valley, southern Poconos and northwest New Jersey. Isolated to scattered showers and thunderstorms will continue push into New Jersey and Pennsylvania into this afternoon and evening. It`ll be a hot day inland with light winds and relatively dry air. Ridging will remain in place across the region through today then a positively tilted trough will approach the region overnight. Surface high pressure remains across northern Quebec. Meanwhile, a broad area of low pressure will remain across the western Atlantic. Thus, weak northeast to east flow is expected through tonight. Temperatures have warmed up across the region early this afternoon. 850 mb temperatures near 18C will support temperatures continuing to warm well into the low 90s inland and even into the mid 70s to near 80 degrees closer to the coast. This afternoon`s high temperatures inland will be about 10-15 degrees above normal, but will be near normal for locations near the coast thanks to the marine layer southeast flow pushing inland. The record highs in jeopardy appear to be Reading (95 in 1925), Allentown (96 in 1925), and Mount Pocono (87 in 1937), otherwise records are well into the mid-upper 90s. Winds around around 5-10 mph with varying direction. A northeast direction is favored, those areas near the coast will have a more southeast flow. Mixed layer instability will increase to the 500-1,000 J/kg range into this afternoon. This combined with no capping and terrain to force convection is expected to result in some isolated to scattered showers and thunderstorms developing. The activity should remain confined mainly to near and northwest of I-95 during the afternoon and early evening. Given the very deep mixed boundary layer (mixing as high as 700 mb) and thus dry airmass, DCAPE will be quite high. This means the showers and storms will be capable of producing gusty winds thanks to the added evaporation in the downdrafts. A rogue damaging wind gust is possible, however severe thunderstorms are not expected at this time. Shear is very low (10 kts or less), so convection will be pulsy and transient in nature, not organized or long lived. Small hail cannot be completely ruled out, although a freezing height near 13kft and the hot surface temperatures should melt any hail before reaching the ground. A wildfire in southeast Burlington County, which began Wednesday afternoon, will continue to result in smokey and hazy conditions downstream across portions of southern New Jersey and Delmarva. As of 5 PM Thursday, the fire was 50% contained. Additional spread of smoke from this fire to areas well south and west from southeast Burlington County is possible if the fire continues into today. For tonight, isolated to scattered showers and a few thunderstorms will linger into the overnight ahead of an approaching backdoor cold front. The front should also allow for more showers to develop farther east and south. Little in the way of impacts are expected overnight with this activity. Winds will become initially light and variable overnight, although winds will shift northeast and increase as the front approaches. Expect mostly cloudy conditions overnight with some low clouds possibly streaming in as well. Lows will be within a few degrees of 60.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... A strong cold front continues to settle to our south Saturday with some showers then much cooler air settles in through Sunday. An upper-level trough is expected to drop southward from eastern Canada and over the Northeastern U.S. on Saturday, with it transitioning into a closed low across the Northeast. As strong cold air advection occurs during Saturday in the wake of the southward moving cold front, some showers should be sliding southwestward across our area mainly Saturday morning with a stronger shortwave nearing the area tied to the based of the upper- level trough before it closes off. The coverage of showers looks to be not all that great, and while the region needs the rain this is not expected to be widespread but at least some spots pick up some rain. Drier low-level air will advect southward across the area Saturday, and with a faster push to this much of the area should be dry in the afternoon. Parts of our far western zones and Delmarva could hang onto some showers in the afternoon, but overall all areas should be getting into the drier airmass. A strengthening northeast wind will occur and this will become rather gusty especially closer to the coast where peak gusts should be 30-35 mph. This will help enhance and deepen the marine influence before the much drier air works southward, therefore cloud cover should hang around through the morning before breaking up some. Temperatures will be on the cooler side with temperatures potentially not rising much especially closer to the coast given the cold air advection and winds off the cool ocean. As the upper-level trough transitions into a closed low Saturday night and Sunday, it is forecast to settle southward and much closer to our area. This would support a surface low well east of southeastern New England. Given the colder air aloft associated with this closed low and shortwave energy rotating around it, a few showers cannot be ruled out. However, with increased confidence that the bulk of the forcing along with the deeper moisture will remain north and northeast of the region, slight chance PoPs (20 percent) were confined to about the I-80 corridor. Otherwise, a cool air mass will be in place due to this strong closed low, with temperatures forecast to be below average, mostly in the 65-75 degree range during the day then falling back into the 40s to low 50s at night. && .LONG TERM /MONDAY THROUGH THURSDAY/... Summary...Temperatures at or below average, with limited chances for showers. Synoptic Overview...A closed low is forecast to drift east or northeastward to just offshore of Nova Scotia Canada early next week, however a strong piece of energy dives southward and results in an upper-level trough strengthening across the East. This may also result in another closed low arriving. The presence of this trough will result in temperatures being at or below average. Shower chances look to be limited, however some cannot be ruled out at times due to the incoming closed low and also a cold front moving through Monday night into Tuesday. The details however will depend on the timing of any embedded stronger shortwaves and the cold front. For Monday and Tuesday...Despite the center of the closed low moving farther away from our area (just south of coastal Nova Scotia Canada), an upper-level trough is forecast to remain in place across the East. This trough may become stronger later Monday and Tuesday as a closed low drops southward from eastern Canada. The associated cyclonic flow will maintain a cooler air mass across our area. In addition, a secondary cold front looks to move through Monday night into Tuesday. Moisture looks to be limited with this front, therefore PoPs were kept in the lower chance range (around 30 percent). A breeze should increase Tuesday as a pressure gradient tightens. Daytime high temperatures are forecast to be at or below average, with it warmer Monday ahead of the cold front. Overnight low temperatures drop into the 40s and 50s. For Wednesday and Thursday...As low pressure moves into the Canadian Maritimes associated with the center of the closed low, we will continue to remain under the influence of a large upper- level trough and therefore cyclonic flow. While the guidance does differ some with the amplitude and positioning of the upper-level trough, there is good agreement that a trough is favored. Some guidance shows the potential passage of a stronger shortwave Wednesday with upstream convection making a run at parts of our region. Given the uncertainty, the PoPs are in the 20-30 percent range. Thursday may be dry as much of the energy is to our north and northeast, however given the presence of the trough still opted to include a slight chance (20 percent) for much of the area. Daytime temperatures each day should be once again at or below average. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Remainder of Today...Mainly VFR expected. Lingering haze and smoke from the southern New Jersey wildfire may impact MIV/ACY today, although we are not currently forecasting any visibility restrictions at this time from this activity. Scattered showers and thunderstorms have begun to develop, mainly northwest of the I-95 terminals. Scattered showers and thunderstorms are expected to continue to develop near and northwest of the I-95 terminals. The chance of a shower impacting a terminal is low, but if one does, brief MVFR visibility may result along with brief wind gusts near 40 kts possible. Winds generally 5-10 kts. Wind direction will tend to be variable at times, although it should favor a north to northeast direction. The exception will be at PHL, ILG, MIV, and ACY where winds will be more south to southeast. Tonight...Mainly VFR with isolated to scattered showers and thunderstorms. MVFR to IFR ceilings may develop after 09Z, but there is low confidence on this. IFR conditions most likely closer to the coast at KMIV/KACY. Light and variable wind early will shift northeast and increase to 5-10 kts after 09Z. Moderate confidence. Saturday...A period of MVFR/IFR ceilings possible in the morning with some showers. Ceilings gradually improving to VFR through the afternoon. Northeast winds 10-15 knots with gusts 20-25 knots. Low confidence. Outlook... Saturday night...VFR. Northeast winds diminish somewhat. Moderate confidence. Sunday...VFR. North to northeast winds around 10 knots. Moderate confidence. Monday...Mainly VFR. A slight chance of showers. North to northwest winds around 10 knots. Moderate confidence. Tuesday...Mainly VFR. A chance for showers, mainly in the afternoon. Northwest winds around 10 knots. Low confidence.
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&& .MARINE... No marine headlines are anticipated through tonight. Winds will be from the south to southeast around 10-15 kts today. Winds becoming lighter tonight and shifting to the northeast. Seas 1-3 feet with a wind driven easterly swell. Some isolated showers or thunderstorms are possible overnight. Outlook... Saturday...Small Craft Advisory issued as northeast winds increase from north to south with gusts up to to 30 knots. There is some potential for a few 35 knot gusts Saturday afternoon and evening. Seas build to 5-9 feet on the Atlantic coastal waters. Sunday...Small Craft Advisory conditions should persist into the morning mainly on our ocean zones, however the winds and seas are anticipated to be lowering during the day. Monday and Tuesday...The conditions should be below Small Craft Advisory criteria. Rip currents... Today...There is a LOW risk for the development of dangerous rip currents for the New Jersey and Delaware beaches. A light and variable wind in the morning becomes southeast to south around 10 mph in the afternoon. Breaking waves of around 2 feet are expected with a medium period easterly swell. Saturday...There is at least a MODERATE risk for the development of dangerous rip currents for the New Jersey and Delaware beaches. Northeast winds 15-25 mph with gusts 30-35 mph are expected. Breaking waves will be 3 to 4 feet with a medium period east/northeasterly swell. && .TIDES/COASTAL FLOODING... A gusty northeast wind is expected on Saturday in the wake of a strong cold front. The onshore flow in combination with the high astronomical tides associated with the full moon on Saturday will result in minor coastal flooding along the New Jersey and Delaware coasts, along the tidal Delaware River and Delaware Bay with the Saturday night high tide. There is some potential for some spots to touch moderate flooding, however confidence is low on this scenario. Minor coastal flooding is possible during the Sunday night high tide as well, though confidence is much lower on this occurrence. Coastal flooding is not expected along our portion of the Marylands Eastern Shore. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 10 AM Saturday to 2 AM EDT Sunday for ANZ430-431. Small Craft Advisory from 8 AM Saturday to 6 AM EDT Sunday for ANZ450>452. Small Craft Advisory from 10 AM Saturday to 6 AM EDT Sunday for ANZ453>455. && $$ SYNOPSIS...Gorse NEAR TERM...AKL/Staarmann SHORT TERM...Gorse LONG TERM...Gorse AVIATION...AKL/Gorse/Staarmann MARINE...Gorse/Hoeflich/Staarmann TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.