Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251054 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 654 AM EDT Fri Jun 25 2021 .SYNOPSIS... High pressure over the Canadian Maritimes through the weekend will slide southward, becoming a Bermuda High through the middle of the week. A slow moving frontal boundary will move through the Great Lakes this weekend, approaching our area late next week. && .NEAR TERM /THROUGH SATURDAY/...
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High pressure prevails through the rest of the evening as marine stratus is just pushing in over the coast. As the sun comes up we can see the marine layer on visible satellite and its basically sitting over Atlantic/Camden/Gloucester counties this morning. BUFkit soundings suggest that the clouds over the shore will likely hold on through much of the morning before finally eroding. Either way, with the weak wave of low pressure starting to pull away towards the north and east, we`ll see another day of mostly dry weather and closer to normal temps through this afternoon. Patchy drizzle will be possible falling out of the low stratus and we`ve already gotten several reports along the Shore of drizzle. I think this wanes heading into the middle of morning as we start to see some of the dry air from the ridge mix down. Southerly flow will start to push higher dew points over the region and we should start to see another round of summer type weather late this afternoon. The warm air continues overnight as temps only fall into the low 70s/ upper 60s setting the stage for a warm day on Saturday. A very weak upper level wave tracks through over central PA into NY during the afternoon on Saturday and may provide enough lift to see some light showers develop over the Poconos, Lehigh Valley, and parts of NW New Jersey. There will be abundant low level moisture across the region so fog remains possible, however given the modest boundary layer flow, and modified Richardson numbers projected to be less than 0.2 I think we`ll be looking at low stratus clouds instead of widespread fog.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... The high will be located over the Canadian Maritimes Saturday night but will start to slide southward, becoming more of a Bermuda High by Sunday night. Generally expecting this period to be dry, though there will be a chance for some showers or thunderstorms Sunday afternoon as a shortwave crosses to the north of the region. Chances look slim at best right now but the best chances for any convection is north and west of the I-95 corridor. Return flow around the high to our northeast will keep us in a south- southwest regime, which will continue the influx of moisture and heat to our region. Overnight lows will be in the upper 60s to lower 70s both nights with daytime highs on Sunday rising into the upper 80s to lower 90s. Cooler temps in the low to mid 80s are expected along the immediate coast and in the southern Poconos. With all of the moisture in place, there will be the potential for fog development each night. && .LONG TERM /MONDAY THROUGH THURSDAY/... This period will feature Bermuda high pressure to the east of the region and a slow moving frontal boundary to the west. With the forecast area sandwiched between the two features, we will generally see a return flow across the area with a south to southwest wind through the middle of the week. This will allow for increasing moisture and increasing temperatures. Guidance continues to show a prolonged period of 850mb temps rising into the mid and upper teens, which translates into max temps in the low to mid 90s. The heat hangs around through at least Thursday as the front slows and possibly stalls near or over our area. Dew points are where we will really start to feel the heat though. Dew points will remain in the upper 60s to lower 70s. With all that moisture in place and no where for it to go, we will feel the stickiness factor rise and heat index values will rise into the mid to upper 90s, especially for Monday through Wednesday. The potential for heat headlines is increasing for the early week period for the urbanized I-95 corridor and possibly the nearby surrounding suburbs. A pre-frontal trough sets up near or across the forecast area which may serve as a focus for mainly diurnally driven showers and convection each day, with increasing chances as the front pushes closer to our area. With several shortwaves rotating through the mid- level flow, we should have enough lift across the region to support convective development. The key will be to see just how much instability is across the area each day. The risk for heavy rain will also be in play as PWATs near (possibly exceed) 2 inches across the region. Additionally, with such moist air over the region and generally light winds, especially at night, it seems likely we will have fog develop, though exactly where and how dense is yet to be determined. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR prevailing for all sites west of the MIV/ACY. MVFR/IFR over the coast will be slow to erode but by late morning expect VFR for all taf sites. Winds will start to pick up in the morning to around 5-10kts out the south, with a more southeasterly component near the coast. High confidence. Tonight...VFR generally expected to start with MVFR/IFR low stratus developing for most sites late. Fog may be possible but generally stratus will be favoured over fog. Winds should be southerly and light overnight. Moderate confidence. Outlook... Saturday...VFR expected through the day as any MVFR ceilings lift in the morning. Showers will be possible for the Lehigh Valley late in the afternoon which could reduce flight conditions. Winds remain out of the south throughout occasionally gusting to 15kts. Saturday night through Tuesday... Mainly VFR. Fog/stratus possible each morning. Afternoon showers and thunderstorms possible. South to southwest winds around 5 to 10 knots with gusts around 15 to 20 knots possible. Moderate confidence.
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&& .MARINE... Through Saturday...Sub SCA conditions expected through the period although winds make get close to 25 kts late Saturday. Seas will be between 3-4 feet generally on a 5-7 second period with onshore flow generally 10-15kts. Outlook... Saturday night through Monday...Mainly sub-SCA conditions expected. A brief period of gusts near 25 knots is possible Saturday night and Sunday, mainly across the northern and central New Jersey coastal waters. Southeast to south winds 10 to 15 knots with gusts around 20 knots. Seas 2 to 4 ft. Rip Currents... Given the long period swell remains and the flow is becoming more onshore, we`ve opted to continue with a MODERATE risk for dangerous rip currents today. Saturday the risk will remain the MODERATE generally only for the afternoon low tide cycle. The risk will likely be low in the morning and late at night however the low tide during the middle of the day is enough to warrant a MODERATE risk. && .TIDES/COASTAL FLOODING... Astronomical tides will be high the next couple of days due to the recent full moon and the continued onshore flow. Some minor tidal flooding is possible with this mornings high tide, mainly along the southern New Jersey and Delaware coasts. However, we are not expecting any advisory level flooding to occur. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Meola Near Term...Deal Short Term...Meola Long Term...Meola Aviation...Deal/Meola Marine...Deal/Meola Tides/Coastal Flooding...WFO PHI is the U.S. government's official web portal to all federal, state and local government web resources and services.