####018007798#### FXUS61 KPHI 170136 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 936 PM EDT Fri May 16 2025 .SYNOPSIS... Spotty showers, thunderstorms, and humidity continue through Saturday morning ahead of a couple of cold fronts that passes through Saturday afternoon into Saturday evening. High pressure builds into the area on Sunday and persists into Tuesday before another period of unsettled weather returns Wednesday into Thursday. && .NEAR TERM /THROUGH SATURDAY/... Evening convection is pretty much done with as the second MCS is now off the coast. Bulk of tonight looks pretty tranquil, though will need to keep an eye on patchy fog development which could necessitate more dense fog advisories. At this time, however, guidance is notably less robust on the fog threat compared to 24 hours ago. Convection well to our west in the Ohio Valley may reach us late tonight into early morning Saturday, but guidance has been less enthusiastic about this compared to earlier model runs. This likely has to do with the efficient overturning of the atmosphere locally, not to mention its arrival late at night/early in the morning. Thus, have some chance pops overnight into the morning, but knocked likelies out of the forecast. Severe and flood risk also look much reduced with any convection overnight into the morning, but not quite zero, especially the flood risk given the copious rain of late. Lows mostly in the 60s tonight. Any morning showers/t-storms should end toward noon as it moves east of the region, with one cold front (perhaps better described as a dry line) moving through towards midday. Dew points will drop into the 50s behind this first boundary, which will make any convective development later in the day notably more difficult. This has been noticed by the guidance, which have become considerably less enthusiastic in thunderstorms after midday Saturday compared to how they looked a day or two ago, so have mostly slight chance POPS, mainly north of Philly, with chance in the far north. Highs will be quite warm with the sun returning, with 80s common and perhaps even a stray 90 or two. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... Secondary front moves through in the evening, with notable cold advection occurring behind it. The threat for storms wanes completely with its passage in addition to the loss of daytime heating. Nighttime lows will be in the mid 50s to low 60s. Sunday is looking like the better half of the weekend as tranquil weather returns with the upper trough moving further east. Partly to mostly cloudy skies are expected with dry conditions and lower humidity. Perhaps an isolated shower is possible north and west, but general thinking is most of the area will stay dry. The one thing to note is winds will increase as diurnal mixing occurs as the area lies wedged between systems resulting in a tightening pressure gradient. Wind gusts up 30-35 mph will be possible. Gusts will diminish into Sunday night under mostly clear skies. Despite the windy conditions, high temperatures should mainly be in the 70s (with 60s in the Poconos). && .LONG TERM /MONDAY THROUGH FRIDAY/... By Monday, low pressure over the Canadian Maritimes will begin to move further east into the North Atlantic. At the same time, high pressure will settle over the Mid-Atlantic before moving offshore on Tuesday. Aloft, the area will be situated under northwest flow in wake of exiting upper trough. All in all, a tranquil weather period is in store with mostly clear skies, light winds and dry weather. By Tuesday night and through the middle of the week, our attention will turn to our next weather system which will take aim at the area. Global and ensemble guidance both feature a deep upper trough moving into the Great Lakes/Northeast region around the middle of the week with a potential coastal low developing before moving up towards New England. This would indicate another period of unsettled weather with periods of rain starting as early as Tuesday night, and more so on Wednesday and Thursday. Still quite a ways out from this potential, so have generally stuck with NBM guidance and capped rain chances at chance (~30-50%). In terms of temperatures, we'll encounter temperatures around average on Monday, before dipping below average for Tuesday through Thursday as the area remains situated within the deep upper trough. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Rest of Tonight...Evening showers/storms moved out already this evening, but the potential for low cigs and low visbys once again due to stratus, mist and fog remains. However, atmosphere was cleansed fairly well by earlier convection, so guidance has backed off on the low cig/vsby threat somewhat. More showers and storms could move in late tonight, however. S to SW winds around 5 knots. Low confidence. Saturday...Sub VFR conditions possible early in the morning with showers and storms around. Otherwise, primarily VFR expected. Very isolated showers and thunderstorms possible in the afternoon and early evening, but much lower coverage than today. Winds WSW around 10-15 kts with gusts to 20 kts. Low confidence on showers and storms in the morning and even lower confidence on activity in the afternoon; moderate confidence otherwise. Outlook... Saturday night...VFR. Winds W to WNW 10 kts or less. Sunday through Tuesday...VFR. Gusty winds up to 25-30 kt possible on Sunday. Otherwise, no significant weather expected. && .MARINE... Generally sub SCA, except storms overnight into early Saturday morning could produce locally strong winds. Will also need to watch fog potential, as guidance still suggests dense fog may try to redevelop, in which case a dense fog advisory may yet be needed on the waters. A few extremely isolated showers and storms possible Saturday afternoon, but overall the threat is much reduced compared to today. SW winds gust to around 15-20 kts in the afternoon, but no headlines expected. Outlook... Saturday night...No marine headlines expected. Sunday through Sunday night...SCA conditions possible due to wind gusts up to 25 kt. Monday through Tuesday...No marine headlines expected. Rip currents... Currently projecting low risk of rip currents over the weekend based on low wave heights of 1-2 feet and winds shifting offshore at 10-15 mph. && .TIDES/COASTAL FLOODING... The Coastal Flood Advisory for northwestern Burlington and lower Bucks Counties has been extended until 8 AM Saturday. Minor coastal flooding is expected with the early morning high tide on Saturday. It's possible minor coastal flooding may occur on Sunday as well, where further extensions may be needed. For areas of the lower tidal Delaware River near Philadelphia may encounter spotty minor coastal flooding through Saturday, but should fall short of advisory levels. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Coastal Flood Advisory until 8 AM EDT Saturday for PAZ106. NJ...Coastal Flood Advisory until 8 AM EDT Saturday for NJZ019. DE...None. MD...None. MARINE...None. && $$ SYNOPSIS...MJL/RCM NEAR TERM...Fitzsimmons/MJL/RCM SHORT TERM...DeSilva/RCM LONG TERM...DeSilva AVIATION...DeSilva/Fitzsimmons/RCM MARINE...DeSilva/Fitzsimmons/RCM TIDES/COASTAL FLOODING...PHI