345 FXUS61 KPHI 260156 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 956 PM EDT Mon Apr 25 2022 .SYNOPSIS... High pressure off the Eastern Seaboard drifts out to sea. A cold front approaches from the west and moves across the region late Tuesday and Tuesday night. High pressure builds in from the west for the mid-week period, moving out to sea over the weekend. Another system may approach for the start of the new week. && .NEAR TERM /THROUGH TUESDAY/... Patchy drizzle and mist is imminent this evening, with onshore flow continuing. Sped up the timing a tough tonight, but otherwise no significant changes were made. It has been a tricky fcst day across the area with the low clouds hanging in there and preventing any decent warming. Approaching the mid-afternoon with lots of low/mid 60s inland an mid/upper 50s for the shore areas and far N. One exception, the SW corner of Sussex County DE where sunshine has resulted in temps in the 70s. Lately, the clouds have been thinning somewhat, so it's possible that we could get mostly sunny skies in some areas later on. Temps will respond accordingly. Its been rather dry, especially across the north with RHs there below 40% and 40% to 60% most other areas. Tonight, most models agree on a continuation of the onshore flow with more low clouds expected. It's also possible that some drizzle and fog could develop too. The more likely spots for fog and drizzle will be across the NW areas and along the shore too. The drizzle/fog fcst is somewhat low confid attm. Low temperatures tonight will remain mild with readings in the upper 40s for the N/W areas and low/mid 50s elsewhere. Tuesday, a cold front will cross the area from west to east during the morning. A weak wave of low pressure will ride along it across DE and the NJ shore areas during the morning. Clouds and showers will accompany the system. Pops are in the high chance to low likely range as some dynamics and convergence are expected. Overall, QPF will probably only range around 1/10th ti 1/4 inch. Later Tue, the low pressure will pull away and cooler drier air will arrive over the area. Clouds will decrease and late day sunshine is expected. Highs Tue will be in the 60s N/W to the low/mid 70s S/E. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... Frontal boundary continues to move offshore Tuesday night. Any lingering showers will taper off through midnight or so from west to east. There may still be enough instability aloft across portions of Delmarva and southeast New Jersey for some elevated convection, as MU CAPE values are generally 200 to 400 J/kg, but any convection would end in the evening. Surface high pressure then builds into the Great Lakes and Ohio Valley while a deep upper trough lies over the Northeast with surface low pressure near the Canadian Maritimes. A prolonged period of gusty northwest flow will be in place Wednesday through Thursday with winds ranging from 15 to 20 mph with 20 to 30 mph gusts, mainly during the daytime hours, and only a bit less at night. Strong cold air advection will be underway as well. High temperatures Wednesday and Thursday will generally range from the 40s in the southern Poconos, to otherwise in the low to mid 50s, and possibly near 60 in southern Delmarva. These highs are some 15 to 20 degrees below normal, and are more in line with highs in late March as opposed to late April. Lows Wednesday night will drop into the 20s and 30s. Although potentially cold enough for frost, dew points may be too low and winds should be too strong for development of frost. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Closed upper low slides to the east on Friday, and surface high pressure along with mid-level ridging builds in from the west. Conditions remain dry into the start of the weekend as this high builds overhead, and then moves offshore. After a cool start with temperature below normal Friday and Saturday, temperatures rebound back closer to normal by Sunday. Another upper trough approaches from the west late in the weekend and into the start of the new week. This will drag a frontal boundary towards the Eastern Seaboard that may produce another round of unsettled weather. Generally stayed close to the NBM guidance for the Long Term period. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight... Decreasing CIGS expected with some drizzle/fog possible. Mostly MVFR or high-end IFR expected, but limited confid with some lower IFR/LIFR possible. Degree of VSBY drop in drizzle/fog is uncertain too. LLWS (limited) with 35 to 40 kts at 020 for the 01Z - 07Z period. Low confid. Tuesday... Slow improvement in CIGS/VSBYS thru the morning from IFR beginning earlier for NW sites (KABE,KRDG) then progressing E/SE thru the rest of the morning and into the afternoon. Winds will shift to W/NW at 5 to 10 knots. Medium confid. Outlook... Tuesday night...Sub-VFR in SHRA, possible TSRA at KACY/KMIV early, then improving conditions late. W-NW winds 5 to 10 kt. Moderate confidence. Wednesday through Wednesday night...VFR. NW winds 15 to 20 kt with 25 to 30 kt gusts during the day, diminishing a bit at night. Moderate confidence. Thursday through Thursday night...VFR. NW winds 15 to 20 kt with 25 to 30 kt gusts during the day, diminishing a bit at night. Moderate confidence. Friday through Saturday...VFR. NW winds 10 to 15 kt with 20 to 25 kt gusts during the day and 5 to 10 kt at night. Moderate confidence. && .MARINE... Onshore flow continues across the waters this evening as high pressure remains to the NE. This flow will remain in place tonight and into Tue morning before a front a low pressure arrive. Overall, winds and seas will remain short of SCA conditions, although seas will run close to 4 ft on the ocean much of the time. Winds will be around 15 kts this evening with some gusts around 20 kts. Fair weather tonight then some drizzle and fog possible late. Showers will arrive Tue with a cold front. Outlook... Tuesday night through Thursday night...A prolonged Small Craft Advisory will likely be needed for NW winds 15 to 20 kt with 25 to 30 kt gusts and seas building to 4 to 6 feet. The strongest winds will likely occur Wednesday evening through Thursday morning. Showers end Tuesday night, and then dry conditions on tap. Friday...Lingering SCA gusts possible in the morning, otherwise, conditions subside to sub-SCA criteria with NW winds 15 to 20 kt and seas 2 to 4 feet. Saturday...Sub-SCA conditions. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...MPS Near Term...Davis/O'Hara Short Term...MPS Long Term...MPS Aviation...Davis/MPS/O'Hara Marine...MPS/O'Hara