Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 210108 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 908 PM EDT Tue Aug 20 2019 .SYNOPSIS... A nearby front will lift slowly northward into New York and New England tonight and on Wednesday. A slow moving cold front is forecast to approach from the northwest on Wednesday night and Thursday. The boundary is expected to pass through our region on Thursday night. High pressure is anticipated to follow for the coming weekend and for the early part of next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... The earlier convection across the lower Susqu Valley has diminished for the most part with one or two surviving cells escaping into the southern Poconos attm. Other dying tstms across Delmarva has morphed into a large area of showers across srn DE/NE MD. Going forward, the models are all over the place with the HRRR showing a dry night and the 18Z NAM showing more tstms developing after 6Z. The the nearby front, it seems that some activity should be expected, so I have just refined the Pops a bit mostly N/W and adjusted for present conditions. Patchy fog will probably develop, but with the drier air today, likely not that widespread. With decent cloud cover overnight, temperatures will remain warm and in the 70s through much of the region, with some mid to upper 60s across the southern Poconos and northwestern New Jersey. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Heat Advisory remains in effect through Wednesday. Another active day is in store for Wednesday as the aforementioned frontal boundary pushes north of the region, placing us firmly in the warm sector. Winds that have been more southeasterly through today will turn more to the southwest and we will see moisture increase across the region once again with dew points rising into the low to mid 70s. Hot and humid conditions will prevail with little relief expected until showers and thunderstorms start to develop and move through the forecast area. A pre-frontal trough will develop ahead of the main front (which arrives Thursday) and will be a focus for thunderstorm development across the region. The main concern will be the potential for severe weather. The SPC has placed portions of our area in the slight risk category, with damaging winds being the main threat. Shear is modest (only around 20- 30 kts) but with CAPE increasing through the day to around 1000-2000 J/KG and plenty of moisture and lift available, we could see some strong to severe storms develop, mainly during the afternoon and evening and primarily to the north and west of the I-95 corridor. Once again, PWATs are running high (up to 2.00") so heavy rainfall will be likely and may result in some flooding concerns. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... We should be solidly in the warm and humid air on Wednesday evening, with ongoing showers and thunderstorms. The warm front is expected to be well up into New England at that time with an approaching cold front extending across the eastern Great Lakes and the lower Ohio River Valley. The showers and thunderstorms are expected to weaken gradually on Wednesday evening with the loss of daytime heating. Partly cloudy and muggy conditions are anticipated for late Wednesday night. The cold front is forecast to extend from northern New England to the Ohio River Valley on Thursday morning. The boundary will likely sink slowly to the south, passing through our region from late Thursday into Thursday night. We are expecting another hot humid day. Heat index values may again approach 100 from the Philadelphia metropolitan area southward. However, conditions seem borderline and we will not extend the Heat Advisory at this point although it may need to be done as we get closer in time. Another round of showers and thunderstorms is forecast ahead of and with the cold front from Thursday afternoon into Thursday evening. Some improvement is expected on Friday as high pressure begins to build down into our region from Ontario. There is a chance of showers and thunderstorms from northeastern Maryland and Delaware into southern New Jersey as the departing front remains nearby to our south. The center of the high is anticipated to shift from Ontario to Canada`s Maritime Provinces over the weekend. This pattern will keep our region in dry conditions with a developing northeast to east flow. Temperatures will be cooler than what we are currently experiencing and humidity levels will be noticeably lower. The onshore flow may bring a return of some moisture early in the new week. We have included a slight chance of showers and thunderstorms at that time. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Isolated showers and thunderstorms this evening. Then more activity N/W after midnight psbl. Otherwise, expect mostly VFR conditions across the region. Some patchy fog psbl and some low clouds S/E. Light and variable winds overnight. Wednesday...Lingering MVFR/IFR conditions (mainly at KACY/KMIV) in the morning should clear by 15Z and then VFR is expected through much of the day. Showers and thunderstorms will again develop across the region and there will be the potential for MVFR or lower conditions to occur during the afternoon and evening, especially from KPHL and northward. South to southwest winds around 5 to 10 knots early will strengthen into the afternoon, with some gusts around 15 to 20 knots possible. OUTLOOK... Wednesday night...MVFR and IFR conditions with a chance of showers and thunderstorms. Southwest wind 5 to 10 knots. Thursday...Conditions improving to VFR. However, there will continue to be a chance of showers and thunderstorms with locally MVFR and IFR conditions. West wind 5 to 10 knots. Thursday night...Mainly VFR. A chance of showers and thunderstorms with locally MVFR and IFR conditions. Northwest wind 5 to 10 knots. Friday...Mainly VFR. A chance of showers. Northwest wind 5 to 10 knots. Friday night...Mainly VFR. Variable wind 6 knots or less. Saturday...Mainly VFR. North to northeast wind 5 to 10 knots. Saturday night...Mainly VFR. Variable wind 6 knots or less. Sunday...Mainly VFR. Northeast to east wind around 10 knots. && .MARINE... Sub-advisory conditions are expected to continue through Wednesday. Seas will generally be around 2 to 4 feet. Winds are expected to pick up from the southwest Wednesday afternoon and gusts may approach 25 knots, especially later in the day. For now, keep winds just below SCA criteria but cannot rule out a few gusts around 25 knots. Isolated showers and thunderstorms may lead to locally higher winds and waves. OUTLOOK... Wednesday night through Sunday...No marine headlines are anticipated. RIP CURRENTS... With waves forecast at 2-3 foot and a 6-7 second period, along with southerly winds 5-10 knots, the risk for dangerous rip currents is low into tonight. Waves in the surf zone will likely remain around 2-3 feet. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Heat Advisory until 8 PM EDT Wednesday for PAZ070-071-102-104- 106. NJ...Heat Advisory until 8 PM EDT Wednesday for NJZ015-017>019. DE...Heat Advisory until 8 PM EDT Wednesday for DEZ001. MD...None. MARINE...None. && $$ Synopsis...Iovino Near Term...Meola/PO Short Term...Meola Long Term...Iovino Aviation...Iovino/Meola/PO Marine...Iovino/Meola is the U.S. government's official web portal to all federal, state and local government web resources and services.