814 FXUS61 KPHI 111546 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1146 AM EDT Thu Oct 11 2018 .SYNOPSIS... A strong cold front will cross the region today, interacting with the remnants of Tropical Storm Michael as it accelerates northeastward and off the Mid-Atlantic coast late tonight into Friday morning. High pressure will then build in from the west later on Saturday, moving offshore on Sunday. Another cold front will cross the region on Monday followed by high pressure returning for Tuesday. Another frontal system may arrive by next Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The first wave of moderate to heavy showers is lifting to the north and east, and for a few hours this afternoon, activity will be more scattered across the area. Any showers that develop will be capable of heavy rainfall due o the tropical airmass over the region. A cold front continues to advance from the west. Southwest flow aloft will allow very moist air continue to spread across our area, with PW values reaching 2.00-2.25 inches across much of the area. Several short wave/vorticity impulses will move across the area trough today within the southwest flow aloft. This will lead to enhanced lift across the area, which combined with the moist airmass will help lead to periods of heavy rainfall. The more steady and concentrated heavy rainfall is expected to develop later this afternoon across southeast Pennsylvania, Central and southern New Jersey, Delaware, and Maryland. These areas are under a Flash Flood Watch starting at 2 pm today and will continue through tonight as rainfall will likely become heavier into the evening for some area. There is also some weak instability forecast, so there will also be a slight chance for isolated thunderstorms as well across the area. Shear does increase across the area through the day, which could help lead to an isolated severe thunderstorm during the day. With mid level winds increasing to 40-45 knots, the main threat is damaging winds && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Heavy rain will be ongoing and may increase in intensity and coverage for a period this evening into the overnight as the cold front moves across the area and the remnants of Tropical Storms Michael move ahead of the frontal boundary. PW values of 2.00-2.25 inches will make very efficient rainfall production. By this evening, the most likely places for the heavy rainfall will be along the I-95 corridor south and eastward. As the front progresses eastward through the overnight period, the heavy rainfall will move eastward as well and move offshore late in the overnight. The Flash Flood Watch will continue through the overnight. There will remain a slight chance for isolated thunderstorms until the front passes through and any instability is lost. As the front moves through the area and Michael passes just to our south, winds will increase across the area out of the northwest. The strongest winds are expected across far southern New Jersey, central and southern Delaware and Maryland where winds could gust 45-50 mph. Therefore we have issued a Wind Advisory for Cape May, NJ; Kent and Susses, DE; and Caroline and Talbot, MD for later tonight. The rest of the area will likely see winds gusting 30-40 mph. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Friday...the remnants of Michael will be offshore by Friday morning and will quickly move off to the northeast, moving into the Canadian Maritimes by Friday evening. Rain should end early Friday with clearing expected through the day. Strong northwest winds will help to dry out the region and we could see some gusts around 20 to 30 mph though Friday, with winds starting to diminish as we head later in the day. Temperatures will feel quite a bit cooler and will be much closer to normal with highs reaching into the 60s across much of the area. Even though the northwest flow will lighten up into Friday night, skies will start to clear and we should have pretty decent radiational cooling conditions. AS a result, low temperatures Friday night will feel cold and are expected to drop down into the 40s. Some areas right along the immediate coast may remain closer to 50 while parts of the southern Poconos may flirt with upper 30s overnight. Saturday...At the surface, high pressure will start to build in from the west. A strong upper trough will cross over the eastern United States through Saturday afternoon. Skies look to remain pretty cloudy through the day and not much warming is expected to take place. Additionally, even though the atmosphere dries out in the northwest flow from Friday, the strength of the upper trough looks to be strong enough to help develop some showers across the area. Best chances for showers looks to be across the northwestern portions of our forecast area. Highs will struggle to break out of the 40s across the higher elevations with mid 50s to lower 60s forecast elsewhere. The trough clears the area by late Saturday afternoon/early evening and clearing is expected to take place as the surface high moves closer to our area. With clearing skies and light winds, another good radiational cooling night is in store with temps expected to be several degrees colder than they were on Friday night. Sunday...High pressure slides across the region and then moves offshore Sunday night. A relatively nice fall day in store for the region with increasing cloud cover through the day. Near normal temperatures with highs into the upper 50s to mid 60s across the region, with some low to mid 50s across the higher elevations of the southern Poconos and northwest New Jersey. Monday...as the high shifts further offshore, we will keep our eyes on the next frontal boundary headed our way. A cold front will drop down from the northwest and cross the region on Monday. Models show the front moving through around Monday afternoon but differ in how much moisture is available as it makes its way offshore. Tuesday through Wednesday...High pressure will briefly return for Tuesday. The cold front should be far enough offshore to allow for a fairly decent day across the region. However, another frontal system will start to approach from the west, potentially moving through our area around mid-week. && .AVIATION /16Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...Conditions vary between MVFR to IFR today as showers move across the area and become moderate to heavy at times. Winds will generally be south to southwest around 5-10 knots early, increasing to 10-15 knots at times during the day and becoming more southwest to west. There is a slight chance of an isolated thunderstorm, but we have not included thunderstorms at this time. Tonight...MVFR to IFR conditions will continue through this evening and into the overnight hours as periods of moderate to heavy rainfall continue. However, a cold front will be moving across the area and rainfall will end from west to east, and conditions will improve from west to east late in the night. There is a slight chance of an isolated thunderstorm, but we have not included thunderstorms at this time. Southwest to west winds 5 to 10 knots will become west then northwest 10 to 15 as the front moves across the area. Winds will also become very gusty behind the front with gusts 20-30 knots likely, possibly higher for some areas. Outlook... Friday...Mainly VFR conditions expected. Gusty northwest winds around 15 to 20 knots with gusts of 35 to 40 knots possible through the morning. Expect winds to diminish through the afternoon and evening. Saturday...Mainly VFR conditions expected. Northwest winds around 10 knots. Chance of showers mainly at KABE and KRDG. Sunday...Mainly VFR conditions expected. Southwest winds less than 10 knots. Monday...A cold front will cross the terminals bringing a chance for MVFR or lower conditions in showers. Mainly west winds around 5 to 10 knots. && .MARINE... Southwest winds today will likely increase and gust around 25 to 30 knots at times today. However, the main winds will be increasing behind a cold front and as Tropical Storm Michael moves near the area overnight tonight. A Gale Warning has been issued for all the waters for the tonight period as the winds increase. Seas will also build through the day today to 4-5 feet, but become even higher tonight as the gale force winds increase. Outlook... Friday...Gale force gusts will continue on the Delaware and on the ocean through Friday. The gale force gusts are expected to diminish on the bay by early afternoon, with gale force gusts on the ocean diminishing by early evening. Seas are expected to remain above 5 feet through Friday, diminishing as we head into Friday night. A Gale Warning is in effect for Friday. Saturday through Monday...Sub-advisory conditions are expected on the area waters. && .TIDES/COASTAL FLOODING... Two periods, and completely different hazards we are concerned about: First, models are depicting spotty minor tidal flooding with the high tide during the day today. Water levels have been slow to return to normal levels after our coastal flooding concerns this past weekend, thanks in large part to continued southerly flow. In addition, heavy rain is expected primarily this afternoon into Friday morning. This could exacerbate any tidal flooding issues. At the present, it looks like the heavy rain will be after the high tide on the oceanfront and lower Delaware Bay, so the threat for widespread tidal flooding in these areas is quite low. On the upper Delaware Bay and the Delaware River, high tide could be coincident with heavy rain. Since the nature of the flood event may be more fresh water than tidal, and in the interest of keeping the messaging simple, we will be highlighting the overall fresh water flooding threat in the HWO and flood watch, but no tidal flood products are anticipated at this time. Secondly, on Friday, expect strong northwesterly winds behind the cold front. This is a classic setup for blowout tides. However, at this time, no guidance is depicting blowout tides (though some does depict the low tide on Friday being below MLLW). We will continue to watch this however, and may have a better idea especially Thursday night when we start to see the base tide anomaly change with the wind shift. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Flash Flood Watch through late tonight for PAZ070-071-101>106. NJ...Flash Flood Watch through late tonight for NJZ008>010-012>027. Wind Advisory from 2 AM to 8 AM EDT Friday for NJZ023-024. DE...Flash Flood Watch through late tonight for DEZ001>004. Wind Advisory from 2 AM to 8 AM EDT Friday for DEZ002>004. MD...Flash Flood Watch through late tonight for MDZ008-012-015-019- 020. Wind Advisory from 2 AM to 8 AM EDT Friday for MDZ019-020. MARINE...Gale Warning from 11 PM this evening to 6 PM EDT Friday for ANZ451>455. Gale Warning from 5 AM to 4 PM EDT Friday for ANZ450. Gale Warning from 2 AM to 2 PM EDT Friday for ANZ430-431. && $$ Synopsis...Meola Near Term...Robertson/MPS Short Term...Robertson Long Term...Meola Aviation...Robertson/Meola/MPS Marine...Robertson/Meola/MPS Tides/Coastal Flooding...