703 FXUS61 KPHI 021942 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 342 PM EDT Thu Apr 2 2020 .SYNOPSIS... An ocean storm will continue to churn offshore of the mid-Atlantic through tomorrow. That storm will finally move out to sea by Saturday as high pressure builds in for the weekend. A weak cold front will move through Sunday night, with weak high pressure then building in for Monday. A large low pressure system centered over southern Canada could result in a cold front arriving mid week next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 12:30 pm update... Few changes to the forecast as breezy northwest winds continue and the coastal low continues to churn to our north and east. A few mid-level cumulus clouds will develop into the afternoon and fill in as the we move into the evening from northeast to southwest as the aforementioned low retrogrades westward. 9:30 am update... Adjusted temperatures and dew points to account for morning trends. Winds are beginning to gust currently and thus, adjusted timing in minor detail to account for this. Otherwise, no significant changes to note. This is the most sunshine we have seen in what feels like ages, so enjoy before clouds retreat back into the region late this afternoon and evening from the northeast. The Northeast and Mid-Atlantic will be caught in between two systems today: surface high pressure building over the Great Lakes and surface low pressure approximately 400 miles southeast of Nantucket Island. Meanwhile, a deep upper trough lies over much of the Northeast and western Atlantic Ocean, with a weak H5 low over eastern Lake Ontario. Several strong shortwaves will rotate around this low and through the local forecast area today. Surface high pressure builds east today. Meanwhile, the oceanic low will lift to the north, then retrograde back a bit towards the mainland, and should be approximately 325 miles due east of nantucket Island. A tight northwest pressure gradient develops over the area, and with a 30-40 kt LLJ passing through the region, will have gusty winds developing throughout the day, generally starting out at 15-20 mph with gusts to 30 mph, increasing as high as 20-30 mph with gusts to 40 mph in the afternoon. Winds will remain below Wind Advisory criteria. Skies start off sunny, but clouds will develop as shortwaves pass through the region, and then clouds associated with the offshore low will rotate back towards northern New Jersey and the southern Poconos. Highs today will be right around normal, generally in the 40s in the southern Poconos, and otherwise in the low to mid 50s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... The coastal low continues to retrograde back towards the mainland tonight, and should be about 180 miles east of Nantucket Island late in the overnight period. Winds diminish after sunset, but remain elevated through the overnight at around 15 mph with 20-25 mph gusts. Waves of light rain will rotate back towards northeast New Jersey and the southern Poconos starting this evening and continuing through the overnight. Not much QPF expected, generally a few hundredths of an inch or so. Lows tonight generally in the mid 30s in the southern Poconos, otherwise in the upper 30s to low 40s north of the Fall Line and in the lower 40s across southeast Pennsylvania, southern New Jersey, and Delmarva. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... Overview: No significant concerns in the long term until we get to mid week next week when a large low pressure system could bring a strong cold front to our region. As mentioned by the previous shift, the blocking pattern that has been in place is expected to gradually break down through early next week. Consequently, we are expecting a progressive ridge to cross the eastern U.S. followed by a large low pressure system crossing southern Canada through the week. Details: Saturday and Sunday...The off shore low is finally expected to shift further off shore as a mid level ridge approaches. The result is a warming trend through the weekend, with highs on Saturday in the 50s. By Sunday we'll see highs in the 60s across most of the region Sunday night and Monday...A very weak cold front is still expected to arrive Sunday night, but models have trended faster with the frontolysis - now should be occuring well before it reaches our region. This means that the front is expected to be even less significant both in terms of precipitation and temperatures. In fact, Monday should even be slightly warmer than Sunday. Tuesday through Thursday...The pattern continues to become more progressive through this period. A large low pressure system is expected to cross southern Canada. An associated strong cold front could reach as far south as our region through this time. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR with clear skies early on with SCT-BKN CIGs around 15000 ft developing in the afternoon. NW winds around 10 kt, increasing to 15-20 kt with 25-30 kt gusts late this morning and through the afternoon. A few gusts to 35 kt possible at KPNE- KPHL-KILG. High confidence. Tonight...VFR. CIGs lowering to 5000-7000 ft through the overnight. NW winds lowering to 10-15 kt with 20-25 kt gusts. High confidence. Outlook... Saturday... VFR conditions are expected. Northeast winds of 5 to 10 kt becoming light and variable for the evening and overnight. High confidence. Sunday-Sunday night... Mainly VFR. Localized MVFR ceilings possible overnight along with a slight chance of showers. Southwest wind 5 to 10 kt, becoming westerly or even northwesterly late Sunday night. Moderate confidence. Monday through Tuesday... Mainly VFR conditions expected. Light westerly or southwesterly winds becoming light and variable. Moderate confidence. && .MARINE... A tight NW pressure gradient will develop on the waters today, and SCA conditions will be in place through tonight. NW winds will range from 15-20 kt with 25-30 kt gusts on the Atlantic Coastal waters and Delaware Bay. A few gusts to 35 kt are possible at the mouth of Delaware Bay and the Delaware and southern New Jersey Atlantic coastal waters late this afternoon, but do not think gusts will be frequent enough nor widespread enough to warrant a Gale Warning. Strong winds and rough seas continue through tonight. Outlook... Saturday-Sunday night...A prolonged period of continued SCA conditions is expected on the Atlantic coastal waters. North- northwesterly winds could gust 25 to 30 kt on Friday, especially early. Beyond then, winds will decrease with gusts no greater than 20 kt through the remainder of this period, so SCA flags will be able to come down for Delaware Bay. However, seas on the ocean will be very slow to subside thanks to a large offshore storm slowly departing the area. Seas will run 5 to 9 ft through the period, slowly diminishing towards Sunday and Sunday night. Monday and Tuesday...Conditions look to finally return to sub-SCA levels with seas 3 to 4 ft and light winds. && .FIRE WEATHER... A tight pressure gradient will develop over the area today between high pressure building in from the west and low pressure over the western Atlantic Ocean. Northwest winds will range from 15-25 mph with 25-35 mph gusts across the region. However, min RH values will range from 35-40 percent across the region, and there has been rain across the region over the last week or so. && .TIDES/COASTAL FLOODING... A large and powerful ocean storm will continue to churn offshore of the region through Friday before it finally starts to move away on Saturday. As it sits offshore it will gradually pile water up along the coast. We will also begin to draw closer to the April 7 full moon. This combination is likely to lead to coastal flooding for the end of the week, especiallly with the Saturday morning high tide cycle. Widespread, advisory level minor flooding appears likely on the oceanfront with that cycle. There is potential for a few areas to reach moderate flood stage especially in coastal southern New Jersey and coastal Delaware, though currently that looks like it would be more the exception than the rule. Coastal interests are encouraged to continue monitoring the tidal forecast over the next few days. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 7 PM EDT Friday for ANZ450>452. Gale Warning until 6 PM EDT this evening for ANZ431-453>455. Small Craft Advisory until 4 PM EDT Friday for ANZ430. && $$ Synopsis...Johnson Near Term...MPS Short Term...MPS Long Term...Johnson Aviation...Davis/Johnson Marine...Davis/Johnson Fire Weather... Tides/Coastal Flooding...