270 FXUS61 KPHI 020130 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 930 PM EDT Wed Apr 1 2020 .SYNOPSIS... A developing surface low will continue to churn over the open Atlantic, making its parade back around towards New England then southwards towards the Mid-Atlantic before finally making a grand exit Saturday as it moves eastward. High pressure briefly builds across the eastern U.S. over the weekend before a weak cold front approaches Monday. An unsettled forecast with periods of showers looks to resolve early next week in wake of this front. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Clouds continue to clear this evening behind a weak surface trough and short wave/vorticity impulse that has pushed out of the area. Mostly clear skies are expected overnight for many areas, although some clouds could begin making their way southward into the area from the north late in the night and toward daybreak Thursday. The question of the night will be how much temperatures cool overnight, and if frost can occur or not. Most places are expected to drop into at least the mid to upper 30s overnight, with some locations in the low 30s. While winds may drop off some for the first half of the night for some areas, they will likely pick up again overnight, especially when temperatures will be their coolest. This should preclude widespread areas of front and the need for a Frost Advisory, although some patchy areas will be possible where winds stay light longer. For areas generally south of I78, the growing season has already started, so this is where any higher concern would be. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... The mid level trough digging south will cross over the region. Still looks like thanks to a lack of moisture advection, and precipitation should remain northeast of our region through the day time hours. There will be little change in the air mass over the next 24 hours. Therefore, Thursday highs will likely be close to the highs on Wednesday. This would be slightly below normal, with highs from the mid 40s to mid 50s. The main story tomorrow will be the winds. Due to the off shore low, we should see a tight pressure gradient over our region. Northwesterly winds could be gusting up to 30 mph during the day tomorrow. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... The coastal low that will by this time have already overstayed its welcome will continue to retrograde westward as a blocking ridge to over the northern Atlantic prevents progression eastward. As a weak shortwave trough pivots south around the mid-level trough, it will begin to absorb into the main synoptic trough, thus pulling the feature westward. Showers will likely push westward into the region as the low occludes and shifts west Friday. Exact coverage and duration are still somewhat uncertain given questions over how this shortwave will phase with the longwave pattern by late week. Rain will likely remain closer to the coast, but may end up pushing as far inland as eastern Pennsylvania. Highs look to reach into the mid to upper 50s for the region Friday. By Saturday, our pesky surface low will finally leave us be and shift eastward as the Rossby Wave pattern finally returns to a more progressive state. Skies should begin to clear with a return to sunshine. Highs will make it into the mid to upper 50s once again. A weak ridge of high pressure builds over the region bringing a return to dry weather Sunday, but this will be short-lived as a cold front crosses the Great Lakes and pushes into the region by Monday morning. Moisture looks limited with this system with somewhat weaker forcing as the parent shortwave and surface low track well to the north across Ontario and Quebec. Thus, this feature will trend to a more dry and transient nature. Highs will range from the low to mid 60s Monday. The forecast turns a little more uncertain early next week with rather zonal flow lacking signal of any impactful weather features. A series of shortwave impulses riding around a surface high to our southwest will bring chances for rain Tuesday through Thursday, but exact timing remains quite uncertain. These days do not look like a washout at this point, but there is room for change in the coming days if guidance converges on any stronger signals. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through the overnight hours...VFR expected. Ceilings between 7-10kft will slowly erode becoming few-sct through the evening hours. Winds generally be northwesterly at 5 to 10 kt increasing towards daybreak. High confidence. Thursday...VFR conditions are expected. Northwesterly winds 10 to 20 kt with gusts up to 30 kt. High confidence. Outlook... Friday...VFR conditions dropping to MVFR as rain moves westward from the coast, especially for MIV and ACY. N to NW winds from 10 to 15 knots with gusts from 15 to 20 knots. Moderate confidence. Saturday...And lingering MVFR conditions will return to VFR with north to northeast winds from 5 to 10 knots. High confidence. Sunday...Mostly VFR conditions expected with the potential for periods of MVFR CIGs. Southerly to southeasterly winds from 5 to 10 knots. Moderate confidence. Monday...Sub-VFR conditions possible as rain showers move across the region, especially in the morning. Southerly winds turning westerly from 5 to 10 knots. Moderate confidence. && .MARINE... On the Delaware Bay...winds are expected to increase through the evening, with gusts above 25 kt possible after midnight. A Small Craft Advisory remains in effect from late tonight into Thursday night. On the Atlantic Coastal Waters...earlier gale force gusts on the Delaware and southern New Jersey coastal waters have subsided to 25 to 30 kt. Small Craft Advisory conditions are expected to continue on the coastal waters tonight and tomorrow. There is a small chance for gusts near gale force on the Delaware coastal waters during the day on Thursday. However, I think this is unlikely as we likely won't see very efficient mixing. Therefore, have maximum wind gusts staying just below gale force. Outlook... Friday through Sunday...SCA conditions are expected, primarily on the coastal waters, mainly due to elevated seas from 5 to 10 feet as a coastal low sits over the Atlantic. North to northeasterly winds from 15 to 20 knots with periods of gust approaching 25 knots Friday and Friday night. Monday...Sub-SCA conditions expected with southwesterly winds from 10 to 15 knots. Seas dropping below 5 feet. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ450>455. Small Craft Advisory from 1 AM Thursday to 6 AM EDT Friday for ANZ430-431. && $$ Synopsis...Davis Near Term...Johnson/Robertson Short Term...Johnson Long Term...Davis Aviation...Davis/Deal/Johnson Marine...Davis/Johnson