316 FXUS61 KPHI 050614 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 214 AM EDT Sat Apr 5 2025 .SYNOPSIS... The cold front settles to our south tonight as high pressure builds across New England. As low pressure tracks up into the Great Lakes on Saturday, the front will lift back north across the area as a warm front. A cold front then crosses through the region on Sunday, followed by a stronger, secondary front that passes through on Monday night. High pressure returns by late Tuesday through Thursday, before another disturbance approaches by the end of next week. && .NEAR TERM /THROUGH TODAY/... Lowered PoPs through the overnight hours as we are currently in a lull of any precip. High pressure north of the Great Lakes will build east tonight, passing north of New York State and moving into the Canadian Maritimes by Saturday morning. Meanwhile, the stationary front remains to our south. There have been some scattered showers that have developed along the front, but not confident it will get as far north and northern Delmarva. Low pressure will organize and develop over the Southern Plains tonight and will lift north towards the Great Lakes and Ohio Valley. As it does, it will slowly pull that stationary boundary back north as a warm front. However, because of the position of the high to the northeast, there are some concerns as to how far north that from will track. Quite possible that with the low moving through the Great Lakes and Ohio Valley on Saturday that the front will snake around the area, with the warm front getting just as far north as southern Delmarva. Several additional waves of rain will pass west and north of the area, so most rain will be confined to areas mainly north and west of the Fall Line. Will carry chance PoPs for rain most elsewhere. High temperatures on Saturday will be seasonally chilly, generally around 5 degrees below normal for most areas. This will be highly dependent on how far north the warm front can get. Highs in southern Delmarva should get into the upper 60s to low 70s, while the rest of the area should be in the 50s to low 60s. But if that front can make its way north just a little bit more, then a bit more of the area would be warmer than forecast. && .SHORT TERM /TONIGHT THROUGH MONDAY/... The front will gradually work its way north on Saturday night, but will continue to struggle with its progress. Showers will also continue especially north and west of the I-95 corridor, where embedded thunder is possible. Elsewhere, just some isolated showers are possible. With onshore flow continuing, expect a widespread swath of fog to develop and push inland as dew points will be on the rise. Low temperatures will vary depending on location, with 40s/50s across most areas with 60s across southern most areas. Heading into Sunday, a strong and deep upper level trough slides across central to eastern Canada and it is forecast to amplify by Sunday night. This trough will cause low pressure to track well to our north with a cold front trailing to the southwest which will cross through our area on Sunday. The temperature gradient on Sunday will be quite diverse, with in the upper 40s/50s north with 70s across the Delmarva. How far the front/warm sector reaches is yet to be known, but will ultimately determine how warm areas get. While the parent trough lags well behind the cold front, height falls arriving with a greater thickness packing also arriving from the west should result in enough forcing for ascent for showers to develop and move in from the west especially in the afternoon and at night. The timing consensus of the cold front looks a bit faster and this resulted in temperatures a bit lower especially north of Delmarva. Some thunder is certainly possible given the strength of the incoming trough, however the best chance for thunder does appear to be over the Delmarva into extreme southern New Jersey where instability and moisture transport is greatest. For Sunday night, we`ll likely see another period of showers move into the region while lingering into the first part of Monday as a secondary wave of low pressure forms along the cold front that moved through during the day on Sunday. Rain may be heavy at times as well, but overall not looking at anything all that significant, just some more beneficial rain with up to 1 inch of rain possible. In fact, we`ll start to see some cooler air ushering in on the back side of the front, so may see some rain mixing with some wet snow across the higher terrain on the Pocono Plateau. All in all, a few tenths of accumulation do look plausible, considering cold air advection filling in its wake. Otherwise, plain rain is expected elsewhere. This disturbance should move off the coast by Monday and we`ll see a much cooler airmass move into the region and some drying from northwest to southeast. High temps on Monday should only range from the upper 40s to mid 50s, which will put us a few degrees below normal for early April. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Summary...A stronger, secondary cold front moves through Monday night followed by high pressure arriving later Tuesday into Thursday. High temperatures will fall several degrees below-normal through the middle of next week, with the return of seasonable temperatures by the end of the week. Synoptic Overview...An upper-level trough is forecast to amplify into and across the East during early next week, before starting to lift out on Wednesday. The next upper-level trough then looks to begin to amplify across the eastern U.S Wednesday night and Thursday with the trough moving into the region by Friday. At the surface, a strong, secondary cold front moves through Monday night. High pressure then builds in late Tuesday into Wednesday before shifting offshore into Thursday. Another low pressure system then approaches Thursday night into Friday. For Monday night and Tuesday...The secondary front may end up moving through our area Monday night with little in the way of precip associated with it as the deeper moisture is shoved offshore with the earlier cold front. Given the strength of the incoming upper- level trough however, cannot ruled out a few rain showers with the second cold front mainly Monday night or early Tuesday. The arrival of the colder air aloft along with cyclonic flow may result in a few rain/snow showers across portions of far northwestern zones. The secondary front should be offshore to start Tuesday with strong cold air advection underway. There will be a tightened pressure gradient in place between departing low pressure well to our northeast and incoming high pressure from the Midwest to the Ohio Valley. This will translate to a gusty wind on Tuesday with peak gusts in the 25- 35 mph range before diminishing some at night. High temperatures Tuesday look to be well below average as much of the area may not get above the 40s during the day. It will be cold Tuesday night with most if not all areas dropping below freezing. There may be to much wind for frost formation, however a freeze warning may be needed where the growing season has started (most of our Delmarva zones). For Wednesday...The strong upper-level trough is forecast to be lifting out with time. This will result in surface high pressure building into our area before it starts to shift offshore at night. There may still be a gusty wind in place before a tightened pressure gradient relaxes as the center of the surface high builds closer. High temperatures will be several degrees below average once again, and the wind will determine how cold it gets at night despite the air mass especially aloft starting to modify. A clear sky with dew points below freezing would typically yield a cold night especially if the wind is able to completely decouple. As a result, there is some risk for frost and/or freeze (the growing season has started for most of our Delmarva zones). For Thursday and Friday...The next upper-level trough looks to begin amplifying into the Eastern U.S. A surface low is forecast to be tracking toward the upper Ohio Valley with a warm front approaching our area from the southwest. This will be dependent on the strength of the developing low relative to the departing high, so much of Thursday may end up remaining dry. Temperatures do look to begin to moderate though as southerly flow returns in advance of this system. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through 12Z...Should keep mostly VFR conditions as it looks like lower ceilings will hold off until after 12Z. Winds should generally favor an easterly direction with speeds less than 10 kt. Today...Ceilings may start for the first few hours as VFR, but are expected to lower to MVFR and eventually IFR through the day. Temporary visibility restrictions possible with passing showers and BR development. Winds should favor ESE direction around 10 to 15 kt. Increasing concern of periods of low level wind shear as will have a SW low level jet near the area through out the TAF period. At this point though, period of most concern is early afternoon, and mostly for TAF sites from the I-95 corridor eastward. Tonight...Continued IFR conditions (primarily due to low ceilings) is expected. KMIV and KACY could see some improvement late overnight as winds shift to more SW, but low confidence on the timing of that. Winds will start E or NE at 10 Kt or less, but could become light and variable late overnight. Another period of low level wind shear with a SW low level jet is possible between 00 and 06Z. Outlook... Saturday night through Monday...Sub-VFR conditions likely with several rounds of showers and isolated thunderstorms possible. Patchy fog on Saturday night too. Monday night through Wednesday...VFR expected. Winds may occasionally gust upwards of 25-30 kt on Tuesday. && .MARINE... W-NW winds 10 to 15 kt, becoming E-SE tonight through Saturday. Seas will average 2 to 4 feet. Sub-Small Craft Advisory conditions on tap for tonight through Saturday. Outlook... Saturday night through Sunday...SCA conditions likely on the Atlantic coastal waters due to wind gusts up to 25 kt and seas around 4-6 feet. Showers likely with isolated thunderstorms. Sunday night through Monday night...Lingering SCA conditions possible mainly due to seas near 3-5 feet. Rain showers likely. Tuesday through Tuesday night...SCA conditions probable due to wind gusts up to 30 kt and seas around 5 feet. Fair weather outside of SCA conditions. Wednesday...No marine headlines expected. Fair weather. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 2 AM to 6 AM EDT Sunday for ANZ451- 452. Small Craft Advisory from 11 PM this evening to 6 AM EDT Sunday for ANZ453>455. && $$ SYNOPSIS...DeSilva/Gorse NEAR TERM...Johnson/MPS SHORT TERM...DeSilva/Gorse LONG TERM...DeSilva/Gorse AVIATION...DeSilva/Johnson MARINE...DeSilva/MPS