


Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
Issued by NWS Mt. Holly, NJ
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532 FXUS61 KPHI 181335 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 935 AM EDT Sat Oct 18 2025 .SYNOPSIS... High pressure cresting over our area this morning will then shift offshore this afternoon into tonight. A strong cold front moves through the region late Sunday night into Monday, followed by weak high pressure returning Monday night into Tuesday. Another cold front moves through Tuesday night, then high pressure builds in from the south Thursday into Friday. && .NEAR TERM /THROUGH TONIGHT/... Heading into the daytime hours today, the center of the high pressure that has been in control of our weather will move through the region, with a period of light and variable winds before winds settle out of the south-southwest this afternoon. Partly cloudy skies and temps warming into the mid to upper 60s are expected. Though the high will now be centered offshore by late this afternoon, it will remain in control through tonight with dry conditions continuing. Temperatures will be milder thanks to the southerly flow returning as well as some increasing cirrus ahead of the next approaching system, with lows in the mid 40s to low 50s expected. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... A strong cold front crosses our area later Sunday night and Monday morning. A strengthening upper-level trough is forecast to slide across our region Sunday night and Monday. Much of the guidance indicates that this trough will take on some negative tilt as it crosses our area. The trough may even close off in our area as a strong low to mid level jet maximum rotates up across the east side of the trough. Surface low pressure tracks near the eastern Great Lakes into Monday, however a secondary low looks to develop at the triple point near our area as the core of the trough arrives. Given the strength of this trough, southerly flow will increase ahead of it and that will peak the warm air advection with many areas getting into the 70s on Sunday despite some increase in cloud cover. The southerly flow will result in moisture advection with surface dew points rising to near 60F during the day Sunday and also Sunday night ahead of the cold front. The timing of the cold front later Sunday night into Monday morning however is not ideal for maximizing instability (thunder), and the model consensus is that the instability is rather weak (low CAPE/high shear). Some model soundings do show a little low/mid level instability developing ahead of the cold front later Sunday night, however convective elements may tend to have little or no lightning especially given the low topped nature of any stronger convection. Given the strength of the trough and associated wind fields though, forcing for ascent should be enhanced for a time. An area of showers arrive ahead of and with the cold front by later Sunday night (daytime hours should be dry). The southerly flow at 925 mb and 850 mb is forecast to increase to 40-50 knots which would increase the low to mid level shear ahead of the cold front. This along with stronger forcing should favor a narrow band of low-topped convection with little to no lightning to our west, and if this can be maintained into our area then some strong wind gusts (40-50 mph) could occur as the stronger flow might be able to be brought down to the surface within some heavier convective cores. Given the meager instability though, the severe weather risk is rather low. The cold front shifts to our east to start Monday, however some lingering cyclonic flow and colder air aloft could keep some showers going at least during the first half of Monday before drier air takes hold. Given an increase in cold air advection and decent mixing during the day Monday, a gusty west to west-northwest breeze should occur before diminishing in the evening. High temperatures on Monday will be 10-15 degrees lower than Sunday. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Summary...A cold front arrives Tuesday night followed by another cold front late Thursday. Synoptic Overview...An upper-level trough, potentially robust, arrives later Tuesday into Wednesday. This trough may lift out some Thursday before amplifying some again across the Northeast Friday. A cold front crosses our area Tuesday night followed by another (weak) cold front late Thursday. For Tuesday and Wednesday...A narrow mid level ridge looks to quickly slide across our area Tuesday along with surface high pressure tracking to our south. Some warm air advection ahead of a cold front will boost afternoon high temperatures Tuesday to near 70 degrees for many spots. The next upper-level trough from the Midwest and Great Lakes to adjacent Canada shifts eastward with a cold front crossing our area Tuesday night. There should be enough available moisture combined with forcing for ascent to result in the chance for at least some showers Tuesday night into Wednesday morning. For Thursday and Friday...An expansive upper-level trough from eastern Canada to the Mid-Atlantic and Great Lakes Thursday is forecast to shift northeastward through Friday. As this occurs, a weak cold front may slide across our area later Thursday but then surface high pressure centered to our southwest and south is forecast to extend across our area. This time frame overall looks to be on the drier side with cooler temperatures. && .AVIATION /13Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR. Light and variable winds early, shifting to southwest around 5 kts by the afternoon. High confidence. Tonight...VFR. South-southeast winds around 5 kts or less, becoming light and variable at the most sheltered terminals. High confidence. Outlook... Sunday and Monday...A period of sub-VFR conditions Sunday night into Monday morning due to showers and low ceilings. Southerly wind gusts to around 25 knots Sunday, becoming west to west-northwest on Monday. Tuesday and Wednesday...Areas of sub-VFR conditions and showers possible Tuesday night, otherwise mainly VFR. && .MARINE... Conditions are expected to remain below Small Craft Advisory criteria through the period. Winds generally northwest through this morning around 10 knots. This afternoon, winds turn southerly around 10-15 kts with a few gusts up to 20 kts possible by late tonight. Seas of 3-4 feet throughout. Outlook... Sunday and Monday...Small Craft Advisory conditions probable with gusts up to 30 knots and seas building to 5-8 feet. Strong southerly winds just above the surface later Sunday night into Monday morning could result in some gale force gusts, however this is low confidence given it is within southerly flow and pronounced warm air advection. Tuesday and Wednesday...Small Craft Advisory conditions possible. && .TIDES/COASTAL FLOODING... With the southerly flow developing, we have now had two consecutive high tide cycles with flooding in back bays, particularly in Ocean County NJ and Sussex County DE. Given that the southerly flow should persist into Sunday, would expect back bay flooding will continue through at least the next high tide cycle this evening, if not the next 3 high tide cycles through Sunday. For now, have issued a coastal flood advisory for those two counties through 11 PM EDT this evening to cover the next high tide cycle. Once we see how tidal departures are trending with that high tide cycle, will have a better idea of what the trend will be with Sunday high tide cycles. We are also closely watching tidal departures on the northeastern portions of the Chesapeake Bay, as this flow regime can result in tidal flooding there as well. However, currently our forecast for the next several high tide cycles remains just below advisory criteria. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...Coastal Flood Advisory until 11 PM EDT this evening for NJZ020- 026. DE...Coastal Flood Advisory until 11 PM EDT this evening for DEZ003- 004. MD...None. MARINE...None. && $$ SYNOPSIS...DeSilva/Gorse NEAR TERM...AKL SHORT TERM...Gorse LONG TERM...Gorse AVIATION...AKL/Gorse MARINE...AKL/Gorse TIDES/COASTAL FLOODING...Johnson