


Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
Issued by NWS Mt. Holly, NJ
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --809 FXUS61 KPHI 012340 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 740 PM EDT Tue Jul 1 2025 .SYNOPSIS... A cold front will move through the region Tuesday night into Wednesday. High pressure builds closer to the area later Wednesday into Thursday before settling over our area on Friday and into the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... As of 610 PM, the Severe Thunderstorm Watch has been cancelled for our PA counties, Mercer/Middlesex counties in NJ northward, New Castle County in DE and Kent County in MD. It remains in effect for the other areas until 9 PM EDT. A Flood Watch remains in effect for locations near and along the I-95 corridor and southeast Pennsylvania until 2AM EDT. Numerous heavy thunderstorms have developed across the I-95 corridor with additional clusters of heavy thunderstorms across the Harrisburg region and the Washington DC metro area. As a cold front across the Ohio River Valley advances east across Pennsylvania late this afternoon and into tonight, supported by an amplified trough pivoting across the Northeast and Mid Atlantic, these clusters of strong thunderstorms will begin to collide and merge across eastern PA and the I-95 corridor, slowly moving east into the Delmarva and New Jersey into tonight. SBCAPE values this afternoon have bubbled up to 3000-4500 J/kg with steep low-level lapse rates of 7.0-8.0 C/km leading to rapid development of strong updrafts and severe thunderstorms capable of producing locally damaging wind gusts. Furthermore, PWAT values are in excess of 2.0 inches, which is at the climatological maximum for this area this time of the year, with forecast profiles indicating that storms could have a tendency to backbuild or train. These factors all indicate that instances of flash flooding could be more numerous than what we see in many events with even the potential for some instances of significant flash flooding possible, especially if storms train over an urban area. High res model guidance suggests the potential for heavier storms to produce a quick 1 to 3 inches of rainfall within just 1 to 2 hours and it`s possible some localized storms totals could reach around 4 inches. For this reason, the WPC has expanded the Moderate Risk in the Excessive Rainfall Outlook to envelop the entirety of southeast PA, including Philadelphia, and into the I-95 corridor for parts of New Jersey, essentially matching the locations we have highlighted in our Flood Watch. These various clusters of thunderstorms will merge into a broad line tonight, likely lessening the severe weather threat with the loss of daytime heating, but maintaining or even exasperating the flash flood threat across the entire region. This massive complex of heavy showers and thunderstorms will slowly shift south and east into southern New Jersey and the Delmarva overnight as the cold front arrives to nudge the storms towards the coast. As a result of the heavy rainfall and slow storm motions, flash flooding concerns may continue through the evening and well into the first part of the overnight period. The storms will gradually begin to lose steam early Wednesday morning, but steady showers and some isolated thunderstorms can still be expected during the predawn hours of Wednesday. Lows will be in the upper 60s to low 70s. Latest guidance suggests this frontal boundary will slow down and possibly become quasi-stationary across southern New Jersey and the southern Delmarva come daybreak Wednesday. As a result, additional showers and thunderstorms may develop across this corridor through Wednesday morning before gradually shifting offshore throughout the day. PWAT values in this narrow corridor will still be near 2 inches, suggesting heavy downpours will still be possible for at least the first half of the day. Skies will be overcast to mostly cloudy to start the day with gradual clearing in the afternoon from west to east. High temperatures will be in the 80s, with some areas that see sunshine in the afternoon further north and west likely seeing the warmest temperatures in the mid to upper 80s. Widespread rainfall amounts once this is all said and done look to be at least around 0.75 to 2.5 inches of rainfall, with locally heavier amounts very possible. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... Dry and quiet weather follows for Wednesday night as high pressure builds in to our south and west. Lows in the 60s. While high pressure will be increasingly in control on Thursday, a weak cold front looks to sink southward during the afternoon and evening on Thursday. This cold front looks to set off some showers and maybe an isolated thunderstorm for areas near and NW of I-78. High temperatures will be in the mid to upper 80s. Nighttime lows will be in the 60s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A lingering upper level trough looks to become reinforced as it remains across much of the Northeast through the end of the work week before moving offshore over the weekend. At the surface, a high pressure system settles over our area on Friday and Saturday and moving offshore on Sunday, keeping the region mostly dry. Daytime temperatures in the 80s for most Friday and Saturday, with temperatures look to warm closer to 90 on Sunday. Dew points are forecast to be in the low to mid 60s before increasing to around 70 on Sunday. Overall, the most pleasant day does look to be Friday which should make for a nice forecast for the 4th of July. Next week looks to begin hot and humid for next Monday and Tuesday but there will be chances for late day showers/storms as the next cold front approaches. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...-- Changed Discussion --The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Visibility restrictions will remain possible in showers and storms into the evening hours for all terminals. Lingering showers could continue through 10-12Z, with thunder not entirely out of the question. An MVFR stratus deck could set in for the I-95 terminals, KMIV, and KACY 03-06Z and continue through the overnight. Periods of IFR ceilings are not out of the question. West- southwest wind 5 kt or less. Moderate confidence. Monday...Sub-VFR ceilings may linger through the morning hours for the I-95 terminals, KMIV, and KACY. Improvement to VFR is expected at all terminals into the afternoon hours with lingering ceilings lifting and scattering. West-southwest wind around 5 kt. Moderate confidence. Outlook... Wednesday night through Sunday...VFR. No significant weather.-- End Changed Discussion --&& .MARINE... Small Craft Advisory conditions continue until early Wednesday morning. There will also be showers/storms moving over the waters and these could produce localized wind gusts over 40 knots. Winds and seas subside below advisory criteria by daybreak Wednesday. Some lingering showers and thunderstorms possible off the Southern New Jersey and Delaware coasts. Outlook... Wednesday night into Saturday...Sub-SCA conditions expected. Rip Currents... For Wednesday, winds go more west/southwesterly and lighten to around 10 MPH or less. Seas decrease as well within the surf zone to around 2 feet. There remains a 1 foot 9 second swell from the ESE along with a frontal boundary just offshore. As a result, we will have a MODERATE risk for rip currents on Wednesday. For Thursday, winds remain light around 10 MPH or less out of the west in the morning, turning southwesterly in the afternoon. Seas decrease further, to around 1 foot. The ESE swell will be diminishing to a 1 ft 8 second swell and the frontal boundary will be further offshore. As a result, we have a LOW risk for rip currents for Thursday. For specific beach forecasts, visit weather.gov/beach/phi && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Flood Watch until 2 AM EDT Wednesday for PAZ060-070-071- 101>106. NJ...Flood Watch until 2 AM EDT Wednesday for NJZ009-010-012-013- 015>019. DE...Flood Watch until 2 AM EDT Wednesday for DEZ001. MD...None. MARINE...Small Craft Advisory until 2 AM EDT Wednesday for ANZ450. Small Craft Advisory until 4 AM EDT Wednesday for ANZ451>455. && $$ SYNOPSIS...Fitzsimmons/MJL NEAR TERM...Gorse/MJL SHORT TERM...Fitzsimmons/MJL LONG TERM...Fitzsimmons/MJL AVIATION...Cooper/MJL MARINE...MJL