Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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088 FXUS61 KPHI 130734 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 334 AM EDT Sun Jul 13 2025 .SYNOPSIS...
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An extended period of very warm, humid, and unsettled weather conditions is expected for the upcoming week. A cold front approaches the region today into Monday before slowly crossing through later Monday into Tuesday. Thereafter, the front stalls near/over the region before lifting back north as a warm front later Wednesday into Thursday. Another cold front approaches towards the end of week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Today looks mostly like a repeat of yesterday as easterly flow continues to dominate. This means more low clouds and patchy fog to start, with sun breaking through towards midday/early afternoon. Also it means that convection will be mostly confined to well inland/higher terrain locales, with I-95 and points southeast seeing just slight chance of a shower or storm. Highs well into the 80s with heat indices in the 90s. Tonight, things start to change as a front approaches. Better chance that some weakening convection from the west reaches our western lower elevation zones than the last few days during the evening, then remnant showers may cross the entire area overnight. Otherwise, looks like another round of low clouds/patchy fog by late at night. Lows mostly near or above 70.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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A cold front will approach our region from the west Monday while slowing down and undergoing frontolysis. Very slowly, this front makes its way through the region Monday into Tuesday before eventually stalling over/near the region for the remainder of the term. Diffluence will be present aloft on Monday as this front approaches, which will help support widespread convection. Upper ridging will begin to build in from the south into Tuesday, which should work to suppress coverage of convection somewhat despite the presence of the decaying frontal boundary. Some spotty showers leftover from tonight could linger for areas during the Monday morning time frame, depending on the timing of frontal movement. The main show will be a round of widespread showers and thunderstorms expected for the region Monday afternoon into the nighttime period, as the front only sags ever so sightly to the southeast with time. PoPs for the inland areas are around 50-80%, and lower toward the coast where instability and forcing will be more limited. As for the convective environment details, we will have a tropical setup with tall, skinny CAPE profiles and low shear. Low to mid level wind fields will be quite light, only around 10-15 kts at most, so deep layer shear will be low. This will support a disorganized, pulsy nature to convection, which will be influenced by meso to microscale factors such as terrain and outflow boundaries. With PWats on the order of 2.0-2.5" across the entire area and SBCAPE near 1500-2500 J/kg, we should see scattered tropical downpours with frequent lightning developing into the afternoon and evening. Given the weak flow, low shear, and low DCAPE, severe thunderstorms are unlikely. However, an isolated damaging wind gust cannot be ruled out due to water loaded downdrafts and weakened tree root systems. WPC has increased the Excessive Rainfall Outlook to a Slight Risk for much of southeast PA, Philly metro and adjacent NJ areas, and portions of Delmarva. This will be the area with the greatest risk for heavy rainfall leading to flash flooding, especially considering recent localized heavy rainfall events. A Flood Watch will need to be considered in a future update, but details on timing, convective evolution, and rainfall amounts remain a little unclear at the moment. PoPs have increased slightly across the board for Tuesday to around 40-60%. This is primarily due to a slightly slower progression of the decaying frontal boundary, however as previously mentioned, the ridge building in from the south should work to suppress coverage of convection compared to Monday. In any case, scattered showers and storms are probable Tuesday afternoon and evening again, especially along and south of where ever the frontal boundary ends up. PWats south of the front will still be near 2", so locally heavy downpours will remain possible. As with Monday, the severe thunderstorm threat will be low. Seasonable temperatures with humid conditions can be expected through this period. High temperatures will be mainly in the mid to upper 80s, with muggy nighttime low temperatures in the low to mid 70s. Fog formation is possible for areas during the late nighttime and early morning periods, but this will be dependent on precipitation occurrence and mixing.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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The stationary frontal boundary looks to plague the region before an approaching low pressure systems lifts it through as a weak warm front Wednesday/Thursday. Thereafter, another cold front approaches, looking to pass through sometime near/during the weekend (e.g, late Friday/early Saturday). The upper ridge will retreat southward some with time from the middle to end of the week, yielding a west/northwest flow aloft and southwesterly return flow ahead of the late week cold front. Unfortunately, this synoptic pattern supports a continuation of the showery and stormy summertime pattern. Chances for showers and thunderstorms Wednesday/Thursday/Friday, mainly during the afternoon and evening time frames with diurnal heating in place. End of the week/weekend cold front will probably end up being a focus for severe thunderstorm potential, but as of now, there are no particular days that stand out among the others regard severe or flash flood potential. PWats will remain high, so heavy downpours will remain possible through the entire week. The severe thunderstorm potentially will probably be more mesoscale drive than synoptic, typical of July. Another hazard to monitor will be the building heat and humidity toward the middle and end of the week with the southwesterly return flow. This won`t be a pattern for extreme temperatures, however highs in the low 90s with high humidity (dewpoints in the low to mid 70s) will result in heat indices near 100 degrees Wednesday through Friday. The hottest day currently appears to be Thursday, but this is subject to change based on how the pattern and convection evolve.
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&& .AVIATION /07Z SUNDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Thru 12Z...Low clouds developing generally with most areas seeing cigs drop to IFR or lower. The set up looks more favorable for low clouds than fog, except near the coast, including KACY, where both the lowest ceilings and lowest visibilities are likely to occur. By 09Z, expect most locations to have IFR conditions. Winds remain light (5 kt or less), generally favoring the southeasterly direction, but could be variable at times. High confidence in overall pattern, low confidence in timing/placement of development of fog and visibility restrictions. Today...Once low clouds and fog dissipate, will see a return to VFR conditions. Storms will begin to approach the area from the northwest by 00Z, but impacts mostly confined to KRDG/KABE. Moderate confidence, Tonight...VFR with a few t-storms near KRDG/KABE to start, then cigs drop to IFR again most terminals. A few showers could make their way across the rest of the terminals after 6Z. Low confidence. Outlook... Monday through Thursday...Overall, prevailing VFR conditions. However, afternoon and evening SHRA/TSRA may result in brief periods of sub-VFR conditions daily. Sub-VFR conditions are also possible overnights/early mornings due to low clouds and fog, but uncertainty remains on this potential, so confidence is low.
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&& .MARINE...
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Winds and seas should stay below Small Craft Advisory criteria through tonight. Outlook... Monday through Thursday...No marine headlines expected. Winds generally remain 15 kt or less with seas around 2-4 feet. Showers and thunderstorms are possible daily, primarily in the late afternoon and evening hours, with the greatest probability of showers and storms being on Monday. Rip Currents... Today, winds will be out of the southeast at around 10 mph with breaking waves around 1 to 2 feet. This combined with a lower southeast swell and lower wave heights results in a LOW risk for the development of dangerous and life threatening rip currents at the Jersey Shore and at Delaware Beaches. Rip currents occur often in the vicinities of jetties and piers and the speed of the currents are generally maximized at low tides. For specific beach forecasts, visit weather.gov/beach/phi
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ SYNOPSIS...RCM/Staarmann/Wunderlin NEAR TERM...Johnson/RCM SHORT TERM...Staarmann/Wunderlin LONG TERM...Staarmann/Wunderlin AVIATION...Johnson/RCM/Staarmann/Wunderlin MARINE...Johnson/RCM/Staarmann/Wunderlin