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Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
Issued by NWS Mt. Holly, NJ
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321 FXUS61 KPHI 180133 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 933 PM EDT Sat Aug 17 2024 .SYNOPSIS... A warm front is forecast to lift north across the area later tonight into Sunday. A cold front is forecast to move across the area later Sunday into Sunday night and stall near the area into Monday. Another frontal boundary is expected to move across the area later Monday into Monday night, followed by a final boundary on Tuesday. High pressure is expected to control the weather for the remainder of next week. && .NEAR TERM /THROUGH SUNDAY NIGHT/... Minor tweaks were made this update, but nothing significant overall. An active and unsettled Sunday awaits with flooding and severe potential in addition to dangerous rip currents at the beaches. Previous full discussion follows... Low pressure passing over the Great Lakes will help nudge a warm front to our west slowly into the region tonight while Hurricane Ernesto passes well off the coast. Convective activity has been a bit underwhelming so far, with just some showers moving through. Things will not remain quiet for long as southerly flow will help a warm front trek northward across the forecast area early Sunday morning, helping develop an initial round of heavy showers and thunderstorms across the region. PWAT values at this point will be pushing into the 2 inch range as southerly flow will tap into some tropical moisture and supporting heavy downpours. Latest guidance suggests the heaviest rainfall from this round will be focused along the I-95 corridor and the fall line where some modest topographic influence may occur. Timing of this first round will be a few hours before and after sunrise, likely pushing north of the region by mid to late morning. A brief lull is possible late morning/early afternoon, though isolated to scattered showers and storms will remain possible during this time. Our second round of heavy rain and storms for the day looks to begin forming across eastern PA during the early/mid afternoon as the cold front associated with this system begins its eastward trek across the region. At this time, the upper level trough will begin to dig and support increased baroclinic forcing along the front. Dew points will rise into the low to mid 70s with PWATs over 2.0 inches ahead of this line of storms. As a result, rainfall forecasts of widespread 1-3 inches total are expected with local amounts of 4 inches or more possible. With this in mind, a Flood Watch was issued for the I-95 corridor and areas north & west into the Lehigh Valley and Berks County. Additionally, though daytime heating will be limited, there is a bit of uncertainty if there will be any breaks in the clouds. If any amount of daytime heating does occur, instability and lapse rates could jump and increase the severe potential for the afternoon and evening. Still a lot of uncertainty with this potential to form, but with deep layer shear around 30kts, parameters could become sufficient to support severe thunderstorms with the best conditions across southern NJ and the Delmarva. SPC has placed this region into a Slight Risk (2 of 5) for severe weather. High temperatures in the afternoon look to be in the low-80s. Heavy showers and strong storms look to persist into the evening hours and move offshore after midnight or so. Flooding and severe risks will persist until the convection departs the region. Overnight lows will cool into the mid 60s to around 70. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... On Monday, the front that moved across the area later on Sunday will remain near the area as is stalls near the coast. During the day, a secondary boundary is expected to move across the area. This will lead to an increased chance of showers and thunderstorms later in the afternoon and evening, before helping to push the initial boundary out of the area. On Tuesday, as the fronts from Sunday/Monday move farther offshore, a final boundary is expected to move across the area during the day and could bring a final push of light showers across the area. The main thing to notice on Tuesday will be the below normal temperatures && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Quiet weather is expected to dominate the long term period as high pressure will be moving in from the west through the day Wednesday. The high centers itself near the area Thursday into Friday, before shifting offshore late Friday into Saturday. Dry weather is expected for the entire extended period Wednesday through Saturday. Below normal temperatures are expected Wednesday, then they inch closer to normal but still below Thursday, returning to right around normal Friday, then back above normal Saturday. All in all, a nice second half of the week into the weekend. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR to start for most sites with showers increasing in coverage after midnight or so. Some thunderstorms could be mixed in as well, especially later tonight mainly along and west of the I-95 corridor. Expecting a mix of MVFR/IFR conditions as ceilings come down and reduced visibility in heavier downpours and/or thunderstorms. Winds out of the east/southeast around 5-10 kt. High confidence in restrictions occurring, moderate to low confidence in timing and extent of restrictions. Sunday...Conditions start out IFR/MVFR and should lift to VFR at most, if not all terminals as model guidance continues to indicate a lull in showers and thunderstorms for the midday time period. Widespread afternoon/showers and thunderstorms expected, that will continue into the night that will bring IFR conditions at times. Winds out of the southeast around 5-10 kt with gusts up to 20 kt possible at KACY. Higher gusts possible in convection as well. Moderate confidence in timing of conditions lifting to VFR. Low confidence in where bulk of showers/thunderstorms set up. Sunday Night...Restrictions possible for the night as some showers/thunderstorms linger with patchy fog developing as well. Southeast winds around 5 kt. Low confidence overall. Outlook... Monday-Monday night...Generally VFR. Chance of showers which could temporarily lead to lower conditions. West-northwest winds5-10 knots, shifting to northwest and with gusts 15-20 knots possible Monday night. Tuesday...Mostly VFR. Chance of showers which could temporarily lead to lower conditions. Northwest winds 5-10 knots, with gusts around 15-20 knots. Tuesday night-Thursday...VFR conditions expected. Northwest winds 5- 10 knots, becoming westerly on Thursday. && .MARINE... Small Craft Advisory in effect for the ocean through Sunday night as seas build to 5 to 7 feet due to larger swells from distant Hurricane Ernesto. Sub-SCA conditions expected for Delaware Bay. VSBY restrictions in showers and thunderstorms beginning Sunday morning and through Sunday night. Locally gusty winds possible with thunderstorms. Outlook... Monday-Monday night...Small Craft Advisory conditions continue through Monday night as seas remain elevated. Tuesday-Thursday...Conditions expected to lower below advisory levels Tuesday and remain below advisory levels through Thursday. Rip Currents... Large swells originating from Hurricane Ernesto are propagating toward our region through the weekend and potentially into the early portion of the week. For Sunday...South-southeast winds around 15-20mph. Breaking waves between 4-7 feet possible with a 11 to 13 second period. As a result, have maintained a HIGH risk for dangerous rip currents for both the Jersey Shore and Delaware Beaches. For Monday...Winds go more south/southwesterly and weaken to around 10-15 MPH. However, wave heights will be around 3 to 6 feet with an 11 second period. With the upcoming full moon and low tide occurring in the afternoon, have elected to extend the HIGH risk for rip currents for the Jersey Shore into Monday. With the wind direction being more offshore, and lower wave heights expected off the Delaware coast, have gone with MODERATE risk for dangerous rip currents at the Delaware Beaches. For specific beach forecasts, visit weather.gov/beach/phi && .TIDES/COASTAL FLOODING... Widespread minor coastal flooding is expected this evening, and especially tomorrow evening as an approaching Full Moon, combined with steady south/southeasterly flow, and swells from passing Hurricane Ernesto impact tidal communities. A Coastal Flood Advisory remains in effect for tonight within the tidal Delaware River and upper Delaware Bay. The Advisory was extended through tomorrow night`s high tide cycle for these locations as further minor tidal flooding is expected. In the lower Bay, and along the NJ and DE coast, only spotty minor tidal flooding is expected for tonight. Tomorrow night`s high tide will bring widespread minor tidal flooding with a Coastal Flood Advisory in effect for all tidal zones with the exception of the Chesapeake. Guidance has been underdoing high tide levels, as it usually does with passing tropical systems, and have had to nudge up the forecast slightly. Regardless, some inundation of low lying areas is possible tonight and especially tomorrow night, though not expecting flooding to get to moderate levels at this time. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Flood Watch from 2 AM EDT Sunday through late Sunday night for PAZ060>062-070-071-101>106. Coastal Flood Advisory until 5 AM EDT Monday for PAZ070-071- 106. NJ...Coastal Flood Advisory until 1 AM EDT Monday for NJZ016. Flood Watch from 2 AM EDT Sunday through late Sunday night for NJZ001-007>010-012-013-015>019. Coastal Flood Advisory until midnight EDT Sunday night for NJZ021. Coastal Flood Advisory from 6 PM Sunday to midnight EDT Sunday night for NJZ012>014-020-022>027. High Risk for Rip Currents through Monday evening for NJZ014- 024>026. Coastal Flood Advisory until 5 AM EDT Monday for NJZ017>019. DE...Coastal Flood Advisory until 1 AM EDT Monday for DEZ001. Flood Watch from 2 AM EDT Sunday through late Sunday night for DEZ001. Coastal Flood Advisory until midnight EDT Sunday night for DEZ002. Coastal Flood Advisory from 6 PM Sunday to midnight EDT Sunday night for DEZ003-004. High Risk for Rip Currents through Sunday evening for DEZ004. MD...None. MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ450>455. && $$ SYNOPSIS...Robertson NEAR TERM...Hoeflich/MJL SHORT TERM...Robertson LONG TERM...Robertson AVIATION...Hoeflich/MJL/Robertson MARINE...Hoeflich/MJL/Robertson TIDES/COASTAL FLOODING...Hoeflich