650 FXUS61 KPHI 071439 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1039 AM EDT Fri Jul 7 2023 .SYNOPSIS... High pressure remains well offshore. A cold front will approach the area later today and cross the area tonight and Saturday before stalling nearby. Low pressure will move along the front Sunday through early Monday. High pressure arrives later Monday and controls the weather until the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... High pressure remains anchored offshore, with the center of the high almost 400 miles south and east of Nantucket Island. Onshore flow behind the high will continue to usher a humid airmass into the region. A cold front approaches from the west later today and will move over the area tonight. Another warm and humid day on tap. Highs will top off in the mid to upper 80s throughout, except in the 70s to near 80 in the southern Poconos and along the New Jersey and Delaware coasts. Surface dew points will once again be in the low 70s, resulting in heat index values in the low to mid 90s, except for the mid and upper 90s in the eastern shores of Maryland. That aforementioned surface cold front with mid-level shortwave energy approaches from the west and will be in eastern Pennsylvania by late afternoon/early evening. As this approaches, scattered showers and thunderstorms will develop by midday, and then showers and thunderstorms will become likely along and west of the I-95 corridor. Surface-based CAPE values will increase to 2000 to 2500 J/kg over southeast Pennsylvania and the eastern shores of Maryland, and from 1000 to 2000 J/kg over New Jersey and Delaware. PWATs will increase to almost 2.0 inches throughout. Although some thunderstorms may produce gusty winds of 35 to 45 mph, the main threat will be heavy rain. Winds from the surface to 500 mb will generally be less than 10 kt, so any storms that go up will not have much movement, resulting the potential for localized flooding. The Weather Prediction Center has a Marginal risk for excessive rainfall for areas along the I-95 corridor, and and a Slight Risk for excessive rainfall mainly north and west of Philadelphia. Storms taper off this evening, and it will be another warm and humid night tonight with patchy fog developing once again. Lows in the upper 60s to low 70s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Weak high pressure and what remains of the front (from Friday) lingers across the region Saturday. The airmass will remain unstable by afternoon with daytime heating, so more showers/tstms are expected. The activity will be scattered and with low/mid level winds still on the light side, severe weather will no be widespread. Highs will be a couple degrees above normal with mid/upper 80s most locations. Sunday will be wet and we will emphasize the potential for excessive rains and severe weather for the afternoon and evening time frames. Models agree on a potent short wave rotating around a developing Canadian upper low and advancing towards the Middle Atlantic. A surface low will move thru concentrating the rains across our CWA. One to two inches of rain is possible Sunday. Pops attm will be categorical for western/northern areas while low likely pops are expected for Delmarva and the shore areas of NJ. The clouds and rains will keep temperatures mostly below normal with upper 70s/low 80s for highs across the region. && .LONG TERM /MONDAY THROUGH THURSDAY/... The upper air pattern next week will feature a H5 closed low dropping across southern Canada and extending its influence over the Northern part of the U.S. Ahead of this low will be one shortwave which exits Monday before East coast ridging begins Tue and extends into Thu. More unsettled weather arrives later Thu and will probably continue into next weekend. After the showery Sun/Sun night, the upper trough and weak surface low will be edging away Mon. Since there is no strong ridge developing right away, we will still be susceptible to the typical summertime showers/tstms for Monday, but the activity will be scattered with 30% pops (South) and 40% pops (North). After that, ridging aloft should keep much of Tue/Wed dry with only isolated afternoon showers at most. Pops will ramp back to chance on Thu afternoon as low pressure and its attached fronts arrive from the west. Temperatures next week will be above normal more often than not. The mildest day will be Monday when readings will be near normal. This time of year that means mostly low/mid 80s for highs. The Tue/Wed/Thu period will be 'low-end' hot with upper 80s/low 90s most areas (Cooler for the shore and southern Poconos). The humidity levels Tue/Wed will be moderate with dew points mostly in the 60s, but Thu will have an oppressive heat & humidity combo. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today (15Z through 00Z)...Some lingering MVFR clouds slowly mixing out. Otherwise, prevailing VFR conditions through 18Z or so. SHRA/TSRA will develop after 18Z, with the main threat after 20Z. Localized IFR or lower conditions, mainly in heavy rain, though 30 kt to 40 kt wind gusts are possible. Will TEMPO TSRA at KRDG/KABE/KTTN/KPNE/KPHL/KILG. E to SE winds 5 to 10 kt. Low confidence. Tonight (00Z through 12Z)...Any SHRA/TSRA taper off in the evening. A period of VFR conditions, then sub-VFR conditions will develop in fog/stratus late tonight. Nearly calm winds. Low confidence. Outlook... Sat/Sat night... Mostly VFR. Scattered showers/tstms with lower CIGS/VSBYS. Low/medium confid. Sun/Sun night... MVFR/IFR mostly with showers/tstms. Scattered severe storms possible. Low/medium confid. Monday... Early MVFR/IFR in fog/scattered showers then VFR. Tuesday... Mostly VFR except in early morning fog. && .MARINE... Sub-Small Craft Advisory conditions today and tonight. S to SE winds 5 to 10 kt with seas 1 to 3 ft. Morning fog with VSBYs as low as 1 nm, but patchy fog with VSBYs 1 to 3 nm from late morning through tonight. Scattered showers and thunderstorms will move into Delaware Bay this afternoon. Outlook... Large scale conditions will remain below SCA levels. Scattered tstms thru the period will create localized higher winds and seas. Best chances for widespread poor conditions is Sunday/Sunday night. Rip currents... There is a LOW risk for the development of dangerous rip currents for the New Jersey and Delaware beaches today. Winds will remain out of the east at 5 to 10 mph. Breaking waves are forecast to be around 2 feet with a medium period southeasterly swell. On Saturday, the risk of rip currents remains LOW. A modest SE swell around 2 ft or so and a bit more onshore wind 10-15 mph possible in the afternoon may kick up the waves a bit more and result in more risk around low tide and locally prone portions of the coast, but not enough to raise to moderate risk at this time. && .TIDES/COASTAL FLOODING... The previous Coastal Flood Advisory has been cancelled. It appears that the upcoming high tides will not be high enough to create any further coastal flooding. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ SYNOPSIS...OHara/RCM NEAR TERM...MJL/MPS SHORT TERM...OHara LONG TERM...OHara AVIATION...MJL/MPS/OHara MARINE...MPS/OHara TIDES/COASTAL FLOODING...