859 FXUS61 KPHI 070056 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 856 PM EDT Thu Jul 6 2023 .SYNOPSIS... A front will continue across the area tonight and Friday. Another disturbance arrives for later Saturday and continues into early next week. High pressure returns for next Tuesday and into Wednesday. && .NEAR TERM /THROUGH FRIDAY/... Latest analysis depicts a very weak warm front just south of the area, pushing north. Meanwhile, a stronger cold front is crossing the Great Lakes. Aloft,a ridge axis is centered over Cape Cod, with a broad trough over the upper Midwest. A shortwave is near Washington DC with another over the Great Lakes. During the day Thursday, a relatively strong flow off the ocean resulted in relatively stable air across coastal regions, keeping these areas storm (and almost cloud) free. Further west, where the air has enough time to heat as it travels northwest over land, storms have been developing, generally isolated or rather widely scattered in nature, and fairly slow- moving, but not too stationary. This evening, storms have continued to focus well northwest of Philadelphia across SE Pennsylvania, as well as across portions of the eastern shore of Maryland and the edge of southern/western Delaware, where the atmosphere remains unstable and outflow boundaries from previous storms continue to interact. The warm, tropical airmass with deep moisture and rather substantial CAPE values but high freezing levels have produced some very high storm 'cores' that would normally suggest severe storms; however with almost no shear and not a tremendous amount of DCAPE, updrafts have been rather short- lived and have not resulted in hail reports or gusty winds more than locally 30-40 mph. While a couple of isolated pesky showers and even a brief heavy downpour may be found around the western Delmarva into southeast PA until close to midnight, model guidance supports that activity should dissipate otherwise for the bulk of tonight through much of Friday morning. Overnight, the continued onshore flow looks even more likely to spread widespread low clouds and fog across the region than last night, so fog advisories may be required again, particularly close to the coast. Lows in the upper 60s to lower 70s again. Friday, low clouds and fog dissipate with some sun by midday. Then the next cold front slowly moves into the area. Forcing and moisture look more than sufficient for widespread storms in the far west, but increasing marine layer stability should reduce storm coverage further east, wih few if any expected right on the Atlantic Coast. However, overall, with the better forcing and instability from the approaching shortwave, expect higher coverage than today, and a better chance of isolated severe weather or flooding. Highs will nudge down slightly given better cloud cover expected, with mostly high 80s to around 90. Humidity will remain quite high. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... Unsettled conditions through the weekend. Overnight lows Friday night will continue to favor the upper 60s/low 70s regionwide with muggy dew points around the same range. Warm and muggy again for Saturday with highs in the mid to upper 80s (low 80s in higher elevations) with muggy dew points in the upper 60s to low 70s. A weak mid level shortwave will lift overhead Saturday, riding along a stalled frontal boundary, providing some ascent that may trigger a few scattered showers and thunderstorms across the region in the afternoon. POPs remain steady around 20- 30%, so expect a "typical" muggy summer afternoon with scattered storms. Saturday night will be muggy and warm again with lows in the upper 60s to low 70s with nearly identical dew points. Sunday remains a very active weather day with an amplified shortwave trough digging across the Mid Atlantic and developing a surface low that will bring widespread heavy rain and the potential for some severe weather. Still some model spread regarding the exact positioning of the surface low as it moves across the region which will determine the overall balance and location of impacts from flooding and severe weather, but the takeaway here is that the chance for a busy weather day are very high. WPC continues to maintain a Slight Risk in the Excessive Rainfall Outlook for a majority of the region with a Marginal Risk along the coast. && .LONG TERM /MONDAY THROUGH THURSDAY/... Models are still in disagreement for the exact evolution for Monday, but an unsettled weather pattern will persist with a lingering frontal boundary across the region. Warm and muggy still, but chances for rain on Monday are down to around 30-40%. As we head towards the middle of next week, slightly drier air returns with dew points retreating back into the 60s for most areas (except for the shore areas). Temperatures will return above normal with more upper 80s and low 90s for the metro Philly areas and Delmarva. A little cooler for the Lehigh Valley and southern Poconos. Weather pattern begins to shift Thursday again, becoming more unsettled by the end of next week. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR to start, then low clouds/fog develop as the night progresses, starting KACY and progressing north and west. Still lots of uncertainty about how widespread low cigs get and how dense fog gets. Thus far, the CIGS along the immediate coast have been only around 010 with no fog onshore, and satellite coverage of low clouds is much less extensive than modeling would have us believe. Have slowed the timing of arrival of low clouds, and raised CIGs/VSBY a bit, but the environment still suggest some fog, locally dense, will be possible across parts of NJ and the Delmarva toward morning. Low confidence. Friday...MVFR/IFR (possibly LIFR/VLIFR in spots) to start, then improving to VFR by mid to late morning before sct TSRA develops. Expect higher coverage than today, but still not much activity near the coast. Low confidence. Outlook... Sat...Early morning for possible. VFR except in scattered showers/tstms which will be mostly during the afternoon and early evening hours. Sun/Mon...More widespread showers/tstms Sun into early Mon with MVFR probable and IFR possible. Slow improvement later Mon. Areas of fog possible overnight. Tue...Better chance for VFR. Cannot rule out an isolated or scattered shower in the afternoon, but overall conditions should be drier. && .MARINE... Sub-SCA thru Friday with light southeast winds around 10 kts and seas of 1-3 ft. Areas of dense fog possible later tonight into early Friday. Isold t-storms possible mainly on the bay this aft/eve, then again Friday. Outlook... Largely sub-SCA thru the weekend and into early next week. Typical summertime weather with scattered showers/tstms for the late afternoon and evening periods. Higher winds and waves near tstms. Rip currents... There is a LOW risk for the development of dangerous rip currents for the New Jersey and Delaware beaches through this evening. Winds will be light out of the southeast at 5-10 mph. Breaking waves will be around 2 feet with a medium period south to southeast swell. For Friday, there is a LOW risk for the development of dangerous rip currents for the New Jersey and Delaware beaches. Winds will remain light out of the east at 5-10 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... Last night's high tide showed sub-advisory conditions along the majority of the coast, but a few areas did see minor coastal flooding. The upcoming higher high tide tonight is generally expected to have lower levels, but only slightly, with one day farther removed from the new moon. Expect overall very similar levels to last night, only perhaps 1-3 inches lower, and with the new guidance, a Coastal Flood Advisory was deemed necessary for minor coastal flooding in a couple spots, namely around Cape May and Kent County DE. With continued lowering astronomical tides and otherwise similar overall sea conditions Friday, doubt we will need more advisories for Friday night. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...Coastal Flood Advisory until 4 AM EDT Friday for NJZ023-024. DE...Coastal Flood Advisory until 4 AM EDT Friday for DEZ002. MD...None. MARINE...None. && $$ SYNOPSIS...OHara/RCM NEAR TERM...Dodd/RCM SHORT TERM...MJL LONG TERM...MJL AVIATION...Dodd/MJL/RCM MARINE...MJL/RCM TIDES/COASTAL FLOODING...DODD