FXUS61 KPHI 070008 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 808 PM EDT Sat Jul 6 2024 .SYNOPSIS... A weak front arriving into our area tonight may dissipate late Sunday into Monday. The next front arrives Tuesday night or Wednesday, followed by another cold front Thursday which may then linger in our area into next Saturday. && .NEAR TERM /THROUGH SUNDAY/... As of 6:15PM...Some minor adjustments to temperatures and dewpoints for the next few hours, but no major changes to the forecast at this time. All current heat headlines remain in effect until 8PM due to heat indicies of 100-105+ degrees. Heading into tonight, any storms should cease with the loss of diurnal heating. However, a surface trough will virtually stall over the coastal plain as some energy aloft streams up from the south and west. Some of the hi-res model guidance is depicting that a few showers or thunderstorms may make their way into the southern Delmarva and even as far north as southern New Jersey overnight. So, have increased PoPs in these areas. Outside of this potential, just a mix of partly to mostly cloudy skies with very mild overnight lows in the upper 60s to mid 70s. Some fog development is possible especially in areas which experienced rainfall earlier this afternoon. For Sunday, there will be some 'relief' from the very hot and humid conditions compared to Saturday as dew points fall back into the 60s, however will remain upwards of 70 degrees along the coast. Temperatures may be a degree or two cooler as well due to lingering cloud cover. All this equates to heat indicies around 95-99 degrees. This keeps the area below heat advisory criteria, so no heat headlines are warranted. The majority of the area should remain dry on Sunday as high pressure builds in from the west, except still cannot rule out a brief shower over southern Delaware where the axis of moisture remains highest. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... The hot and humid conditions continue, although the dew points may be lowering at least some especially Monday. Our region initially is forecast to be on the northwestern periphery of a western Atlantic ridge, although there is an upper-level low closed off tracking west and then southwest toward the Southeast U.S. coast. Our sensible weather will be driven by surface high pressure centered well to our east and keeping a southerly flow of very warm and moist air. A weak front should be across our area, although this may dissipate or become a surface trough. There may not be much convective chances through Monday as some drying looks to occur. Still cannot rule out a spotty shower or thunderstorm though Monday afternoon and evening especially near and north/west of I-95 given ample instability once again. Some guidance suggests that the surface dew points though mix down more Monday afternoon, and if this occurs then the peak heat indices would tend to stay below advisory criteria for the entire area. As we go through Tuesday, the ridge starts to shift southward some as an upper-level trough slides across the Midwest and Great Lakes regions. This will send another front into our area and help provide some increase in lift for some convection. The greater chances for this looks to be across our northern and western areas which are closer to the incoming trough and also the front. Temperatures should be a little cooler with the anticipation of more clouds and an increase in some convection, however it will still be hot and humid across the region. While peak heat indices may end up being below advisory criteria across the region, they are currently forecast to be near 100 degrees especially for the I-95 corridor down into Delmarva. While the stronger flow aloft may be displaced farther to our north and west, high moisture content air will lead to locally heavy rainfall with any stronger convection. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Summary...At least some cooling should take place for a time along with increasing convective chances as remnant tropical moisture may team up with a cold front. Synoptic Overview...An upper-level trough sliding across eastern Canada is forecast to mostly glance the Northeast U.S. Wednesday into Thursday. This drives another cold front into our area, however given the trough aloft lifting away from our region this front may stall in place. At least some tropical moisture may then increase across our area from about Thursday and Friday, as the remnant moisture from Beryl gets tangled up with the aforementioned cold front. Given the lack of a stronger trough aloft, the front may linger across our area right through Saturday. For Wednesday...Hot and humid as a weak front bisects the region and an upper-level trough slides across New England. Our region looks to be glanced by this upper-level trough, however its associated front should be enough within a hot, humid and buoyant air mass to develop some convection. This should be mostly during the afternoon and evening. Some additional tropical moisture potentially starting to stream in from the west or southwest with the remnants of Beryl may enhance the convection chances at least some. Afternoon temperatures should get into the lower 90s for many places and with dew points in the 70s, peak afternoon heat indices should top out right near 100 degrees for parts of the I-95 corridor and points south and east especially (away from the coast due to a sea breeze). For Thursday through Saturday...At least a portion of this time frame could become increasingly convectively active. Some building of a ridge is forecast overall across the western Atlantic with a front potentially stalled across our region. A shortwave trough, which could very well be the remnants of Beryl, may track near or across our area Thursday and Friday. If this were to occur, additional tropical moisture will be feed into the shearing mid level shortwave associated with it. As a result, increasing convective development could be realized with areas of very heavy rain. The unsettled conditions may linger right through Saturday as a conduit for tropical moisture and lift becomes positioned across our area. This will depend on where this zone sets up between a ridge to our east and a trough across the Mississippi Valley. The extent of the cloud cover and convection will also have an impact on temperatures. As of now, some cooling should occur for a time with increased convection, however it is forecast to remain rather humid. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR expected for most sites. VCSH possible at times for sites southeast of the I-95 corridor. KACY may see MVFR ceilings 6Z onwards. Chance of lower visibilities for KMIV/KACY with areas of fog. SW winds will gradually veer and become NW around 5 kts or less. Many sites will see winds go light and variable for periods of time. Moderate confidence. Sunday...VFR. No significant weather expected. Light and variable winds around 5 kts. Winds should become SE-S at KACY due to seabreeze development in the afternoon. High confidence. Outlook... Sunday night...VFR overall. Monday through Thursday...Some mainly afternoon showers and thunderstorms, with these possibly the most numerous on Thursday, should result in times of sub-VFR conditions. && .MARINE... Into tonight, south-southwest winds around 15-20 kt will diminish to 5-15 kt overnight. Seas around 3-4 feet. South- southwest winds around 10 kt continue for Sunday with seas around 2-3 feet. There remains the potential for some dense marine fog to develop late tonight into Sunday due to warm air over the cooler upwelled waters of the Atlantic. Outlook... Sunday night through Thursday, the conditions are anticipated to be below Small Craft Advisory criteria. However, some thunderstorms especially each afternoon and evening could produce locally gusty winds (most numerous possibly on Thursday). Rip Currents... Through this evening, south winds will average 10 to 15 mph with gusts up to 20 mph. With an onshore component in New Jersey, this results in a MODERATE risk for the development of dangerous rip currents for the Jersey Shore. Since this direction is a bit more parallel to the coast, if not a bit offshore, in Delaware, this results in a LOW risk for dangerous rip currents at the Delaware Beaches. On Sunday, winds will be lighter and a bit more onshore. This results in a MODERATE risk for the development of dangerous rip currents at the Jersey Shore, mainly south of Monmouth county. For Monmouth county and the Delaware Beaches, there is a LOW risk for the development of dangerous rip currents. For specific beach forecasts, visit weather.gov/beach/phi && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Excessive Heat Warning until 8 PM EDT this evening for PAZ070- 071-104-106. Heat Advisory until 8 PM EDT this evening for PAZ060>062- 101>103-105. NJ...Excessive Heat Warning until 8 PM EDT this evening for NJZ010- 012-013-015>023-027. Heat Advisory until 8 PM EDT this evening for NJZ001-007>009. Air Quality Alert from 11 AM to 11 PM EDT Sunday for NJZ008>010-012>015-017>020-026-027. DE...Excessive Heat Warning until 8 PM EDT this evening for DEZ001>003. MD...Excessive Heat Warning until 8 PM EDT this evening for MDZ012- 015-019-020. MARINE...None. && $$ SYNOPSIS...Gorse NEAR TERM...DeSilva/Wunderlin SHORT TERM...Gorse LONG TERM...Gorse AVIATION...DeSilva/Gorse/Wunderlin MARINE...DeSilva/Gorse/Wunderlin