Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
Issued by NWS Mt. Holly, NJ
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283 FXUS61 KPHI 171016 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 616 AM EDT Wed Jul 17 2024 .SYNOPSIS... A ridge of high pressure will weaken across the area today. Meanwhile, a strong cold front will cross the Middle Atlantic region later today and tonight. It will be followed by high pressure for the end of the week and into the weekend. Another upper system and surface front will arrive for early next week. && .NEAR TERM /THROUGH THURSDAY/... 615 AM...The large scale pattern continues to feature a ridge of high pressure in the western Atlantic with low pressure over northern Quebec into Labrador. A cold front extends south and west from this low across the lower Great Lakes. This setup will keep the area in a SW flow with dangerous heat continuing into today. Once again, expect to see many locations seeing heat index values over 100 by the afternoon. While cloud coverage and possible storms (severe weather and hydro discussion below) may limit temperatures from getting too out of hand, dew points will likely increase a bit and linger in the low 70s during the afternoon hours, leading to continuing oppressive heat. As a result, the heat headlines continue through today given the compounded effect from numerous days with dangerous heat. For the storms later today, a slow-moving cold front will create a marathon of severe weather and hydro concerns beginning early afternoon through at least the evening hours into the overnight. Abundant instability and PWAT values over 2 inches will fuel the potential for training thunderstorms across the region. Much of the storms during the afternoon will stay north and west of the I-95 corridor with storms in the evening and nighttime largely impacting areas near and south and east of the I-95 corridor. SPC now has our entire area in a s SLIGHT Risk of severe weather (level 2 out of 5). T he biggest threat looks to be damaging winds given deep layer shear around 25 to 30 knots and ML CAPES of 1500-2000+ j/kg. The WPC has a Slight Risk for excessive rainfall for the urban corridor with a Marginal Risk for the rest of the CWA. Scattered thunderstorms are expected to continue through the first half of tonight ahead of the advancing cold front. Heavy rain and locally gusty winds will be the main threats as the line of storms work their way through the area. Storms should eventually give way to just some residual showers before tapering off from northwest to southeast overnight. Low temps will fall in the upper 60s to low 70s. The cold front should fully cross through the region by Thursday morning but will begin to slow down as it passes to our south and east. So while, the northern half of the area will begin to see some clearing, the southern half of the area (especially near the coast), will see cloud cover linger throughout the day. Isolated showers and storms may hang up along the coast as well, but overall, this chance remains uncertain/low. On the bright side, this cold front will knock down temps and humidity with highs mainly in the low to mid 80s. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... A great stretch of more pleasant weather is expected during the short term. Thursday night will be the first in a while without significant amounts of humidity and temperatures will be cool as well. Lows are expected to drop into the upper 50s/low 60s for the far NW areas while the remaining locations will have lows in the mid/upper 60s. There could be some patchy fog around too, especially in areas that get some heavier rains in the near term. Weak high pressure ridges across the Middle Atlantic region Friday. A dry day is expected with seasonable temperatures and comfortable humidity levels. High temperatures will mostly be in the low/mid 80s for the region. The dew points will be in the upper 50s/low 60s for the area, so much lower humidity levels which are welcome. Winds will be West to Northwest at 5 to 10 mph. Fair weather continues Friday night with temperatures seasonably mild, just like the previous night. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Compared to the temperatures and humidity of the week so far, the long term is going to be quite an improvement. However, the more pleasant conditions of the weekend will gradually yield to a return of uncomfortable humidity as we get towards the middle of next week. As is usually the case, more humid conditions will be across Delmarva and southern NJ while the Southern Poconos and north NJ will be drier and more comfortable. An upper trough that will bring the more seasonable conditions will move away over the weekend and the upper high will build back northward next week. Temperatures for the weekend and into next week will generally be within a few degrees of normal with Sunday being the warmest day and Tuesday the `coolest`. Highs will range from the mid/upper 80s for the NW areas and upper 80s/low 90s for Delmarva and metro Philadelphia. Lows mostly 60s N/W and low 70s S/E. Precipitation will be limited to just slight chance pops for Delmarva for the weekend. As we head into next week, the moisture begins to return from south to north so chance pops will be common for next week. Lowered pops in many areas Tue. from the NBM 50%. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas... Today...VFR in the morning before showers and thunderstorms in the afternoon and into the evening could result in sub-VFR conditions beginning by as early as around 18-20z for ABE and RDG but mainly after 21z for the I-95 TAF sites and points south/east. Winds mainly out of the southwest around 10 kts. Moderate confidence. Tonight...Sub-VFR conditions likely with scattered thunderstorms. A few storms may be severe with locally damaging winds. Storms should move out by the overnight but sub VFR cigs likely in their wake. Winds southwest around 10 knots early this evening veering to northwest 5 to 10 knots overnight. Moderate confidence. Outlook... Thursday...Some lingering sub VFR cigs early in the morning with a few lingering showers possible at MIV and ACY. Otherwise VFR. NW winds around 5 to 10 knots. Moderate confidence. Thursday night through Sunday... Mostly VFR. Patchy pre-dawn fog possible. && .MARINE... Winds and seas will be increasing into today with Small Craft Advisory conditions expected for the ocean zones beginning this afternoon. Generally expect southwest winds 20 gusting up to 25 knots with seas around 5 feet. SCA conditions continue tonight and there will also be some storms moving over the waters that could bring locally stronger winds potentially gusting over 40 knots. By Thursday, winds/seas should be sub SCA but there still could be some lingering showers and storms over the waters. Outlook... sub-SCA conditions are expected for the end of the week and into the weekend. Fair weather will be around much of the time. Scattered showers and tstms will arrive for Monday and Tuesday. Rip currents... For today, the south-southwest flow will increase to around 15- 20 mph with gusts up to 25 mph. Wave heights in the surf zone are again forecast to be around 1-3 feet with a 5-7 second period. Therefore, a MODERATE RISK for the development of dangerous and life threatening rip currents is in place for the Jersey Shore and a LOW risk is in place for the Delaware Beaches. Late day showers and thunderstorms are possible along both the Jersey Shore and Delaware Beaches. Some areas of fog at times will cause reduced visibility along the shoreline. For Thursday, winds will turn more offshore out of the west to northwest and decrease to around 10 mph. Wave heights will mainly remain around 1-2 feet with a 5-7 second period. As the winds should be weaker and directed offshore across the region, the risk for the development of dangerous and life threatening rip currents is forecast to decrease to LOW on Thursday for all coastal zones. For specific beach forecasts, visit weather.gov/beach/phi && .CLIMATE... One more day of forecast high temperatures near the record levels. Here are the records for today. Record High Temperatures (today) July 17 Site Record/Year Allentown (ABE) 99/1999 AC Airport (ACY) 99/2012 AC Marina (55N) 95/1937 Georgetown (GED) 100/2019 Mount Pocono (MPO) 91/1999 Philadelphia (PHL) 102/1988 Reading (RDG) 102/1988 Trenton (TTN) 100/1988 Wilmington (ILG) 100/1988 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Excessive Heat Warning until 8 PM EDT this evening for PAZ060>062-070-071-101>106. Heat Advisory until 8 PM EDT this evening for PAZ054-055. NJ...Excessive Heat Warning until 8 PM EDT this evening for NJZ007>010-012-013-015>023-027. Heat Advisory until 8 PM EDT this evening for NJZ001-014. DE...Excessive Heat Warning until 8 PM EDT this evening for DEZ001>003. Heat Advisory until 8 PM EDT this evening for DEZ004. MD...Excessive Heat Warning until 8 PM EDT this evening for MDZ012- 015-019-020. MARINE...Small Craft Advisory from 2 PM this afternoon to 8 AM EDT Thursday for ANZ450>455. && $$ SYNOPSIS...OHara NEAR TERM...Fitzsimmons SHORT TERM...OHara LONG TERM...OHara AVIATION...Fitzsimmons/OHara MARINE...AKL/Fitzsimmons/OHara CLIMATE...