textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated aviation section for 18Z TAFs.

KEY MESSAGES

1. Low pressure developing well off the East Coast will strengthen and move north towards the Mid Atlantic coast and southern New England this weekend. This will bring periods of rain across the region and strong winds near the coast.

2. Multiple rounds of significant tidal flooding expected into this weekend. Coastal Flood Warnings and Advisories remain in effect.

3. Dangerous rip currents and high surf are expected at the Jersey Shore and Delaware Beaches through Sunday. Beach erosion is likely and breaching of sand dunes is possible.

DISCUSSION

KEY MESSAGE 1...Low pressure developing well off the East Coast will strengthen and move north towards the Mid Atlantic coast and southern New England this weekend. This will bring periods of rain across the region and strong winds near the coast.

Strong high pressure remains in place across eastern Canada, and it will slowly weaken into the weekend. Meanwhile, low pressure is organizing and strengthening well offshore of the North Carolina coast and it will further deepen and track northward through Saturday. The exact track of this low as it approaches our coast is still somewhat uncertain, though guidance has come into good consensus at this point that the center of the storm will lift north to about 150 miles offshore of Delmarva by sometime tonight before stalling out through Saturday. From there, the storm looks to weaken late Saturday night into Sunday as it begin to draw closer to the coast. Many models have the low tracking near or even into the coast of New Jersey, however it and it's larger synoptic wind field will be weakening considerably by this point. Any significant winds by then will likely be confined to near the center of the low and any associated convection. The remnant low will then move out to sea Sunday night and into early next week.

The strengthening pressure gradient between the approaching low and high to the north will continue to result in persistent north to northeast winds across our region through Saturday and into Saturday night, strongest along the immediate coast. The Wind Advisory for the Atlantic coastal zones remains through today, as sustained winds will likely remain near 25-35 mph with gusts of 40-50 mph at times.

The main impacts of the approaching storm still look to be primarily for Marine and Coastal-land areas, with tidal flooding and strong gusty winds along the coast and most of our tidal water bodies and waterways. However, the forecast for the inland winds has increased, and northerly winds gusting 30-45 mph are forecast to occur as early as tonight through Saturday night. Thus, a Wind Advisory was issued inland through all of Delaware, the Philly metro, and into portions of northern New Jersey. It's possible that this gets expanded into our Eastern Shore of Maryland counties, though they should be far enough west of the storm to preclude any significant concerns there. Likewise for the Lehigh Valley and far northwest New Jersey. It should be noted that strong winds may not occur during the entire duration of the advisory inland, but bands of moderate rainfall and soggy ground combined with these winds may cause tree damage and isolated power outages.

A High Wind Warning was issued for the immediate Atlantic coasts of New Jersey and Delaware, valid tonight through Saturday night. Sustained winds of 30-40 mph with gusts up to 60 mph are forecast to occur within this area. Power outages and tree damage are possible.

The wind hazards may need to be extended into Sunday, depending on the exact track of the surface low and how strong it still is once it approaches land. If it stays far enough offshore, winds Sunday may not be too concerning, but if it approaches the coast, winds gusting between 40-60 mph may be possible near the coast.

The further west trend has resulted in an increase of the probability of rain over the weekend, and PoPs continue to increase into the 70-90% range, especially for the Saturday into Sunday period. However, excessive rainfall and fresh water flooding related issues still appear unlikely at this time. Rainfall amounts range from 0.5-1" in the far western areas to around 1-2" across the Philly metro, northern New Jersey, and Delaware, and 2-4" along the northern New Jersey coast over the course of 48+ hours. Any flood impacts from the 2-4" of rain in coastal New Jersey will already be covered by the Coastal Flood Warnings.

KEY MESSAGE 2...Multiple rounds of significant tidal flooding expected into this weekend. Coastal Flood Warnings and Advisories remain in effect.

The Coastal Flood Advisory is no longer in effect for the Chesapeake Bay, and outside of spotty minor coastal flooding through this weekend, additional Coastal Flood Advisories are not expected for this area.

With a slow moving nor'easter and multiple days of strong northeast winds expected, the confidence in the threat for tidal flooding remains high. Strong onshore flow that has persisted for several days is resulting in water piling up across tidal tributaries and within back bays of coastal communities. Tidal levels will also be enhanced with astronomical tides increasing with the upcoming Full Moon Saturday. This combination of factors will lead to widespread tidal flooding, some of which will get well into Moderate stage. While not currently forecast, the threat for Major flooding is not off the table, especially getting near the full moon. Guidance is starting to come into better focus regarding tidal levels. While oceanfront tide gauges have yet to reach moderate flood stage, back bay locations have. Expecting tide levels to continue to increase as we get closer to the Full Moon. As a result, all Coastal Flood headlines were extended through Saturday night or Sunday.

For the tidal Delaware River, guidance has come up pretty significantly and our forecast actually is on the lower side of guidance. Confidence has increased in widespread minor tidal flooding continuing and the Coastal Flood Advisory was extended through Saturday Night for the tidal Delaware River. Somewhat surprising given the setup, but we cannot rule out Moderate tidal flooding getting to Delaware River communities.

For Delaware Bay communities, north/northeast winds will keep pushing water to the west side of the Bay and onto the Delaware coast. This will result in moderate tidal flooding around southern and central Delaware. The Coastal Flood Warning was extended through 2 AM Sunday for Kent and Sussex, DE. Tide levels are high enough though on the New Jersey side of the Bay to result in minor tidal flooding, even with the wind pushing water away from the NJ Delaware Bay coastline. Confidence is high enough to warrant an extension to the Coastal Flood Advisory for Cumberland through 2 AM Sunday.

As mentioned above, more north/northeasterly winds will limit the tidal flooding threat for the Chesapeake Bay. Some spotty minor tidal flooding is anticipated at Claiborne, but nothing higher than that at this time.

KEY MESSAGE 3...Dangerous rip currents and high surf are expected at the Jersey Shore and Delaware Beaches through Sunday. Beach erosion is likely and breaching of sand dunes is possible.

A nor'easter off our coast will bring strong north to northeast winds and high seas for our marine zones. Breaking waves within the surf zone of 6 to 12 feet are expected through Sunday. Dangerous rip currents will accompany the high surf, making it extremely dangerous to enter the water at any time through Sunday. The high surf and strong winds will likely result in areas of beach erosion across the Jersey Shore and Delaware Beaches. Large breaking waves in the surf zone and high water levels may result in breaching of sand dunes.

The High Risk for life threatening rip currents remains in effect through Sunday for all beaches. A High Surf Advisory is in effect for all beaches through Sunday as well.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

Rest of this afternoon...VFR. North/northeast winds 15-20 kt gusts up to 35 kt east of the Delaware River. Light rain starting after 19Z along the New Jersey coast.

Tonight...VFR west, MVFR east. Rain makes slow progress inland reaching Delaware River by 10Z. Winds out of the north/northeast around 15 kt with gusts around 25-35 kt. Lighter winds anticipated at KRDG/KABE, where winds will be around 10 kt.

Saturday...MVFR, but IFR conditions along the New Jersey coast. Areas of rain especially east of the Delaware River. Winds northerly 10 to 20 knots gusts to 30 knots. Coastal locations gusting to 40 knots.

Outlook...

Saturday night through Sunday...MVFR and even IFR conditions from I-95 TAF sites and eastward toward the coast with showers likely. VFR to MVFR conditions likely to prevail farther inland. North to northeast winds 10-20 kts with gusts 30-35 kts at times. Along the shore areas, gusts to 35-40 kts are possible.

Monday-Monday night...Conditions may begin to improve to MVFR or VFR. A few scattered showers possible.

Tuesday and Wednesday...VFR.

MARINE

Widespread gales expected through at least Saturday into Saturday night. Winds and seas should lessen by Sunday, though some gale force winds may linger near the center of the storm's track. There is potential for storm force gusts near 50-55 kts across all Atlantic waters, but this will be dependent on the track of the strengthening storm lifting north into the region Friday into Saturday.

The Storm Watch was upgraded for the coastal waters to a Storm Warning for tonight through Saturday night. The Gale Warning remains in effect from for the near shore coastal waters through 6 pm today. Gale Warning issued for Delaware bay through Saturday night. Periods of rain and seas ranging from 8-22 feet through the period.

Outlook...

Sunday night...Conditions expected to improve considerably. Small Craft Advisory conditions likely.

Monday-Monday night...Conditions continue to improve. Seas may remain above advisory levels while winds continue to diminish below 25 knots.

Tuesday...Conditions expected to be below advisory levels.

Rip Currents...Please see Key Message 3 above.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Wind Advisory from 6 PM this evening to 6 AM EDT Sunday for PAZ070-071-101>106. Coastal Flood Advisory until 5 AM EDT Sunday for PAZ070-071- 106. NJ...Coastal Flood Advisory until 3 AM EDT Sunday for NJZ016. Wind Advisory from 6 PM this evening to 6 AM EDT Sunday for NJZ008>010-012-013-015>023-027. Coastal Flood Warning until 2 AM EDT Sunday for NJZ022>025. High Risk for Rip Currents through Sunday evening for NJZ014- 024>026. High Surf Advisory until 8 PM EDT Sunday for NJZ014-024>026. Wind Advisory until 6 PM EDT this evening for NJZ014-024>026. High Wind Warning from 6 PM this evening to 6 AM EDT Sunday for NJZ014-024>026. Coastal Flood Warning until 3 PM EDT Sunday for NJZ012>014-020- 026-027. Coastal Flood Advisory until 5 AM EDT Sunday for NJZ017>019. Coastal Flood Advisory until 2 AM EDT Sunday for NJZ021. DE...Coastal Flood Advisory until 3 AM EDT Sunday for DEZ001. Wind Advisory from 6 PM this evening to 6 AM EDT Sunday for DEZ001>003. Coastal Flood Warning until 2 AM EDT Sunday for DEZ002>004. High Risk for Rip Currents through Sunday evening for DEZ004. High Surf Advisory until 8 PM EDT Sunday for DEZ004. Wind Advisory until 6 PM EDT this evening for DEZ004. High Wind Warning from 6 PM this evening to 6 AM EDT Sunday for DEZ004. MD...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ430. Gale Warning from 6 PM this evening to 6 AM EDT Sunday for ANZ430. Gale Warning until 6 AM EDT Sunday for ANZ431. Gale Warning until 6 PM EDT this evening for ANZ450>455. Storm Warning from 6 PM this evening to 6 AM EDT Sunday for ANZ450>453. Storm Warning from 6 PM this evening to 6 PM EDT Saturday for ANZ454-455. Storm Warning until 6 AM EDT Sunday for ANZ480>483. Storm Warning until 6 PM EDT Saturday for ANZ485.