textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Coastal Flood Discussion updated. Monmouth and Middlesex County were added to the Coastal Flood Warning.

All coastal flood headlines were extended through Saturday or Saturday Night with the exception of the Chesapeake Bay, where a Coastal Flood Advisory remains in place until 8 AM.

Updated discussion for 06z 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 potential for 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 Saturday. 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 potential for rain across the region and strong winds near the coast.

Strong high pressure remains in place across eastern Canada, and it will hold fast through today before slowly weakening. 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 that this low is still somewhat uncertain. Still, 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, strongest along the immediate coast. The Wind Advisory for the Atlantic coastal zones remains through Friday, 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. Inland winds will be gusty as well (mostly 20-30 mph). Details regarding the surf and coastal flooding can be found in the relevant Key Messages below.

The latest 12Z suite of guidance has continues with a westward trend with the track of the low moving north, most concerning during the Friday night through Saturday time frame. There is still a spread in the track guidance, especially for being only 24-48 hours out from the storm approaching the coast. Examination of the modeled upper level wind fields and jet dynamics suggest an "out to sea" track is highly unlikely. The question is how close will the low get to our coastline locally, and how strong will it be when it gets there. The latest trends suggest it could certainly get close enough Friday night and/or Saturday during its peak strength to cause high winds along our immediate coastline (storm force wind gusts over the ocean waters). The exact track and strength will also dictate the exact wind direction, and thus whether winds will be more offshore (best case scenario), shore parallel, or onshore (worst case scenario). These details remain unclear, and guidance will be monitored closely to assess and fine tune details regarding relevant impacts to our coastal areas.

Due to the potential for high winds along the immediate coast, a High Wind Watch remains in effect 6 PM Friday through 6 PM Saturday. Sustained winds of 30-40 mph with gusts up to 60 mph are not out of the realm of possibility within the watch area. If the storm tracks very close to the coast, wind gusts of 40-50 mph could potentially reach inland across the coastal plain southeast of I-95, but again, this would be a worst case scenario.

The further west trend has resulted in an increase of the probability of rain over the weekend, and PoPs continue in the high chance to likely category, 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 0.10-0.25" in the far western areas to around 1-1.50" along the northern New Jersey coast over the course of 48+ hours.

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

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 tomorrow. 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 or Saturday Night. The one exception was the Chesapeake Bay, where the Coastal Flood Advisory remains in place through 8 AM. Beyond that, high tides should only touch spotty minor.

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 PM Saturday 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 1 PM Saturday

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 Saturday. 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 Saturday. Dangerous rip currents will accompany the high surf, making it extremely dangerous to enter the water at any time through Saturday. 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 Saturday for all beaches. A High Surf Advisory is in effect for all beaches through Saturday as well.

AVIATION /03Z FRIDAY THROUGH TUESDAY/

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

Through 12z... VFR. North/northeast winds around 10 kt, gradually increasing through the night. Gusts above 20 kt possible beginning at 07z-08z for KMIV and KACY and then after 10z-11z at the I-95 terminals. Moderate confidence.

Today...VFR. North/northeast winds increase with 15-20 kt sustained winds with 20 to 30 kt gusts through the day. Gusts 30 to 35 kt possible at KMIV/KACY. Showers possible at KMIV/KACY in the afternoon and evening, but no restrictions expected. High confidence.

Tonight...Primarily VFR with the exception of KMIV/KACY. More widespread showers move in with a stratus deck moving onshore. Conditions drop down to MVFR/IFR at KMIV/KACY, with MVFR conditions possible by daybreak at the I-95 terminals. Winds out of the north/northeast around 15 kt with gusts around 25 kt. Lighter winds anticipated at KRDG/KABE, where winds will be around 10 kt. Moderate confidence.

Outlook...

Saturday thru 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 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 shower possible

Tuesday...Conditions likely return to VFR everywhere.

MARINE

Gale Warnings remain in effect for the Atlantic Ocean Waters through tonight. Small Craft Advisory remains in effect for Delaware Bay through 6 am Friday.

Outlook...

Friday thru Sunday...Widespread gales expected through at least Saturday into Saturday night. Winds and seas should lessen by Sunday. There is potential for storm force gusts near 50 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 offshore waters to a Storm Warning from 6 am Friday through 6 pm Saturday. The Gale Warning remains in effect from for the near shore coastal waters through 6 pm Friday and the Storm Watch remains in effect for the near shore coastal waters from 6 pm Friday through 6 pm Saturday. Periods of rain and seas ranging from 8-15 feet through the period.

Sunday night...Conditions expected to improve considerable. Small Craft Advisory conditions likely, with Gale Force possible early in the day.

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...Coastal Flood Advisory until 5 AM EDT Sunday for PAZ070-071- 106. NJ...Coastal Flood Advisory until 3 AM EDT Sunday for NJZ016. Coastal Flood Warning until 2 PM EDT Saturday for NJZ012>014- 020-022>027. High Risk for Rip Currents through Saturday evening for NJZ014- 024>026. High Surf Advisory until 8 PM EDT Saturday for NJZ014-024>026. Wind Advisory until 6 PM EDT Friday for NJZ014-024>026. High Wind Watch from Friday evening through Saturday afternoon for NJZ014-024>026. Coastal Flood Advisory until 5 AM EDT Sunday for NJZ017>019. Coastal Flood Advisory until 1 PM EDT Saturday for NJZ021. DE...Coastal Flood Advisory until 3 AM EDT Sunday for DEZ001. Coastal Flood Warning until 2 PM EDT Saturday for DEZ002>004. High Risk for Rip Currents through Saturday evening for DEZ004. High Surf Advisory until 8 PM EDT Saturday for DEZ004. Wind Advisory until 6 PM EDT Friday for DEZ004. High Wind Watch from Friday evening through Saturday afternoon for DEZ004. MD...Coastal Flood Advisory until 8 AM EDT Friday for MDZ015-019- 020. MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ430-431. Gale Watch from 6 AM EDT Friday through Saturday afternoon for ANZ430-431. Gale Warning until 6 PM EDT Friday for ANZ450>455. Storm Watch from Friday evening through Saturday afternoon for ANZ450>455. Gale Warning until 6 AM EDT Friday for ANZ480>483-485. Storm Warning from 6 AM Friday to 6 PM EDT Saturday for ANZ480>483-485.