textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Wind Advisory issued for Atlantic coastal New Jersey and Delaware for Wednesday.

Gale Watches upgraded to Gale Warnings for all coastal waters.

Aviation section updated for 12Z TAFs.

KEY MESSAGES

1. Periods of rain showers will impact the area through much of the day, and lingering into tonight for Delmarva and far southern New Jersey.

2. A strengthening surface low off the Eastern Seaboard during the middle and latter parts of this week will keep persistent northeast to north flow in place through at least Friday. Depending on the track of the low, it could bring increased rainfall chances to the region Thursday night through Saturday.

3. Multiple rounds of potentially significant tidal flooding expected for this week. The first batch of Coastal Flood headlines remain in effect with more likely to come.

4. Dangerous rip currents and high surf are expected at the Jersey Shore and Delaware Beaches through the end of the week. Significant beach erosion is also likely.

DISCUSSION

KEY MESSAGE 1...Periods of rain showers will impact the area through much of the day, and lingering into tonight for Delmarva and far southern New Jersey.

The cold front that crossed through our region Sunday night has stalled well to our south across the Carolinas. Strengthening diffluence aloft, falling heights from an approaching trough, and plenty of moisture will support periods of showers through much of the day, mainly south of I-78. Strengthening surface ridging to our north into the evening and overnight will allow some drier air to filter in, ending the chances of rain showers from the Philly metro and north. South of there, a few showers will remain possible overnight and into Wednesday morning. However, the main show for today's rain will be through midday and wind down into the afternoon and evening hours.

Confidence is high that temperatures will be below normal starting today. Highs today will be mainly in the upper 50s and 60s, perhaps briefly reaching near 70 degrees for our southern coastal areas near the warm ocean water. In fact, temperatures will likely struggle to get out of the 60s areawide through most of this week. Lows will range from the mid 40s to 50s this week.

KEY MESSAGE 2...A strengthening surface low off the Eastern Seaboard during the middle and latter parts of this week will keep persistent northeast to north flow in place through at least Friday. Depending on the track of the low, it could bring increased rainfall chances to the region Thursday night through Saturday.

Confidence continues to increase that as a mid-level trough tracks eastward out of portions of the Midwest and Ohio Valley towards the Eastern Seaboard, surface cyclogenesis will occur off the coast of the Carolinas today into tonight. The initial track of the developing low is expected to be to the northeast, well offshore. However, with a strong high centered over portions of Quebec, a sharp pressure gradient over the region will at least lead to breezy conditions beginning today through Thursday near the coast. The strongest pressure gradient, and thus winds, are forecast to occur on Wednesday into Wednesday night. It should remain mostly dry during the Wednesday through Thursday period, though some showers may linger across Delmarva Wednesday morning.

Given a consistent forecast for sustained winds 25-35 mph along the Atlantic coasts of New Jersey and Delaware on Wednesday, we have issued a Wind Advisory for the immediate coastal strip. The advisory is in effect from 6 AM Wednesday through midnight Wednesday night. Some gusts near 45 mph are also possible.

Friday and beyond, significant uncertainty remains. Models now fall into two relatively distinct camps, with one camp continuing to take the low northeast and away from the region. The other camp has the low deviating due northward or even northwestward to our region. The EC ensembles are generally clustered fairly tightly near the deterministic EC, which would favor this scenario. On the other hand, the deterministic GFS has the low continuing northeastward and the GEFS only has a few members bringing the low towards the coast.

Unfortunately, the difference in sensible weather outcomes between these two scenarios is substantial. Should the low track northeastward away from the region, any rain would be confined to the immediate coast, if any, and winds would decrease quicker. A track closer to the coast or even into the coast would lead to potentially significant impacts from rain and wind. For now, PoPs are maintained in the 20-40% range, and highest southeast of I-95. It is worth noting that there are several members in the ensemble suites which feature a middle ground scenario, where the low does deviate some but still remains fairly comfortably offshore. This scenario would lead to some impacts from rain and wind, but the inland extent would be fairly limited. We will continue to monitor trends closely as we try to nail down specific impacts and timing over the coming days.

KEY MESSAGE 3...Multiple rounds of potentially significant tidal flooding expected for this week. The first batch of Coastal Flood headlines remain in effect with more likely to come.

With a slow moving coastal storm increasingly likely, the threat for tidal flooding has increased. Strong onshore flow that is projected to last for several days will result 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 on Saturday. This combination of factors will lead to widespread tidal flooding, some of which could get to the Moderate stage. While not currently forecast, the threat for major flooding is not off the table, especially getting near the full moon.

Minor tidal flooding begins as early as tomorrow afternoon and evening for some locations. A Coastal Flood Advisory was issued for Ocean, Atlantic, and Cape May County in New Jersey and Kent and Sussex County in Delaware. For those same areas, tide levels are expected to increase for Wednesday and Thursday, potentially getting to Moderate stage. A Coastal Flood Watch was issued for Wednesday and Thursday evening's high tide. Moderate tidal flooding could even continue into the weekend. As mentioned above, cannot rule out tide levels reaching major, given the setup.

For the rest of the NJ coast north of Barnegat Inlet, tide levels are currently forecast to reach Minor on Wednesday and Thursday. Coastal Flood Advisories likely will be needed, but tide levels are currently forecast to stay below Moderate at this time and lower water levels than in areas in southern Delaware and South Jersey. The same goes for the New Jersey side of Delaware Bay and tidal Delaware River.

Widespread minor tidal flooding is not currently expected within the Chesapeake Bay. Usually, strong northeast winds do not result in tidal flooding in these areas.

KEY MESSAGE 4...Dangerous rip currents and high surf are expected at the Jersey Shore and Delaware Beaches through the end of the week. Significant beach erosion is also likely.

A coastal storm is expected to form offshore, resulting in hazardous conditions along the coast. The surface low will linger off our waters for multiple days, bringing strong winds and high seas for our marine zones. By Wednesday, breaking waves within the surf zone of 6 to 12 feet are expected. This will continue through at least Friday with the coastal storm currently progged to be right around the benchmark by the end of this week. Dangerous rip currents will accompany that high surf, making it extremely hazardous to enter the water at any time this week. The high surf and strong winds could also result in significant beach erosion for the Jersey Shore and Delaware Beaches.

With high confidence in the rip current and high surf forecast, the High Risk for life threatening rip currents remains in effect through Friday for all beaches. A High Surf Advisory remains in effect for all beaches as well beginning tonight (Wednesday for coastal Monmouth County) through at least Friday, when breaking waves within the surf zone will be around 6-12 feet.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

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

Today...MVFR developing early with low ceilings and periods of rain showers, then an improvement to VFR is likely for most terminals between 18-21Z (except for ACY/MIV). Some showers linger into late morning, mainly south. Probability of IFR is low. Northeasterly winds around 10 kts prevail with 15-20 kt gusts. Moderate confidence.

Tonight...MVFR restrictions are possible at times, mainly for ACY/MIV where MVFR ceilings are most likely to persist overnight. Elsewhere, VFR ceilings are more likely. Northeast winds around 10 kts, gusting near 20 kts possible after 06Z. Moderate confidence.

Outlook...

Wednesday through Thursday...VFR conditions should generally prevail, but low clouds at times could still lead to restrictions. Gusty northeast winds.

Thursday night through Saturday...A high degree of uncertainty remains, but restrictions will be possible. Gusty northeast to north winds.

MARINE

Small Craft Advisory conditions will continue today.

Beginning tonight, northeast winds will strengthen with gale force gusts likely developing by Wednesday morning across all coastal waters, including Delaware Bay. The strongest winds are forecast to occur Wednesday into Wednesday night, peaking around 25-35 kts with gusts up to 40 kts possible. Dangerous seas building 8-15 feet.

The Gale Watches were all upgraded to Gale Warnings for all coastal waters through Thursday. Gale force winds may linger into Friday and Saturday depending on the evolution of the coastal low, which is uncertain in this time frame.

Visibility restrictions will be possible at times in rain showers and sea spray.

Rip Currents...see Key Message 4.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...Coastal Flood Advisory from 4 PM this afternoon to 10 PM EDT this evening for NJZ020-022>027. Coastal Flood Watch from Wednesday afternoon through late Thursday night for NJZ020-022>027. High Risk for Rip Currents through Friday afternoon for NJZ014- 024>026. High Surf Advisory from 8 PM this evening to 6 PM EDT Friday for NJZ024>026. Wind Advisory from 6 AM Wednesday to midnight EDT Wednesday night for NJZ014-024>026. High Surf Advisory from 6 AM Wednesday to 6 PM EDT Friday for NJZ014. DE...Coastal Flood Advisory from 4 PM this afternoon to 10 PM EDT this evening for DEZ002>004. Coastal Flood Watch from Wednesday afternoon through late Thursday night for DEZ002>004. High Risk for Rip Currents through Friday afternoon for DEZ004. High Surf Advisory from 8 PM this evening to 6 PM EDT Friday for DEZ004. Wind Advisory from 6 AM Wednesday to midnight EDT Wednesday night for DEZ004. MD...None. MARINE...Small Craft Advisory until 6 AM EDT Wednesday for ANZ430. Gale Warning from 6 AM Wednesday to 6 AM EDT Thursday for ANZ430. Small Craft Advisory until 6 PM EDT this evening for ANZ431- 450>455. Gale Warning from 6 PM this evening to 6 PM EDT Thursday for ANZ431-450>455-480>483-485.