textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

The Coastal Flood Warnings were pushed up to begin at 10 PM for Kent and Sussex County, DE.

KEY MESSAGES

1. Periods of rain showers will impact the area 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 and windy conditions to the parts of the region Friday and into the weekend.

3. Multiple rounds of significant tidal flooding expected for this week. Coastal Flood Warnings and Advisories issued.

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 into tonight for Delmarva and far southern New Jersey.

Massive High pressure well to the north is beginning to push its influence southward across the southern Poconos and north NJ this afternoon. Clouds are thinning as a North to Northeast flow strengthens. The north edge of the steady rains (currently across Delmarva and south NJ) continues to slowly push southward. These showers will continue tonight before largely ending by Wednesday as drier air continues to push southward.

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 and windy conditions to the parts of the region Friday and into the weekend.

A mid-level impulse currently traversing portions of the Midwest into the Ohio Valley will continue eastward towards the Eastern Seaboard tonight into Wednesday. Weak surface cyclogenesis has begun off the coast of the Carolinas, with the low expected to continue intensifying through late this week. 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, a Wind Advisory will be in effect for the immediate coastal strip from 6 AM Wednesday through midnight Wednesday night. Some gusts near 45 mph are also possible.

For late this week into this weekend, model guidance remains largely split into two camps. One camp allows the low to continue to track northeastward away from the region, and the other camp features a westward deviation of the low, or even additional surface cyclogenesis closer to the coast. Given these factors, uncertainty for Friday and beyond remains quite high, with a large range of potential outcomes. The deterministic EC and all of its ensembles continue to feature the scenario that would lead to greater impacts. The deterministic GFS remains far enough out to sea to keep impacts confined to the immediate coast with gusty winds and minimal rainfall. However, it should be noted that the GFS has trended westward somewhat this afternoon, and a few GEFS members feature solutions fairly similar to the EC. It is unclear whether this is a single-run deviation or the beginning of the development of better model consensus. For now feature PoPs in the 20-40% range along the coast Friday, expanding inland to the I-95 corridor Saturday and areawide Saturday night into Sunday. Regardless of which scenario pans out, precipitation chances and winds will be highest close to the coast and decrease with inland extent.

Sunday night into Monday, regardless of which scenario ultimately pans out, the low will begin to track away from the area, allowing rain chances to decrease and winds to subside.

KEY MESSAGE 3...Multiple rounds of significant tidal flooding expected for this week. Coastal Flood Warnings and Advisories issued.

With a slow moving coastal storm expected, 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 is expected to 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. Tidal guidance diverges greatly beyond Thursday Night at nearly all of our forecast points. Some guidance has moderate to even major flooding for the weekend while some barely has tide levels getting into minor flood stage. It all will depend on the track of the coastal storm.

Most areas within the Coastal Flood Advisory saw widespread minor flooding, especially back bay communities. The first Coastal Flood Advisories expired at 10 PM for the South Jersey coast and Delaware Coast. However, new guidance for some of our back bay gauges within the Indian River and Rehoboth Bay show water levels potentially staying near minor even towards low tide. As a result, the Coastal Flood Warning was pushed up to begin at 10 PM for Kent and Sussex County, DE. The rest of the forecast remains on track. Coastal Flood Warnings begin tomorrow afternoon through early Friday Morning for the NJ Atlantic coastline south of Barnegat Inlet. The northern Delaware Bay still has a Coastal Flood Advisory through early Friday morning.

For the tidal Delaware River as well as the rest of the NJ coast north of Barnegat Inlet and along the Delaware Bay, tide levels are expected to reach widespread minor on Wednesday and Thursday. Coastal Flood Advisories have been issued as a result. As with the areas mentioned above, widespread minor tidal flooding may continue through Friday and into the weekend.

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 the high surf, making it extremely dangerous 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 /02Z WEDNESDAY THROUGH SUNDAY/

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

Tonight...Mainly VFR except for MIV and ACY as these sites are likely to go back down to MVFR cigs by around 4z. Also expect some rain around this evening from around PHL southward but this should largely come to an end by the overnight period. Northeast winds 10 to 15 kts with some gusts to 20 kts. Medium confidence.

Wednesday...MVFR may continue into the morning at MIV and ACY but otherwise VFR. Northeast winds increasing 15 to 20 kts with gusts 25 to 30 kts. Gusts around 35 kts possible along the shore areas. High/medium confidence.

Outlook...

Wednesday night through Thursday night...Prevailing VFR conditions expected, but low clouds could lead to sub-VFR conditions at times. Gusty northeast winds.

Friday through Sunday...Uncertainty remains high, but sub-VFR conditions are possible at times in low clouds and rain. Gusty northeast to north winds.

MARINE

Small Craft Advisory conditions will continue today, with gales beginning this evening.

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.

Advisory conditions are anticipated with periods of gales likely through most of the weekend, though this will be dependent on the track of the surface low and therefore uncertainty remains high.

Visibility restrictions will be possible at times in rain and sea spray Friday through Sunday.

Rip Currents...see Key Message 4.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Coastal Flood Advisory from 10 PM Wednesday to 4 AM EDT Friday for PAZ070-071-106. NJ...Coastal Flood Advisory until midnight EDT Thursday night for NJZ016. High Risk for Rip Currents through Friday afternoon for NJZ014- 024>026. High Surf Advisory until 6 PM EDT Friday for NJZ024>026. Wind Advisory from 6 AM Wednesday to midnight EDT Wednesday night for NJZ014-024>026. Coastal Flood Advisory from 4 PM Wednesday to 1 AM EDT Friday for NJZ012>014-021. High Surf Advisory from 6 AM Wednesday to 6 PM EDT Friday for NJZ014. Coastal Flood Advisory from 10 PM Wednesday to 4 AM EDT Friday for NJZ017>019. Coastal Flood Warning from 4 PM Wednesday to 1 AM EDT Friday for NJZ020-022>027. DE...Coastal Flood Advisory until midnight EDT Thursday night for DEZ001. Coastal Flood Warning until 1 AM EDT Friday for DEZ002>004. High Risk for Rip Currents through Friday afternoon for DEZ004. High Surf Advisory until 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. Gale Warning until 6 PM EDT Thursday for ANZ431-450>455- 480>483-485.