textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Coastal Flood headlines have been issued. A Coastal Flood Advisory is in effect for tomorrow evening's high tide for coastal counties south of Barnegat Inlet and for Kent County, DE. For those same areas, a Coastal Flood Watch is now in effect for Wednesday and Thursday evening's high tide as Moderate tidal flooding is possible.

KEY MESSAGES

1. A frontal boundary south of the region will keep rain chances around through mid-week, especially across southern portions of the area.

2. A closed mid-level low ejecting from the Ohio Valley is expected to lead to the development of a surface low off the Eastern Seaboard during the middle and latter parts of this week. Depending on the track of the low, it could bring increased rainfall chances to the region.

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

DISCUSSION

KEY MESSAGE 1...A frontal boundary south of the region will keep rain chances around through mid-week, especially across southern portions of the area.

The cold front that crossed through our region Sunday Night is expected to stall to our south today, and remain there through Tuesday. It continues to look like it will lift a little closer to our region Monday Night into Tuesday morning as a warm front, but remain just south of the area. Due to the closer proximity, and a mid level short wave trough, mean that that period will have the highest chance for rain across our region. Given that our low will be on the cool side of the front, showers are going to be the main mode of any precipitation. However, isolated, embedded thunderstorms will be possible over Delmarva, particularly during the day on Tuesday.

For Wednesday into Thursday, the front should again be on the move southward, lessening rain chances across the area.

Confidence is high that temperatures will be below normal starting Tuesday. In fact, temperatures will likely struggle to get out of the 60s areawide through most of this week.

KEY MESSAGE 2...A closed mid-level low ejecting from the Ohio Valley is expected to lead to the development of a surface low off the Eastern Seaboard during the middle and latter parts of this week. Depending on the track of the low, it could bring increased rainfall chances to the region.

Most of the models came into better agreement on the track and the evolution of the coastal low through Thursday. Through this time, the center of the low should stay far enough off shore that rain chances across our region will be very low, except at immediate coastal areas. However, it looks to be a deep and intense low, so expect a large pressure gradient, even for inland areas, and thus breezy to windy conditions. For coastal areas, we could get close to wind advisory thresholds, particularly later in the day on Wednesday through Thursday.

Friday into the weekend, some models have this becoming a cutoff low and retrograding eastward. Notably though, this solution is primarily with the deterministic, physical equation models. Several ensemble members and some of the main AI models depict this low continuing northeastward. All that being said, the forecast, particularly the rain and wind forecast, is very uncertain from Friday onward.

KEY MESSAGE 3...Multiple rounds of potentially significant tidal flooding expected for this week. The first batch of Coastal Flood headlines have been issued 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.

In addition to coastal flooding, several days of onshore flow and high waves will likely result in beach erosion at the Jersey Shore and Delaware Beaches.

AVIATION /18Z MONDAY THROUGH SATURDAY/

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

For KPHL, KPNE, KILG, KTTN, KABE, and KRDG...Expect prevailing VFR conditions through the day. A brief period of MVFR ceilings is possible this afternoon for KPHL and KILG, but are expected to lift this evening. Near or after 05Z, more MVFR ceilings, and an additional round of rain will likely move through the region. Once the MVFR ceilings move in, expect that to be the controlling factor in flight category through Tuesday. Northeasterly winds around 10kt, though occasional gusts up to 20 kt will be possible. Gusts up to around 20 kts will become more frequent for daytime Tuesday.

For KMIV and KACY...Prevailing MVFR ceilings expected through Tuesday. IFR ceilings possible at times, especially after 21Z. Northeasterly wind gusts at or just above 20kt will be possible, particularly through 21Z this afternoon, then after 09Z Tuesday.

Outlook...

Wednesday through Friday...While uncertainty is high, sub-VFR conditions will remain possible at times in rain or low clouds. Gusty northeast winds are possible.

MARINE

Small Craft Advisory conditions continue to develop on the Atlantic Coastal Waters, and will develop by Tuesday Morning for the Delaware Bay. Even though this is an unusual wind direction for SCA conditions on the Bay, multiple models depict a several hour period of wind gusts at or above 25 kt, so have issued the SCA for the Bay from Tuesday morning through Tuesday Night.

Gales are looking increasingly likely for at least a period of the mid to late week. Consequently, a gale watch has been issued for all of the Atlantic forecast zones starting Tuesday Evening, and for the Delaware Bay starting Wednesday Morning. The watch currently goes through the day on Thursday, when we have the most confidence in gale conditions.

Gale conditions may linger into Friday and Saturday depending on the evolution of the coastal low, which is uncertain in this time frame.

Rip Currents...

Monday... There is a MODERATE risk for dangerous rip currents Today thanks to the onshore component of the persistent northeasterly winds. Breaking waves in the surf zone will be around 2 to 4 feet.

Tuesday...Northeasterly winds strengthen to 20 to 30 mph with wave heights in the surf zone building to 3 to 5 feet. As a result, there is a HIGH risk of rip currents both for the New Jersey shore and the Delaware Beaches.

For specific beach forecasts, visit weather.gov/beach/phi

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...Coastal Flood Advisory from 4 PM to 10 PM EDT Tuesday for NJZ020-022>027. Coastal Flood Watch from Wednesday afternoon through late Thursday night for NJZ020-022>027. High Risk for Rip Currents from Tuesday morning through Tuesday evening for NJZ014-024>026. DE...Coastal Flood Advisory from 4 PM to 10 PM EDT Tuesday for DEZ002>004. Coastal Flood Watch from Wednesday afternoon through late Thursday night for DEZ002>004. High Risk for Rip Currents from Tuesday morning through Tuesday evening for DEZ004. MD...None. MARINE...Small Craft Advisory from 5 AM Tuesday to 6 AM EDT Wednesday for ANZ430-431. Gale Watch from Wednesday morning through Thursday afternoon for ANZ430-431. Small Craft Advisory until 6 PM EDT Tuesday for ANZ450>455. Gale Watch from Tuesday evening through Thursday afternoon for ANZ450>455-480>483-485.