textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated aviation discussion for the 06Z TAFs

KEY MESSAGES

1. A weak cold front is expected on Monday.

2. A coastal low may drift near the region late in the week.

DISCUSSION

KEY MESSAGE 1...A weak cold front is expected on Monday.

In general, upper-level troughing will remain in place over much of the Northeastern US through the first half of the week. At the surface, a weak cold front is expected to pass through the region on Monday.

The first chance for showers and perhaps a storm or two will be on Monday with the passage of the weak front. Models have trended drier, however, with the probability of showers dropping to 25% or less mainly along the coast. Consensus now has Tuesday as the marginally better day for a few light showers as broad troughing aloft may bring about a 20-30% chance for precipitation. Some guidance suggest a weak surface high wedging in from off the New England coast on Tuesday as well, making for a weak backdoor front or at least prevailing onshore flow. Regardless, no significant impacts are expected.

Temperatures through Wednesday look to be fairly close to seasonal norms across the area, with highs generally in the mid 70s and lows in the mid 50s.

KEY MESSAGE 2...A coastal low may drift near the region late in the week.

By mid-week, an upper- low is expected to begin to close off near the North Carolina coast before tracking slowly northeastward away from the coast. A surface low will likely form in association with the closed upper-low off the coast as it pulls away.

There remains a high level of discrepancy across all guidance as to how close to the coast the low will get due in part to strong high pressure building in from the northwest. A more progressive low lifting to the northwest will likely result in fewer impacts. A slower moving or even stalled coastal low could result in breezier conditions that could. The latest trend has now been favoring the slower moving cut-off low, at least with the deterministic GFS/AIGFS/ECMWF/AIFS. Consensus guidance keeps it mostly dry, however, with only a 15% chance of showers Wednesday night with high pressure remaining in prevailing control across the region. There does, however, remain a level of uncertainty with the temperature forecast. At the moment, NBM consensus has temperatures warming back up to the 80s Thursday and Friday. Should this coastal low progress slower and remain nearby Thursday and Friday, the resultant breezy northeast flow will likely cause temperatures to cool down.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

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

Through Today...Prevailing VFR. A few to scattered afternoon clouds. Winds will start light and variable, before settling out of the northwest around 5-10 kt. By later this afternoon, winds will gradually veer to southwesterly. High confidence.

Tonight...Prevailing VFR. Increasing mid level cloud between 6000 and 9000 ft AGL are forecast. Winds should favor southwesterly, but wind speeds will likely be near or below 5 KT.

Outlook...

Monday through Thursday...Primarily VFR. There will be a slight chance of a few periods of sub-VFR conditions each day with a few rain showers. A thunderstorm cannot be ruled out.

MARINE

Small Craft Advisories for the Delaware Bay have been allowed to expire. A Small Craft Advisory for the Atlantic Coastal Waters from Sandy Hook to Manasquan Inlet remains in effect until 11 AM Sunday. Small Craft Advisories for the Atlantic Coastal Waters from Manasquan Inlet to Fenwick Island have been extended until 6 PM Sunday.

While wind gusts continue to diminish across marine waters, seas are expected to remain elevated from offshore low pressure through at least the first half of Sunday. Seas up to 4-7 feet will continue before gradually abating late Sunday. Otherwise, winds will largely remain between 5-15 kt before increasing up to 20 kt late in the day. Outside of SCA conditions, fair weather is expected.

Outlook...

Sunday night...Seas 3-5 feet gradually diminish below SCA criteria.

Monday and Tuesday...Winds and seas should stay below SCA criteria.

Wednesday and Thursday...There is a chance for SCA conditions primarily due to elevated seas.

Rip Currents...

On Sunday, a light northwest flow will turn to the south- southwest around 10 mph in the afternoon. There will be an easterly swell with a period around 10 seconds and breaking waves of 2 to 4 feet. As a result, there is a MODERATE risk for the development of dangerous and life threatening rip currents at the Jersey Shore and at Delaware Beaches.

On Monday, light south winds in the morning will turn east at 5 to 10 mph in the afternoon. There will be light easterly swells with a period of 6 to 9 seconds and breaking waves of 2 to 3 feet. As a result, there is a MODERATE risk for the development of dangerous and life threatening rip currents at the Jersey Shore and at Delaware Beaches.

Ocean water temperatures are in the 50s to low 60s. These chilly water temperatures can quickly cause hypothermia and physical incapacitation to anyone suddenly immersed in the water.

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

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 11 AM EDT this morning for ANZ450. Small Craft Advisory until 6 PM EDT this evening for ANZ451>455.