textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Precipitation chances have increased for this afternoon and evening. The threat for severe weather and flash flooding remains the same though with a Marginal Risk in place for both.

KEY MESSAGES

1. Another round of showers and thunderstorms develops this afternoon and continues into the early evening.

2. Drier conditions for Sunday and into the upcoming week. Above normal temperatures are expected for Tuesday and especially Wednesday.

3. Minor tidal flooding possible this weekend for coastal communities and areas around Delaware Bay.

DISCUSSION

KEY MESSAGE 1...Another round of showers and thunderstorms develops this afternoon and continues into the early evening.

A cold front is currently entering our area at this hour and will slowly sag south as the morning goes on. The front becomes nearly stationary over Delmarva this afternoon. An area of low pressure will ride along the boundary this afternoon, resulting in widespread showers and scattered thunderstorms developing for the PM hours.

No changes to both the Excessive Rainfall and Severe Weather Outlook for today. A Marginal Risk for Excessive Rainfall is in place from I-80 on south with a Marginal Risk for Severe Weather from Philadelphia on south. More instability will develop out ahead of the front due to daytime heating, focusing the severe weather threat on the southern half of the region. Shear is weak though still so a Marginal is about right. Some soundings show an inverted signature as well. This will result in the primary threat for today being damaging wind gusts for the southern half of the area. The timing remains from about 1 to 8 PM for the strong to severe thunderstorms, but showers could linger into the first half of the night.

In terms of the hydro threat, still seeing PWATs towards the higher climatological percentiles indicating a muggy and moist airmass. Periods of heavy rain are certainly possible but thinking rainfall rates will not be as impressive as a few days ago when we saw several instances of flash flooding. Storms should also be moving just quickly enough and there isn't much of a signal for training or backbuilding storms. The Marginal Risk for Excessive Rainfall remains in place, and thinking flooding should be limited to urban areas or areas that have seen significant rainfall over the past 7 days. Otherwise, we should continue to make inroads on the continuing rainfall deficit and drought.

The front should finally drop south of the region by tonight, with high pressure and drier air working in. Cannot rule out some patchy fog tonight especially over areas that see some rainfall today, though the incoming dry air should limit the fog threat a bit.

KEY MESSAGE 2... Drier conditions for Sunday and into the upcoming week. Above normal temperatures are expected for Tuesday and especially Wednesday.

Beyond today, things turn drier with an expansive area of high pressure moving in. Some short range guidance wanted to develop showers over the higher terrain in the Poconos on Sunday afternoon, but thinking anything will be very isolated and non- impactful. Otherwise, it will be dry across the area through mid-week.

Seasonable temperatures and a pleasant stretch are expected from Sunday through Monday. The heat returns for the middle of next week as ridging moves into the Mid-Atlantic. Wednesday looks to be the warmest day with temperatures potentially getting well into the 90s and heat indices flirting with Heat Advisory criteria. The above normal temperatures look to continue through the end of the week, though a cold front may lower temperatures a smidge at some point.

KEY MESSAGE 3...Minor tidal flooding possible this weekend for coastal communities and areas around Delaware Bay.

A light onshore flow sets up for this weekend, resulting in a minor push of water towards the coastline. Astronomical tides also begin to increase with the upcoming New Moon on Tuesday. This will result in elevated tides with minor tidal flooding possible beginning with the high tide Saturday evening. Guidance hints at tidal flooding continuing with the evening/nighttime high tide cycles into early next week before flow turns more southerly. However, there will be a stronger influence of astronomical tides as we get towards the New Moon which could keep elevated tides through the middle of next week. The areas most at risk of seeing minor tidal flooding are along the Atlantic Ocean coastline and within Delaware Bay. The severity looks to remain within minor levels but will monitor how things trend over the coming days. No plans for Advisories yet but it would not be a surprise for some Coastal Flood Advisories being needed for the weekend.

Cannot rule out some spotty minor tidal for communities along the Delaware River with the upcoming elevated tides. No tidal flooding is expected in our Eastern Shore zones along the Chesapeake Bay.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

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

Rest of Tonight (through 12z)...Primarily VFR but some patchy fog is likely to develop (or in KMIV's case already has developed). Not expecting fog and stratus to result in as low conditions as yesterday, but periods of MVFR conditions are possible (40-50%) over the Lehigh Valley and South Jersey terminals. Given that no new rain fell over the I-95 terminals today, things are a bit more dry at the surface and the probabilistic guidance is only around 10-15% for fog at KILG/KPHL/KPNE/KTTN which is low enough to not include in the TAF at this time. Similar to yesterday, any fog dissipates not long after daybreak and by 11z. Winds generally light and variable to calm but a light west/northwest direction may be favored at times. Moderate confidence.

Today...VFR to start and through the morning but showers and thunderstorms are expected to develop in the afternoon as a slow moving boundary sags southward. Have added TSRA and TEMPO TSRA groups at all terminals, though coverage of storms should be higher from KPHL on south. Storms should clear the area by 23z as the front pushes through. Winds will start northerly around 5 to 10 kt and then become more northeasterly by the mid to late morning, still around 5 to 10 kt though locally higher gusts are possible in thunderstorms. Moderate confidence overall.

Saturday Night...Primarily VFR. Cannot rule out some patchy fog late, especially where areas today see rainfall. However, some drier air should be moving in, which will be a limiting factor in fog development. Northeast winds around 5 to 8 kt. Moderate confidence.

Outlook...

Sunday through Wednesday...VFR. No significant weather.

MARINE

Sub-SCA conditions expected through Sunday. East/northeast winds around 10-15 kt and seas 2 to 4 feet.

Some showers and thunderstorms develop this afternoon and evening which could result in frequent lightning and a brief increase in winds as well as visibility restrictions.

Outlook...

Sunday Night through Wednesday...No marine headlines expected.

Rip Currents...

For today, flow turns more onshore, but winds will be light around 10 MPH or less. Multiple weak swell groups around, but with relatively calm surf (1 to 3 foot breakers). Rip current risk remains LOW at all shore points.

For Sunday, light onshore flow persists with winds around 10 mph. Multiple weak swell groups linger with 1 to 3 foot breakers again. Rip current risk remains LOW at all shore points.

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

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...None.