textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated Aviation Section for 0Z TAFs.

KEY MESSAGES

1) Cloudy and cool weather through this evening with the return of sunshine and warmer weather on Wednesday.

2) Rounds of showers and thunderstorms return for Thursday through Saturday as a cold front approaches and crosses through the region.

DISCUSSION

KEY MESSAGE 1...Cloudy and cool weather through this evening with the return of sunshine and warmer weather on Wednesday.

A strong marine layer continues to infiltrate the region this afternoon. While some showers have passed by earlier in the day, some additional shower or perhaps thunderstorm activity cannot be ruled out across the Delmarva into this evening which lies in closer proximity to a stalled boundary. Elsewhere, expect the cool, cloudy weather to continue under mainly dry conditions.

Overnight tonight, the marine layer will likely remain in place. Given relatively moist low-levels from recent rainfall, guidance indicates that there may be some patchy areas of fog that develop overnight. Hard to pin point where exactly this may occur at this time.

Otherwise, the frontal boundary that has been nearby the past several days will finally push well south of the area on Wednesday. With high pressure building in, this will yield the return on some sunshine with temperatures in the 70s and 80s.

KEY MESSAGE 2...Rounds of showers and thunderstorms return for Thursday through Saturday as a cold front approaches and crosses through the region.

Isolated showers start to develop Wednesday night into Thursday morning before coverage starts to increase more for Thursday afternoon into Thursday night as a piece of upper-level energy moves through the region. Winds out of the southwest on Thursday will allow moisture to increase through the day. From these showers and thunderstorms, there is the potential for heavy rain. PWAT values will increase to upwards of 2 inches along with a warm cloud layer process. All of this said, these showers and thunderstorms will have the ability to be efficient rainfall producers. There is also the signal for a marginal severe weather threat. Increasing instability as temperatures reach the 80s for many along with rising humidity and some supportive lapse rates are forecast. The magnitude of shear values supporting storm organization is a little more uncertain. The primary concern with any strong to severe thunderstorm is damaging wind gusts. The Storm Prediction Center has outlooked the Eastern Shore of MD in a Marginal risk for severe thunderstorms. These showers and thunderstorms look to diminish in coverage into Thursday night.

On Friday, another round of showers and thunderstorms look to develop ahead of the cold front moving through the area into Saturday. Once again, as moisture increases ahead of the front, PWAT values look to increase upwards of 2 inches with these showers and thunderstorms having the potential to produce heavy rain. In terms of any severe weather threat, there is forecast to be instability present as temperatures reach near 90 for many along with increasing humidity. Shear values and lapse rates look more marginal currently. There remains uncertainty in how the whole set-up evolves in terms of support for severe thunderstorms. Some machine learning guidance does hint at a potential for a marginal severe weather potential though.

Depending on how quickly the front sinks south of our area on Saturday will play a role in how much shower and thunderstorm activity lingers. A high pressure system will try to build in from the north this weekend which will start to limit the precipitation potential, particularly on Sunday.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

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

Tonight...Prevailing MVFR ceilings likely to continue through much of the night. Breaks likely overnight, and where they occur, patchy fog may develop. For now will only put a little BR in KRDG TAF and keep out of rest. Northeast winds generally around 3-7 kt. Moderate confidence overall

Wednesday...Generally VFR. Winds become southwest by the afternoon around 5-10 kt. Moderate- high confidence.

Outlook...

Thursday through Saturday...Prevailing VFR, but scattered showers and storms could result in temporary restrictions to MVFR or even IFR.

Sunday...VFR. No significant weather.

MARINE

North-northeast winds around 10-15 kt are expected to continue through tonight with seas mainly around 3-4 feet. Some seas offshore may approach 5 feet overnight, but right now kept just below as guidance has waned a bit. Observations will continue to be monitored this evening.

For Wednesday, northeast winds around 15 kt in the morning will diminish and settle out of the south around 5-10 kt in the afternoon. Seas around 3-4 feet. Fair weather expected.

Outlook...

Thursday through Sunday...Conditions are anticipated to be below Small Craft Advisory criteria. Scattered showers and thunderstorms are forecast Thursday through Saturday.

Rip Currents...

For Wednesday, northeast winds will linger much of the day, strongest in the northern beaches, which when combined with moderate easterly swell at 7-8 seconds will result in a MODERATE risk of rip currents across northern NJ beaches but LOW further south where winds are a little more relaxed (DE) and/or the shoreline is more parellel to the wind (southern NJ).

For Thursday, winds are more southerly, and the moderate swell also becomes more southeasterly. This combination gives a MODERATE risk for the northern NJ beaches and DE beaches, but a LOW risk for the southern NJ beaches.

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

PHI WATCHES/WARNINGS/ADVISORIES

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