textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

There has been no significant changes to the forecast.

KEY MESSAGES

1) A much drier air mass will be in place through the end of the week and to start the weekend.

2) Shower and thunderstorm chances increase early next week with the potential for areas of heavy rain and strong thunderstorms.

DISCUSSION

KEY MESSAGE 1...A much drier air mass will be in place through the end of the week and to start the weekend.

Much drier air has filtered in from the northwest today in wake of a cold front. An upper-level trough will gradually weaken across the Northeast and northern Mid-Atlantic this afternoon, tonight and Friday. At the same time, surface high pressure will build across the Northeast and down into the Mid-Atlantic through Friday before shifting offshore of New England on Saturday. A northerly flow will keep a much drier air mass across our area along with cooler temperatures. The lighter low- level flow due to high pressure in place will result in some enhancement to the sea/bay breezes later today and again on Friday. High temperatures will generally range in the upper 70s to mid 80s with lows ranging from the mid 50s to mid 60s.

KEY MESSAGE 2...Shower and thunderstorm chances increase early next week with the potential for areas of heavy rain and strong thunderstorms.

As a strong upper-level ridge expands into the Plains early next week, northwesterly flow aloft will occur across much of the East. This ridge looks to get pushed back some as a potentially strong upper-level trough in eastern Canada sends spokes of energy southeastward across the Great Lakes and Northeast. Some guidance has stronger shortwave energy which results in the trough closing off across the Northeast with time during the first half of next week. This will also drive surface low pressure and a cold front our way around the Tuesday time frame. Some convection from upstream may try and get into parts of our area later Sunday, however this is less certain.

It looks like we may turn convectively active early next week, especially Tuesday into Wednesday. While there are differences among the model guidance on the timing and strength of the features diving southeastward early next week, the setup would tend to favor upstream convective development given northwesterly flow aloft. This would be enhanced if the trough aloft closes off. Deeper moisture advecting northward ahead of this feature with eventually colder air aloft arriving may result in widespread showers and some thunderstorms. While the specifics are uncertain at this time range, some areas of heavy rainfall and strong thunderstorms are possible given the overall synoptic setup that is forecast.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

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

Rest of Today...VFR. Northwest to northeast winds this afternoon around 5-10 kt, will settle out of the east-southeast late in the afternoon, primarily after 21Z. Moderate-high confidence.

Tonight...VFR. Winds may occasionally favor a southerly direction around 5 kt early in the evening, but will generally become light and variable overnight. High confidence.

Friday...VFR with increasing clouds. East-northeast winds around 7-12 kt. High confidence.

Outlook...

Saturday...VFR.

Sunday...Mainly VFR.

Monday...Times of sub-VFR conditions along with some showers and thunderstorms possible.

MARINE

No marine headlines are in effect through Friday. East winds this afternoon will become more northeasterly around 5-10 kt tonight. East-northeast winds will then increase on Friday around 10-15 kt. Seas range from 2-4 feet. Fair weather.

Outlook...

Friday through Monday...The conditions are anticipated to be below Small Craft Advisory criteria.

Rip Currents...

For today, north to northeast winds 10-20 mph will become east to southeast later this afternoon and evening. Breaking waves in the surf zone are expected to be 2-4 feet with a 7 second period. With the onshore component of the wind and multiple swell groups expected, will maintain a MODERATE risk for the development of dangerous rip currents at all beaches.

For Friday, very similar conditions to Thursday so we will go with a MODERATE risk for the development of dangerous rip currents for all beaches once again.

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

PHI WATCHES/WARNINGS/ADVISORIES

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