textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Small Craft Advisories extended and expanded, now in effect for all marine zones.

KEY MESSAGES

1. A high risk of rip currents and cold ocean water temperatures will create dangerous conditions tomorrow at the New Jersey and Delaware coasts.

2. Times of much needed rainfall through most of the holiday weekend and significantly cooler temperatures continuing, then some warming to end the holiday weekend.

DISCUSSION

KEY MESSAGE 1...A high risk of rip currents and cold ocean water temperatures will create dangerous conditions tomorrow at the New Jersey and Delaware coasts.

For tomorrow, an increasing east-northeast wind will range from 15 to 20 mph with 25 to 30 mph gusts. Seas will be increasing to 4-6 feet through the day. There will be a southeast 2 to 4 foot swell with a period of 10 to 13 seconds. As a result, there is a HIGH risk for the development of dangerous rip currents on Friday and a Rip Current Risk Statement has been issued for all of the New Jersey and Delaware coasts.

Ocean temperatures continue to remain mainly in the 50s to low 60s. These cold water temperatures can quickly cause hypothermia and physical incapacitation to anyone suddenly immersed in the water.

KEY MESSAGE 2...Times of much needed rainfall through most of the holiday weekend and significantly cooler temperatures continuing, then some warming to end the holiday weekend.

A front will continue to settle to our south through Friday before trying to lift back northward over the weekend. Some mid level ridging slides over our area during Friday and this will result in surface high pressure building to our north across New England. This will help keep areas around Philly northward mostly dry during the day on Friday while areas across the Delmarva and extreme southern New Jersey will see some light rain. While the surface high across New England will remain in place through Saturday, a developing low tracking up the Ohio Valley across the eastern Great Lakes will help increase warm air advection aloft and help pull the frontal boundary back northward while running into the surface high. This will lead to a robust "cold" air damming setup across the region, resulting in a cool, cloudy, and rainy weekend. Guidance is in good agreement that showers fill in by later Friday across the southern zones and then spread northward Friday night into Saturday, with a more steady rain evolving Saturday and Saturday night before tapering off Sunday. While the precipitable water values will be up to about 1.5 inches, this will be within a more stable low to mid level environment. Some heavier embedded rain is possible however the risk of thunder looks very low. This will also result in a rather chilly Saturday with a noticeable onshore breeze. The system them departs on Sunday with rain/showers ending overall, and temperatures should warm some however still be below average.

The pattern looks to remain active early next week, with some showers around on Memorial Day. It does look warmer for Memorial Day, but to what extent will depend on cloud cover and shower chances. While not great timing for the holiday weekend, our region needs more rain as a long-term drought continues. Rainfall totals through Friday night are mostly in the 0.10-0.50 inch range, and then 1-2 inches Saturday into Sunday. In total, around 1.50-2.50 inches of beneficial rainfall are expected over the next three days.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

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

Friday...Ceilings mainly VFR. Some showers start to arrive from the south later in the day, which is also expected to bring MVFR cigs across ILG/MIV/ACY. East- northeast winds 10-15 knots, with some gusts 15-25 knots. Low confidence.

Friday night...VFR gives way to MVFR as rain spreads south to north across the region. Winds E to ENE around 10 kts. Low confidence.

Outlook...

Saturday through Saturday night...MVFR/IFR conditions with rain.

Sunday...MVFR/IFR conditions with some rain ending, however conditions should then improve some.

Monday and Tuesday...Mostly VFR. Some showers still possible.

MARINE

East-northeast flow increases Friday morning. Seas will build through late Friday. The Small Craft Advisory will be in effect for all marine zones beginning Friday morning with the inclusion of the waters off coastal Monmouth County. ENE winds gust to 20-25 kts with seas 4 to 6 feet during the day Friday. Winds may begin to gust close to 30 kts overnight Friday into early Saturday morning with seas building to 5 to 7 feet.

Outlook...

Saturday through Saturday night...Small Craft Advisory conditions forecast. Brief period of Gale conditions probable.

Sunday through Monday... Small Craft Advisory conditions probable.

Tuesday...Conditions are forecast to remain below advisory criteria.

Rip Currents...

For Friday, east-northeast winds will range from 15 to 20 mph with 25 to 30 mph gusts. There will be a southeast swell with a period of 10 to 13 seconds and breaking waves of 2 to 4 feet. As a result, there is a HIGH risk for the development of dangerous rip currents on Friday and a Rip Current Risk Statement has been issued for all of the New Jersey and Delaware coasts.

On Saturday, winds are more out of the east and will range from 20 to 25 mph with 30 to 35 mph gusts. Seas will reach 6 to 8 feet with a period of 10 to 13 seconds and breaking waves of 2 to 4 feet. This should result in a HIGH risk for the development of dangerous rip currents.

Ocean temperatures continue to remain mainly in the 50s to low 60s. These cold 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...High Risk for Rip Currents through this evening for NJZ014-024>026. DE...High Risk for Rip Currents through this evening for DEZ004. MD...None. MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ430-431- 451>455. Small Craft Advisory until 6 PM EDT Saturday for ANZ450.