textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

The aviation section has been updated.

KEY MESSAGES

1. High pressure keeps the area dry through the end of the week.

2. Late this weekend into early next week, a trough will bring cooler weather and a chance for rain.

DISCUSSION

KEY MESSAGE 1...High pressure keeps the area dry through the end of the week.

High pressure over the Great Lakes will gradually build east and will be over the Appalachians late tonight. Low pressure will develop off the Mid-Atlantic coast and will track out to sea tonight. However, high pressure will keep that low well offshore. Mostly sunny and warm today with highs in the low to mid 80s with the warmest temperatures along the I-95 corridor and the coolest temperatures, generally in the low 70s, along the coasts due to the influence of the colder ocean waters. Afternoon sea breezes will develop, and onshore flow behind the sea breeze will result in locally cooler temperatures.

Mostly clear and mild tonight with lows in the 50s.

High pressure is expected to remain in control across the region through the end of the week leading to dry conditions. The pleasant weather will continue through most of Saturday with a slight chance for a shower or thunderstorm Saturday afternoon and evening mainly for the Poconos.

A gradual warming trend will also take place this week with temperatures reaching near or into the low 90s for both Friday and Saturday. Shore areas and the southern Poconos are expected to be cooler with highs in the 80s.

KEY MESSAGE 2...Late this weekend into early next week, a trough will bring cooler weather and a chance for rain.

After the period of dry and tranquil conditions, a positively tilted upper-level trough digs in from the northwest Sunday into the beginning of next week. Our surface high pressure system weakens and moves offshore over the weekend. When the trough moves in, a surface low pressure system should develop in response. There are differences between the deterministic guidance as to if this will be a closed surface low or a trough, but regardless, the net effect appears to be a cooling trend, especially going into Monday as a cold front sinks southward.

On the precipitation side of things, showers become possible Saturday night with perhaps a thunderstorm. The bulk of the precipitation is on Sunday with scattered showers developing along with some thunderstorms as our cold front moves south. Depending on the timing and how the atmospheric conditions evolve, the potential for an isolated stronger to severe thunderstorm may be possible. The exact extent of the precipitation and timing is a bit more uncertain given the variations among deterministic guidance on how the surface pattern takes shape. Beyond Sunday, a few showers may linger into Monday with the cold front remaining close to the area.

AVIATION /00Z THURSDAY THROUGH MONDAY/

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

Tonight...VFR/SKC. LGT/VRB winds. High confidence.

Thursday...VFR with some cirrus. West/northwest winds around 5-10 kts. Afternoon sea breezes potentially turn winds more southerly, most likely at KMIV and KACY. Moderate confidence.

Outlook...

Thursday night through Saturday...VFR. No significant weather.

Saturday night through Monday...Sub-VFR possible due to showers and thunderstorms.

MARINE

Sub-SCA conditions continue through Thursday.

Southeast winds 10 to 15 kt this evening. Winds turn southerly around 5 to 10 kt tonight, becoming west around 5 kt late. Southerly winds increase to around 10-15 kts during the day on Thursday with occasional gusts up to 20 kts possible.

Seas 2 to 3 feet throughout the period.

Outlook...

Thursday night through Friday...Sub-SCA conditions probable.

Saturday...SCA conditions possible Saturday night with a southwest wind 15-20 kt with gusts to 25 kt and seas of 4-5 feet.

Sunday through Monday...Another period of SCA conditions possible Sunday night into Monday with northeasterly winds potentially gusting up to 25 kts and seas around 4-6 feet.

Rip Currents...

On Thursday, winds will turn southerly and seas/swells will continue to lessen. Seas 1-3 feet, low to medium period swells, and relatively light winds will result in a LOW risk of rip currents for the New Jersey Shore and Delaware Beaches.

On Friday, southerly winds will become a bit stronger, sustained near 10 to 20 mph. For the southwestern facing portion of the New Jersey Shore, this will add a more onshore component to the winds. Thus, will go with a MODERATE risk of rip currents for Cape May, Atlantic, and Ocean Counties, and LOW elsewhere.

Ocean water temperatures are in the upper 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...None.