textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

The Aviation section updated for the 12Z TAFs.

No significant changes otherwise.

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 Appalachians will build south towards the Mid-Atlantic. Abundant sunshine on tap today with highs in the upper 80s to near 90, except in the low 80s in the higher elevations of the southern Poconos and in the 70s to near 80 at the Jersey Shore and Delaware Beaches due to the influence of the colder ocean temperatures. 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 low 60s.

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 /10Z THURSDAY THROUGH MONDAY/

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

Today...VFR/SKC. W to NW winds 5 to 10 kt, backing to the W to SW in the afternoon. Sea breezes will turn winds to the S, mostly at KACY/KMIV/KILG, but KPNE/KPHL/KTTN may be impacted by sea breezes as well late in the day. Moderate confidence due to timing of wind shifts.

Tonight...VFR/SKC. S to SW winds 5 kt or less. High confidence.

Outlook...

Friday through Saturday...Mainly VFR. A slight chance (20%) for a shower or thunderstorm at KABE/KRDG.

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

Monday...VFR. No significant weather.

MARINE

Sub-Small Craft Advisory conditions at least through tonight.

South winds 5 to 10 kt, increasing to 10 to 15 kt with gusts up to 20 kt in the afternoon as sea breezes develop. Southwest winds 10 to 15 kt tonight. Seas 2 to 3 feet.

There may be some visibility restrictions in fog developing this afternoon, mainly on the open ocean waters.

Outlook...

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...

Today, winds will be south 5 to 10 mph in the morning, increasing to 10 to 15 mph with gusts up to 20 mph in the afternoon as sea breezes develop. Breaking waves will be 1 to 3 feet with a light easterly swell with a period around 8 seconds. As a result, there is a LOW risk for the development of dangerous and life threatening rip currents at the Jersey Shore and Delaware Beaches.

On Friday, winds take on more of a southwest flow at 10 to 15 mph with gusts up to 20 mph with breaking waves of 2 to 3 feet, light easterly swells, and a period around 8 seconds. This change in wind direction is enough to result in a MODERATE risk for the development of dangerous and life threatening rip currents for the Jersey Shore in Ocean, Atlantic, and Cape May counties and a LOW risk for the development of dangerous and life threatening rip currents for the Jersey Shore in Monmouth county and at Delaware Beaches.

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.