textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated wording for Server Weather possibilities on Saturday.

KEY MESSAGES

1. High pressure keeps the area dry through into much of Saturday.

2. A cold front will come through on Saturday Night, bringing scattered showers and thunderstorms, a few of which could be strong to severe.

3. Mainly dry next week with gradually warming temperatures through the week.

DISCUSSION

KEY MESSAGE 1...High pressure keeps the area dry through into much of Saturday.

High pressure over the Appalachians will slide off the Mid- Atlantic coast later today, and then will remain off the Southeast and Mid- Atlantic coasts into Saturday.

Warm air advection continues today with highs generally in the lower 90s, with the warmest temperatures over Philadelphia, the I-95 corridor, and interior portions of Delmarva. Temperatures will be a bit cooler in the southern Poconos, and in the 70s to around 80 owed to the colder ocean temperatures.

Though warm, it will be pleasant, given surface dew points will generally be in the mid 50s in the morning, mixing down to the upper 40s and low 50s this afternoon. As a result, max heat index values will be in the upper 80s to around 90.

Late day sea breezes will develop near the coasts.

Warm and muggy tonight with lows in the 60s.

Continued warm with similar high temperatures on Saturday, though dew points will begin to creep up into the upper 50s and low 60s in the afternoon, resulting in slightly higher max heat index values.

KEY MESSAGE 2...A cold front will cross the area Saturday night, bringing scattered showers and thunderstorms, a few of which could be strong to severe.

The summer-like pattern breaks with a cold front coming through late Saturday Night/early Sunday morning. Showers and thunderstorms are expected to form out to the west along the front and move towards our area. Daytime Saturday looks mainly dry but Saturday night looks to be at least somewhat active.

The latest SPC severe weather outlook (as of 8AM Friday) shows that most areas North/West of I-95 have a Marginal risk for severe weather Saturday. Further North/West (the southern Poconos and North NJ) have been upgraded to a Slight risk for severe weather. Hail and damaging winds appear to be the main threats. The timing looks most likely to be after sunset which is not favorable for widespread severe weather, but storms that develop off to the west could maintain their strength into eastern PA and northern NJ.

Any convection will weaken as the night goes on, limiting the severe risk for areas along and south/east of the I-95 corridor. Latest model guidance runs have also been trending downward with the QPF amounts, especially in areas outside of the Marginal Risk. This is a bit problematic given that this is the only real chance for measurable precipitation over the next 7 days and all four states in our CWA have either a Drought Watch or Drought Warning. Current QPF for areas north/west of the I-95 corridor is around a tenth to a quarter of an inch with higher amounts in any thunderstorms. It isn't much but its at least something. Some areas likely will not see any precipitation with this frontal passage.

Showers could linger along the coast into Sunday but should clear out once a secondary front passes later Sunday. It should mainly be dry to close out the weekend though.

KEY MESSAGE 3...Mainly dry next week with gradually warming temperatures through the week.

High pressure moves in from the north in the wake of the front, resulting in cooler temperatures in the 70s and 80s to start next week. There is some signal in medium range guidance for another stretch of above normal temperatures though as that area of high pressure slides offshore, with southerly return flow setting up. The heat will be the main thing to watch with the forecast for the latter half of next week, though there are some low precipitation chances as well. Details will come into focus over the next few days.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

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

Today...VFR. W to NW winds 5 to 10 kt, backing to the SW around 10 kt in the afternoon. Late day sea breezes possible at KACY. High confidence.

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

Outlook...

Saturday...VFR. Southwesterly wind gusts around 20-25 kt.

Saturday Night through Sunday Morning...Sub-VFR conditions likely with scattered showers and thunderstorms moving through.

Sunday Afternoon through Tuesday...VFR. No significant weather.

MARINE

Sub-Small Craft Advisory conditions continue through tonight. West to southwest winds around 10 kt this morning, becoming south 10 to 15 kt with gusts up to 20 kt this afternoon and tonight. Seas 2 to 3 feet today, building to 3 to 4 feet tonight.

Outlook...

Saturday through Saturday Night...SCA conditions possible (40-50%) as south/southwest wind gusts could get near 25 kt at times.

Sunday through Tuesday...No marine headlines expected.

Rip Currents...

Today, southwest winds around 10 mph will turn to the south at 10 to 15 mph with gusts up to 20 mph. Breaking waves will be 1 to 3 feet with a light southeast swell around 8 seconds. As a result, there is a LOW risk for the development of dangerous and life threatening rip currents for the Jersey Shore and Delaware Beaches.

On Saturday, winds will be slightly more southwest at 10 to 15 mph with gusts up to 20 mph. Breaking waves will be 2 to 3 feet with a light easterly swell around 8 seconds. This results in a MODERATE risk for the development of dangerous and life threatening rip currents at the Jersey Shore and a LOW risk 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.