textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated aviation discussion for 06z TAFs.

KEY MESSAGES

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

2. A cold front will cross the area 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 this evening. It'll remain off the Southeast and Middle Atlantic coasts into Saturday.

Very warn but rather dry conditions will continue through the evening as warm air advection and a strong sun angle contribute to excellent radiational warming. It will remain warm and become more 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 2PM Friday) shows that most areas North/West of I-95 and across the urban corridor have a Slight risk for severe weather on Saturday. Areas just to the S/E of the Slight risk (including south NJ and northern DE) have a Marginal risk for severe weather. Lastly, our southern Delmarva areas have just a general risk for tstms. For severe areas, Hail and Damaging winds appear to be the main threats. The timing for the strongest storms looks to be mid/late afternoon for the NW areas and near/after sunset for the Delaware Valley and areas S/E of that.

Any convection will weaken as the night goes on, limiting the severe risk for areas over the coastal plains. Guidance continues to depict paltry QPF amounts. 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 may not see any measurable 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 increasing confidence in another stretch of above normal temperatures during the second half of next week 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 /06Z SATURDAY THROUGH WEDNESDAY/

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

Through 12z...VFR. Light winds favoring a south/southwest direction around 5 kt or less. High confidence.

Today and Tonight...Primarily VFR. Showers and thunderstorms are expected to develop off to the west later today and push into our area this evening. Have maintained VCTS at KRDG/KABE from 22z-02z but kept out thunder for the I-95 corridor TAFs. Any thunderstorms, if they make it to the I-95 corridor, would likely be after 00z. It is even more unlikely that any thunderstorms make it to KACY/KMIV, but have added a VCSH category after 03z. Restrictions are likely if a thunderstorm moves over the terminal as well as a brief period of gusty winds. Have around a 30-40% chance of thunderstorms moving over KABE/KRDG between 22z-02z, a 20-30% over KPHL/KILG/KTTN/KPNE between 00z-03z, and around a 15-20% chance over KACY/KMIV. Given the lower probabilities outside of the Lehigh Valley, will keep thunder out of the TAFs at the I-95 and South Jersey terminals but will leave open the chance to add in subsequent updates.

Winds will be out of the southwest for today, increasing to around 10-15 kt with gusts 20-25 kt by midday.

Moderate confidence in the overall forecast.

Outlook...

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

Wednesday... VFR probable. Scattered showers late.

MARINE

Sub-Small Craft Advisory conditions continue tonight and Saturday morning. West to southwest winds 10 to 15 kt with gusts up to 20 kt the rest of the afternoon and tonight. Seas 2 to 3 feet tonight then, building closer to 4 feet Saturday.

For Saturday afternoon, a SCA flag was raised as winds will increase closer to 15 to 20 kts with gusts closer to 25 kts. Seas will build closer to 5ft. Fair weather into the evening.

Outlook...

Saturday Night...SCA conditions across the northern waters but remaining just below for the DE and off srn NJ waters. Showers and a few tstms overnight but then diminishing by Sunday morning.

Sunday through Tuesday...No marine headlines expected.

Rip Currents...

On Saturday, southwest winds of 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. Have maintained a MODERATE risk for the development of dangerous and life threatening rip currents at the Jersey Shore and a LOW risk at Delaware Beaches.

On Sunday, west-northwest winds of 5-15 mph. Breaking waves will be 2-3 feet. There may be an increased south-southeasterly swell around 7-8 seconds. Given the increased swell, there is a MODERATE risk for the development of dangerous and life threatening rip currents at the Jersey Shore. There is a LOW risk at Delaware beaches where it currently appears the increased swell will not have as much influence.

Ocean water temperatures are generally near 60 degrees for much of the Jersey shore and the low 60s for Delaware beaches. 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...Small Craft Advisory from 2 PM this afternoon to 6 AM EDT Sunday for ANZ450>452.