textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated Rip Currents section.

KEY MESSAGES

1. High pressure continues to result in tranquil conditions today.

2. A cold front will cross through the area on Thursday bringing the potential for a round of showers and storms.

3. Another disturbance will approach the area on Saturday night into Sunday causing another round for showers and storms.

DISCUSSION

KEY MESSAGE 1...High pressure continues to result in tranquil conditions today.

Bermuda high pressure off the Mid-Atlantic coast continues to affect the region today. A southerly pressure gradient will tighten as a cold front approaches from the west. Temperatures will be warmer today compared to Monday with highs in the mid to upper 80s. Humidity levels will also creep up with surface dew points rising into the mid and upper 60s.

High pressure over the region today will shift offshore tonight and remain offshore through Wednesday. Overall, very pleasant and tranquil conditions are expected to continue through Wednesday.

Clear skies and light winds will prevail for the rest of today with highs in the upper 70s to mid 80s. Temps tonight will be warmer than the last couple due to a combination of light southerly flow and increasing high clouds keeping temps steady in the upper 50s to upper 60s. Wednesday's highs will be a few degrees warmer than those of today as southwesterly flow ramps up in the afternoon. Breezy conditions are expected with winds gusting up to 20-25 mph for inland locations and up to 25-30 mph near the coast.

KEY MESSAGE 2...A cold front will cross through the area on Thursday bringing the potential for a round of showers and storms.

Mid-level ridging will begin to break down on Wednesday across the region as an upper-low traverses portions of the Hudson Bay and into Quebec. Thursday into Thursday night, a pronounced shortwave will pass through the region, with a cold front tracking from northwest to southeast across the region during the evening into overnight hours.

Some showers and a few embedded storms are expected late Wednesday night into early Thursday morning for mainly the Lehigh Valley, Poconos, and adjacent portions of northern NJ as a decaying line of showers originating from the eastern Great Lakes will be tracking toward the area. Some guidance is now bringing this activity as far southeast as the I-95 corridor by around daybreak Thursday. PoPs during this timeframe are generally 50-60% across the Poconos, 20-40% for the Lehigh Valley and far northern NJ, and around 20% along I-95. Elsewhere, conditions will likely remain dry.

On Thursday, the cold front will begin to approach the region by the afternoon and progress through the region into Thursday night. The strongest shear (0-6km Bulk Shear exceeding 40 kts) looks to remain across northern parts of the area and weaken with southern extent. Meanwhile, destabilization looks modest at best and confined to southern parts of the area. Given these factors, the most likely scenario is scattered showers and storms with very limited severe threat. However, some limited hydro concerns could evolve Thursday afternoon into Thursday night across mainly Delmarva into southeastern PA and southern NJ. WPC has a Marginal (1 of 4) Excessive Rainfall Outlook over these areas. Showers and storms look to clear southern parts of the forecast area by daybreak Friday.

KEY MESSAGE 3...Another disturbance will approach the area on Saturday night into Sunday causing another round for showers and storms.

Behind the front, a drier and more comfortable airmass looks to settle into the region for Friday and into at least the start of Saturday as high pressure temporary settles in.

Beyond the first half of Saturday though, the forecast becomes a bit more uncertain as the front may stall off the southern Mid- Atlantic coast or lift slowly northward towards the area with waves of low pressure riding along it. If this is to come to fruition, there may be several periods of unsettled weather for Saturday night into Sunday. At this point, the highest chances for showers and storms appears to be Saturday night with PoPs in the 40-60% range areawide.

The front looks to finally clear the area fully beyond Sunday, with warm and dry conditions to start next work week.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

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

Early this morning...VFR. S winds less than 5 kt to nearly calm. High confidence.

Today...VFR. S winds 5 to 10 kt this morning, then 10 to 15 kt with 15 to 20 kt gusts in the afternoon. High confidence.

Tonight...VFR. S-SW winds 10 kt or less. Some SHRA, perhaps a TSRA, may approach KRDG/KABE late. Moderate confidence.

Outlook...

Thursday through Thursday night...Sub-VFR conditions will be possible at times in scattered showers and storms.

Friday through Friday night...VFR. No significant weather.

Saturday through Sunday...Primarily VFR. Isolated to scattered showers and storms at times could lead to brief periods of sub- VFR conditions.

MARINE

Small Craft Advisories remain in effect for the ocean waters starting later this afternoon, then for Delaware Bay and the ocean waters tonight. South to southwest winds will increase to 15 to 20 kt with 25 to 30 kt gusts later today and tonight. Seas will be 2 to 4 feet today, then 4 to 6 feet tonight.

Outside of SCA conditions, fair weather is expected.

Outlook...

Thursday...SCA conditions to start the day with southwest winds 15-20 kt and gusts 25-30 kt. Seas 4-6 feet. Conditions are expected to gradually improve through the day, with winds and seas likely falling below SCA criteria by late afternoon.

Thursday night through Sunday...No marine headlines currently anticipated with winds below 25 kt and seas below 5 feet.

Rip Currents...

Today, south to southwest winds will start out at 5 to 10 mph and will increase to 15 to 20 mph with gusts up to 25 mph later this afternoon. Breaking waves will be 1 to 2 feet. There will be a light easterly swell with a period of 9 to 10 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 Thursday, southwest winds will range from 15 to 20 mph in the morning, gradually diminishing to 5 to 10 mph late. Breaking waves will be 1 to 3 feet. Southerly swells will increase in the afternoon with an 8 to 9 second period. Given the increased swell, there will be a MODERATE risk for the development of dangerous and life threatening rip currents for the Jersey Shore and a LOW risk for Delaware Beaches.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 6 PM this evening to 8 AM EDT Thursday for ANZ430-431. Small Craft Advisory from 4 PM this afternoon to 2 PM EDT Thursday for ANZ450>453. Small Craft Advisory from 4 PM this afternoon to 10 AM EDT Thursday for ANZ454-455.