textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

A front has stalled off to the southwest. Increased onshore flow will result in cooler temperatures and eventually developing clouds through tonight. Rain looks highly likely, especially over northeast PA and northern NJ down into the Philly metro Saturday into Saturday night.

KEY MESSAGES

1. Today will be cooler with less wind and higher humidity levels compared to yesterday.

2. A low pressure system will pass through the region this weekend with widespread showers and seasonably chilly temperatures.

DISCUSSION

KEY MESSAGE 1...Today will be cooler with less wind and higher humidity levels compared to yesterday.

High pressure to our north along with low pressure east of the Canadian Maritimes has driven a backdoor cold front southward through the area. This will bring cooler temperatures this afternoon, with increasing cloud cover heading into tonight. Most rain shower activity today should remain near the front, generally confined to southeast PA, DE, and the eastern shore of MD. Expect partly to mostly cloudy skies with light NE winds and cooler temperatures compared to yesterday. Highs will be mainly in the 60s to around 70 except cooler near the coast and a bit warmer over our eastern MD counties in Delmarva since this will be closer to the front. The cooler temperatures will result in humidity levels being higher than yesterday along with lighter winds, so we don't expect there to be fire weather concerns.

Showers and a few thunderstorms are likely to develop off to the east from central PA down toward Washington DC, but these are expected to weaken reather readily as they move past the front and into a much more stable airmass locally late this afternoon.

Clouds increase further tonight with a steady east wind. Low temperatures will drop into the 40s and 50s for most. Rain chances increase west to east after midnight and especially toward daybreak Saturday as low pressure approaches.

KEY MESSAGE 2...A low pressure system will pass through the region this weekend with widespread showers and seasonably chilly temperatures.

A high pressure system to the north in eastern Canada will extend down into the Northeast this weekend. As a result, winds will be out of the east on Saturday and then turn more out of the northeast Sunday. This onshore flow will help keep temperatures on the chillier side through the weekend. Highs on Saturday will be in the mid 40s to upper 50s for most. On Sunday, highs are in the 50s.

During the weekend, a low pressure system will move into the region Saturday and then offshore Sunday. This low pressure system will bring rain showers to the area through the weekend. The most widespread coverage of the rain showers looks to be Saturday into Saturday night. Showers taper off through Sunday morning with perhaps a lingering shower into Sunday afternoon near the coast. Our weekend is shaping up to be wet, breezy, and chilly, especially Saturday. Rainfall totals this weekend, from Friday night through Sunday, will range from around 1 to 1.50 inches across much of the area. While this may be unpleasant, especially since it will be over the weekend, it is good to remember that this is a beneficial rainfall.

With cooler air wrapping in from the north late Saturday night, it is possible some wet snow mixes in over northeast PA especially at higher elevations. Little to no impactful accumulation is expected, however.

Temperatures then start to moderate for the beginning and middle of next week. Our next system arrives for Tuesday through Thursday bringing more rain showers to the area.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

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

Today...VFR with BKN mid/high-level clouds at times. Winds northeast shifting to southeast 5-10 kt. Moderate confidence.

Tonight...Mostly VFR, but with lowering cigs, possibly becoming MVFR by dawn. Showers possible in the evening will be more likely toward dawn. Winds southeast, shifting east, 5-10 kts. Moderate confidence.

Outlook...

Saturday through Saturday night...Sub-VFR conditions in SHRA, patchy fog, and low stratus. LIFR possible Saturday night.

Sunday...Lingering sub-VFR conds in SHRA/stratus in the morning. Gradual improvement through the afternoon and evening.

Sunday night through Monday night...VFR. No significant weather.

Tuesday through Wednesday...Sub-VFR conditions in SHRA/stratus.

MARINE

Sub-Small Craft Advisory conditions through tonight. Winds will generally be around 10-15 knots or less with seas generally 2 to 4 feet through tonight.

Outlook...

Saturday through Sunday night...SCA conditions will develop on Saturday with 15 to 20 kt winds with 25 to 30 kt gusts and seas 6 to 8 ft. Gale-force wind gusts, mainly on the Atlantic ocean waters, look to develop late Saturday night through early Sunday evening with seas of 6-10 feet. A Gale Watch is in effect. Winds look to drop to SCA criteria Sunday night with seas remaining at 6-8 feet. VSBY restrictions in rain and fog.

Monday through Monday night...SCA conditions likely Monday due to seas of 5-7 feet. Lingering SCA conditions early Monday night due to seas of 3-5 feet before diminishing to 2-4 feet through the night. Winds Monday night are out of the NE at 10-15 kt.

Tuesday through Wednesday...Sub-SCA conditions likely. Winds 10-15 kt and seas of 2-4 feet.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 6 AM Saturday to 6 PM EDT Sunday for ANZ430-431. Small Craft Advisory from 11 AM Saturday to 6 PM EDT Sunday for ANZ450. Small Craft Advisory from 6 AM to 6 PM EDT Saturday for ANZ451>455. Gale Watch from Saturday evening through Sunday afternoon for ANZ451>455-481>483-485.