textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated Key Message 1 and the Aviation Section for 00Z TAFs.

KEY MESSAGES

1. A cold front this evening will bring scattered showers and cooler temperatures for tonight and into the weekend.

2. Showers are expected to impact portions of the region Sunday and Sunday night, followed by much cooler temperatures during the first half of next week.

3. Canadian high pressure will bring much cooler temperatures during the first half of next week, including some potential for frost near and north of I-78 Tuesday night.

DISCUSSION

KEY MESSAGE 1...A cold front this evening will bring scattered showers and cooler temperatures for tonight and into the weekend.

A cold front will push through the area this evening, and will be offshore and south of the forecast area before midnight. Scattered showers and perhaps a few rumbles of thunder are expected to accompany the frontal passage. PoPs are mainly in the 50-60% range area wide, and were adjusted to match closer to the latest guidance's timing of the frontal progression.

Some anafrontal showers and/or sprinkles will likely linger overnight and perhaps into the first half of Saturday, mainly south of the I-95 corridor to as far north as Philly. Event total rainfall through Saturday will not amount to much, mainly around 0.10-0.20" at most. Saturday afternoon should be mainly dry area wide with decreasing cloud cover, except for southern Delaware and Cape May.

High pressure will build into the region from the north during Saturday. Mainly cloudy skies along and southeast of I-95 early will given way to clearing skies by afternoon for most of the area. Mostly cloudy skies will likely remain the theme all day across Delmarva and extreme southern New Jersey though, where the showers may linger into the early afternoon. Seasonable, but slightly below normal temperatures expected with highs in the upper 60s to low 70s.

KEY MESSAGE 2...Showers are expected to impact portions of the region Sunday and Sunday night.

Low pressure developing along the stalled frontal boundary to our south Sunday and Sunday night will provide another round of showers across portions of the region. The timing of the showers will be focused during the afternoon hours Sunday, but could begin near/south of Philly in the morning and linger area wide into the evening or overnight hours. PoPs have increased some, and now range from around 30-40% along and north of I-80 to around 50-70% within the I-95 corridor and Philly metro, to 70-90% across Delmarva and far southern New Jersey. The latest QPF forecast ranges from around 0.10" in the far north, to about 0.25" within the I-95 corridor and Philly metro, to 0.50-1" across Delmarva and far southern New Jersey. It's possible the showers don't make it much farther northwest than the I-95 corridor. There still remains spread in the guidance as to exactly how far inland the showers will make it.

Given overcast skies, easterly winds, and showers, temperatures Sunday will be cooler with highs likely only reaching the low to mid 60s in many areas.

KEY MESSAGE 3...Canadian high pressure will bring much cooler temperatures during the first half of next week, including some potential for frost near and north of I-78 Tuesday night.

Canadian high pressure and a much cooler air mass will then build into the region starting Monday into Tuesday. Monday will remain mild with highs within a few degrees of 70, though a northwest breeze will make it feel cooler. Some lingering clouds early should give way to mostly sunny skies later in the day. Lows mainly in the 40s to low 50s Monday night.

High temperatures Tuesday are only in the low 60s for much of the region, which is upwards of 10 degrees below normal. Tuesday will feature clear and sunny skies though. Some areas of frost are possible by Tuesday night into Wednesday morning, especially north of I-78. Forecast lows are in the mid 30s north of I-78, and in the low to mid 40s elsewhere.

As cold advection wanes by midweek, the air mass will begin to modify and trend notably warmer by Thursday and into Friday. Highs will trend closer to normal near 70 degrees.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

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

Tonight...VFR conditions will prevail following any brief MVFR conditions in showers with the FROPA. Some showers lingering overnight, mainly for MIV/ACY. These are unlikely to cause any restrictions, though some very brief MVFR restrictions cannot be ruled out for MIV/ACY. West winds early, becoming northerly behind the FROPA around 5-10 kt. Moderate-high confidence overall.

Saturday...VFR conditions expected. Showers lingering at MIV/ACY through early afternoon, otherwise dry. Cannot completely rule out some brief MVFR conditions with this activity early, but probability is too low to include TAF mention at this time. North winds early shifting northeast and then more east in the afternoon around 5-10 kt. Moderate-high confidence overall.

Outlook...

Saturday night...VFR but patchy rural fog possible.

Sunday...Widespread MVFR with IFR possible S/E. Frequent showers Delmarva and south NJ. For N/W areas more VFR CIGS with some MVFR in scattered showers.

Monday through Wednesday...VFR. Gusty winds possible Monday. Fair weather expected.

MARINE

No marine headlines expected through Saturday. Sub-SCA expected with scattered showers this evening. Winds will be southwest before shifting northwest this evening behind a cold front. Continued sub-SCA conditions are expected on Saturday with high pressure moving in from the north. Scattered showers possible early for Southern NJ/Delaware and Delaware Bay waters. North winds becoming 10 to 15 kt with gusts around 20 kt.

Outlook...

Saturday night through Sunday...Advisory conditions possible. Low pressure will move along a stalled front and bring showers across the waters at times. Easterly winds increasing to near 15-20 kts by Sunday morning, with some gusts up to 25 kts possible.

Sunday night into next week. High pressure builds across the waters with Fair weather expected. While winds and seas remain below advisory levels much of the time, some 4-5 ft seas and Gusts around 25 kts are possible late Monday and into Tuesday.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...None.