textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Aviation section updated for 18Z TAFs.

KEY MESSAGES

1. Some areas of frost tonight. Otherwise, generally tranquil weather is expected to prevail through the early portion of next week.

2. Rain is expected to return late next week.

DISCUSSION

KEY MESSAGE 1...Some areas of frost tonight. Otherwise, generally tranquil weather is expected to prevail through the early portion of next week.

High pressure will remain in place within the vicinity of our area through the middle of next week with continuing mild and dry conditions expected.

Cooler, more seasonable weather is expected for the weekend. Highs will be coolest today, in the upper 50s to low 60s, under partly cloudy skies. Partly to mostly cloudy skies from high cloud cover expected Sunday, but a bit milder with highs in the low to mid 60s.

Lows tonight and Sunday night will be mainly in the low 30s to low 40s. There is increasing probability for some frost development both nights, especially for the remaining PA and NJ zones where the growing season remains active (save for Philly and DelCo). Temperatures should fall quickly during the evening into the upper 30s and low 40s as winds decouple with the high pressure center nearby, then continue slowly falling overnight. We do anticipate thickening cirrus late tonight, which should help put the brakes on runaway radiational cooling. Nevertheless, some ares of frost development may certainly still occur in the usual colder locales prior to the thicker cloud cover arriving. Opted to go with a Frost Advisory tonight for most of the remaining PA and NJ active zones. Some patchy frost is possible across interior Delmarva as well, but dewpoints and temperatures are forecast to be a few degrees warmer there than farther north.

Scattered to broken high cloud cover will persist into early next week despite surface high pressure. Temperatures are expected to increase back to above normal values early next week, with highs in the mid 60s to low 70s and milder overnights (no frost/freeze potential).

KEY MESSAGE 2...Rain is expected to return late next week.

The stretch of dry weather is expected to come to an end late next week. It appears increasingly likely that a period or periods of rainfall will move into the area as a storm system affects the region Thursday through at least Friday. Early in the week, a cold front will be moving across the central part of the country. The parent low moves across the Great Lakes and into Canada later in the week, while a secondary low develops and moves into the southern states by mid week. This low is expected to strengthen as it moves into the Mid Atlantic and northeast states later in the week, bringing our area a likely window to end our dry streak. At this time, this appears to be just a beneficial rainfall event with no significant weather hazards anticipated.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

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

This afternoon...VFR. North to northwest winds backing more to northwest through the afternoon at speeds of around 5-10 knots. High confidence.

Tonight...VFR. Northerly winds less than 5 kts to calm. High confidence.

Sunday...VFR with just some high cloudiness around at times. Winds north to northeast early in the day backing to west/southwest by later in the day. Winds speeds expected to be light at around 5 knots or less.

Outlook...

Monday through Wednesday...VFR. No significant weather.

Thursday...Next chance for rain arrives with the potential for sub VFR conditions.

MARINE

Winds will remain near 10-20 kts across the waters through the remainder of today, weakening this afternoon and through the overnight with fair weather expected.

Outlook...

Sunday through Tuesday...No marine hazards expected. Fair weather.

Wednesday...Winds and seas may build close to advisory levels, especially overnight.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Frost Advisory from midnight tonight to 8 AM EDT Sunday for PAZ102-104-106. NJ...Frost Advisory from midnight tonight to 8 AM EDT Sunday for NJZ016>018-021-023. DE...None. MD...None. MARINE...None.