textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

All sections refreshed. No major changes to the forecast but added a third key message discussing the next system for later Sunday into Monday.

KEY MESSAGES

1. A cool air mass in place will likely brings frost to parts of the region tonight, particularly across the Poconos and northwestern New Jersey.

2. Tranquil weather will prevail this week continuing into the weekend with no significant weather hazards anticipated.

3. The next system will approach the area later this weekend bringing chances for rain as early as Sunday afternoon.

DISCUSSION

KEY MESSAGE 1...A cool air mass in place will likely brings frost to parts of the region tonight, particularly across the Poconos and northwestern New Jersey.

Canadian high pressure has brought a cool airmass to the area with highs this afternoon only topping out in the low to mid 60s for most areas. The high will crest over the area through this evening before gradually beginning to slide offshore later tonight. This setup will lead to very good radiational cooling conditions tonight due to the mainly clear sky and diminishing winds under the center of the high. For these reasons our forecast continues to undercut NBM temps for most areas with the mention of patchy frost in the normally cooler areas including interior southern NJ. Farther north, frost is likely to be a little more extensive so we continue with the Frost Advisory for tonight for our Pocono zones and Sussex County Nj. These area have the best chances for temperatures radiating to near freezing. That said, wouldn't be shocked if some colder locations farther south, particularly across the NJ Pine Barrens, made a run at 32 tonight.

KEY MESSAGE 2...Tranquil weather will prevail this week continuing into the weekend with no significant weather hazards anticipated.

High pressure will be in control through most of the week resulting in mostly clear/sunny skies. Following tonight's chilly weather temperatures will moderate Wednesday through Thursday as the flow turns southwesterly ahead of the next cold front. In fact highs by Thursday afternoon look to reach the middle to upper 70s for most of the area. The cold front moves through by late Thursday as a dry front and will be followed by high pressure re-establishing itself over the area for Friday through at least Saturday with seasonable temperatures.

KEY MESSAGE 3...The next system will approach the area later this weekend bringing chances for rain as early as Sunday afternoon.

High pressure shifts offshore Sunday as the next low pressure system approaches from the south and west. There are some model differences regarding this system and its arrival time in the area. The ECMWF has the rain shield from the system arriving in the areas beginning Sunday afternoon while most of our other guidance holds the system off until Sunday night into Monday. In any event, the system should be fairly progressive but will likely have significant moisture with it (PWATs potentially reaching around 2 inches) so the rain could be heavy at times with the potential for some areas to see 1-2 inches.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

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

Rest of today...VFR. Northwest winds around 5 to 10 kt with some occasional gusts of 15-20 knots possible. High confidence.

Tonight...VFR. Winds becoming light/variable. High confidence.

Wednesday...VFR. Winds light/variable becoming southwest 5-10 kts. High confidence.

Outlook...

Wednesday night through Saturday...VFR. No significant weather expected.

Sunday...VFR to start but restrictions possible by late day depending on on when next system arrives with low stratus and rain.

MARINE

Relatively tranquil over the waters through tonight. Generally expect northwest winds around 10-15 knots with these winds diminishing to around 5 knots tonight. Seas around 2-3 feet this afternoon diminishing to around 2 feet or less for tonight.

For Wednesday, winds will be southwest and increase to 15-20 knots by late day into Wednesday night. Some gusts of 20 to 25 knots will be possible so it will be at least close to Small Craft Advisory levels. However given that it's marginal, we are holding off on issuing a Small Craft Advisory at least at this point.

Outlook...

Thursday through Sunday...No marine hazards expected.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Frost Advisory from 11 PM this evening to 9 AM EDT Wednesday for PAZ054-055. NJ...Frost Advisory from 11 PM this evening to 9 AM EDT Wednesday for NJZ001. DE...None. MD...None. MARINE...None.