textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

The aviation section has been updated.

KEY MESSAGES

1. Below normal temperatures take hold after a strong cold front moves through. Frost and Freeze products are in place for the next two nights, with Monday Night/Tuesday morning being the coldest part of the stretch. A return to above average temperatures then occurs later this week.

2. Minor tidal flooding (advisory level) along the lower Delaware Bay late tonight into early Monday morning.

DISCUSSION

KEY MESSAGE 1...Below normal temperatures take hold after a strong cold front moves through. Frost and Freeze products are in place for the next two nights, with Monday Night/Tuesday morning being the coldest part of the stretch. A return to above average temperatures then occurs later this week.

Cold air works in tonight behind a cold front. Initially, skies will be clear and winds quickly falling off, resulting in temperatures dropping quickly. Increasing cloud cover as the night goes on will prevent the bottom from falling out, though temperatures are likely to drop into the 30s. Some spots even should fall below freezing, mainly in the Poconos and northwestern NJ. In fact, Sussex County, NJ was added to the Freeze Warning for tonight, joining Carbon and Monroe County in PA.

With some moisture at the surface with Sunday's rainfall and temperatures dropping into the 34 to 36 degree range, some Frost is possible outside of the Freeze Warning. A Frost Advisory was issued for interior northern NJ (Warren/Morris/Hunterdon/Somerset) and Northampton County in PA.

After an uneventful Monday day period, high pressure will then slide over our region on Monday night before gradually shifting offshore during Tuesday. This combined with a clearing sky, winds becoming very light to calm and low dew points will result in efficient radiational cooling conditions Monday night. A widespread freeze looks to occur early Tuesday morning, and the Freeze Watch remains in place except for the immediate coast. All of our counties now have an active growing season due to the recent excessive warmth. Blooms/vegetation have quickly initiated and in some cases are ahead of schedule. Fruit trees and other cold sensitive plants already planted are the most concern. Frost formation might be somewhat limited given a much drier low-level air mass in place. Outside of the urban city centers and away from the immediate coast, temperatures are expected to drop below freezing. In some cases, well below freezing and into the low 20s.

High temperatures both Monday and Tuesday are forecast to be in the 40s and 50s across the region, which is several degrees below average. A few light rain/snow or graupel showers are possible on Monday as the core of the cold air aloft is overhead along with some mid level energy sliding through with the trough axis. The air mass below cloud base looks rather dry and therefore anything that develops could be mostly virga outside of the higher terrain. It will feel much colder Monday with a breeze and the very dry air in place. A return, southerly, flow will then become established Tuesday and continue into Wednesday. This along with an increase in warm air advection and rising heights will result in temperatures climbing back above average Wednesday through Saturday.

KEY MESSAGE 2...Minor tidal flooding (advisory level) along the lower Delaware Bay late tonight into early Monday morning.

A Coastal Flood Advisory has been issued for the lower Delaware Bay for minor tidal flooding. While winds have shifted offshore into tonight, water levels remain elevated. Being now two days removed from a new moon and a departing storm system, no additional advisory level coastal flooding is expected after tonight's minor tidal flooding ends early this morning.

AVIATION /06Z MONDAY THROUGH FRIDAY/

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

Rest of Tonight...Mainly VFR conditions. Westerly winds around 5 knots or less with periods of light and variable winds. SCT to BKN ceilings move in from west to east through 12Z. High confidence.

Monday...VFR. A few light/brief showers or sprinkles possible during the day. BKN ceilings around 5000-6000 feet. West-northwest wind gusting to around 20 knots during the afternoon. High confidence.

Monday night...VFR. A north wind around 5 knots. High confidence.

Outlook...

Tuesday through Tuesday Night...VFR. No significant weather.

Wednesday...MVFR/IFR conditions possible with some showers and low clouds around.

Wednesday Night through Friday...VFR. No significant weather.

MARINE

After a tranquil overnight period, winds pick back up for Monday. Gusts could get near 25 kt at times, mainly for Delaware Bay and adjacent ocean zones. A Small Craft Advisory may be needed for these areas.

Seas of 2 to 4 feet expected through the period.

Outlook...

Monday Night through Friday...No marine headlines expected.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Freeze Watch from late tonight through Tuesday morning for PAZ054-055-060>062-070-071-101>106. Freeze Warning until 10 AM EDT this morning for PAZ054-055. Frost Advisory until 8 AM EDT this morning for PAZ062. NJ...Freeze Watch from late tonight through Tuesday morning for NJZ001-007>010-012-013-015>023-027. Coastal Flood Advisory until 3 AM EDT early this morning for NJZ021>025. Freeze Warning until 10 AM EDT this morning for NJZ001. Frost Advisory until 8 AM EDT this morning for NJZ007>010. DE...Freeze Watch from late tonight through Tuesday morning for DEZ001>003. Coastal Flood Advisory until 3 AM EDT early this morning for DEZ002>004. MD...Freeze Watch from late tonight through Tuesday morning for MDZ012-015-019-020. MARINE...None.