Marine Weather and Tide Forecast for Millbourne, PA

KEY MESSAGES
1. While the Tornado Watch is no longer in effect, there remains the potential for strong to severe thunderstorms with the passage of the cold front later tonight. Even outside of storms, strong winds are likely, especially closer to the coast.

2. Some minor coastal flooding along the back bays with high tide this evening.

3. Cold and dry for the middle of the week, then temperatures moderate late this week and through this weekend.

DISCUSSION
KEY MESSAGE 1...While the Tornado Watch is no longer in effect, there remains the potential for strong to severe thunderstorms with the passage of the cold front later tonight. Even outside of storms, strong winds are likely, especially closer to the coast.

A warm and humid airmass remains over the area ahead of an approaching cold front. Clouds and rain ahead of this line has stabilized the airmass over the area, and the lack of any CAPE inhibited widespread severe weather from developing late this afternoon and early this evening. As a result, the Tornado Watch that was in effect until 7 pm is no longer in effect. However, a strongly amplified upper level trough that is through the Ohio and Tennessee Valleys is turning negatively tilted, and sharp height falls and temperature falls will occur behind the passage of the cold front.

Low level wind shear is quite strong just ahead of the frontal passage, and the combination of dynamic lift, sufficient moisture, and modest instability (for mid March standards) may still support convection, but it will not be until later tonight with the actual passage of the cold front. 20Z/16 HRRR still showing a thin squall line that will pass through the region with the frontal passage, and this may still result in strong to severe thunderstorms in the 11 pm to 1 am timeframe. Locally heavy rain is still possible with brief, localized flash flooding.

Finally, it should be noted that even outside of any thunderstorms the strong wind fields will support southerly winds. A burst of strong westerly winds is also likely during and immediately after the cold frontal passage late this evening, with gusts up to 55 mph possible. Therefore, the Wind Advisory was expanded to include the entire forecast area. The strong southerly winds has ushered in an unseasonably warm and humid airmass. Temperatures this evening will be in the mid 60s to low 70s inland, and closer to 60 degrees near the coast and higher terrain.

In addition to the severe weather and strong wind threat, the showers/storms will likely be producing heavy rainfall as PWATs are progged to be 1.1-1.4" which is above the 90th percentile for early March. MMEFS guidance is showing modest rises in rivers, so we'll continue to watch for any potential hydro concerns, especially where any training of convection occurs.

KEY MESSAGE 2...Some minor coastal flooding along the back bays with high tide this evening.

South winds will continue to increase through this evening with gales developing by or just after sunset. This will keep water from draining out of Barnegat Bay, Rehoboth Bay, and Little Assawoman Bay, resulting in elevated tide levels and some minor coastal flooding around the high tide this evening. The most likely areas to experience impacts will be along the northern end of Barnegat Bay in Ocean County NJ, Rehoboth Bay and Little Assawoman Bay in Sussex County DE. These bays are particularly susecptible to flooding during strong southerly wind events, as the winds prevent water from draining normally during low tide.
Thus, impacts may not follow typical astronomical tide cycles.
These advisories are in effect through 2 AM Tuesday, however extensions may be needed if impacts linger after winds shift offshore.

The Eastern Shore of Chesapeake Bay and upper portion of the tidal Delaware River (north of Philadelphia) could also experience some minor coastal flooding, though confidence is lower for these areas. Trends will continue to be monitored to determine if any additional advisories may be needed.

KEY MESSAGE 3...Cold and dry for the middle of the week, then temperatures moderate late this week and through this weekend.

Canadian high pressure will be centered over the southern Appalachians and Mid-Atlantic Tuesday night, then will lift to the northeast, with the center of the high passing over New Jersey on Wednesday. The high then lifts into the Canadian Maritimes Wednesday night through Thursday. A weak cold front will pass through the region Thursday night, followed by a stronger cold front Friday night. High pressure will mostly be over the area this weekend until another cold front potentially passes through the area Sunday night.

Temperatures Tuesday night through Wednesday will more resemble that of January than mid-March with lows in the 20s and low 30s and highs in the upper 30s to low 40s. Thereafter, a much warmer airmass begins to build east with highs warming into the 40s and low 50s Thursday, then generally in the low to mid 50s north and west of the Fall Line and in the mid and upper 50s south and east of the Fall Line Friday through Sunday.

With the passage of the first front Thursday night, generally 20 to 30 percent PoPs, mostly for rain, but some spotty freezing rain is possible for the southern Poconos. With the stronger front Friday night, PoPs will generally be in the 30 to 50 percent range, again, mostly rain.

AVIATION /22Z MONDAY THROUGH SATURDAY/
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

Rest of today... Most terminals likely range in the VFR to MVFR, except IFR more likely at KACY. Showers/t-storms crossing the region will bring further restrictions particularly to vsby.
Winds S/SW gusting up to 30-35 kts, with LLWS up to 45 kts at 020 from the S. Strongest storms may produce higher surface gusts or even an isolated tornado. Medium confid overall, low confid in details.

Tonight...A strong cold front will cross the terminals this evening into the early overnight. LIFR conditions with +SHRA/+TSRA and very gusty winds with the activity... strongest storms may produce surface gusts to 55kts. LLWS with S/SSW winds 55 to 75 kts at 020 and closer to 90 kts at 030. Rapidly improving conditions following the front with VFR within a few hours after the frontal passage. Medium confid overall, low confid in details.

Tuesday...VFR with winds from the west gusting up to 25-35 kts much of the time.

Outlook...

Tuesday night...VFR. Gusty west winds early in the evening, diminishing by midnight.

Wednesday through Friday...VFR. NSW.

MARINE
Gale Warning continues on the waters through tonight, may need extension into the day Tuesday. Southerly flow continues to increase, with gales likely by late day/evening just ahead of cold front. Then westerly winds likely produce gales along/just behind front for a few hours into the early morning Tuesday.
Winds will relax a bit as we get into Tuesday but some lingering gale gusts may continue past dawn. Seas building thru this evening until peaking at 10-15 feet, then starting to slowly diminish late tonight through Tuesday.

Outlook...

Tuesday night...Gusty west winds diminish in the evening, but seas remain elevated. SCA may continue to be needed. No significant weather.

Wednesday through Friday...VFR. Sub-SCA conditions. No significant weather.

PHI WATCHES/WARNINGS/ADVISORIES
PA...Wind Advisory until 2 AM EDT Tuesday for PAZ054-055-060>062- 070-071-101>106.
NJ...Wind Advisory until 2 AM EDT Tuesday for NJZ001-007>010- 012>027.
Coastal Flood Advisory until 2 AM EDT Tuesday for NJZ020-026.
DE...Wind Advisory until 2 AM EDT Tuesday for DEZ001>004.
Coastal Flood Advisory until 2 AM EDT Tuesday for DEZ003-004.
MD...Wind Advisory until 2 AM EDT Tuesday for MDZ012-015-019-020.
MARINE...Gale Warning until 6 AM EDT Tuesday for ANZ430-431-450>455.