Marine Weather and Tide Forecast for Elverson, PA

KEY MESSAGES
1. A strong cold front will bring rain showers to the area Tonight into Sunday.

2. Widespread minor tidal flooding along the Atlantic coasts of New Jersey and Delaware, Delaware Bay, and the tidal Delaware River with tonight's high tide.

3. Much colder air early next week with frost/freeze conditions, followed by a return to above average temperatures later in the week.

DISCUSSION
KEY MESSAGE 1...A strong cold front will bring rain showers to the area Saturday night into Sunday.

A cold front will move into the area late Tonight and should move off the coast by mid day Sunday. This front, combined with the surface low sliding along the front, will provide enough lift for widespread rain across the area. Chances for measurable rain range from 70 to 80 percent. That being said, this is unlikely to result in substantial rain amounts. Storm (shower)
motions should be relatively fast, and the front itself has trended faster. Thus, rain amounts are forecast to be a few hundredths of an inch up to one half an inch.

In terms of other hazards, instability, especially surface or low level based instability is forecast to be very limited (less than 50 J/kg of CAPE). Thus the risk for other thunderstorm hazards is very low. That being said, there is some very elevated instability (for parcels above 850 mb), especially west of the fall line, so can't rule out a rumble of thunder or gusty winds.

Though this is a strong cold front, the temperature difference won't feel as dramatic as it could, thanks to a marine layer staying mostly in place over our region today. None the less, for most inland areas, temperatures on Sunday will be 5 to 20 degrees colder as compared to Saturday; highs on Saturday will range from the mid 50s to mid 70s, compared with highs on Sunday ranging from the mid 40s to mid 60s.

KEY MESSAGE 2...Widespread minor tidal flooding along the Atlantic coasts of New Jersey and Delaware, Delaware Bay, and the tidal Delaware River with tonight's high tide.

A Coastal Flood Advisory remains in effect for the Atlantic coasts of New Jersey and Delaware, as well as along Delaware Bay and up the tidal Delaware River for the high tide cycles tonight.

High astronomical tides associated with the New Moon that occurred yesterday and onshore flow today and tonight is forecast to result in widespread minor tidal flooding with tonight's high tide along the Atlantic coasts of New Jersey and Delaware, Delaware Bay, and the tidal Delaware River. A northeast to east wind will become southeasterly by later today into this evening, with surge values increasing to near 1 foot above normal. This will put most tidal areas into minor flood stage during high tide tonight.

A modest offshore wind will develop in the wake of a cold front on Sunday, which should limit the risk of any additional flooding for Sunday night's high tide.

No tidal flooding is forecast for our portion of the Eastern Shore of Chesapeake Bay.

KEY MESSAGE 3...Much colder air early next week with frost/freeze conditions, followed by a return to above average temperatures later in the week.

As a strong upper-level trough pivots across the East Sunday night and Monday, surface high pressure with a much colder air mass with it will be in place. The high itself will settle over our area Monday night into Tuesday morning before shifting offshore. A breeze will occur Sunday night and Monday with a lingering pressure gradient ahead of surface high pressure. While it will be much colder Sunday night, just enough wind may limit frost formation.
Much lighter to nearly calm wind Monday night along with a mostly clear sky should result in more efficient radiational cooling conditions. As a result, widespread frost and/or freeze conditions are probable early Tuesday morning. Frost early Tuesday morning could be somewhat limited given a much drier low-level air mass in place, however areas outside of the larger cities and away from the immediate coast area forecast to drop to and below freezing. The recent excessive warmth has quickly started the vegetation sooner, therefore all of our counties are now active regarding the growing season.

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 return, southerly, flow becomes established during Tuesday and it continues into Wednesday. This along with an increase in warm air advection and rising heights will result in temperatures climbing back above average Wednesday through Friday. A warm front may arrive at the end of the week. As of now, the chance for a much needed widespread rainfall Monday through Friday of next week looks to be very low.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

Today...The low clouds are likely to clear from KRDG the earliest, most other sites by 15Z. At KACY, there is a 40% chance that the low clouds (at least MVFR) persist through the day. For the other TAF sites, once the low clouds dissipate, conditions should stay VFR through at least 21Z. After 21Z, another low cloud deck may start encroaching on the area, though this is more likely not to move back in until after 00Z. Winds have already begun to shift to southeasterly, and should generally favor that direction, with wind speeds around 10 kt or less.

Tonight...Another low cloud deck will move over the region, with widespread MVFR, and localized IFR conditions expected.
Additionally, some visibility restrictions to MVFR with SHRA is possible, particularly after 06Z. Winds should generally favor southeasterly through most of the night, with wind speeds of 5 to 15 kt.

Outlook...

Sunday...Widespread MVFR and localized IFR conditions continue (mostly due to low clouds). SHRA are likely, but an isolated thunderstorm cannot be ruled out. Expect an abrupt shift to northwesterly winds before 15Z, with a subsequent increase in wind speeds (gusts up to 25 kt) as well.

Sunday night through Tuesday...VFR. West-northwest wind gusts to around 20 knots Monday, quickly diminishing Monday night.

Wednesday...Some MVFR conditions are possible at times.

MARINE
Through Tonight...Winds and seas should stay below Small Craft Advisory criteria. A large area of fog has been impacting the NJ and DE coastal waters early this morning, with visibilities less than one nautical mile roughly from Manasquan Inlet NJ to the MD/DE border. Expect the fog to continue into the afternoon.

Sunday...Winds will shift to northwesterly and increase quickly behind a cold front Sunday Morning. Expect SCA conditions on all waters through the day time. There is a 40% chance that wind speeds exceed gale criteria for a brief period behind the front, particularly at the mouth of the Delaware Bay. However, for now, widespread SCA looks more likely, so have issued an SCA for the coastal waters out to 20 nmi. For the outer marine areas (20 to 60 nmi), winds are likely to stay below gale criteria.

Outlook...

Sunday night through Wednesday...The conditions are anticipated to be below Small Craft Advisory criteria.

PHI WATCHES/WARNINGS/ADVISORIES
PA...Coastal Flood Advisory from 1 AM to 6 AM EDT Sunday for PAZ070- 071-106.
NJ...Coastal Flood Advisory from 11 PM this evening to 3 AM EDT Sunday for NJZ016.
Coastal Flood Advisory from 8 PM this evening to 2 AM EDT Sunday for NJZ012>014-020>027.
Coastal Flood Advisory from 1 AM to 6 AM EDT Sunday for NJZ017>019.
DE...Coastal Flood Advisory from 11 PM this evening to 3 AM EDT Sunday for DEZ001.
Coastal Flood Advisory from 8 PM this evening to 2 AM EDT Sunday for DEZ002>004.
MD...None.
MARINE...Small Craft Advisory from 8 AM to 6 PM EDT Sunday for ANZ430- 431-450>455.
Dense Fog Advisory until 4 PM EDT this afternoon for ANZ431- 451>455-481>483-485.