Marine Weather and Tide Forecast for Slaughter Beach, DE

NEAR TERM /THROUGH TONIGHT/
Only significant change with this update was to expand the mention of fog across the region. Fog will likely be short lived as once the winds increase out of the west, that should erode any fog that has already developed.

We will be in a lull with rain until a short wave trough digging on the back side of the big upper level low arrives this afternoon/evening. Rain with this round is expected to be less widespread and more showery than what we have seen the last few days. Instability is extremely limited and moisture is also a bit limited, so don't expect anything impactful or any significant rain amounts.

Pressure gradient will tighten by mid day, so wind gusts up to 25 mph will be possible through the day.

By this evening, mid level dry air advection will be in place as the northwesterly flow continues. Additionally, expect to see clearing skies. The combination of this will lead to efficient radiational cooling conditions; temperatures overnight will be able to drop into the 40s for most of the area.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
Our region will remain within cyclonic flow aloft as an upper-level trough remains across the Northeast and into the Mid-Atlantic Saturday. This may then ease some Saturday night into Sunday before stronger shortwave energy sharpens the western extent of the trough across the Northeast Sunday. Overall though, improving conditions are forecast, including warmer temperatures.

Some instability driven showers should occur mainly toward the Poconos during Saturday. While an isolated shower cannot be ruled out farther south, drier air below cloud base may keep this development at bay overall. Given the continued cooler air aloft associated with the lingering trough, cumulus development is expected during Saturday and again Sunday, although it should be less overall on Sunday. A tight pressure gradient remains in place Saturday between low pressure well to our northeast and high pressure extending into the Ohio Valley. This will result in a notable west-northwest breeze Saturday (wind gusts 20-30 mph), and then not as strong on Sunday. A lead impulse well south of the Northeast trough should produce a shield of rain/showers to our south later Sunday. Much of the guidance keeps this to our south given a more confluent flow over our area. For now though, included slight chance (20 percent) PoPs across our far southern Delmarva zones later Sunday.

High temperatures are forecast to remain below average through the holiday weekend. For those of you heading to the Jersey Shore and the Delaware Beaches, even with surf temperatures in the upper 50s, you will experience similar temperatures compared to inland locales given an offshore wind.

LONG TERM /MONDAY THROUGH THURSDAY/
Summary...Warmer and dry conditions forecast for Memorial Day, followed by some mid week cooling and also with some increasing shower chances.

Synoptic Overview...The western side of an upper-level trough is forecast to be shifting out of the Northeast during Monday, Memorial Day. Some mid level ridging then arrives during Tuesday into Wednesday. An upper-level trough shifting eastward across the Great Lakes, adjacent Canada and Ohio Valley will start to move into the Northeast during Thursday. At the surface, high pressure centered near the Midwest will extend into our area to start early in the week. Low pressure then across the Tennessee Valley tracks eastward Tuesday and Wednesday then offshore into Thursday.

For Monday...As an upper-level trough shifts out of the Northeast a more confluent flow in the mid levels is forecast to be across our area. A baroclinic zone is draped from west to east well to our south, and the confluent flow should keep precipitation south of our Delmarva zones during Memorial Day. Some guidance gets some measurable rain just south of southern Delaware, however overall the synoptic setup currently looks to support a drier day. Meanwhile, surface high pressure centered near the Midwest to upper Great Lakes is forecast to extend southeastward into our area. Despite a northerly wind, it may become lighter in the afternoon, offering sea/bay breeze development. Temperatures are forecast to top out into the low to mid 70s for most of the region, although some cooling would occur at the coast if the wind becomes lighter and results in a sea/bay breeze.

For Tuesday and Wednesday...Some mid level ridging slides across our area Tuesday and this may linger into Wednesday. Surface high pressure is forecast to be shifting offshore. An upper-level trough settles across the Midwest and more zonal to its south will allow energy to slide eastward along a lingering baroclinic zone. This should support surface low pressure, one which may lift into the Ohio Valley by Wednesday and another one sliding off the Carolina coast. The forecast challenge will be how quickly moisture increases across our area, as some guidance is much slower in bringing in deeper moisture northward. Warm air advection aloft will support increased cloud cover. More of an onshore low-level flow will support a moisture increase, however the forcing for ascent may lag for a while. We may have an overrunning scenario as the warm air advection strengthens above a possible marine layer that develops into our area. Some showers looks to arrive into our Delmarva zones by later Tuesday and then this spreads northward through Wednesday.
It is possible though that the bulk of the moisture and forcing slides to our south in conjunction with the main surface low, and we are left with a weakening system from the west. Given cloud cover Wednesday with more of an onshore flow, temperatures are forecast as of now to be cooler than Tuesday.

For Thursday...An upper-level trough is forecast to be shifting eastward across the Great Lakes, adjacent Canada and the Ohio Valley. This drives low pressure across the eastern Great Lakes and then north of our area. This entire system may be slow to shift eastward especially if the trough becomes closed off for a time, however there is a chance for some showers developing during the course of the day, especially near and north/west of I-95. The timing, strength of the forcing and also instability will determine the shower coverage and intensity including any thunderstorm risk.
Temperatures recover ahead of this system with high temperatures forecast to be in the 70s for most of the region.

AVIATION /10Z FRIDAY THROUGH TUESDAY/
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

Today.. MVFR and IFR conditions should improve quickly to VFR by 15Z. Prevailing VFR for the remainder of the day with the exception of potential for brief restrictions with showers generally between 18 and 23Z. Northwesterly winds around 10 kt gusting up to 20 kt.

Tonight...VFR conditions expected with light (less than 10kt)
northwesterly winds.

Outlook...

Saturday...VFR overall. Some isolated afternoon showers possible especially near KRDG and KABE. West-northwest wind gusts 20-25 knots during the day, then diminishing at night.

Sunday...VFR. West-northwest wind gusts up to 20 knots during the day.

Monday...VFR. Lighter winds may result in a sea/bay breeze at KACY and KILG.

Tuesday...Sub-VFR conditions and some showers possible.

MARINE
On the Atlantic coastal waters, seas have been slower to subside than previously expected with buoys 44009 and 44091 still showing seas well above 6 feet. Therefore, extended the Small Craft Advisory through the morning to account for this.

Once seas subside, winds and seas should stay below Small Craft Advisory thresholds through tonight.

Outlook...

Saturday...Small Craft Advisory conditions possible, mainly due to wind gusts to 25 knots.

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

Rip Currents...

There is a MODERATE risk for the development of dangerous rip currents through Saturday. For both today and Saturday, winds will be offshore at 10 to 20 mph. Expecting a longer period dominant swell (around 8 to 10 seconds) today. By Saturday, the waves may be more wind dominant, and thus shorter period, but winds are expected to be slightly higher Saturday.

For specific beach forecasts, visit weather.gov/beach/phi

TIDES/COASTAL FLOODING
Some guidance suggests some minor flooding within the tidal Delaware River today, but confidence is not high enough to issue further advisories in those locations. Higher water levels could also be a result of freshwater runoff, similar to what happened last week.

However, lingering tidal flooding is possible (and in some cases already occurring) on back bays in Sussex County Delaware and Ocean County New Jersey. Specifically, the back bays of most concern are Little Assawoman Bay, Indian River Bay, and Rehoboth Bay in Sussex County and Barnegat Bay in Ocean County, along with any smaller tidal water ways connected to these Bays.
Although tidal flooding is not expected on the oceanfront, a coastal flood advisory has been issued to cover the back bay flooding.

Once the winds shift to off shore later this morning, water will be able to efficiently evacuate out of these bays, and the threat for tidal flooding should come to an end.

PHI WATCHES/WARNINGS/ADVISORIES
PA...None.
NJ...Coastal Flood Advisory until 2 PM EDT this afternoon for NJZ020-026.
DE...Coastal Flood Advisory until 2 PM EDT this afternoon for DEZ003-004.
MD...None.
MARINE...Small Craft Advisory until noon EDT today for ANZ450>455.