Delaware Bay south of East Point NJ to Slaughter Beach DE Marine Forecast
|Tonight...Sw Winds 5 To 10 Kt. Waves 2 Ft Or Less.|
|Wed...N Winds Around 5 Kt, Becoming E In The Afternoon. Waves 2 Ft Or Less. A Chance Of Tstms In The Afternoon.|
|Wed Night...Se Winds 5 To 10 Kt. Waves 2 Ft Or Less. A Chance Of Tstms Early In The Evening.|
|Thu...Se Winds 5 To 10 Kt. Waves 2 Ft Or Less. A Chance Of Tstms In The Afternoon.|
|Thu Night...Sw Winds 5 To 10 Kt. Waves 2 Ft Or Less. A Chance Of Tstms.|
|Fri...Nw Winds 5 To 10 Kt. Waves 2 Ft Or Less.|
|Fri Night...N Winds 5 To 10 Kt. Waves 2 Ft Or Less.|
|Sat...N Winds 5 To 10 Kt, Becoming W In The Afternoon. Waves 2 Ft Or Less.|
|Sat Night...Sw Winds 5 To 10 Kt. Waves 2 Ft Or Less.|
|Sun...S Winds 5 To 10 Kt. Waves 2 Ft Or Less.|
|Sun Night...Sw Winds 5 To 10 Kt, Becoming W After Midnight. Waves 2 Ft Or Less. Winds And Waves Higher In And Near Tstms.|
| Area Forecast Discussion|
National Weather Service Mount Holly NJ
350pm EDT Tuesday July 27 2021
A weak cold front will slowly push through the region tonight and Wednesday. A stronger cold front will move through the area late Thursday. Strong high pressure builds in for Friday and Saturday. Another front may move through the region on Sunday into Monday. High pressure will return early next week.
Near Term - Through Wednesday
The forecast remains quiet through the early afternoon as brief high pressure remains. A sea breeze has triggered and is slowly advancing west across coastal New Jersey. It looks like the sea breeze is moving inland on the slower side so I'm not too bullish on much convective initiation along the boundary. There's clearly instability over the region as spotty cumulus clouds have popped up due to the diurnal heating. This doesn't look to make a large impact on temps this evening as we've already warmed into the low 90s for most of the region. Dewpoints haven't quite mixed out so there is potential to warm another degree or so as we are currently deeply mixing.
The main story will be how the convection that is ongoing over northern and central New York evolves through the evening. A mid-level trough and associated cold front will approach the northern portion of the region this evening and tonight. This is a fairly vigorous disturbance, but is on track to deliver only a glancing blow to the northern portion of the area. Latest runs of the HRRR (High-Resolution Rapid Refresh) and similar CAM guidance suggests the bulk of this activity will remain north of us, where forcing and shear are better.
With a rather dry air mass in place and the timing not being very favourable, this system is unlikely to be a big deal for us. Particularly for the urban corridor and areas south, any rain tonight is unlikely. Overnight lows should fall towards seasonal averages, mid 60s to near 70.
Our attention then turns to the potential for an active day Wednesday as an outflow boundary from the disturbance that glances by this evening pushes south over the region. Behind that boundary the flow turns northerly and mid level dry air becomes strongly advected over the Mid Atlantic. Even as dry air moves in aloft, we should see sufficient moisture and surface convergence across central NJ and south such that diurnally driven showers with embedded thunderstorms will develop during the afternoon hours although coverage will be scattered and not widespread.
The challenge to the forecast is how high the temps warm over the region as we may be looking at a decent "Sussex Index" which is simply just the difference in temps between Sussex NJ and Sussex DE. We anticipate that a cold front should be draped over northern NJ with cooler air to the north and plenty of heating to the south. Forecast temps on Wednesday are for low 90s from the Philly area and south, with low 80s to upper 70's for the Poconos/NW NJ.
Short Term - Wednesday Night Through Thursday Night
The cold front should be starting to find its way out of area by Wednesday night but may remain draped across our southern areas, eventually pushing offshore into Thursday. Showers and thunderstorms may still be ongoing as we head into Wednesday night but most will be diurnally driven and we should see them start to taper off after sunset.
Several shortwaves will move through the mid level flow on Thursday, sparking off another round of showers and thunderstorms ahead of the next approaching cold front. This second cold front will move into the region Thursday with chances for showers and thunderstorms across the area, eventually moving towards the coast and offshore Thursday night into early Friday.
With so much cloud cover around on Thursday, it may end up being less active than models are currently depicting but with the chance for some breaks of sun to peak through, it won't take much to get instability going across the region.
Long Term - Friday Through Tuesday
High pressure will be in place for Friday and Saturday and we should have two really nice days to end the month of July. Some lingering light showers across the northern and eastern zones may exist early on Friday but shouldn't hang around for too long, clearing out by mid-morning. Dry air will settle over the region and with highs only into the low to mid 80s on Friday, and a few degrees cooler than that on Saturday, it will certainly be quite pleasant outside.
A cold front will drop down from the northwest on Sunday, moving offshore late Sunday into Monday. With the region in the warm sector ahead of the front, we should see some warm air advection take place at the surface and moisture will start to increase. With a building upper trough, we may end up staying slightly cooler overall and closer to or just below normal temperatures. Ahead of the front we will see some showers and thunderstorms develop, though they will mostly be aligned with the boundary as it starts to make its way through the region.
A large area of surface high pressure will slide through the Midwest and into the Mid-Atlantic early in the week. Meanwhile an upper trough will dig down through the Tennessee Valley. Some big differences in the guidance this far, especially with the trough, but as the high slides towards us, we should start to dry out again.
Through Wednesday... Sub-SCA (Small Craft Advisory) conditions are expected. Winds south or south- southeast winds of 10 to 15 kt will develop, shifting to southwest overnight. On Wednesday anticipate northern winds initially becoming easterly by the afternoon. Seas 2 to 3 ft.
Outlook... Sub-Small Craft Advisory conditions will continue on the area waters through Sunday.
Wednesday night through Thursday night... Southeast winds will back to the south overnight becoming southwest around 10 to 15 knots on Thursday. Seas 2 to 4 feet. Winds and waves higher in and around thunderstorms.
Friday through Friday night...Northwest winds around 10 to 15 knots. Seas 3 to 4 feet.
Saturday through Sunday...Light winds becoming southwest around 10 knots overnight, increasing to 10 to 15 knots on Sunday. Seas 2 to 4 feet.
Rip Currents... With generally light winds and seas, the risk for the formation of dangerous rip currents is expected to remain low for New Jersey and Delaware through at least Wednesday. However, for today, a fairly long (~10 second) swell period becomes dominant this afternoon. With a late afternoon low tide, the rip current risk could increase a bit this afternoon. Seas will still likely be too low to warrant a moderate risk, but conditions will be monitored.
NOAA Mount Holly NJ Office: Watches - Warnings - Advisories
PA...None. NJ...None. DE...None. MD...None. MARINE...None.