Great Egg Inlet to Cape May NJ out 20 NM Marine Forecast
|Overnight...E Winds Around 5 Kt, Becoming Ne. Seas 3 To 4 Ft. Swell Mainly From The E With A Dominant Period Of 6 Seconds. A Slight Chance Of Rain Late This Evening. A Chance Of Drizzle. Patchy Dense Fog. Vsby 1 Nm Or Less.|
|Sun...Se Winds 5 To 10 Kt. Seas 3 To 4 Ft. Swell Mainly From The Se With A Dominant Period Of 7 Seconds. Patchy Dense Fog Early In The Morning. Areas Of Dense Fog Late In The Morning. A Chance Of Drizzle In The Morning. A Chance Of Showers Late. Vsby 1 Nm Or Less In The Morning.|
|Sun Night...S Winds 5 To 10 Kt, Becoming W In The Late Evening And Overnight. Seas 3 To 5 Ft. Swell Mainly From The S With A Dominant Period Of 7 Seconds. A Chance Of Showers Until Early Morning.|
|Mon...W Winds 5 To 10 Kt, Increasing To 10 To 15 Kt In The Afternoon. Seas 3 To 5 Ft. Swell Mainly From The Se With A Dominant Period Of 7 Seconds.|
|Mon Night...Nw Winds 10 To 15 Kt. Gusts Up To 20 Kt After Midnight. Seas 3 To 4 Ft.|
|Tue...N Winds 10 To 15 Kt, Becoming Ne In The Afternoon. Seas Around 3 Ft In The Morning, Then 2 Ft Or Less.|
|Tue Night...E Winds 10 To 15 Kt, Increasing To 15 To 20 Kt After Midnight. Gusts Up To 25 Kt. Seas 3 To 5 Ft. A Chance Of Rain.|
|Wed...Ne Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 4 To 6 Ft. A Chance Of Rain.|
|Wed Night...Ne Winds 10 To 15 Kt, Becoming Nw After Midnight. Gusts Up To 25 Kt. Seas 4 To 6 Ft. A Chance Of Rain In The Evening.|
|Thu...Nw Winds 10 To 15 Kt. Gusts Up To 20 Kt In The Morning. Seas 3 To 5 Ft.|
|Thu Night...W Winds 10 To 15 Kt. Gusts Up To 20 Kt After Midnight. Seas 3 To 4 Ft.|
Area Forecast Discussion|
National Weather Service Mount Holly NJ
914pm EDT Sat Mar 28 2020
A warm front will move slowly northward through the Mid-Atlantic tonight and Sunday. Meanwhile, a strong surface low in the central Plains will lift northeast toward the Great Lakes on Sunday, with secondary low development near the East Coast. A cold front will sweep through the region Sunday night, with a reinforcing front moving through on Monday. Another surface low will move through the Southeast on Tuesday and off the Carolina coast by Wednesday. High pressure will build into the Northeast Wednesday night and Thursday. Another system may affect the region Friday or Saturday.
Near Term - Through Sunday
Tonight... As of 9pm a band of primarily stratiform rain (with one convective element just south of Philly) was moving through the central third of the forecast area. This precipitation (which is largely the remnants of earlier upstream convection) is largely being sustained by ascent ahead of a westerly shortwave and ascent along the 925mb FGEN zone. Once this precipitation moves offshore in the next 1-2 hours, rainfall will be light and intermittent through the remainder of the night, with the best chances being in the warm advection/upslope regime in the Poconos/NW NJ.
Otherwise it will be a dreary night with some combination of drizzle, fog, and low stratus likely as low-level moisture remains pinned near the surface under an increasing robust low-level inversion. Given usual uncertainties in the cool sector BL (e.g. whether there is sufficient vertical mixing and moisture depth to support drizzle/stratus vs fog) don't have confidence on the dense fog potential. For now left mostly patchy fog in the grids, but did add some potential for dense fog over the southern part of the area where hi-res guidance favors it. Temps and dewpoints should largely flatline through the night given the robust cloud cover.
Sunday (Previous discussion):
The main forecast challenge for Sunday is the ultimate positioning of the warm front, with models very likely too aggressive with its northward push. A strong surface low will begin to weaken as it becomes vertically stacked over the Great Lakes region. A cold front will extend eastward then southward from the low and surge toward the area during the day as a strong midlevel jet streak races northeastward to the Northeast. As a result, the warm front should lift northward during the day, but I suspect the ageostrophic contribution to the onshore flow via upslope is being underplayed. Confidence is high enough to keep the northern CWA quite chilly tomorrow (around or below 50), whereas southern Delmarva will approach 80. Of course, temperatures in between are the tricky part and will ultimately depend on very short-term trends/guidance. In other words, expect the temperature forecast to be susceptible to considerable error in portions of the CWA. To illustrate, the latest MET MOS for PHL is 57 for tomorrow, and the latest MAV MOS projects 70. Even worse for GED: 66 versus 84. Yikes. For now, the forecast is generally weighted toward the colder NAM- based guidance but with some input from statistical guidance as well.
The wind profile in the region tomorrow will be quite impressive, with 0-6 km bulk wind difference exceeding 60 kt and helicity approaching 300 J/kg (with considerable curvature in the low-level winds), especially near the warm front. Convection-allowing models depict isolated to widely scattered storms developing near the front as it advances toward the area late in the day. With instability increasing in the warm sector (e.g., NAM Nest showing SBCAPE exceeding 1000-1500 J/kg), these storms may become severe, especially if updrafts are able to sustain themselves. However, the overall sparse coverage in guidance suggests this threat is conditional. Will be watching this potential closely, to be sure.
Short Term - Sunday Night Through Tuesday Night
Any lingering convection on Sunday evening will move offshore overnight as the cold front sweeps off the coast. However, a large midlevel vortex will struggle to move eastward from the Great Lakes on Sunday evening. The northern portions of the CWA may be close enough to the stronger ascent downstream of the vortex to see remnant showers through Monday night. The best chance for this appears to be Monday afternoon, when the vortex will make its closest approach to the area. Despite a cold front moving through the region on Sunday night, the colder air will be upstream of a reinforcing front moving through the area Monday afternoon/evening. As a result, it will be mild on Monday, with highs near/above 60 southeast of the Poconos. Lows Monday night and highs on Tuesday will be about 10 degrees colder than the previous day's readings.
The next system of interest is a southern-stream perturbation moving through the Mid-South and Tennessee Valley on Tuesday. Surface low pressure will organize on the Carolina coast Tuesday night, with a precipitation shield extending northward from the low into at least the central Mid-Atlantic. Deterministic models still differ considerably on extent of coverage into the CWA, with the GFS looking awfully dry versus the CMC, and the ECMWF somewhere in between. Took a consensus approach with Probability of Precipitation for now, which leaves values in the slight-chance to chance range generally near/south of the I-76 corridor. The heaviest precipitation will be south of the area, with light amounts expected (for now) in our area. If the track of the low trends northward, however, heavier rainfall can be expected.
Long Term - Wednesday Through Saturday
Temperatures will trend cooler on Wednesday as the region lies upstream of the departing surface low. However, lingering rain should exit the area fairly quickly. There may be some lingering showers in the northwest CWA owing to glancing ascent from a weak perturbation digging southeast from the Saint Lawrence Valley. Otherwise, the Wednesday night and Thursday period will likely be dry as high pressure briefly builds into the region.
The next system will likely affect the area Friday or Saturday, though timing differences remain with the deterministic models. Notably, the ECMWF (European Centre for Medium-Range Weather Forecasts) and GFS appeared to converge somewhat from previous runs, though frontal passage differences are still rather high (6-12+ hour variations). Broad-brushed slight- chance to low-chance Probability of Precipitation Friday night and Saturday for now until better agreement is observed.
Temperatures Thursday through Saturday should be close to seasonal averages.
900 pm update: Added a dense fog advisory for the southern Atlantic zones and DE Bay until 7am based on deteriorating visibilities near the coast. It is possible this may need to be extended spatially or temporally based on overnight trends.
Farther north, winds will increase this afternoon, with seas approaching 5 feet this evening. Expect a period of seas around 5 feet or so through tomorrow before seas subside Sunday night.
Perhaps the bigger threat for marine interests is fog potential tonight. A favorable setup of onshore flow and fairly high dew points should allow areas of fog to develop on the waters overnight. Fog may become dense enough for the issuance of an advisory and may occur through most of the overnight into Sunday morning.
Finally, isolated storms this afternoon may produce small hail and erratic wind gusts in their proximity. Additional storms are possible late Sunday afternoon, with a higher likelihood for strong wind gusts.
.Outlook... Sunday night through Tuesday evening...Sub-advisory winds/seas expected. A slight chance of storms Sunday evening.
Tuesday night through Wednesday night...Winds are expected to increase from the east or northeast up to 30 kt (especially off the Delaware Atlantic coast) with seas building to 5 to 7 feet. A chance of rain Tuesday night and Wednesday.
Thursday...Sub-advisory winds/seas expected.
NOAA Mount Holly NJ Office: Watches - Warnings - Advisories
PA...None. NJ...None. DE...None. MD...None.
Small Craft Advisory until 6am EDT Monday for ANZ450>452. Dense Fog Advisory until 7am EDT Sunday for ANZ430-431- 453>455.