Cape Henlopen to Fenwick Island DE out 20 nm Marine Forecast
|Tonight...S Winds 10 To 15 Kt. Seas 3 To 4 Ft. Patchy Fog Late This Evening And Early Morning. A Chance Of Showers With A Slight Chance Of Tstms After Midnight. Showers Likely With A Slight Chance Of Tstms Late. Vsby 1 To 3 Nm Late This Evening And Early Morning. Swell Mainly From The E With A Dominant Period Of 11 Seconds.|
|Sun...S Winds 10 To 15 Kt. Gusts Up To 20 Kt In The Morning, Then 20 Kt Late. Seas 3 To 5 Ft. Showers Likely, Mainly In The Morning. Swell Mainly From The E With A Dominant Period Of 10 Seconds.|
|Sun Night...S Winds 10 To 15 Kt, Becoming Nw 5 To 10 Kt After Midnight, Then Becoming N Late. Seas 3 To 5 Ft. A Chance Of Showers Early In The Evening, Then A Chance Of Tstms In The Late Evening And Early Morning. Swell Mainly From The E With A Dominant Period Of 10 Seconds, Becoming Mainly From The Se With A Dominant Period Of 9 Seconds After Midnight.|
|Mon...Ne Winds 10 To 15 Kt. Gusts Up To 20 Kt Late. Seas Around 3 Ft. Swell Mainly From The Se With A Dominant Period Of 8 Seconds.|
|Mon Night...Ne Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 3 To 4 Ft.|
|Tue...Ne Winds 5 To 10 Kt. Seas 3 To 4 Ft.|
|Tue Night...Se Winds 5 To 10 Kt, Becoming Ne After Midnight. Seas Around 3 Ft.|
|Wed...N Winds 5 To 10 Kt, Becoming Ne In The Afternoon. Seas Around 3 Ft.|
|Wed Night...N Winds Around 10 Kt. Seas 3 To 5 Ft.|
|Thu...N Winds 5 To 10 Kt. Seas 4 To 6 Ft.|
|Thu Night...N Winds 5 To 10 Kt, Becoming Nw After Midnight. Seas 4 To 6 Ft. Winds And Seas Higher In And Near Tstms.|
| Area Forecast Discussion|
National Weather Service Mount Holly NJ
355pm EDT Sat April 10 2021
Developing low pressure over the Mid- Mississippi Valley will lift north into the Great Lakes tonight through Sunday. A warm front extending out from that low will lift north through the region tonight, and then a cold front will pass through the region Sunday night. A broad area of low pressure will meander over the region into next week.
Near Term - Through Sunday Night
We will start tonight much like last night, with patchy fog developing, especially in areas where the low clouds stay in place until right around sunset. By late tonight, as the warm front approaches the first round of rain is expected to move into our region from south to north. High resolution guidance is in relatively good agreement with the timing of this first round between 06 and 18Z. With the relatively high dewpoints and lower clouds (especially during the second half of the night), lows tonight will be well above normal in the 50s for most locations.
There is still a question as to where the warm front will end up by mid day tomorrow. The NAM is showing the front lifting almost entirely north of the region, while most other guidance depicts the warm front either stalling or even transitioning to a cold front briefly in the afternoon. This will be key both for temperatures as well as thunderstorm potential. The weak flow in the lower levels and a secondary surface low developing along the cold front to our west during the day would favor the non-NAM solution with the warm front staying generally along or south of the I-78 corridor. Consequently, for areas along and south of Reading to Philadelphia, expect temperatures to get into the 70s (temperatures near 80 may even be possible in interior portions of Delmarva). North of this area though, highs should be in the 50s and 60s.
The second round of showers and thunderstorms should arrive with the cold front. For the most part, it looks like this won't arrive in our region until the evening hours, but I could see this being slightly faster depending on if the secondary low along the front doesn't deepen as much as currently depicted. Assuming the warm front stays over our region, most of the region should have limited instability. However, over Delmarva (or the rest of the region if the warm front lifts further north), ML CAPE values near 1000 J/Kg are possible. Bulk shear values could be 20 to 35 kt. Based on this, some strong storms (primarily for wind gusts) are certainly possible, but it doesn't appear to be a widespread threat.
Clouds and rain should clear out quickly in the wake of the cold front Sunday night.
Short Term - Monday Through Tuesday
A weakening closed upper low will be located northwest of the area on Monday, which is forecast to open with its associated vorticity maxima ejecting east across the area on Tuesday. At the surface, broad low pressure will also be located northwest of the area with surface ridging impinging from the northeast. Basically the main takeaways for this pattern in this period will be cool, mostly cloudy, and damp especially across New Jersey and eastern Pennsylvania. Delmarva actually looks to stay west of the cold air damming boundary, so warmer temperatures and less sky cover can be expected there. As far as precipitation goes, some light rain showers are possible across Pennsylvania and New Jersey with generally better chances toward the north and west closer to the upper low. Confidence on the coverage and timing of the showers remains low however, so we've maintained slight chance to chance Probability of Precipitation at most.
Long Term - Tuesday Night Through Saturday
The long term period will start Wednesday with 2 closed upper lows across the CONUS. The polar jet will be located well to the north of the region. The closed lows should open with the pattern trending more progressive by Friday or Saturday. There will be a possibility of more diurnally driven showers just about every day, with the highest chances Wednesday with the closed upper low nearly overhead. This should also be the most cloudy of the days in the period, with cloud cover generally lessening toward the end of the week as the upper low moves offshore and flow becomes zonal across the CONUS. Temperatures should be largely near climatological normals (highs ~60s/lows ~40s).
Winds and seas should stay below Small Craft Advisory tonight. On Sunday, seas could approach 5 ft on the Atlantic coastal waters, but conditions should mostly stay below SCA (Small Craft Advisory) criteria. Sunday night, seas are expected to exceed 5 ft on the central and northern NJ coastal waters.
A period of fog is possible tonight before the rain moves in. There is potential for visibility values to drop below 1 mile, but not confident enough to issue a dense fog advisory at this point.
Outlook... Monday...Northeast winds are forecast to be around 15-20 kts with seas building to 4-6 feet across the ocean waters. A Small Craft Advisory has been issued through Monday for the northern ocean waters, but this may need to be extended in time or expanded in area later.
Tuesday through Wednesday...Easterly winds of 5-10 kts and and seas 2-4 feet are forecast for this period. Marine headlines are not anticipated.
NOAA Mount Holly NJ Office: Watches - Warnings - Advisories
PA...None. NJ...None. DE...None. MD...None.
Small Craft Advisory from 11pm Sunday to 6pm EDT Monday for ANZ450-451.