Cape May NJ to Cape Henlopen DE out 20 nm Marine Forecast
|Today...S Winds 10 To 15 Kt. Gusts Up To 20 Kt This Afternoon. Seas Around 3 Ft. A Slight Chance Of Showers With Patchy Drizzle Early This Morning. Patchy Fog Early This Morning. Swell Mainly From The Se With A Dominant Period Of 7 Seconds.|
|Tonight...S Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 3 To 4 Ft. A Chance Of Showers After Midnight. Swell Mainly From The Se With A Dominant Period Of 9 Seconds.|
|Tue...S Winds 10 To 15 Kt. Gusts Up To 20 Kt Early In The Morning. Seas 3 To 4 Ft. A Chance Of Showers In The Morning, Then Showers Likely In The Afternoon With Vsby 1 To 3 Nm. Swell Mainly From The Se With A Dominant Period Of 8 Seconds.|
|Tue Night...S Winds Around 15 Kt With Gusts Up To 25 Kt. Seas 4 To 6 Ft. Showers. Vsby 1 To 3 Nm Early In The Evening. Swell Mainly From The Se With A Dominant Period Of 7 Seconds.|
|Wed...Sw Winds 10 To 15 Kt With Gusts Up To 25 Kt, Becoming W In The Afternoon. Seas 4 To 6 Ft. Showers.|
|Wed Night...N Winds 5 To 10 Kt, Becoming Nw 10 To 15 Kt After Midnight. Gusts Up To 25 Kt. Seas 3 To 5 Ft. Showers Likely, Mainly In The Evening.|
|Thu...W Winds 10 To 15 Kt. Seas 3 To 4 Ft. A Chance Of Showers In The Morning.|
|Thu Night...W Winds 5 To 10 Kt. Seas Around 3 Ft.|
|Fri...Nw Winds 5 To 10 Kt. Seas Around 3 Ft.|
|Fri Night...Nw Winds Around 10 Kt. Seas Around 3 Ft In The Evening, Then 2 Ft Or Less.|
| Area Forecast Discussion|
National Weather Service Mount Holly NJ
535am EDT Monday September 28 2020
A cold front will move into western Pennsylvania tonight. A few areas of low pressure riding north along the front, will slow down the progress of the front as it moves through our region Tuesday through Wednesday. Another cold front will arrive Thursday night into Friday. In it's wake, cooler air will settle in over the region into next weekend.
Near Term - Until 6pm This Evening
Showers continue to move northward through the region in response to a shortwave crossing the area overnight. As the wave continues to push east, we can expect continued light showers with areas of patchy fog and drizzle into the early morning hours.
The shortwave should cross the region by midday, allowing for a rapid clearing on the back side. Showers should end pretty quickly by early afternoon from southwest to northeast with skies starting to clear and becoming mostly sunny through the afternoon.
Unfortunately, we hold onto the southerly flow, which will keep the moist air across our area for another day. With clearing expected, high should be similar to that of Sunday and reach into the 70s to near 80 but with moisture around it will feel pretty muggy outside.
Short Term - 6pm This Evening Through 6am Tuesday
Tonight should start off pretty benign weatherwise but as the southerly flow starts to lighten up, clouds will start to fill back into the region. With plenty of moisture still across our area, wouldn't be surprised to see another round of fog and showers moving through our area overnight. Another mild night across the forecast areas as lows will not drop much and remain in the 60s.
Long Term - Tuesday Through Sunday
Overview: The focus of the long term is a slow moving cold front expected between Tuesday night into early Thursday. There will be multiple areas of low pressure riding north along the front. During this period, heavy rain is possible. Another cold front will move through late Thursday into Friday. Cooler air will filter in behind these fronts.
Tuesday and Wednesday...A cold front will approach the region through this period. The front will initially be associated with a surface low centered over Ontario/Quebec. However, another low is expected to develop along the front over the southeastern U.S. in response to a digging mid level trough. This should lead to the front slowing, and possibly even stalling over our region.
What has changed: The 00Z GFS is back to being a more progressive solution, with the front off shore by early Wednesday morning. If this solution comes true, we will still have a threat for heavy rain on Tuesday, but the threat for heavy rain on Wednesday will decrease significantly. Given the poor run to run consistency, and the lack of agreement among the main operational models, have stayed close to the previous forecast and a blend of 00 and 18Z guidance.
Timing: Showers are expected to begin ahead of the arrival of the front. The front should enter Eastern PA no later than mid day Tuesday. As far as how long it will take to progress off shore, it could be off shore as early as late Tuesday night/early Wednesday morning, or if it stalls over our region, it may not be off shore until late in the day Wednesday.
Hazards: The main hazard is still expected to be heavy rain. The longer it takes the front to cross the region, the longer the heavy rain could last, and the more likely it is to lead to flash flooding concerns. Precipitable water values over the coastal plains are likely already well above normal with an observed value from Long Island of 1.5 inches which is right around the 90th percentile for late September. Other nearby soundings (from Wallops Island and IAD) were right around one inch which is only slightly above normal. The southerly return flow has yet to become established, so expect PWAT (Precipitable Water) values to increase further before Tuesday. Additionally the warm cloud layer will likely be very deep for late September. Also, low and mid level flow could be close to parallel of the front (if it stalls), which could increase the threat for training storms or showers. Still have too much uncertainty with the timing of the front to issue a flash flood watch, but will continue with a mention in the HWO. As for the threat of severe storms, models continue to show significant effective shear (30 to 40 kt). However, guidance is in poor agreement as to how much instability will develop (anything from MU CAPE values near 0 to near 1000 J/kg). Even if sufficient instability develops, it will likely be only for a brief window on Tuesday afternoon. Thus, think the threat for severe storms is still very limited.
Thursday And Friday
In the wake of the main cold front, cooler air settles in over the region. A secondary cold front is expected Thursday night into Friday morning. However, dry air advection beginning in the wake of the earlier front should limit rain chances with this front.
Saturday and Sunday...A trailing mid level short wave trough could lead to some rain in this period, but as with the Thursday and Friday period, moisture could be a limiting factor. Even if we do get rain, it should be isolated at most.
Winds and seas are expected to stay below Small Craft advisory criteria through Monday however winds may gust up to 20 knots Monday afternoon with seas increasing to around 4 feet.
Monday night...Winds and seas will approach SCA (Small Craft Advisory) criteria.
Outlook... Tuesday and Wednesday...Seas ans southwesterly winds will increase ahead of a cold front on Wednesday night. SCA (Small Craft Advisory) conditions, especially for seas are possible.
Thursday And Friday
Decreasing winds and seas will fall below SCA (Small Craft Advisory) criteria.
Rip Currents... There is a low risk for the development of dangerous rip currents Today. On Tuesday, a moderate risk for the formation of rip currents is expected for the New Jersey coast due to increasing southerly winds and wave heights. For the Delaware coast, the forecast risk for rip currents on Tuesday is expected to be low at this time.
NOAA Mount Holly NJ Office: Watches - Warnings - Advisories
PA...None. NJ...None. DE...None. MD...None. MARINE...None.