National Weather Service Mount Holly NJ
228pm EDT Fri July 12 2024
Synopsis
Stationary front plagues the region into Saturday with several waves of low pressure riding along it. Broad high pressure then returns and persists through Tuesday before another cold front approaches the area around the Wednesday-Thursday timeframe.
Near Term - Through Saturday
A frontal boundary has lifted northward into the area from the coast. Bermuda high pressure will continue to advect a ribbon of rich tropical moisture back into the region along and south of this front as well. Meanwhile, a broad jet located to our northeast will result in broad diffluence aloft, strengthening through Saturday. Meanwhile, a closed upper low is passing by just offshore.
Showers and a few thunderstorms continue to spread across the area this afternoon. The heaviest rain has occurred near the coast, which was farther south than anticipated for the daytime period. Localized amounts of 3-5" of rainfall have been observed. The showers and storms should continue into this evening, however a break in activity is expected overnight as a lull in synoptic forcing occurs. PWATs (Precipitable Waters) will remain around 2-2.5", near climatological maxima, along with MUCAPE near 1,000 J/kg. The more robust showers and thunderstorms that develop will be capable of producing very heavy rainfall, with rainfall rates near 2" per hour. The threat for severe thunderstorms is very low. Probability of Precipitation was adjusted to match the latest guidance, including a lull overnight.
Temperatures will remain below normal through this afternoon, topping out in the upper 70s to low 80s in most areas. With all the cloud cover and moisture around tonight, temperatures will remain quite mild, with lows ranging from the low to mid 70s. Light southerly winds through Saturday, though winds will become light and variable at times.
While the heaviest rainfall so far today has occurred near the coast, guidance continues to pinpoint the heaviest rainfall potential from across portions of Delmarva and into the urban corridor through early Saturday afternoon. An additional wave of widespread heavy showers and thunderstorms is expected to impact this area beginning around daybreak Saturday through around midday. Widespread rainfall amounts near 1-2" can be expected, with locally higher amounts up to 5" possible. Rainfall rates may exceed 1-2" per hour at times. While much of the area has been dry recently, the rainfall rates may lead to some areas of flash flooding, especially in urbanized and poor drainage areas. The Flood Watch remains in effect as previously issued through 2pm Saturday to highlight this threat.
Short Term - Saturday Night Through Sunday Night
Surface stationary front and low pressure riding along it will continue to plague the region Saturday. Luckily, the stationary front should begin to dissipate some Saturday night as weak surface high pressure builds in. Weak surface high pressure looks to hold influence over us Saturday night through Sunday night.
Overall, short term looks impactful for Saturday morning into Saturday afternoon and rather benign thereafter, at least Probability of Precipitation wise. The concern remains for moderate to heavy rainfall Saturday leading to flooding concerns. Plenty of low-level moisture, showers and storms will continue to stream northwards from the south Saturday morning; storm motions will remain relatively slow. Any area of rain will be more than capable of producing heavy rainfall and localized flash flooding; grounds cold very well be saturated from Friday night. Please see the NEAR TERM for more details.
PoPs will begin to diminish later Saturday afternoon. The I-95 corridor and areas west should actually start to see clearing skies in the late afternoon. Highs mainly in the mid to upper 80s can be anticipated. Other than for some areas near the coast early on, no Probability of Precipitation is included in the forecast for Saturday night. Fog formation across the region is possible Saturday night with an overall saturated boundary layer, mostly clear skies, and very light and/or calm winds.
Heat returns for Sunday with highs mainly in the low to mid 90s across the region. With dewpoints in the 70s, heat indices will once again climb back up. Right now, some areas of the I-95 corridor hit advisory criteria in the forecast for Sunday; Sunday may be the first day advisories are needed. A stray and isolated shower is not out of the question for Sunday and Sunday night with the proximity of the decaying front, but the forecast mainly remains dry.
Long Term - Monday Through Thursday
The high heat and humidity returns for the beginning to midweek time frame before a cold front crosses through Wednesday- Thursday. Afternoon highs in the mid to upper 90s with dew points in the 70s are anticipated for at least Monday and Tuesday, maybe continuing into Wednesday depending on the timing and placement of the mentioned cold front. With heat indices of 100-110 across the region, widespread heat headlines are anticipated for Monday and Tuesday. Headlines may continue into Wednesday as well. More seasonable conditions will likely return once the cold front has crossed through.
Diurnally-driven thunderstorms are likely to occur each afternoon, but with the lack of any forcing nearby, the threat does not appear to be severe. Eventually, the cold front will approach from the northwest Wednesday into Thursday, which may result in a more widespread chance of showers/thunderstorms across the region.
Marine
Southerly winds 10-15 kts with some gusts near 20 kts possible. Seas will be around 4-5 feet through this evening, so we've extended the Small Craft Advisory through 10 PM.
VSBY restrictions in showers and fog. Rain may be heavy at times. Scattered thunderstorms possible as well.
Outlook... Saturday night...SCA (Small Craft Advisory) flag possible due to seas around 5 feet. Some fog development possible Saturday morning and Saturday night.
Sunday through Tuesday...No marine headlines expected. Winds up to 20 kt and seas 2-4 feet.
Rip Currents... South to southeast winds will range from 10 to 15 mph with breaking waves of 2 to 4 feet. With the flow slightly onshore or parallel to the shore in New Jersey, there is a MODERATE risk for the development of dangerous rip currents at the Jersey Shore. For Delaware, the flow will be more onshore if not a bit offshore. As a result, there is a LOW risk for the development of dangerous rip currents at Delaware Beaches.
Conditions on Saturday will be similar to conditions today, though Jersey Shore beaches in Monmouth county will have a LOW risk, while the rest of the Jersey Shore will have a MODERATE risk for dangerous rip currents. Delaware Beaches will once again have a LOW risk for the development of dangerous rip currents.
For specific beach forecasts, visit weather.gov/beach/phi
NOAA Mount Holly NJ Office: Watches - Warnings - Advisories
PA...Flood Watch through Saturday afternoon for PAZ070-071-101>106. NJ...Flood Watch through Saturday afternoon for NJZ001-007>010-012- 013-015>019. DE...Flood Watch through Saturday afternoon for DEZ001-002. MD...Flood Watch through Saturday afternoon for MDZ012-015-019-020.
Marine
Small Craft Advisory until 4pm EDT this afternoon for ANZ450>455.
