textproduct: Philadelphia/Mt Holly

SYNOPSIS

High pressure will remain in control through the remainder of the weekend, resulting in seasonable temperatures and tranquil weather conditions. Warmer, more humid, and unsettled conditions will return next week, with daily chances for showers and thunderstorms.

NEAR TERM /THROUGH SUNDAY/

Pleasant weather conditions continue into Sunday thanks to large scale subsidence and high pressure largely remaining in control, even as it is now centered offshore. As a result, conditions will also remain mostly dry through the near term forecast period.

Under a mostly clear to partly cloudy sky, temperatures will fall toward near normal conditions tonight with lows settling into the low to mid 60s. With the high offshore, the southerly flow and increase in humidity continues with dew points in the low 60s overnight so some patchy ground fog may be possible in areas that see the winds completely decouple overnight.

For Sunday, the return of increasing heat and humidity continues with southerly flow increasing as the high pressure shifts further offshore. Highs on Sunday will be largely in the upper 80s to low 90s as a result. Significant moisture will also begin to surge into the region with Tropical Storm Chantal moving into the Carolinas. The main effect will be increasing dew points, particularly Sunday afternoon. Lingering subsidence from the departing high should keep most of the region dry but a few afternoon showers may spark off in Delmarva.

SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/

A more tropical air mass starts to stream northward Sunday night into Monday morning. There will also be some moisture moving northward from what will be left of Tropical Storm Chantal as it is expected to dissipate over North Carolina Sunday night into Monday morning. There is the potential for some stray showers or thunderstorms in Delmarva and southern New Jersey. The tropical air mass continues to be in place Monday through Tuesday night.

What to expect during this timeframe is highs in the 80s to near 90 both Monday and Tuesday with dew points in the 70s both days. Heat indicies for part of the area on Tuesday will be near 100 degrees. This shows how warm and humid the air mass will be for the beginning of next week. A cold front moves in from the west Monday into Tuesday which will enhance shower and thunderstorm coverage. The stray shower and thunderstorm coverage Sunday night becomes more scattered to even at times more widespread during the second half of the day Monday. A lot of this activity is diurnally driven and becomes more isolated Monday night. Once again, the coverage becomes more scattered the second half of the day Tuesday with it once again becoming stray to isolated in coverage Tuesday night.

As mentioned, this will be a tropical air mass which will allow PWAT values to reach 2-2.3 inches across the area with at times localized values of 2.5 inches. Model soundings during this timeframe show a favorable warm cloud layer depth and tall skinny CAPE. All of this points to these showers and storms being sufficient rainfall producers that can pose the threat for localized flash flooding. Speaking of CAPE, the warm and humid air mass will allow for growing instability with modeled values of MLCAPE around 1000 J/kg but there will be little shear. Now, the environment will not be overly conducive for severe weather but isolated severe thunderstorms will be possible Monday and Tuesday with damaging winds being the primary threat from water loaded downdrafts.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

We continue with an unsettled weather pattern for the long term period. The cold front that moves through Monday into Tuesday stalls across the southern half of our area leading to continuing periods of showers and thunderstorms. The lowest coverage of showers and storms will be on Wednesday before they become more scattered again Thursday and Friday.

We will continue to also see high temperatures mainly in the 80s Wednesday through Friday. Dew points will also be in the 60s and 70s, so we will continue to hold onto the humidity as well.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

Tonight...VFR. Southwesterly winds 5-10 knots, becoming light and variable to locally calm. High confidence.

Sunday...VFR. Light and variable winds becoming south-southwest around 10 knots. High confidence.

Outlook...

Sunday night...MVFR or IFR ceilings may develop.

Monday...MVFR or IFR ceilings possible to start, then VFR.

Tuesday through Thursday...Prevailing VFR with daily chances for thunderstorms. Areas of fog possible at night.

MARINE

No marine headlines are in effect through Sunday. Winds mainly out of the south-southwest around 5-10 knots through tonight, increasing to around 10-15 knots on Sunday. A few gusts up to 20 knots possible on Sunday. Seas of 2-3 feet and fair weather throughout the period.

Outlook...

Sunday night...No marine hazards expected.

Monday through Thursday...Daily chances of showers and thunderstorms, otherwise fair weather.

Rip Currents...

For Sunday, southerly winds will remain 5-10 mph. Breaking wave heights of 1-2 feet with a primary SE swell around 2 feet and a 6-8 second period. Guidance is hinting at some longer period swells potentially becoming dominate with swells ranging from 10-14 seconds. This would increase the Rip Current risk to at least moderate however given the swells should be less than 3 feet and breaking waves are small, will continue a LOW risk for dangerous rip currents for all beaches at this time.

For Monday, southerly winds will increase to 10-15 mph. Breaking wave heights increase to 2-3 feet with a primary S swell around 3 feet and a 6-8 second period. Given slightly stronger winds and slightly higher waves with slightly higher swell, went with MODERATE at the more southerly facing NJ beaches of Cape May, Atlantic and Ocean, and LOW for the easterly facing beaches of Monmouth and DE.

Rip currents occur often in the vicinities of jetties and piers and the speed of the currents are generally maximized at low tides.

For specific beach forecasts, visit weather.gov/beach/phi

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...None.