Marine Weather and Tide Forecast for Lewes, DE

KEY MESSAGES
1. Some severe thunderstorms possible this afternoon and early this evening, then again Thursday afternoon and Friday afternoon.

2. Dangerous heat (potentially record heat) and humidity for much of the region Thursday and Friday, then much less humid over the weekend.

DISCUSSION
KEY MESSAGE 1...Some severe thunderstorms possible this afternoon and early this evening, then again Thursday afternoon and Friday afternoon.

A weak shortwave trough will slide across our area early this evening and this will be timed with a surface trough in place. An embedded MCV looks to be enhancing the forcing for ascent within the trough axis. Southerly flow ahead of these features will continue to advect increasingly humid air into our area along with increased warm air advection.

The warm and more humid conditions will result in an unstable airmass into this evening despite areas of cloud cover. Some showers and thunderstorms are forecast to cross our region from west to east through early this evening (3-9 PM) associated with the aformentioned shortwave trough/MCV. MLCAPE is forecast to be on the order of 1000-1500 J/kg, however the deep layer shear is only 10-20 knots. As a result, convection should be more of the pulse variety although the unstable environment may result in some convective clustering from the west. Any more organized convection that can maintain stronger cores will be capable of local/isolated damaging wind gusts from water loaded downbursts. The low-level lapse rates are not very steep into this evening given the much more humid air mass now in place, therefore minimizing the DCAPE and thus not enhancing the wind threat. Precipitable water values are near 2 inches, therefore brief torrential downpours will be possible with any stronger cores into this evening which could cause some localized urban flooding.

Warm and muggy tonight with lows in the mid 60s to low 70s. Some fog or low clouds may develop late, especially near any areas that get a decent amount of rain through early this evening.

The pattern in place will continue to support some additional showers and thunderstorms across the region Thursday and Friday, mainly during each afternoon and evening. Better synoptic forcing will arrive on Friday however with a cold front.

Large scale forcing and shear are expected to remain relatively weak on Thursday, however we will have a convectively enhanced shortwave from remnant convection upstream in the Midwest to contend with.
This will enhance the forcing at the mesoscale, however the timing and location of this feature is less certain. Hotter temperatures and high dew points will yield steeper low-level lapse rates.
This is a pretty typical severe thunderstorm setup for our region, and will likely trigger at least some diurnally driven convection mainly from mid afternoon through early evening. The details remain less certain as it will also depend on how things evolve upstream through tonight. A SLIGHT risk (level 2 out of 5) for a severe thunderstorm potential remains in place for Thursday. Damaging winds will be the main threat as storms may cluster or evolve into one or more short lines with some bowing, however large hail cannot be ruled out given the magnitude of the instability that is forecast.

On Friday, the region is expected to begin feeling the influence of the upper-level trough to the west of the region, in addition to a cold front that will be arriving from the west. Some showers and thunderstorms should focus near and ahead of this front, and with strong destabilization and slightly better wind fields aloft, a severe threat will once again be present. The convective coverage could be once again enhanced by a convectively induced shortwave from the Great Lakes or upper Ohio Valley. This evolution is less certain, however our entire area is highlighted in a SLIGHT risk (level 2 out of 5) for severe thunderstorms. Damaging winds will once again be the main threat as storms may tend to cluster or evolve into one or more short lines with some bowing.

KEY MESSAGE 2...Dangerous heat (potentially record heat) and humidity for much of the region Thursday and Friday, then much less humid over the weekend.

A mid-level ridge slides across the Mid-Atlantic and Northeast Thursday and Friday, however a shortwave trough crosses New England for a time. At the surface, high pressure remains centered off the Southeast U.S. coast which will continue to direct a hot air mass across our area.

Dangerous heat is expected across much of our region on Thursday and Friday, with even some record high temperatures potentially getting challenged. High temperatures both Thursday and Friday are forecast to peak into the low to mid 90s across most of the area, though highs may be a little warmer on Friday compared to Thursday. Dew points will start out in the low to mid 70s, but with afternoon heating and mixing, these should mix down to the upper 60s and low 70s. This still results in peak heat index values of 95 to 105 degrees across the majority of the area, outside of the southern Poconos. This level of heat and humidity can become dangerous quickly for sensitive individuals and those outdoors for extended periods of time. A Heat Advisory remains in effect Thursday through Friday for areas where the heat index criteria starts at 96F and 100F. For coastal Monmouth County, the advisory is only in effect for Thursday as some onshore flow Friday may result in some more immediate cooling off the ocean.

A cold front is forecast to move through the region late Friday, which will knock the temperatures and especially the dew points down several degrees. Though it will still be hot with high temperatures in the upper 80s to low 90s over the weekend, dew points will return to much more comfortable levels and this minimizes the risk for additional heat related advisories.

AVIATION /19Z WEDNESDAY THROUGH MONDAY/
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

Rest of Today...After MVFR ceilings this morning, we see prevailing VFR. Scattered thunderstorms will impact the terminals this afternoon, and will carry TEMPO groups for this.
Southwest winds 10 to 15 kt with gusts up to 20 kt this afternoon. Low confidence on timing and restrictions resulting from any SHRA and TSRA.

Tonight...Most terminals should see a period of VFR conditions before 06Z following the afternoon/evening storms. After around 06Z, some low stratus/patchy fog develops leading to MVFR conditions. Winds remain out of the southwest near 5 kts. Low confidence.

Thursday...After sub-VFR conditions in the morning due to fog/low stratus, prevailing VFR is expected. Winds become more westerly in the morning at 5-10 kt. Another round of showers and thunderstorms in the afternoon and evening will lead to the potential for sub- VFR conditions being possible. Moderate confidence.

Outlook...

Friday...Prevailing VFR expected through the period. Brief periods of sub-VFR conditions are possible, with isolated to scattered showers and thunderstorms during the afternoon and evening hours.

Saturday through Sunday...VFR. No significant weather expected.

Monday...Sub-VFR possible with the chance for rain showers.

MARINE
Winds out of the south are expected to continue to increase through this evening with seas also continuing to build. For the Atlantic coastal waters, winds gusting up to 25 kts and seas near 4-5 feet are expected. A Small Craft Advisory remains in effect through midnight tonight. Some isolated thunderstorms may impact the nearshore waters and Delaware Bay this evening.
Winds and seas decrease overnight.

For Thursday, conditions are expected to remain below Small Craft Advisory criteria. A southwest wind at 10 kt with gusts 15-20 kt and seas of 3-4 feet. Some isolated to scattered showers and thunderstorms may impact the nearshore waters and Delaware Bay Thursday evening.

Outlook...

Friday through Saturday...No marine headlines anticipated.
Winds will generally remain between 5-15 kt through Saturday.
Seas generally around 2-3 feet. Isolated to scattered showers and thunderstorms possible on Friday. Fair weather expected for Saturday.

Sunday...A brief period of marginal Small Craft Advisory conditions are possible Sunday afternoon and evening with wind gusts near 25 kt.

Monday...No marine headlines anticipated with winds 5-10 kt and seas 2-3 feet.

Rip Currents...

On Thursday, south to southwest winds will be around 10 mph with breaking waves of 1 to 2 feet and a southerly swell with a period around 6 seconds. As a result, there is a LOW risk for the development of dangerous and life threatening rip currents for the Jersey Shore and Delaware Beaches.

Conditions will be fairly similar on Friday, so the LOW risk for the development of dangerous and life threatening rip currents continues for the Jersey Shore and Delaware Beaches.

Ocean water temperatures are mostly in the 60s.

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

CLIMATE
A very hot and humid air mass will overspread our area through Friday. Some record high temperatures could be challenged Thursday and/or Friday.

Location 6/11 Record Highs/Year

Mount Pocono 91/1911 Allentown 94/1984 Reading 98/1911 Philadelphia 95/1986 Trenton 96/1911 Atlantic City Airport 97/1984 Atlantic City Marina 91/1959 Wilmington 95/1973 Georgetown 95/1959

Location 6/12 Record Highs/Year

Mount Pocono 87/1967 Allentown 92/2017 Reading 95/1984 Philadelphia 95/2015 Trenton 94/1933 Atlantic City Airport 94/2017 Atlantic City Marina 93/1914 Wilmington 96/1933 Georgetown 95/2017

PHI WATCHES/WARNINGS/ADVISORIES
PA...Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for PAZ060>062-070-071-101>106.
NJ...Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for NJZ001-007>010-012-013-015-017>020-027.
Heat Advisory from 11 AM to 8 PM EDT Thursday for NJZ014.
DE...Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for DEZ001.
MD...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ450>455.