Marine Weather and Tide Forecast for Atlantic, VA

KEY MESSAGES
1) While very warm/hot conditions prevail, areas of smoke will likely suppress daytime high temperatures through Friday. Given this scenario, highs have been lowered and no additional Heat headlines will be issued at this time.

2) Thunderstorm chances increase this weekend, bringing the potential for locally heavy rain, along with very warm and humid conditions persisting into early next week.

DISCUSSION
As of 300 PM EDT Wednesday...

KEY MESSAGE 1...While very warm/hot conditions prevail, areas of smoke will likely suppress daytime high temperatures through Friday. Given this scenario, highs have been lowered and no additional Heat headlines will be issued at this time.

The latest WX analysis indicates an anomalously strong upper level ridge extending E-SE from the mid/upper MS Valley into the lower mid-Atlantic. A strong upper level low is spinning over eastern Canada. At the surface, high pressure has weakened as a sfc trough of low pressure has developed across the region. The main story today has been a rather dense area of smoke aloft that has been in place along and S of the I-64 corridor. This has significantly limited the temperatures, with much of this area only in the upper 80s to lower 90s, or roughly 5 degrees cooler than what the models depict. To the N/NE, under full sunshine and a westerly sfc wind, most of the MD eastern shore is experiencing temps in the mid to upper 90s, with dew pts in the 70s and resultant heat indices of 105+ at SBY/OXB. The Heat Advisory remains in effect until 8 PM, though the southern portions closer to the smoke aloft will likely fall short of criteria and generally have heat indices peak ~100F. Have manually added "haze" wording to the gridded database tonight, spreading NE to encompass all zones overnight (following close to the HRRR/RFS Vertically integrated smoke forecasts which have been handling the current conditions well).

With a W-NW flow aloft continuing Thursday, high temperatures have been lowered 3-5 degrees from NBM and numerical MOS given the expected smoke aloft. The HRRR/RFS even show some potential for near sfc smoke and reduced sfc VSBYs (currently located from the northern 1/2 of lower Michigan to upstate NY), to drop as far south of the lower Maryland eastern shore during the day.
While the precise scenario is uncertain, there is a high probability that the smoke will at least be present aloft so no additional Heat headlines will be issued w/ this forecast cycle as highs will generally be in the mid to upper 90s with heat indices staying below 105F. Convection should remain suppressed away from the area through most of Thursday, though we will maintain a slight chance (~20%) PoP Thursday evening across the MD Eastern Shore, as upstream convection approaches from the north before washing out. On Friday, in the wake of the sfc boundary pushing through Thu night, the low level flow is forecast to become onshore, with high temperatures dropping a few degrees (even without the smoke). In addition, the HRRR/RFS show a higher concentration of vertically integrated smoke (and sfc based smoke into much of the CWA). Highs are forecast to mostly be in the low-mid 90s (and even this may be too high). Somewhat lower dew pts filter in from the north keeping heat indices below 100F for much of the region (potentially could see heat indices up to 105 for interior NE NC if the smoke stays north).
An isolated shower/storm moves in from the NW Friday evening, as isolated convection riding along the ridge could make it into the area before weakening, but chances are very low.

Additional Air Quality alerts are possible later this week and we will continue to monitor potential further impacts in the days ahead.

KEY MESSAGE 2...Thunderstorm chances increase this weekend, bringing the potential for locally heavy rain, along with very warm and humid conditions persisting into early next week.

The upper level ridge continues to gradually break down over the weekend as upper troughing re-establishes itself over the northern Mid-Atlantic and northeast CONUS. A series of shortwaves will track across the area from Saturday through Monday ahead of the next front approaching from the north. It now seems likely that this weakening front will linger across the area into Monday.

While considerable uncertainty remains regarding the exact timing and coverage of storms, the upper flow turning WNW-NW over a hot, increasingly humid, and moisture-pooled boundary layer sets up a climatologically-favored pattern for locally heavy rainfall and downbursts. Low-level frontal forcing still appears weak, typical of mid-July, but moisture pooling along the slow-moving boundary beneath steep mid-level lapse rates will favor a hot, muggy, high DCAPE setup capable of producing isolated to scattered damaging wind gusts each day this weekend, potentially lingering into Monday. Areal coverage of these storms will ultimately depend on the timing of each shortwave, which remains highly uncertain at this time range.

High temperatures trend a bit cooler with the increasing PWs and cloud cover. However, with that comes higher dewpoints. This appears especially likely across SE VA and NE NC, where max heat indices will likely linger near 105 F through Sunday, if not Monday.

AVIATION /00Z THURSDAY THROUGH MONDAY/
As of 712 PM EDT Wednesday...

Mainly VFR conditions prevail across all terminals through the 00z TAF period with smoke from Canadian wildfires remaining aloft (~25 k ft). Winds will generally be light from the S-SW.
There is some potential for reduced VSBYs in near sfc smoke mainly at SBY on Thursday and a slight chc for evening tstms at SBY Thu evening. Elsewhere, all terminals could potentially see reduced VSBYs in near sfc smoke by Friday.

Outlook: Higher chances for SHRA/TSRA are expected Sat aftn/evening and again Sunday.

MARINE
As of 255 PM EDT Wednesday...

- Sub-SCA marine conditions persist through Saturday. Southerly flow becomes E-NE 10-15 kt behind a weak boundary Friday.

- Potential for marginal Small Craft Advisory conditions in elevated southerly flow Saturday night into Sunday.

Winds are SW around 10 kt this afternoon as weak high pressure remains south of the waters. Expecting another nocturnal increase in the winds tonight (to 10-15 kt) and a few gusts to 20 kt are again possible on the ocean and Chesapeake Bay. Sub-SCA boating winds and seas, however, prevail through the end of the week. Still keeping an eye on a wind shift to the E-NE Friday as a weakening boundary sags southward into the region. While wind speeds should generally stay below 15 kt, some of the model guidance indicates a brief uptick to 15-20 kt in the afternoon. These winds would be more likely in the northern waters, but especially N of Cape Charles. Southerly flow could then approach SCA thresholds Saturday night into Sunday morning ahead of another frontal system. Seas average around 2 ft this week, but could briefly increase to 3+ ft Friday with the NE winds. Seas increase further to 3-5 ft as S winds increase later Saturday-Sunday.

There is a moderate risk for rip currents across the northern Outer Banks, NC today with a low risk elsewhere. A low risk is favored everywhere Thursday and Friday. Depending on the strength of the NE winds Friday (and the resultant seas and nearshore waves), a moderate rip could eventually be required.

CLIMATE
As of 650 AM EDT Wednesday...

- Record Highs:

- Today 7/15 Thu 7/16 Fri 7/17

- RIC: 100 (1995) 101 (1980) 100 (1980)
- ORF: 101 (1995) 102 (1879) 100 (1887)
- SBY: 100 (1995) 99 (1915) 99 (2012)
- ECG: 97 (1997) 98 (1995) 99 (1942)

- Record High Mins:

- Thu 7/16 Fri 7/17

- RIC: 77 (1983) 77 (2025)
- ORF: 80 (1995) 80 (2024)
- SBY: 78 (2024) 80 (1983)
- ECG: 79 (2012) 80 (2019)

AKQ WATCHES/WARNINGS/ADVISORIES
MD...Heat Advisory until 8 PM EDT this evening for MDZ021>025.
NC...None.
VA...Heat Advisory until 8 PM EDT this evening for VAZ064-075>078- 084>086-099-517>522.
MARINE...None.