Marine Weather and Tide Forecast for Aquia Harbour, VA

KEY MESSAGES

- 1)High heat and hazy skies look to continue through Friday.

- 2)Thunderstorm chances increase this weekend and could potentially linger into Sunday as a front drops into the region.

DISCUSSION

KEY MESSAGE 1...High heat and hazy skies look to continue through Friday.

Heat Advisories have been allowed to expire with additional heat headlines potentially needed Thursday pending the thickness of the Canadian wildfire smoke sinking south tonight and how much mixing can occur Thursday afternoon. Similar conditions are expected Friday making the temperature/heat index forecast more complex as an even thicker plume of Canadian wildfire smoke descends upon the region.

Current hi-res guidance suggest a steady increase in smoke concentrations tonight as the outflow from earlier storms over NJ/PA force smoke south into northern and central MD. Concentrations will continue to increase Thursday as an additional wave of smoke is sent southward from fires raging over Quebec and western Ontario. With that said, hi-res guidance (such as the RRFS-A and HRRR) hint at some slightly lower air temperatures and higher dewpoints Thursday and Friday which could negate the need for heat headlines. This will be something that will need to monitor given what played out earlier today with the smoke aloft and subdued mixing. With the smoke, will come a few more days of poor air quality.The respective air quality agencies in MD and VA have issued Code Orange Air Quality Alerts for the DC/Baltimore metros Thursday with additional alerts likely Friday as air quality worsens.

In addition to the heat and smoke/poor air quality will be the concern for a few isolated showers/strong thunderstorms. The atmosphere looks less capped Thursday and Friday for convective development. Height falls/PVA will be negligible as most forcing for ascent will be associated with shortwaves in cyclonic flow passing to the north and northeast. However, a halt in height rises paired with a slowly southward sagging cold front and potentially bay breezes in areas where low-level flow goes weak in the vicinity of the front, may be enough when coupled with heating to result in a couple of isolated thunderstorms. There is further uncertainty given continued smoke aloft, as that could hamper heating and instability/convective initiation.Upstream over NE PA into NJ and the NYC tri-state area from earlier today may offer a clue as we will be in a similar environment across the MD/PA border Thursday afternoon. Any storms that manage to develop will have ample MLCAPE (2000-3000 J/kg) and DCAPE (1000-1500 J/kg) to work with, as well as notable flow in the mid and upper levels for mid July (40-50+ kts).
If any storms manage to develop by late afternoon, they could at least briefly congeal into a small cluster and propagate south/ southeast toward and across the Chesapeake Bay during the evening hours. Damaging winds would be the primary (conditional) risk, but large hail is also possible given ample CAPE, shear, and low seasonably low wet-bulb zero heights around 11.5 kft. ANy storms that we do see will help scrub out some of the smoke and improve air quality.

KEY MESSAGE 2...Thunderstorm chances increase this weekend and could potentially linger into Sunday as a front drops into the region.

The surface front will drop further southward Friday. Additional smoke likely mixes into the region. Any convection on Friday will likely be limited to the higher terrain as the front washes out and pairs with orographic lift. Again, any storm that does form could be on the strong side.

Friday night, the aforementioned front will begin to lift north ahead of a wave of low pressure and stout shortwave approaching from the Upper Midwest/Great Lakes. Increasing MLCAPE late at night with some moisture advection and modest low-level flow overtop the front may result in a few thunderstorms heading into early Saturday morning, especially east of the Blue Ridge where a bit richer low- level theta-e ridge looks to pivot through.

Forcing and shear will be ample on Saturday, but the amount of instability is in question due to potential morning precip.
Should enough instability develop, severe weather is certainly possible with all hazards (damaging straight-line winds, large hail, a few tornadoes, and isolated instances of flash flooding) on the table. This aligns with CSU/NSSL/CIPS probabilities which suggest a 5 to 15 percent probabilities of severe weather during the weekend period. If the front does not make it entirely through the area, repeated strong storms will be possible on Sunday.

After a brief lull possible on Monday, another strong wave may approach by the middle of next week.

AVIATION /01Z THURSDAY THROUGH MONDAY/
VFR conditions will likely continue through Friday under mostly dry conditions. One thing of note will be smoke aloft from fires burning over western Ontario. This will result in a hazy appearance of the sky through Friday. Vsby reductions of 5-6 SM are possible corridor Thursday and Friday afternoons with lower vsbys (2-4 SM) Thursday night into Friday, especially north and east of IAD/DCA as smoke mixes south and closer to the surface behind a weak front. Winds will vary between N/NW and SW over the next few days as that front sits nearby. A thunderstorm can't be ruled out Thursday late afternoon and evening, mainly east of the Blue Ridge and in northern MD but confidence is very low. Did add a PROB30 between 20-24z at both BWI/MTN where the confidence seems the highest for storm development off the bay breeze. Can't rule out a thunderstorm near the mountains Friday afternoon.

Periods of sub-VFR restrictions can be expected at times through the weekend due to thunderstorms. The greatest coverage of storms will likely be on Saturday potentially lingering into Sunday. Expect early morning low CIGS or patchy fog with afternoon/evening convection. Winds will remain light overall with chaotic motions in around thunderstorms.

MARINE
Winds will waver between N/NW and SW over the next few days as a cold front dangles near the waters. Depending on the strength of the front and how far north or south it pushes, there may be at least brief/marginal periods of SCA level gusts, though these currently appear too brief with certainty too low for any headlines at the moment. A couple of thunderstorms can't be ruled out along the cold front Thursday late afternoon and evening, and anything that does manage to form could produce rather gusty winds.

More widespread thunderstorm activity and the need for SMWS will be needed over the weekend as a cold front sags into the region.
Southerly channeling also returns to portions of the waters Saturday into Sunday.



CLIMATE
Well above normal temperatures will persist through Thursday.

Below is a list of record daily high and warm low temperatures for July 15 (Wednesday) and July 16 (Thursday).

================================================================= July 15 Record Daily High/Warm Low Temperatures ================================================================= Baltimore MD 102 (2024, 1995) 79 (1995, 1936)
Washington DC 102 (2024) 81 (2024)
Sterling-Dulles Airport VA 99 (2024) 75 (2024)
Baltimore (Downtown) MD 101 (2024) 85 (1988)
Annapolis MD 101 (1995) 81 (1896)
Hagerstown MD 102 (1954) 78 (2024)
Martinsburg WV 107 (1936) 75 (1995)
Charlottesville VA 102 (1954) 76 (1936)

================================================================= July 16 Record Daily High/Warm Low Temperatures ================================================================= Baltimore MD 104 (2024, 1988) 78 (1879)
Washington DC 104 (2024, 1988) 84 (1983)
Sterling-Dulles Airport VA 104 (1988) 74 (2013)
Baltimore (Downtown) MD 105 (2024) 85 (2013)
Annapolis MD 98 (1997, 1900) 79 (2024, 2013, 1955)
Hagerstown MD 104 (1988) 76 (2024)
Martinsburg WV 107 (1988) 77 (1983)
Charlottesville VA 102 (1988) 82 (1983)

Period of Record (POR) information (records since): Baltimore MD - July 1872 Washington DC - January 1872 Sterling - Dulles Airport VA - January 1960 Baltimore (Downtown) MD - July 1950 Annapolis MD - January 1894 Hagerstown MD - January 1899 Martinsburg WV - January 1891 Charlottesville VA - January 1893

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.