Marine Weather and Tide Forecast for Dumfries, VA

KEY MESSAGES
- 1) A strong cold front will arrive Monday, bringing strong winds and the potential for severe thunderstorms.

- 2) Gusty winds continue across the area through early Saturday morning.

DISCUSSION
KEY MESSAGE 1...A strong cold front will arrive Monday, bringing strong winds and the potential for severe thunderstorms.

The Mid Atlantic should be in the warm sector of a powerful low pressure system over the Great Lakes on Monday. A deep upper trough pushing east of the Mississippi Valley will be taking on a negative tilt. Winds throughout the atmosphere will be very strong, along with notable low level wind shear (though more speed than direction). Dew points in the upper 50s to lower 60s and modest mid level lapse rates will limit instability but there should still be enough to support convection. The thermodynamic profile could be one of the primary factors into just how significant the severe weather is. There is some threat for some leading cellular development in the warm sector which could pose a wind and tornado risk. Then, a squall line is likely to develop ahead of the sharp cold front.
Damaging winds, some potentially significant, will be a threat with the squall line. A QLCS tornado threat could also be present, although the shear vectors will be more parallel to the line vs. the more favorable perpendicular. Seasonally high precipitable water will also result in heavy rain, although storms will be moving quickly. Timing is still a bit uncertain, but the most favorable conditions combined with afternoon/early evening timing are projected east of the Blue Ridge. SPC has highlighted a somewhat rare 30 percent day 4 severe outlook for this area. Besides the convective winds, gradient winds will also be strong immediately ahead of and behind the front which could cause additional localized tree damage and/or complicate recovery efforts. Cold air will be rushing in immediately following the frontal passage. At a minimum, the Allegheny Mountains will change to snow for a time in upslope conditions. It remains uncertain if any postfrontal precip lingers to the east long enough to change over.

Cold and windy conditions linger into Tuesday with the upper trough overhead. Tuesday night will likely be the coldest night of the stretch with widespread temperatures in the teens and 20s. A warming trend will then take place the remainder of the week as surface high pressure slides off the coast.

KEY MESSAGE 2...Gusty winds continue across the area through early Saturday morning.

Gusty south winds continue this afternoon as high pressure shifts offshore and a warm front lifts through the forecast area. Surface low pressure tracks northeast across the Great Lakes with the associated cold front pushing through the forecast area this evening and into early Saturday morning.
There will be a brief lull in winds this evening before winds shift to northwesterly and increase in the wake of the cold front. High Wind Warnings remain in effect for portions of the Alleghenies with Wind Advisories in effect along and west of the I-95 corridor until 00Z. Advisories for the ridges along the Blue Ridge and Alleghenies remain in effect through late this evening.

In the wake of the cold front, dry conditions are expected on Saturday. Precipitation returns Sunday night as a warm front lifts through the forecast area.

AVIATION /19Z FRIDAY THROUGH WEDNESDAY/
VFR conditions are expected across the terminal through Saturday as dry conditions continue. The main aviation hazard will be gusty winds and wind shear through this evening. South winds gust 30 to 40 knots this afternoon before diminishing slightly overnight during a lull. A cold front pushes through the forecast area Saturday morning with winds shifting to northwesterly and increasing to gusts between 15 and 25 knots Saturday afternoon.

A warm front lifts through the terminals on Sunday, bringing southeast winds and increased precipitation chances. Sub-VFR conditions are possible during precipitation Sunday evening and into the overnight.

Sub-VFR ceilings will lift through Monday morning. A strong cold front will cross the area Monday afternoon or evening with showers and potentially a squall line of severe thunderstorms. Winds shift from southerly to west-northwesterly behind the front with potential gradient gusts of 30 to 40 knots. Tight gradients persist into Tuesday with westerly gusts to around 20 to 30 knots. No significant weather Wednesday as high pressure slides by.

MARINE
A Gale Warning is in effect for all of the waters through early this evening. Southerly winds will gust around 30 to 40 knots before diminishing just after sunset. A Small Craft Advisory is in effect for portions of the waters tonight.

Small Craft Advisories were extended to include portions of the waters through Saturday midday Saturday. The strongest winds will be across the northern portion of the Bay, and westerly winds may approach gale-force levels.

Winds diminish gradually below advisory criteria later Saturday afternoon through Saturday night. Additional SCAs may be needed Sunday afternoon as southeast winds gust up to 20 knots.

Either high end SCA or low end gale conditions in gradient winds are expected Monday into Monday evening both ahead of and behind a sharp cold front that will sweep across the area. Severe convection, likely in the form of a squall line, will also accompany the front.
SCA conditions in westerly flow will continue Tuesday before diminishing Tuesday night. High pressure will provide lighter winds on Wednesday.

FIRE WEATHER
Windy conditions will continue ahead of a cold front which will cross the area tonight. There is elevated fire danger across portions of eastern West Virginia this afternoon due to the combination of wind gusts up to 50 mph and relative humidity less than 30 percent. These areas also saw a relative minimum of precipitation over the past two days.

Saturday will be the driest day region wide, behind the frontal passage from tonight. RH values could drop into the upper teens to 20s across much of the area. Winds will be lower compared to Friday, but will remain somewhat elevated, especially along/north of the Interstate 66 corridor, where 20-35 mph wind gusts can be expected.
A Special Weather Statement may be needed.

Gusty winds but increasing RHs are forecast Sunday ahead of another front, which looks to bring wetting rains Sunday evening/night.
There is less of a threat Sunday, but any ongoing fires could feel the impacts of some gusty southeasterly flow (20-30 mph gusts).
Showers and thunderstorms look likely on Monday before strong west- northwesterly winds overspread the area Monday evening into Tuesday.

LWX WATCHES/WARNINGS/ADVISORIES
DC...Wind Advisory until 7 PM EDT this evening for DCZ001.
MD...Gale Warning until 8 PM EDT this evening for MDZ008.
Small Craft Advisory from 8 PM this evening to 2 PM EDT Saturday for MDZ008.
Wind Advisory until 7 PM EDT this evening for MDZ004>006-011- 013-014-016-503>506.
Wind Advisory until 8 PM EDT this evening for MDZ003-502.
Wind Advisory until 2 AM EDT Saturday for MDZ501-509-510.
VA...Wind Advisory until 7 PM EDT this evening for VAZ053>055-501- 502-505-506-526-527.
Wind Advisory until 8 PM EDT this evening for VAZ025>031-504.
High Wind Warning until 2 AM EDT Saturday for VAZ503.
Wind Advisory until 11 PM EDT this evening for VAZ507-508.
WV...Wind Advisory until 8 PM EDT this evening for WVZ050>053-055- 502-504-506.
Wind Advisory until 2 AM EDT Saturday for WVZ503.
High Wind Warning until 2 AM EDT Saturday for WVZ501-505.
MARINE...Gale Warning until 8 PM EDT this evening for ANZ530>543.
Small Craft Advisory from 8 PM this evening to 2 PM EDT Saturday for ANZ530>532-538>540.
Small Craft Advisory from 8 PM this evening to 6 AM EDT Saturday for ANZ533-534-537-541>543.
Small Craft Advisory from 9 AM to 2 PM EDT Saturday for ANZ533>537-541>543.
Small Craft Advisory from 8 PM this evening to 4 AM EDT Saturday for ANZ535-536.