Marine Weather and Tide Forecast for Port Royal, VA

NEAR TERM /THROUGH TONIGHT/
A cold front, currently near or along I-66, will propagate farther to the south late this afternoon and evening before becoming stationary tonight through the remainder of the weekend. Multiple clusters of showers are developing along the Appalachian Front and moving toward the east. Individual thunderstorms, some strong, are developing ahead of or within these clusters of showers and are drifting toward the southeast.
More showers and strong to possibly isolated severe thunderstorms are expected to develop during the warmest time of the afternoon and linger into the middle part of this evening, mainly along the cold front and across northern and central Virginia and southern Maryland where SPC has this area in a Marginal Risk for severe thunderstorms. The main threats will be large hail, lightning, and torrential rainfall. WPC has this same area in a Slight Risk for excessive rainfall that could lead to flash flooding. There is currently a Flood Watch from near Washington D.C. and areas to the southwest, south, and southeast from 6pm to 2am tonight. Rainfall amounts could reach 1 to 3 inches with locally 4 to 5 inches. Surface based CAPE is 2500-3500 J/kg with MLCAPE of around 1000 J/kg. Wind shear has also become a factor contributing to potential heavy convection with values of 35 to 45 knots. Lack of cloud cover has allowed for our high temperatures to reach the middle to upper 80s easily with slightly lower values in the west.

Showers and strong to severe thunderstorms should dissipate or become less numerous overnight with patchy fog or drizzle developing in areas. Some fog may be locally dense. Lows tonight will be in the 60s and 70s for most areas.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
A cold front will stall across the central zones of our region through the day Saturday. An upper level low will move closer to the area from the west. A lull in shower and any thunderstorm activity more likely through Saturday morning with and thereafter the fog. Another heavy round of showers and thunderstorms is expected Saturday afternoon and evening. There is still some uncertainty as to exactly where this will setup, but latest guidance continues to suggest areas south and west of the Potomac River as the areas most likely to get the strongest convection. All the ingredients are there for a flash flood threat. Will continue to monitor, because the position of the front will be vitally important as to exactly where the strongest convection will be. For areas to the northeast of the boundary. A few showers and a thunderstorm are still possible, especially late in the day into the evening as stronger convection upstream propagates into the area.

The upper level low will shear apart as it moves into the area Sunday, but latest guidance shows the boundary pushing a little farther south and west. This is most likely in response to subsidence associated with a departing jetmax in the northern stream, causing high pressure to strengthen off the New England Coast. The threat for heavy rain is most likely across central Virginia into the Allegheny Highlands, but that can change if the location of the front is off. Will continue to monitor.

LONG TERM /MONDAY THROUGH FRIDAY/
The stalled front will remain nearby in our region through the day on Monday with cool marine air remaining in place for most areas. The boundary will dissipate and move north Tuesday as a warm front and high pressure over the Atlantic will likely control the weather pattern for the middle of next week with a return of hotter and humid conditions. Unsettled conditions will likely persist during this time with chances for showers and thunderstorms. Perhaps the best chance for stronger storms will be Thursday as a cold front approaches from the west.

AVIATION /19Z FRIDAY THROUGH WEDNESDAY/
VFR conditions will continue through much of the rest of the afternoon. Showers and thunderstorms will increase in coverage through this evening. A few stronger storms are possible with gusty winds and brief IFR conditions. The best chance for stronger storms is between 23Z and 04Z. Incorporated the potential for heavy thunderstorms between 00Z and 03Z with a TEMPO group.

Low clouds and areas of fog/drizzle are likely to develop late tonight behind a stalling front that moves into the area. There is still some uncertainty as to exactly where the boundary will set up, but latest indications are that most areas will end up in the marine air for Saturday through Monday. This means that low clouds and subVFR conditions are likely most of the time with IFR/subIFR conditions possible, especially at night into the morning hours each day. Unsettled conditions will continue with the likelihood for showers and perhaps a few storms. The best chance for storms will be around KCHO, KMRB and KIAD Saturday afternoon and evening and KCHO for Sunday afternoon and evening. However, storms are possible everywhere.

More low clouds and fog will likely hang around through Tuesday morning, but cigs/vsbys should improve as the backdoor boundary dissipates and moves northward.

MARINE
A southerly flow will increase into this evening, but winds should remain below SCA criteria. Thunderstorm coverage will increase through this evening. Gusty winds associated with storms may warrant Special Marine Warnings.

A stalling front will slide across the central areas for later Saturday through Monday night. An easterly flow will bring low clouds and areas of fog, and the likelihood for showers and perhaps a thunderstorm will persist. Winds should be below SCA criteria. The boundary will dissipate Tuesday and a southerly flow will develop for the middle portion of next week.

LWX WATCHES/WARNINGS/ADVISORIES
DC...Flood Watch from 6 PM this evening to 2 AM EDT Saturday for DCZ001.
MD...Flood Watch from 6 PM this evening to 2 AM EDT Saturday for MDZ013-016-017-504.
VA...Flood Watch from 6 PM this evening to 2 AM EDT Saturday for VAZ037>039-050-051-053>057-502-527.
WV...None.
MARINE...None.