Marine Weather and Tide Forecast for Vienna, MD

KEY MESSAGES
1) Very warm Sunday, followed by a good shot for rain areawide Sunday night into Monday.

2) Seasonable temps Tuesday through Friday with another chance of rain and potential storms Wednesday into Thursday.

DISCUSSION
As of 325 PM EDT Saturday...

KEY MESSAGE 1...Very warm Sunday, followed by a good shot for rain areawide Sunday night into Monday.

Seasonably mild temperatures and partly cloudy skies prevail across the forecast area this afternoon. A few showers have skirted along the coast of VA and MD in association with a weak surface trough and shortwave aloft. The rest of the afternoon and evening will probably be dry but a few of the CAMs show spotty shower activity through about 7-8 PM or so. Will maintain a 20% PoP to cover this possibility. The chance for thunder remains very low.

The flow becomes more zonal on Sunday as the shortwave moving through today pivots well NE of the region. Resultant height rises and increasing thickness values will yield warmer temperatures and highs should be well into the 80s for most of the area, even on the Eastern Shore. The day starts out sunny followed by increasing clouds late in the afternoon as a weak cold front and lee trough sets up north and west of the area, respectively. These features could spark a few late-day showers or storms for far NW portions of our CWA However, neutral or slightly positive height tendencies and a slow frontal progression suggest low coverage and most CAMs keep most of the activity to our N.

Shower/rain potential becomes more widespread Sunday night into Monday as a stronger upper trough pushes the front south and weak low pressure sets up along the boundary. Probabilities from the various modeling suites for at least a tenth of an inch of rainfall have remained quite steady in the 60-90% range, but drop off significantly for >0.5". The storm potential on Monday also continues to appear muted due to the unfavorable morning timing of the front. However, some instability could develop in the late morning (just ahead of the front) in northeast North Carolina, most likely along the Albemarle Sound and points S. Temperatures will drop behind the front as it drops through the area Monday morning.
Thus, the high temperatures shown in the forecast are likely to occur early in the diurnal cycle, potentially near or just after midnight. Temps may attempt to recover a few degrees late in the morning across southern VA and NC before the anafrontal rain shield moves in during the afternoon.

KEY MESSAGE 2...Seasonable temps Tuesday through Friday with another chance of rain and potential storms Wednesday into Thursday.

Below average temps behind the cold front expected Tuesday with highs in the upper 60s. Near normal temps in the mid to upper 70s then return for the rest of the week.

Still looking at another front moving through the area Wednesday into Thursday bringing a round of showers and maybe some thunderstorms. A deeper trough is likely to accompany this front, overspreading some stronger upper-level flow over our area. However, the current deterministic guidance depicts a Wednesday evening/overnight timing, which would be unfavorable for storms. The 12z ECMWF also confirms this idea by showing little to no thunderstorm activity in its lightning density product. So, while there is a conditional possibility for a stronger storm or two, limited instability should preclude any greater severe wx threat at this time. Will continue to monitor, however.
Additional showers or storms are possible during the day Thursday, especially E of I-95, as an upper low spins nearby.
Mostly dry conditions to end the work week into next weekend as sfc high pressure builds in.

AVIATION /19Z SATURDAY THROUGH THURSDAY/
As of 115 PM EDT Saturday...

Mainly VFR conditions prevail through the period, outside of isolated showers which could lead to brief MVFR VSBY and CIGs .
Otherwise, SCT-BKN CU, with bases ranging from 3k-6k ft AGL (lowest SE), and SCT high clouds prevail through most of the afternoon hours today. As previously mentioned, cannot rule out a shower or two through the evening, but confidence and probabilities (<20%) are too low for any explicit mention at this time. Breezy SSW winds this afternoon with gusts of 15-20kt diminish after 00z. Late tonight, some guidance highlights a low-end chance of patchy fog. There is little agreement on placement, timing, and coverage, so will refrain from any mention of this in the TAFs at this point.

Outlook: VFR conditions are expected during the daytime hours Sunday. An area of low pressure approaches the region Sunday night into Monday, bringing the potential for showers and occasional flight restrictions.

MARINE
As of 325 PM EDT Saturday...

Key Messages:

- Sub-SCA conditions should prevail through Sunday night.

- Small Craft Advisories are likely Monday into Tuesday, with increasing N winds, as deepening low pressure moves offshore, followed by high pressure building in from the NW.

Afternoon wx analysis shows high pressure centered near Bermuda and low pressure tracking across the northern Great Lakes. There is enough of a pressure gradient for S winds of 15 kt with occasional gusts to 20 kt. Seas are 3-4 ft (locally a bit higher in NE NC), with ~2 ft waves on the bay. Fairly benign marine conditions are expected tonight and Sunday as the pressure gradient weakens considerably, allowing for an aftn sea/bay breeze with winds becoming E-SE at ~10 kt.

Sub-SCA conditions likely last through Sunday night before a stronger cold front crosses the waters Monday morning. This will allow the winds to shift to the N-NE and increase to near 20 kt with gusts to 25 kt on Monday as low pressure deepens while tracking east along the frontal boundary to our south. The low continues to intensify offshore Mon night as the next area of high pressure builds in from the NW Tuesday. There are some model differences with respect to timing and the exact position of the sfc features and the 12z guidance is a bit weaker with winds than last night's 00z suite.
Regardless, SCAs appear very likely for the bay, nearshore coastal waters, Lower James, and Currituck Sound Monday into Tuesday. Will note that there may be a brief decrease in winds Monday evening well after the initial FROPA...before winds increase again Mon night as a secondary CAA surge arrives. Local wind probs for 18 kt sustained winds in the Bay are ~50% south of Windmill Point and probs for 25 kt gusts on the Ocean have decreased to 20-40%. Regardless, seas will build to 5-6 ft nearshore due to the N-NE flow even if frequent gusts on the ocean don't quite meet SCA criteria. Conditions improve later Tuesday as the system moves well offshore with high pressure becoming centered over the local area.

AKQ WATCHES/WARNINGS/ADVISORIES
MD...None.
NC...None.
VA...None.
MARINE...None.