Marine Weather and Tide Forecast for Gwynn, VA

KEY MESSAGES
1) Typical summer weather today and Monday with near average temperatures and late afternoon-evening showers/storms.

2) Widespread showers and thunderstorms expected Tuesday afternoon with the potential for damaging wind gusts and hail.

DISCUSSION
As of 250 AM EDT Sunday...

KEY MESSAGE 1...Typical summer weather today and Monday with near average temperatures and late afternoon-evening showers/storms.

Northwest upper/mid level flow has set up over the forecast area now that the axis of a seasonably deep trough has shifted offshore. At the surface, a cold front is positioned southeast of the NC coast and high pressure has moved in over the Mid- Atlantic. Today actually looks pretty decent overall with highs in the mid 80s and partly to mostly sunny skies. Could be a touch humid, but it's definitely not the worst humidity we've seen. Later this evening, a shortwave traveling down the trough is expected to trigger at least a few thunderstorms across the Mid-Atlantic. CAMs indicate a relatively late initiation (~7-9pm) and storms staying mostly in the Piedmont. The later start time would of course mean waning instability, but NW flow has historically been good at producing storms with strong wind gusts around here. The 25-30kt of shear expected is pretty good for July. While storms will be isolated to widely scattered, there is the potential for one or two stronger storms that produce damaging wind gusts or even some hail. SPC has put the piedmont in a Marginal Risk for today. Another round of scattered storms is expected Monday, but with an earlier initiation time and coastal areas being included in the action.
Will still have that NW flow in place, about 30kt of bulk shear, and 1500-2000 J/kg of CAPE, so stronger storms will still be possible. SPC also has a marginal risk for much of the area Monday.

KEY MESSAGE 2...Widespread showers and thunderstorms expected Tuesday afternoon with the potential for damaging wind gusts and hail.

Tuesday still looks like the best shot at widespread thunderstorms and at least scattered instances of severe storms. The Mid-Atlantic will still be under NW flow as a cold front sweeps through at the surface. The GFS and Canadian have trended toward the more aggressive ECMWF solution regarding the upper trough. Now all three want to cut the low off somewhere over the upper Mid-Atlantic or southern New England, but there are differences in timing. Regardless, confidence is increasing in a strong synoptic set up for severe weather. Bulk shear of 35kt and MLCAPE of 1000-1500 J/kg would be sufficient support. Main threats would be damaging wind gusts and large hail.
As always though, timing of the storms will be important to how much severe WX occurs (as has been the case with some recent events).
Morning showers may inhibit instability, which could also lead to a bust. It is likely that the SPC will carry over the slight risk from the day 4 extended outlook into the day 3 outlook, which will come out later this morning.

AVIATION /12Z SUNDAY THROUGH THURSDAY/
As of 645 AM EDT Sunday...

Some patchy fog may linger at ECG right at the start of the 12z period, but anticipate it will quickly burn off before 13z.
SCT skies then prevail during the day. Cloud cover increases later this evening once storms get going in western VA. Could see widely scattered storms within the forecast area after 00z, but confidence in impacts at the terminals is too low for inclusion in the TAF at this time. RIC would have the highest chance at seeing a storm tonight with a much lower chance for the coastal terminals.

Outlook: Isolated to widely scattered late aftn/evening showers/storms are possible both Sunday and Monday, with a higher chance for storms Tuesday aftn/evening as the next front approaches the region from the NNW. Additional SHRA/TSRA possible Wednesday.

MARINE
As of 250 AM EDT Sunday...

- Sub-advisory conditions are expected to prevail with northerly winds today.

- Another front approaches on Tuesday, which could bring a period of low-end SCAs with SW winds.

N winds of 5-10 kt prevail early this morning as weak low pressure continues to move well offshore. Seas are 2-3 ft, with 1-2 ft waves.
We will likely see a modest increase in northerly winds by sunrise (to 10-15 kt). As the low continues to lift farther away, the gradient across the region will relax and winds will shift to the southeast Monday, then to the south on Monday night. The gradient is expected to tighten on Tuesday ahead of the next front. S and SW winds are forecast to increase to 15-20 kt in the Ches Bay and 20-25 kt offshore. A few strong storms are possible Monday evening with a better chance Tuesday afternoon and evening with gusty winds the primary threat. In the wake of the front, winds will decrease to 5- 15 kt and shift to the NW. Northwesterly winds will prevail from Wednesday-Thursday, with light and variable winds expected Friday.

A moderate rip risk continues this afternoon for the southern beaches today due to seas around 3 ft. The rip current risk drops to low for all beaches on Monday and Tuesday.

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