Marine Weather and Tide Forecast for St. James, MD

NEAR TERM /THROUGH TONIGHT/
Latest water vapor satellite imagery continues to depict a potent upper-low spinning across the lower Ohio Valley into the southern Appalachains. Showers are pivoting to the northeast concurrently with the low level jet associated with this system, which is pushing further to our east with each passing hour.
A few showers are lingering across northeastern Maryland, and will likely do so for the next hour or two. Thankfully, have seen a downward trend in intensity in the last hour, so not expecting to see any sort of flooding threat develop from this feature.

After this departs, all that is left is some light drizzle/showers, which should decrease in coverage by around noon or so. This break in the rain has allowed most of our small streams to recede. However, mainstem river flooding will continue to be an issue for at least the next 24 to 48 hours.

PREVIOUS DISCUSSION: The upper-low will begin opening as it continues northeast today. While cloud breaks might be limited, especially across the northern half of the area, some low level drying may begin to take place, allowing instability to build, especially over the southern half of the area. A vort max will approach during peak heating, and with little inhibition, widespread showers and scattered thunderstorms are expected to develop by afternoon. This activity should gradually spread northeastward through the remainder of the afternoon and evening. Shear will be marginal, around 20-30 kt, but this could support a few stronger storms. Lowering freezing levels suggest a hail threat, but the marginal shear combined with moist profiles will likely limit the threat for severe winds and hail.
00Z CAMs suggest the strongest storms will be over southeastern Virginia, perhaps making a run toward the lower Potomac area.
The severe threat will lessen with northward extent due to decreasing instability. Renewed flooding will also be a concern.
Heavy rain will not be as widespread as Tuesday with average rainfall amounts less than an inch expected. Precipitable water values are also lower, and the forcing should be somewhat progressive. However, slow storm motions less than 20 kt could pose an issue in any storms that could produce rain rates of 1-1.5 inches in an hour or two. At the moment, the threat for flooding seems to be isolated. However, given many sensitive areas and high streams across the area, this will continue to be evaluated. Temperatures should push into the 70s for most areas, warmest in the southwest.

Remnant showers will gradually lift to the northeast tonight with low clouds and fog possible again. Lows will be in the mid 50s to mid 60s.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
The weakening trough axis and possible weak surface low will be near the Chesapeake Bay Thursday morning. This means any remaining showers northeast of the Potomac should pivot away during the morning hours. More breaks of sun are likely, which will allow temperatures to rise toward 80. Not a lot of confidence in the precipitation forecast thereafter. Advection of a high theta-e airmass will be approaching from the west.
Other than possible terrain lift, forcing is otherwise nebulous through the day. However, CAMs suggest some storms may develop over the central Appalachians at a minimum. Given steepening lapse rates and increasing shear, some storms could be severe.
However rising heights could limit storm strength. SPC has added a Marginal Risk for severe for now.

The uncertainty theme continues Thursday night through Friday night as possible upstream convection moves toward the area. The airmass will be characterized by steep lapse rates and strong shear, so storms may be able to maintain themselves. Depending on how the airmass is modified by upstream convection, Friday in particular could have a high end CAPE/shear parameter space across the area. However, the atmosphere may remain capped with little to no storm development. Hopefully this becomes clearer with time. What's more certain is that it will turn hot and humid Friday, with highs well into the 80s and dew points in the mid 60s to lower 70s.

LONG TERM /SATURDAY THROUGH TUESDAY/
A low pressure system will bring a cold front across the region on Saturday. Showers and thunderstorms will develop ahead of and along this front Saturday afternoon. Temperatures will be on the warm side with highs in the middle 80s.

A drier day in store for the region Sunday through Tuesday with high pressure building across the region. Highs in the upper 70s to lower 80s with lower humidity.

The next chance for showers or thunderstorms could come with a front late Tuesday into Tuesday night.

AVIATION /13Z WEDNESDAY THROUGH SUNDAY/
Light rain and drizzle continue across all terminals at this time, accompanied by IFR to LIFR CIGs . This should gradually start to improve to some extent through mid-late morning as drier air starts to push into the region from the SW. Starting to see some evidence of improvement at CHO already in terms of VSBYS, but not expecting CIGs to improve substantially until probably close to noon.

Ceilings will gradually lift to MVFR and potentially even VFR during the afternoon hours. Showers and thunderstorms will form during the afternoon, generally progressing southwest to northeast. Thunderstorms are most likely at CHO, but may be more scattered once they reach the metro terminals (thus PROB30 groups for now). Showers may linger at BWI/MTN into the night.
Otherwise, expect a return to IFR to perhaps LIFR ceilings.
Light E to S winds are expected through the TAF period.

Conditions improve to VFR on Thursday. The highest chance for an afternoon/evening thunderstorm appears to be at CHO, but this is highly uncertain. Sub-VFR conditions (ceilings or fog) may return to mainly MRB/BWI/MTN Thursday night. There is also potential for one or more rounds of showers and thunderstorms late Thursday night through Friday night, but details are very uncertain at this time.

MVFR conditions could arise with showers and thunderstorms Saturday afternoon into early evening. Winds will be southerly before shifting to southwesterly by Friday. Winds southwest becoming west 5 to 10 knots Saturday and Saturday night. Winds west becoming northwest 5 to 10 knots Sunday and Sunday night.

MARINE
With the latest forecast package this morning, SCAs were cancelled in the northern Chesapeake Bay, so no marine hazards are in effect at this time. Winds will generally diminish today as the low-level jet continues its departure north and east.

For the remainder of the day, light east to south winds are expected through Thursday. Strong thunderstorms could approach from the south later this afternoon into the evening, which could warrant Special Marine Warnings.

South to southwest winds should remain sub-SCA Thursday night through Friday night . The main concern will come from thunderstorms, although the timing, coverage, and strength of any storms is very uncertain at this time.

Showers and thunderstorms that develop Saturday afternoon over or near the waters could pose for a Special Marine Warning in places.
Otherwise, no marine hazards expected Saturday night through Sunday night. Winds southwest to west 10 knots Saturday and Saturday night.
Winds becoming northwest 10 knots Sunday.

TIDES/COASTAL FLOODING
Tidal anomalies have really fallen off this morning, down to around 1-1.25 feet above normal at this time. Many of the Coastal Flood Advisories that were in effect have either come and gone, or never quite reached minor flood stage to begin with. General improvement is expected for most in the coming days, but a generally light southerly flow will continue to bring the more sensitive tidal sites near/into action stage.
However, Georgetown will likely have some freshwater related flooding by Thursday, and a Coastal Flood Watch remains in effect for this threat. Current forecast brings Georgetown to Moderate for much of the day on Thursday as a result of the freshwater influence flowing down from the west.

LWX WATCHES/WARNINGS/ADVISORIES
DC...Coastal Flood Watch from Thursday morning through Friday afternoon for DCZ001.
MD...Coastal Flood Advisory until 10 AM EDT this morning for MDZ011- 014.
Coastal Flood Advisory until 3 PM EDT this afternoon for MDZ508.
VA...None.
WV...None.
MARINE...None.