Marine Weather and Tide Forecast for Colonial Beach, VA

KEY MESSAGES
- 1) Monitoring potential for localized urban flooding tonight as a warm front lifts north.

- 2) Daily shower and thunderstorm chances Wednesday through early next week.

DISCUSSION
KEY MESSAGE 1...Monitoring potential for localized urban flooding tonight as a warm front lifts north.

A stalled frontal boundary is currently located over the Virginia Tidewater region while extending back into central North Carolina. Any associated shower activity remains well south of the local area this morning. However, clouds do continue to lift up from southern Virginia, with further expansion of cloud cover expected through the day. Looking at dry conditions for most of the area today as the boundary remains nearly stationary through the remainder of the morning.
However, the boundary is going to start lifting north as a warm front this afternoon, then make steadier progress through the area tonight. Showers and some thunderstorms push into parts of Central Virginia this afternoon.

A cutoff mid-level low over the Deep South today retrogrades north this evening, and that is what will push the warm front into our area. As the front presses north, expect additional slow moving shower and thunderstorms to develop across central VA, then up toward the Washington DC and Baltimore Metro areas overnight tonight into Wednesday morning.

There is a concerning signal in some of the high res guidance that indicate potential for flash flooding in the metro areas tonight. Convection appears to be enhanced from the development of a broad wave of surface low pressure, or an MCV that develops in the aftermath of diurnal convection. Either way, any slow moving shower or thunderstorm tonight is going to be cable of producing heavy rainfall in a short period of time. Tropical moisture returns as PWATs surge to over 2" once again. This likely yields high rain rates of 1-3" per hour in the heaviest showers/thunderstorms. A Flood Watch may be needed for parts of the area, but confidence is too low at this time. Will need to carefully analyze the 12Z and later guidance to determine if the threat for urban flash flooding is there tonight.

KEY MESSAGE 2...Daily shower and thunderstorm chances Wednesday through early next week.

Ongoing showers and thunderstorms continue into Wednesday morning as the warm front remains somewhere north of I-66. The cut-off low over the southeastern U.S. weakens/shears while subtropical ridging retrogrades toward the Atlantic coast. Increasing warmth and humidity around the west side of the subtropical Atlantic ridge, coupled with weak disturbances aloft will lead to afternoon and evening showers and thunderstorms each day Thursday into early next week. Mid-level flow appears strongest Thursday through the weekend.
Given the degree of instability with temps in the 90s and 70s dewpoints, there could be a risk for severe thunderstorms each day.
Locally heavy rainfall is going to be possible each day, as well.
Increasing warmth and humidity yield heat indices around 100 Thursday through Sunday.

AVIATION /14Z TUESDAY THROUGH SATURDAY/
VFR conditions are expected through this evening for most of the area. A stalled boundary south of the area is going to lift north as warm front this afternoon into tomorrow. Sub-VFR conditions quickly arrive at CHO early this evening, then at IAD/DCA late this evening, and BWI/MTN/MRB late tonight. A period of moderate to heavy showers, and possibly some thunderstorms, is likely to move across the area tonight. IFR CIGs are becoming increasingly likely, with reductions in visibility from heavy rainfall possible.

Sub-VFR conditions persist into Wednesday, though there is likely to be a return to VFR conditions during the afternoon. Beyond that, expect an active weather pattern through the weekend with daily chances for showers and thunderstorms.

MARINE
A stalled boundary south of the waters will lift north as a warm front tonight. Southerly channeling is expected to develop at times Wednesday through Friday, with Small Craft Advisories likely needed for most of the waters. Additionally, daily chances for showers and thunderstorms return to the forecast Wednesday through the weekend.
Any thunderstorm will be capable of producing wind gusts over 35 knots, in addition to lightning strikes.

TIDES/COASTAL FLOODING
Tidal anomalies continue to decrease today as north winds continue.
Southerly winds will return tonight behind a warm front that lifts north through the area. Anomalies climb again mid to late week in response to return southerly flow. Additional periods of coastal flooding are possible at times of high tide at sensitive locations.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 11 AM EDT this morning for ANZ534- 537-543.