Marine Weather Net

Tidal Potomac from Cobb Island MD to Smith Point VA Marine Forecast


TONIGHT

NW
WINDS
15 - 20
KNOTS

THU

NW
WINDS
10 - 15
KNOTS

THU NIGHT

E
WINDS
5 KNOTS

FRI

SE
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
ANZ537 Forecast Issued: 737 PM EDT Wed May 05 2021

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING
Tonight...Nw Winds 15 To 20 Kt With Gusts To 30 Kt. Waves 2 To 3 Ft. Scattered Showers This Evening.
Thu...Nw Winds 10 To 15 Kt. Gusts Up To 25 Kt. Waves 2 To 3 Ft.
Thu Night...E Winds 5 Kt. Waves Less Than 1 Ft.
Fri...Se Winds 5 To 10 Kt. Waves 1 Ft. Showers.
Fri Night...Nw Winds 10 Kt With Gusts To 20 Kt. Waves 2 Ft. Showers.
Sat...Nw Winds 10 To 15 Kt With Gusts To 20 Kt. Waves 2 Ft.
Sat Night...Nw Winds 5 To 10 Kt With Gusts To 20 Kt. Waves 1 To 2 Ft.
Sun...W Winds 5 Kt...Becoming Se. Waves 1 To 2 Ft. A Chance Of Showers.
Mon...Nw Winds 5 To 10 Kt. Waves 1 To 2 Ft. A Chance Of Showers.
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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
317pm EDT Wednesday May 5 2021

Synopsis
A cold front will pass through the area late this afternoon into this evening. High pressure will build in from Canada Thursday before another low pressure crosses the region Friday. High pressure will return for Saturday before low pressure possibly impacts the area Sunday.

Near Term - Through Thursday
A cold front is moving into northeastern Maryland and eastern Virginia. Showers and a couple of severe thunderstorms have formed ahead of the front from BWI Airport, into southern Maryland, and extending southwestward into the eastern portions of the Virginia Piedmont. The main threat with severe thunderstorms are large hail and damaging winds. Additional strong to severe thunderstorm could form farther to the south into eastern Virginia, over the Tidal Potomac, and the central Chesapeake Bay. Cooler and drier air will push into the region behind the front this evening and overnight. Dewpoint temperatures, indicating the drier air, will drop nearly 20 degrees over an 18 to 24 hour period starting late this afternoon. A Freeze Warning has been issued for western Pendleton and western Highland Counties from 3am to 9am tonight into Thursday morning. Patchy frost is not out of the question either in sheltered valleys in the west. Frequent wind gusts should be in the range of 20 to 30 mph.

High pressure will build overhead Thursday allowing for cool conditions for this time of year, despite some sunshine. There will be some high clouds due to a jetstreak around the base of a broad upper-level trough over the region, but the cloud deck should be thin.

Short Term - Thursday Night Through Friday Night
An upper-level trough will become sharply defined Thursday night. Low pressure will develop over North Carolina. A second low that will develop over southwestern PA. A boundary will set up between these two systems, and an onshore flow will develop ahead of them. However, much of Thursday night should be dry as this is taking place, since most of the dynamics will remain to our south and west and moisture will still be limited. A few showers may develop over our western areas near the Allegheny Highlands into central Virginia overnight though.

The forcing associated with these systems will strengthen as the upper-level trough axis swings negatively tilted, allowing these systems to continue phasing. Coastal low pressure will develop, but likely too far offshore to have a significant impact. However, forcing along the boundary between the northern and southern stream low will strengthen, and that boundary will slowly pass through from west to east. At the same time, moisture will be in the increase as an onshore flow component draws moisture from the Atlantic. As a result, widespread showers are expected to develop, and with the clouds and onshore flow it will be very cool for this time of year. Bottom line, is that Friday looks like a wet, dreary and chilly day for this time of year.

This system will exit Friday night, and a northwest flow will bring more chilly conditions for this time of year. However, it should dry out.

Long Term - Saturday Through Wednesday
As the trough moves offshore Saturday, a weak area of surface high pressure will build over the region. The upper level flow will become more zonal and temperatures will increase slightly Sunday, but still remain slightly below average. An area of low pressure will approach the region Sunday with rain chances increasing later in the day into Sunday night and Monday. As we remain in the cool sector, do think we stay stable so the severe threat is likely minimal. However, the potential for flooding will need to be monitored, especially west of the Blue Ridge where the greatest potential exists for 1 to locally 2 inches of rain.

A weak cold front looks to move through the region Monday, before potentially lifting back north through the region as a warm front by midweek. This results in the residual chance for showers almost daily. Upper level flow looks to stay west or west-northwest, so temperatures do look to stay near or below the (new) normals across the CWA through Midweek. There may be some frost/freeze concerns across the higher terrain of the Allegheny Front if there are no clouds or precipitation Monday and again Tuesday night.

Marine
A cold front will pass through this afternoon. Strong to severe thunderstorms along the cold front will move out of the waters by early evening. Special Marine Warnings have been issued and will be issued over the next hour or two as severe storms march across the region.

A pressure surge behind the cold front will cause gusty northwest winds, and an SCA (Small Craft Advisory) is in effect for the waters this afternoon through tonight. Gusts around 30 knots are expected.

High pressure will settle overhead Thursday, and an SCA (Small Craft Advisory) is in effect for portions of the waters ahead of the building high for Thursday morning. More SCA (Small Craft Advisory) conditions are possible Friday as low pressure develops and tracks offshore.

SCA (Small Craft Advisory) conditions are likely Sunday through the first part of next week.

Tides / Coastal Flooding
A southerly flow will cause elevated water levels this afternoon, but confidence is too low for any advisories at this time since the flow is expected to turn west of south.

NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...None. MD...None. VA...Freeze Warning from 3am to 9am EDT Thursday for VAZ503. WV...Freeze Warning from 3am to 9am EDT Thursday for WVZ505.
MARINE...
Small Craft Advisory until noon EDT Thursday for ANZ530>534- 537>543. Small Craft Advisory until 6am EDT Thursday for ANZ535-536.