Marine Weather Net

Tidal Potomac from Key Bridge to Indian Head MD Marine Forecast


REST OF THIS AFTERNOON

NW
WINDS
15
KNOTS

TONIGHT

NW
WINDS
5 - 10
KNOTS

TUE

W
WINDS
5 - 10
KNOTS

TUE NIGHT

W
WINDS
5 KNOTS

The Marine Weather Forecast In Detail:
ANZ535 Forecast Issued: 437 PM EDT Mon Oct 18 2021

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 PM EDT THIS EVENING
Rest Of This Afternoon...Nw Winds 15 Kt With Gusts To 25 Kt. Waves 1 Ft.
Tonight...Nw Winds 5 To 10 Kt. Waves 1 Ft.
Tue...W Winds 5 To 10 Kt. Waves 1 Ft.
Tue Night...W Winds 5 Kt. Waves Less Than 1 Ft.
Wed...W Winds 5 To 10 Kt. Waves 1 Ft.
Wed Night...Sw Winds Around 5 Kt. Waves 1 Ft Or Less.
Thu...Sw Winds 5 To 10 Kt. Waves 1 Ft.
Fri...Nw Winds Around 5 Kt. Waves 1 Ft.
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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
300pm EDT Monday Oct 18 2021

Synopsis
High pressure is expected to slowly build eastward across the southeastern US through the middle of the week. A cold front will likely cross the region late in the week.

Near Term - Through Tonight
High pressure is located over the lower Mississippi Valley this afternoon while low pressure persists over the Canadian Maritimes. Gusty northwest winds up to 20-30 mph at times continue between these systems. Mid level moisture associated with this system is gradually retreating, with partly cloudy skies confined generally northeast of the Potomac River. These clouds should dissipate around or shortly after sunset.

The center of the high will move toward the southern Appalachians tonight. The pressure gradient will weaken, so most areas should decouple to some extent, although a light westerly wind may persist. With clear skies expected, the most sheltered locations could drop close to the dew points the mid 30s as was seen this morning. Besides marginal temperatures, the limiting factor for frost is stronger winds around 1000 ft AGL, which may promote some turbulence in the boundary layer. Therefore kept only a patchy frost mention in the forecast, but trends will be monitored this evening. The most likely areas to see some patchy frost would be the central Shenandoah Valley and the Culpeper Basin (Virginia Piedmont). Most other locations will be in the 40s.

Short Term - Tuesday Through Wednesday Night
Tuesday and Wednesday will feature a warming trend of a few degrees each day as the surface high continues to slide eastward off the southeast coast and shortwave ridging builds overhead. A still-noticeable wind will remain Tuesday (gusts 15-20 mph), but should be light thereafter. Dry weather is expected, with only a few passing patches of high clouds. Low pressure will be moving into the Great Lakes by Wednesday night, but any precipitation is expected to remain well to the west.

Long Term - Thursday Through Monday
A weak front will pass through our region late Thursday into Friday. This front will not have much moisture to work with given the lack of return flow on the backside of the departing high pressure. There will be some shower activity and perhaps a rumble of thunder in parts of the northwest. There should be better shear than instability, so gusty winds could be the main threat with any thunderstorms that develop late Thursday into Thursday evening. Temperatures will warm into the middle 70s ahead of the front with overnight lows in the 50s.

A secondary front could pass across the region Friday evening into Saturday, but is expected to be the weaker of the two. High temperatures Friday may only reach the 60s prior to dropping into the upper 30s to lower 40s Friday night.

The cooler air continues Saturday into Sunday as high pressure builds on the north side of the departing cold front. Dry conditions most likely could lead into some frost or freeze conditions Saturday night and early Sunday. While the chilly air lingers Sunday into Sunday night, some light rain could develop along and on the north side of the front to the south Sunday night.

Marine
Brisk northwesterly flow will only gradually wane over the next 36 hours. SCA (Small Craft Advisory) will be in effect for all waters through 8pm this evening, with a few gusts in the 25-30 knot occurring. Winds should subside on the sheltered waters tonight, but remain elevated on the bay and lower Potomac. Overall winds will trend downward Tuesday, but will still be near SCA (Small Craft Advisory) thresholds. Expanded the area of the existing SCA (Small Craft Advisory) to cover more of the waters. The Potomac will be close, but wind fields are slightly lower there. Winds are uncertain Tuesday night, as westerly flow will remain elevated just off the surface and could mix down with cool air over the warmer waters. It does appear light winds are likely Wednesday with high pressure centered near South Carolina.

Winds southwest around 10 knots Thursday and Thursday night and gusts could approach SCA (Small Craft Advisory) criteria on portions of the waters. Winds becoming northwest 10 knots Friday and Friday evening.

NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...None. MD...None. VA...None. WV...None.

Marine
Small Craft Advisory until 6pm EDT Tuesday for ANZ530>534-537- 539>541-543. Small Craft Advisory until 8pm EDT this evening for ANZ535- 536-538-542. Small Craft Advisory from 9am to 6pm EDT Tuesday for ANZ538.